The Supratek phono stages are designed for moving coil cartridges only.
Why no provision for moving magnet?
Well I'm sorry but if you are going to spend considerable money on a phono preamp then you may as well buy a quality cartridge, and in my experience moving coil cartridge always gives a better result.
Yes there are some good MM's but even a good quality budget MC will always sound better.
Its my opinion, and some will disagree, but I build the preamps to what I consider the highest standard , so MC it is.
In some ways I'm making it harder for myself- as I've pointed out MC have tiny voltages and need enormous gain , and to achieve that gain with tubes, and no feedback is difficult.
There's two ways to get the extra required gain for MC compared to MM. Passive and Active.
Passive is a step up transformer , and its the method most manufacturers of phono stages use.
They are quiet, reliable , and I'm a big fan of transformers in audio, but not for phono stage inputs, phono step ups always sound limited in dynamics and "choked" to me, they just bore me , its as though someone turned the excitement down.
Actives use electronic methods to get the gain, either more tubes (too noisy) or with FET transistors in front of the first tube.
They are very dynamic sounding and handle the tiny voltages perfectly, I dont think there is any comparism in sound quality, and its not a small difference, active is alive and exciting.
So why are most tube phonos designed to use passive step-ups?
Tubes are wonderfully linear devices that dont require feedback to give very accurate preformance, but they are not as quiet as solid state devices , or passive transformers - they have a noise floor that is louder than solid state or passives and when you amplify thousands of times the noise floor can become audible as hum or hiss.
So you cant simply add more tube stages to get the required gain as noise will become a problem.
If one is determined to use an active method, for the most realistic sound ,then fet's are the ideal solution, these little guys work more like a miniature tube than a transistor and are quiet.
In combination with very quiet and substantial power supplies, very well designed and implemented grounds and good circuit layout, the gain for low output moving coil cartridges with outputs of 0.2mV can be realized .
Its not easy, which is why very few manufacturers even attempt it, but the noise can be down below the noise floor of a vinyl record, which is all that is required.
Still not as quiet as a passive , its true, but the combination of a low output MC cartridge and an active tube phono stage easily surpasses any passive method, even the ultra expensive passive phono devices struggle to come close to the excitement of active vinyl.
Tomorrow, LCR and LR phonostages.
Saturday, January 13, 2018
Thursday, January 11, 2018
Recording Quality
Is DSD audibly superior to MP3?
Yes of course it is, provided the recording process and equipment is of equal quality.
I have MP3's in my hard drives that sound quite wonderful, because the recording equipment and process , the mastering etc were first class.
I also have DSD recordings that are terrible, because they were made from a bad recording.
Sound quality is determined primarily by the recording quality- you cant turn a poor recording into a good one by increasing the bit rate or converting mp3 into flac or dsd.
Years ago I built a tube based microphone preamp for a pair of ribbon microphones, which are consider to be the most "analogue" sounding by musicians- they like the sound compared to cardoid , omnis etc.
We taped a small guitar/banjo combo at a local pub , ribbon mics straight into the tube preamp , then into a reel to reel tape deck.
Minimal mastering and then converted to CD. The recording was exceptional , did a really good job of recreating the performance.
Unfortunately someone brought a little kid who cried all the way through, and it came through just as well!
Tube Microphone Preamp. 6SJ7/ECC88 tubes. Balanced/Unbalanced in and out.
Has matching regulated power supply.
Ribbon mics.
Would consider selling this, makes very nice class A recordings.
Yes of course it is, provided the recording process and equipment is of equal quality.
I have MP3's in my hard drives that sound quite wonderful, because the recording equipment and process , the mastering etc were first class.
I also have DSD recordings that are terrible, because they were made from a bad recording.
Sound quality is determined primarily by the recording quality- you cant turn a poor recording into a good one by increasing the bit rate or converting mp3 into flac or dsd.
Years ago I built a tube based microphone preamp for a pair of ribbon microphones, which are consider to be the most "analogue" sounding by musicians- they like the sound compared to cardoid , omnis etc.
We taped a small guitar/banjo combo at a local pub , ribbon mics straight into the tube preamp , then into a reel to reel tape deck.
Minimal mastering and then converted to CD. The recording was exceptional , did a really good job of recreating the performance.
Unfortunately someone brought a little kid who cried all the way through, and it came through just as well!
Tube Microphone Preamp. 6SJ7/ECC88 tubes. Balanced/Unbalanced in and out.
Has matching regulated power supply.
Ribbon mics.
Would consider selling this, makes very nice class A recordings.
Tuesday, January 9, 2018
Vinyl
What they say about vinyl being more tangible , of more substance, relates not only to the musical quality.
Back in the day, buying a new vinyl record meant more than just the presentation of a new recording.
It was something that you held in your hands, something that was a source of interest, of information, and stimulation, more than just the pretty woman on the cover.
Playing a vinyl record involved unpacking, placing it on turntable and placing cartridge needle in the groove, and in 20 minutes you did it all over again.
The 60's, 70's and 80's were also when music broke fresh ground, the time was ripe for a brand new sound , and a plethora of songwriters and musicians wrote groundbreaking new forms of music and song. Its no coincidence the golden age of songwriting happened along with the golden age of vinyl.
I've been listening to vinyl for nearly 50 years now - these days its not my main source of music.
I listen to music while I'm working and its simply easier to turn the computer on and listen to a whole album or leave the music on shuffle.
And its true that digital audio is very good these days, there's still a lot of bad digital around, but when its good its very good.
I actually believe good digital is more accurate than vinyl, and with a good recording, which is the actual quality determining factor of any source, digital can be closer to the recording than vinyl.
Vinyl has a lot of potential for coloration, mostly on playback in our systems , whereas digital software and hardware is very constant and uniform.
BUT, there is something about vinyl, its totally immersive , and its seems to be far easier to sink into the music listening to vinyl than digital.
Vinyl washes over you, it makes you forget what you were doing, and the 20 minutes goes far quicker than you thought.
Being a tube guy, I naturally think the only way to listen to vinyl is through a tube preamp, with a tube phono stage.
There's good technical reasons for this , vinyl playback through a cartridge tip is feedback free, its a perfectly physical process , that converts magnetic movement into electrical signals.
The resulting frequency response is far from linear , and massive amounts of EQ are needed to get it back to flat.
Combine this with the fact that the signal from the cartridge will be as low as half of a thousandth of a volt for a moving coil cartridge and 5 thousandths of a volt for moving magnet.
To get it up to typical line stage input levels we need to amplify it by at least 5000 times, not an easy task.
Well it is an easier task if you use lots of feedback , which simplifies a lot of problems.
Feedback can be very useful, and it can be the devil, the amount of feedback that is typically used in a solid state phono stage chokes all the life and soul out of vinyl playback.
Its very hard to build a solid state phono stage without a lot of feedback , it can be done, but the royalty of phono stages is the zero feedback tube phono stage.
There are compromises , when you are using tubes for gains of between 5000 and 10000 you are also amplifying the noise floor, so its hard to get a tube phono stage dead quiet.
However it is possible to get them quieter than the noise floor of a vinyl record , so its really not a big issue.
The massive EQ required of a phono stage is always almost done with large amounts of negative feedback with solid state devices , but can be done with zero feedback with tubes.
Feedback with vinyl is bad m'k , something so expressive and free, just doesn't deserve to be castrated and chained.
Vinyl can be beautiful, impressive, strong, expansive and simply great fun.
A good bottle of red or a fine craft beer, give me vinyl!
In other blogs I will explain virtues and compromises of the 300+ tube phono circuits I have designed and built (in conjunction with Kevin Covi)
One of my turntables , the mighty Micro Seiki RX-5000
Sunday, January 7, 2018
Exotic components-2
Bob pointed out I didn't mention volume controls.
Its the obvious DIY approach for many as its relatively easy to do (and also pretty easy to get wrong)
There's ladder resistor pots, and variations on them, transformer volume controls, autotransformer controls, electronic stepper pots.
Some of them can sound good, some of them are more properly called tone controls , and some are terrible.
I tried to get along with some of the more exotic VTC, ATC's but long term they are nothing but trouble.
Like exotic caps, they just sound different, not necesarily better . Its very important to use the right values of pot in a preamp circuit, as just putting anything in can cause serious frequency inaccuracies.
Like wise, impedance matching is critical when using VTC, ATC's.
In my opinion, the best pot is what's been the standard for a very long time- the carbon resistive pot.
I use high quality Alps pots in my preamps, but to be truthful even a cheap carbon pot will always sound pretty good, and I doubt anyone could hear the difference in a double blind test.
The Alps have better channel to channel specs, but its minimal, and any good preamp will have a balance control to enable pin point imaging and sound-staging.
The old faithful carbon pot is transparent, accurate and reliable.
And they can be easily configured for remote operation, which just makes relaxing and listening to good music more enjoyable and fun.
Nothing worse than having shuffle on and the next track 3dB louder than the last, at least with a remote volume its nothing to adjust from listening position.
Alps Blue Pot, motorized.
Its the obvious DIY approach for many as its relatively easy to do (and also pretty easy to get wrong)
There's ladder resistor pots, and variations on them, transformer volume controls, autotransformer controls, electronic stepper pots.
Some of them can sound good, some of them are more properly called tone controls , and some are terrible.
I tried to get along with some of the more exotic VTC, ATC's but long term they are nothing but trouble.
Like exotic caps, they just sound different, not necesarily better . Its very important to use the right values of pot in a preamp circuit, as just putting anything in can cause serious frequency inaccuracies.
Like wise, impedance matching is critical when using VTC, ATC's.
In my opinion, the best pot is what's been the standard for a very long time- the carbon resistive pot.
I use high quality Alps pots in my preamps, but to be truthful even a cheap carbon pot will always sound pretty good, and I doubt anyone could hear the difference in a double blind test.
The Alps have better channel to channel specs, but its minimal, and any good preamp will have a balance control to enable pin point imaging and sound-staging.
The old faithful carbon pot is transparent, accurate and reliable.
And they can be easily configured for remote operation, which just makes relaxing and listening to good music more enjoyable and fun.
Nothing worse than having shuffle on and the next track 3dB louder than the last, at least with a remote volume its nothing to adjust from listening position.
Friday, January 5, 2018
Exotic Components
Another contentious issue perhaps.
You can spend a lot of money on exotic capacitors, resistors, switches etc.
Gold/Silver paper in oil capacitor?
Pure Silver wound transformer?
How much money do you have sir?
I recently had a preamp returned for a modification upgrade.
It had been filled with expensive capacitors , silver plated switches and ridiculous amount of cap bypassing, along with some questionable soldering skills.
Unfortunately the "technician" who did the work had also made the preamp un-operational and it was returned to me for a repair and upgrade to latest circuit.
Over the years I've tried lots of premium parts in my preamps, and there is definitely a place for the best quality possible, some components are very critical - transformers for example, and my distaste for electrolytic capacitors doesnt have to be repeated again- Supratek preamps have about half a dozen electros at most while most preamps have hundreds of the nasty devices.
For signal capacitors I use polypropylene film or good quality paper in oil caps, yes there is a difference in quality between a cheap and nasty polyprop , but once you get to a certain level of quality , differences become just differences, not significant steps in quality.
Just some of the caps tested over the years.
And these differences are quite minimal, mostly inaudible, although the cost of some of these items requires the brain to justify some audible "improvement".
I left the expensive caps in the preamp when I rebuilt it, at the customers request, but on listening to it I had to take one expensive pair out, as they were just horrible sounding.
This preamp did sound different, albeit it was minor, compared to the stock preamp built with my choice of high quality, but non exotic components.
It certainly wasn't "better" in terms of sound quality, it had a slightly different tone, very minor, but probably enough for a zealot to proclaim as significant.
The fact is changing the current running through a tube, like the 6SN7 for example, from 4 to 8 milliamps will make an audible difference, changing the operating voltages, or the type of plate loading will make a difference, as will an output transformer designed and optimised for the application.
Most of the time these changes can be measured (not all the time) - the role of the circuit design is paramount to sound quality, not the level of exotic components.
Good circuit design, over engineered and high quality components ( not necessarily overly expensive) are far more important than filling a chassis with so called exotica which has profit for the vendor as its main purpose.
As an aside, I do like a Russian military teflon paper in oil cap I use in my preamps as it seems to have a nice synergy with the circuit and other poly caps in preamp.
Its not cheap, but a fraction of the cost of an exotic Teflon capacitor that frankly sounds brittle and nasty.
You can spend a lot of money on exotic capacitors, resistors, switches etc.
Gold/Silver paper in oil capacitor?
Pure Silver wound transformer?
How much money do you have sir?
I recently had a preamp returned for a modification upgrade.
It had been filled with expensive capacitors , silver plated switches and ridiculous amount of cap bypassing, along with some questionable soldering skills.
Unfortunately the "technician" who did the work had also made the preamp un-operational and it was returned to me for a repair and upgrade to latest circuit.
Over the years I've tried lots of premium parts in my preamps, and there is definitely a place for the best quality possible, some components are very critical - transformers for example, and my distaste for electrolytic capacitors doesnt have to be repeated again- Supratek preamps have about half a dozen electros at most while most preamps have hundreds of the nasty devices.
For signal capacitors I use polypropylene film or good quality paper in oil caps, yes there is a difference in quality between a cheap and nasty polyprop , but once you get to a certain level of quality , differences become just differences, not significant steps in quality.
And these differences are quite minimal, mostly inaudible, although the cost of some of these items requires the brain to justify some audible "improvement".
I left the expensive caps in the preamp when I rebuilt it, at the customers request, but on listening to it I had to take one expensive pair out, as they were just horrible sounding.
This preamp did sound different, albeit it was minor, compared to the stock preamp built with my choice of high quality, but non exotic components.
It certainly wasn't "better" in terms of sound quality, it had a slightly different tone, very minor, but probably enough for a zealot to proclaim as significant.
The fact is changing the current running through a tube, like the 6SN7 for example, from 4 to 8 milliamps will make an audible difference, changing the operating voltages, or the type of plate loading will make a difference, as will an output transformer designed and optimised for the application.
Most of the time these changes can be measured (not all the time) - the role of the circuit design is paramount to sound quality, not the level of exotic components.
Good circuit design, over engineered and high quality components ( not necessarily overly expensive) are far more important than filling a chassis with so called exotica which has profit for the vendor as its main purpose.
As an aside, I do like a Russian military teflon paper in oil cap I use in my preamps as it seems to have a nice synergy with the circuit and other poly caps in preamp.
Its not cheap, but a fraction of the cost of an exotic Teflon capacitor that frankly sounds brittle and nasty.
Thursday, January 4, 2018
Music
This hobby/passion is all about music, so occasionally I will post some music I'm enjoying
.
I've liked Bruce Cockburn for years, although some of his work can be a bit "different".
I really like this one, not bad for an old geeezer 72yo.
It's been six years since Bruce Cockburn delivered a studio offering. His daughter was born in 2012, he assembled a career-spanning box set, and wrote a candid memoir, Rumours of Glory. When he was finally free of his writing and curatorial chores, he wondered if there was anything left to say. A book of poems by Canada's greatest 20th century poet, Al Purdy, provided inspiration. The song "3 Al Purdys," in which Cockburn sings and speaks the yarn of a homeless wanderer under the spell of the poet (and weds his words to Purdy's) is one of the finest tracks here (and one of four to feature jazz cornetist Ron Miles). Cockburn's less concerned with perfection, particularly when it comes to his vocals. In his seventies, his instrument is gruffer, but via Colin Linden's immediate production, it proves a benefit. "States I'm In" is a searing, insightful, rearview look at what Cockburn's witnessed – beautiful and horrible – in his global travels as a musician and an Amnesty International observer.
He transforms the song from reverie to a meditation on the present realities and in his own life and society. There's a more overt engagement with Christianity on this record, balanced by a sense of "growing tenser with the times" while living in a country led by Donald Trump. The bumping rockabilly shuffle "Stab at Mater" (a wonderful wordplay on the Latin "Stabat Mater") illustrates the experiential grind between spiritual insight and everyday life that deepens them both. Members of his local San Francisco church were recruited as a chorus here and elsewhere, including on the folk-inflected, poetic, yet urgent "Forty Years in the Wilderness." ("…getting to the know the beasts….") "Looking & Waiting" is wafting acoustic reggae. Buoyed by the chorus, it's a hymn to knowing full well that waiting is indeed the hardest part of faith. The title track is a gorgeous instrumental acoustic guitar workout, while "Mon Chemin" is a jazzy, Latinized folk song buoyed by charango and dulcimer, with Miles' cornet, accordionist nephew John Aaron Cockburn, bassist John Dymond, and drummer Gary Craig. The final two tracks also use blues as jumping-off points. On "Jesus Train," Cockburn delivers them through fingerpopping, house-rocking 21st century gospel. It's followed by the traditional "Twelve Gates to the City" (so closely associated with the Rev. Gary Davis). Cockburn makes it his own by adding some new lyrics and a radical NOLA-styled R&B arrangement – Miles' Louis Armstrong-esque fills and the chorus add soulful weight to the proposition. Bone on Bone is a fine, deep return. This somewhat grimier and edgier Cockburn is clearly inspired, his lyrics are both jagged and elegant; they dovetail in songs that question and reveal the rough-hewn beauty of a life guided by spiritual principles. He continues to question these principles while affirming their primacy as a witness to the world's brutality. They also struggle with the next right thing and how to accomplish it, even when it seems pointless to try, and that kind of struggle is the kind of hope we need more of.
Eilen Jewell's country-blues flavored folk on Boundary County will remind listeners of many new, talented women singer/songwriters without ever seeming like a copy. Like Jolie Holland, she slurs her muffled vocals on a series of original songs and accomplishes the neat trick of evoking tradition. Like the Be Good Tanyas, Jewell relies on fairly eclectic arrangements, though she's more progressive in her marriage of electric and acoustic elements. The slow, sad "So Long Blues" ventures toward pure country with Jerry Miller's lap steel underpinning Jewell's lonesome vocal, while the spunky "Gotta Get Right" captures a more folksy feel with banjo and mandolin.
On both, Johnny Sciascia's upright bass is heavy in the mix and sounds more like an electric bass. Jewell is also frequently joined on the choruses by drummer Jason Beek's deeper, raspier voice, an intriguing combination in which both voices intertwine while keeping their identities. A couple of the songs – "The Flood" and "Blow It All Away" – seem a bit long, and it's easy, especially with the latter, to allow Jewell's lazy, bluesy vocal to fade into the background. These tracks, along with the two that follow and bring the album to a close, lack the vim and vigor of the album's earlier tracks. The first two-thirds of Jewell's Boundary County, however, is well-written, well-sung, and well performed, and will please fans progressive traditional-flavored music.
.
I've liked Bruce Cockburn for years, although some of his work can be a bit "different".
I really like this one, not bad for an old geeezer 72yo.
It's been six years since Bruce Cockburn delivered a studio offering. His daughter was born in 2012, he assembled a career-spanning box set, and wrote a candid memoir, Rumours of Glory. When he was finally free of his writing and curatorial chores, he wondered if there was anything left to say. A book of poems by Canada's greatest 20th century poet, Al Purdy, provided inspiration. The song "3 Al Purdys," in which Cockburn sings and speaks the yarn of a homeless wanderer under the spell of the poet (and weds his words to Purdy's) is one of the finest tracks here (and one of four to feature jazz cornetist Ron Miles). Cockburn's less concerned with perfection, particularly when it comes to his vocals. In his seventies, his instrument is gruffer, but via Colin Linden's immediate production, it proves a benefit. "States I'm In" is a searing, insightful, rearview look at what Cockburn's witnessed – beautiful and horrible – in his global travels as a musician and an Amnesty International observer.
He transforms the song from reverie to a meditation on the present realities and in his own life and society. There's a more overt engagement with Christianity on this record, balanced by a sense of "growing tenser with the times" while living in a country led by Donald Trump. The bumping rockabilly shuffle "Stab at Mater" (a wonderful wordplay on the Latin "Stabat Mater") illustrates the experiential grind between spiritual insight and everyday life that deepens them both. Members of his local San Francisco church were recruited as a chorus here and elsewhere, including on the folk-inflected, poetic, yet urgent "Forty Years in the Wilderness." ("…getting to the know the beasts….") "Looking & Waiting" is wafting acoustic reggae. Buoyed by the chorus, it's a hymn to knowing full well that waiting is indeed the hardest part of faith. The title track is a gorgeous instrumental acoustic guitar workout, while "Mon Chemin" is a jazzy, Latinized folk song buoyed by charango and dulcimer, with Miles' cornet, accordionist nephew John Aaron Cockburn, bassist John Dymond, and drummer Gary Craig. The final two tracks also use blues as jumping-off points. On "Jesus Train," Cockburn delivers them through fingerpopping, house-rocking 21st century gospel. It's followed by the traditional "Twelve Gates to the City" (so closely associated with the Rev. Gary Davis). Cockburn makes it his own by adding some new lyrics and a radical NOLA-styled R&B arrangement – Miles' Louis Armstrong-esque fills and the chorus add soulful weight to the proposition. Bone on Bone is a fine, deep return. This somewhat grimier and edgier Cockburn is clearly inspired, his lyrics are both jagged and elegant; they dovetail in songs that question and reveal the rough-hewn beauty of a life guided by spiritual principles. He continues to question these principles while affirming their primacy as a witness to the world's brutality. They also struggle with the next right thing and how to accomplish it, even when it seems pointless to try, and that kind of struggle is the kind of hope we need more of.
Eilen Jewell's country-blues flavored folk on Boundary County will remind listeners of many new, talented women singer/songwriters without ever seeming like a copy. Like Jolie Holland, she slurs her muffled vocals on a series of original songs and accomplishes the neat trick of evoking tradition. Like the Be Good Tanyas, Jewell relies on fairly eclectic arrangements, though she's more progressive in her marriage of electric and acoustic elements. The slow, sad "So Long Blues" ventures toward pure country with Jerry Miller's lap steel underpinning Jewell's lonesome vocal, while the spunky "Gotta Get Right" captures a more folksy feel with banjo and mandolin.
On both, Johnny Sciascia's upright bass is heavy in the mix and sounds more like an electric bass. Jewell is also frequently joined on the choruses by drummer Jason Beek's deeper, raspier voice, an intriguing combination in which both voices intertwine while keeping their identities. A couple of the songs – "The Flood" and "Blow It All Away" – seem a bit long, and it's easy, especially with the latter, to allow Jewell's lazy, bluesy vocal to fade into the background. These tracks, along with the two that follow and bring the album to a close, lack the vim and vigor of the album's earlier tracks. The first two-thirds of Jewell's Boundary County, however, is well-written, well-sung, and well performed, and will please fans progressive traditional-flavored music.
Wednesday, January 3, 2018
Balanced V Unbalanced
Ok this is going to upset a few people.
I don't like balanced operation and only use it when I have to.
I do supply balanced inputs and outputs on some of my preamps, but only because people want them, and because sometimes you have no choice.
Balanced operation comes from the pro-audio world, music venues etc, and is used to cancel out noise that is caused by very long cables, and less than ideal electronic applications.
It doesn't cancel all the noise but does a pretty good job of making it inaudible.
But balanced operation doesn't do a better job than a properly designed and implemented unbalanced design in normal hi fi home situation, if you are using 200 metre long cables you need another house!
Balanced operation in hi fi situations is a clever marketing ploy based on fashion.
Below is a simplified circuit of a cascaded tube preamp.
The round circles are tubes, the squiggly lines are resistors and the parallel lines are capacitors.
It's very simple and very effective, has nice harmonics , good phase response, all you need really.
If it has a good power supply, is designed and constructed properly it will be very quiet with very little, if any, hum and noise.
Below is the same circuit in balanced mode.
Note how there are double the components , two different phases and operating in differential or push pull operation.
It wont be audibly quieter than the above unbalanced circuit, unless you want to drive 200 metre long cables. Harmonics aren't as nice as single ended and there's no guarantee it will be perfectly balanced between tubes and components.
After many years of building both balanced and unbalanced preamps, I've still to hear a balanced circuit sound better than a simpler unbalanced circuit.
To my ears there's always a slight veiling, a lack of cohesion and clarity with balanced operation.
Yes there are plenty of good sounding balanced power amps , but I've never heard a good balanced preamp.
The perfect place to use a balanced circuit would appear to be with moving coil phono cartridges. The voltages from MC cartridges are minuscule , around 0.5 mV , that's half of a thousandth of 1V!
Using tubes to get the required gain of 5000 is tricky , as the noise floor is also amplified, so balanced operation makes sense in this situation.
I built hundreds of differential balanced phono-stages and never heard one that sounded as good as a really well built single ended phono stage.
Yes they are quieter but a well built single ended phono will be quieter than the noise floor of a vinyl record anyway, so there's really no point.
Below is how Supratek preamps provide balanced operation.
The Single ended circuit remains but I use transformers to accept the balanced input and provide balanced outputs.
Good quality transformers, brands like Lundahl , Jensen and Magnequest provide perfect phase splitting and combining- without any of the complications of a doubled-up balanced circuit.
Nice even harmonics are maintained throughout the circuit , and it can be easily switched for balanced or non balanced operation.
Its a win-win, gives true balanced output, there's no price to pay, no compromises and sounds as good as balanced gets.
I don't like balanced operation and only use it when I have to.
I do supply balanced inputs and outputs on some of my preamps, but only because people want them, and because sometimes you have no choice.
Balanced operation comes from the pro-audio world, music venues etc, and is used to cancel out noise that is caused by very long cables, and less than ideal electronic applications.
It doesn't cancel all the noise but does a pretty good job of making it inaudible.
But balanced operation doesn't do a better job than a properly designed and implemented unbalanced design in normal hi fi home situation, if you are using 200 metre long cables you need another house!
Balanced operation in hi fi situations is a clever marketing ploy based on fashion.
Below is a simplified circuit of a cascaded tube preamp.
The round circles are tubes, the squiggly lines are resistors and the parallel lines are capacitors.
It's very simple and very effective, has nice harmonics , good phase response, all you need really.
If it has a good power supply, is designed and constructed properly it will be very quiet with very little, if any, hum and noise.
Below is the same circuit in balanced mode.
Note how there are double the components , two different phases and operating in differential or push pull operation.
It wont be audibly quieter than the above unbalanced circuit, unless you want to drive 200 metre long cables. Harmonics aren't as nice as single ended and there's no guarantee it will be perfectly balanced between tubes and components.
After many years of building both balanced and unbalanced preamps, I've still to hear a balanced circuit sound better than a simpler unbalanced circuit.
To my ears there's always a slight veiling, a lack of cohesion and clarity with balanced operation.
Yes there are plenty of good sounding balanced power amps , but I've never heard a good balanced preamp.
The perfect place to use a balanced circuit would appear to be with moving coil phono cartridges. The voltages from MC cartridges are minuscule , around 0.5 mV , that's half of a thousandth of 1V!
Using tubes to get the required gain of 5000 is tricky , as the noise floor is also amplified, so balanced operation makes sense in this situation.
I built hundreds of differential balanced phono-stages and never heard one that sounded as good as a really well built single ended phono stage.
Yes they are quieter but a well built single ended phono will be quieter than the noise floor of a vinyl record anyway, so there's really no point.
Below is how Supratek preamps provide balanced operation.
The Single ended circuit remains but I use transformers to accept the balanced input and provide balanced outputs.
Good quality transformers, brands like Lundahl , Jensen and Magnequest provide perfect phase splitting and combining- without any of the complications of a doubled-up balanced circuit.
Nice even harmonics are maintained throughout the circuit , and it can be easily switched for balanced or non balanced operation.
Its a win-win, gives true balanced output, there's no price to pay, no compromises and sounds as good as balanced gets.
Tuesday, January 2, 2018
New Year New Models
Happy new year to everyone. Sorry for lack of blogs lately, I had some commitments I had to take care of, but all done now and from Jan 2nd I can devote all my time and effort towards Supratek.
I'll try to do a blog every day, and should be able to find some interesting audio topic each day.
Also this year I'll be bringing out some new models, an entry level preamp and a stand alone phono stage.
Also will finish off Bob's field coil PSU!
Tomorrow I will do an article on balanced v unbalanced operation and why I generally don't like balanced . It will be a bit contentious, so have a read and decide for yourselves.
Here's a pix of what I got up to over the holiday period, the most fun you can have with clothes on (as they say)
I'll try to do a blog every day, and should be able to find some interesting audio topic each day.
Also this year I'll be bringing out some new models, an entry level preamp and a stand alone phono stage.
Also will finish off Bob's field coil PSU!
Tomorrow I will do an article on balanced v unbalanced operation and why I generally don't like balanced . It will be a bit contentious, so have a read and decide for yourselves.
Here's a pix of what I got up to over the holiday period, the most fun you can have with clothes on (as they say)
Sunday, December 10, 2017
Passive/Active
I see a lot of guys going through rounds of speakers, amps, preamps, dacs in the quest for the perfect sound. Or at least the sound they could finally be happy with.
But the sound they wanted could have been in front of them all the time.
The fact is, there is no perfect sound, we all hear, and seek different audio nirvana.
What I consider important to sound quality, you may dismiss in favour of some other aspect, and that is perfectly correct, audio is personally subjective.
There are many ways to voice a loudspeaker, from monitor quality, accurate frequency speakers for studio use to romanticly flavored midrange accentuated ear pleasers.
But no speaker will sound exactly as the designer intended in every room, or system.
There are so many variables that affect the sound, that a speaker can sound vastly different from room to room, and system to system.
One way to get closer to the sound that suits you is to actively drive the speakers individual drivers , thus providing some adjustment to tonal balance, with other important advantages.
I'll describe a couple of my own passive/active systems to explain.
Btw passive /active means the original passive crossovers are retained but split so they can be driven by a set of amps. So a two way speaker would have 4 amplifier channels, and a 3 way would have 6 channels.
Fully active means no passive crossover and crossover done by electronics, either digital or analogue. This can give even more control over the sound, at some compromise.
I have an old set of AR-LST speakers , a legendary speakier that has a reputation for excellent sound, but difficult to drive and match to an amplifier.
It is a 3 way speaker, but with 9 drivers per speaker, and a rather complicated crossover.
In stock form it needs a very capable amp with lots of power , yet high quality as it is very revealing.
I could never get it to sound quite like I wanted, so decided to run it actively, to see if I could manipulate the sound into shape.
I had to modify the crossover so that an amplifier could be connected to each of the bass, midrange and treble sections.
While I was there I replaced some of the older electrolytic caps for more reliable and accurate polyprop caps.
Now that the load to each amp was now only a single section rather than the complete crossover, it is much easier to drive, and I can even use low power tube amps for the mid and treble sections, giving a much nicer and realistic sound.
But the real advantage is that now I can adjust the levels of each amp and the balance of the overall tone of the speaker.
It takes some time, and persistence, but there will come a result of each amps level adjustment that will result in the perfect combination of room and speaker , and your own taste, that will be very pleasing.
You will find that there is much more distinction between the bass ,mid and treble. They will have more entity and seperation, more openness, you will simply hear more as you now have amplifiers operating with specific and achievable functions.
I think this is one of the most rewarding ways to achieve good sound, you are actually making major changes to the speaker/room/taste equation, rather than wasting money on cables, equipment, or another set of speakers.
You need a good preamp that can easily drive 3 sets of amps, a Supratek of course.
Digital or analogue active crossovers give even more control over the sound, with the ability to do room EQ , crossover frequencies and slopes. But apart for bass applications I'm not a fan of fully active systems, they always sound compromised to me, although maybe essential with a really difficult room/speaker.
Many speakers these days have jumpers on the crossover connections , especially 2 way speakers , so that they can be bi-amped, but it seems few take advantage of this excellent opportunity to customise the sound to your own ears.
Ive been building the Dual Cabernet preamp, with this specific purpose in mind, for years now, but sadly few seem to see the obvious advantages.
My Acoustat 2+2 electrostatic speakers have two panels per speaker , one bass and one treble.
Each panel is driven by a very high power amp, which stats need, so 2 amps for each channel.
I use a Dual Cabernet preamp which has a level control for the second preamp section , which is used for the bass amp.
The master volume control adjusts the overall volume and the level control for second preamp section adjusts the bass panel amplifier level.
The Acoustat is very sensitive to this adjustment and even fine adjustments can make a big difference to the tone and overall quality of sound.
Its hard to site a 7'10" tall speaker that needs to be a fair distance from rear wall, and this precise form of level control is very useful.
But any speaker that can be bi-amped will immediatly be transformed by using the Dual Cabernet and an extra set of amps.
I'd suggest you could spend a pile of money to get an expensive new pair of speakers , that still wont get you where you want to be, when going to bi or triamping will give you exactly what you want.
But the sound they wanted could have been in front of them all the time.
The fact is, there is no perfect sound, we all hear, and seek different audio nirvana.
What I consider important to sound quality, you may dismiss in favour of some other aspect, and that is perfectly correct, audio is personally subjective.
There are many ways to voice a loudspeaker, from monitor quality, accurate frequency speakers for studio use to romanticly flavored midrange accentuated ear pleasers.
But no speaker will sound exactly as the designer intended in every room, or system.
There are so many variables that affect the sound, that a speaker can sound vastly different from room to room, and system to system.
One way to get closer to the sound that suits you is to actively drive the speakers individual drivers , thus providing some adjustment to tonal balance, with other important advantages.
I'll describe a couple of my own passive/active systems to explain.
Btw passive /active means the original passive crossovers are retained but split so they can be driven by a set of amps. So a two way speaker would have 4 amplifier channels, and a 3 way would have 6 channels.
Fully active means no passive crossover and crossover done by electronics, either digital or analogue. This can give even more control over the sound, at some compromise.
I have an old set of AR-LST speakers , a legendary speakier that has a reputation for excellent sound, but difficult to drive and match to an amplifier.
It is a 3 way speaker, but with 9 drivers per speaker, and a rather complicated crossover.
In stock form it needs a very capable amp with lots of power , yet high quality as it is very revealing.
I could never get it to sound quite like I wanted, so decided to run it actively, to see if I could manipulate the sound into shape.
I had to modify the crossover so that an amplifier could be connected to each of the bass, midrange and treble sections.
While I was there I replaced some of the older electrolytic caps for more reliable and accurate polyprop caps.
3 sets of amplifier connectors, split crossover sections.
Now that the load to each amp was now only a single section rather than the complete crossover, it is much easier to drive, and I can even use low power tube amps for the mid and treble sections, giving a much nicer and realistic sound.
But the real advantage is that now I can adjust the levels of each amp and the balance of the overall tone of the speaker.
It takes some time, and persistence, but there will come a result of each amps level adjustment that will result in the perfect combination of room and speaker , and your own taste, that will be very pleasing.
You will find that there is much more distinction between the bass ,mid and treble. They will have more entity and seperation, more openness, you will simply hear more as you now have amplifiers operating with specific and achievable functions.
I think this is one of the most rewarding ways to achieve good sound, you are actually making major changes to the speaker/room/taste equation, rather than wasting money on cables, equipment, or another set of speakers.
You need a good preamp that can easily drive 3 sets of amps, a Supratek of course.
Digital or analogue active crossovers give even more control over the sound, with the ability to do room EQ , crossover frequencies and slopes. But apart for bass applications I'm not a fan of fully active systems, they always sound compromised to me, although maybe essential with a really difficult room/speaker.
Many speakers these days have jumpers on the crossover connections , especially 2 way speakers , so that they can be bi-amped, but it seems few take advantage of this excellent opportunity to customise the sound to your own ears.
Ive been building the Dual Cabernet preamp, with this specific purpose in mind, for years now, but sadly few seem to see the obvious advantages.
My Acoustat 2+2 electrostatic speakers have two panels per speaker , one bass and one treble.
Each panel is driven by a very high power amp, which stats need, so 2 amps for each channel.
I use a Dual Cabernet preamp which has a level control for the second preamp section , which is used for the bass amp.
The master volume control adjusts the overall volume and the level control for second preamp section adjusts the bass panel amplifier level.
The Acoustat is very sensitive to this adjustment and even fine adjustments can make a big difference to the tone and overall quality of sound.
Its hard to site a 7'10" tall speaker that needs to be a fair distance from rear wall, and this precise form of level control is very useful.
But any speaker that can be bi-amped will immediatly be transformed by using the Dual Cabernet and an extra set of amps.
I'd suggest you could spend a pile of money to get an expensive new pair of speakers , that still wont get you where you want to be, when going to bi or triamping will give you exactly what you want.
Friday, December 8, 2017
NOS 6SN7 Tubes
The 6SN7 and its derivatives 6H8C, ECC33, CV1988, CV181, VT-231, 5692 are excellent tubes and eagerly sought by tube enthusiasts after the "best" sound.
I've been buying 6SN7's for more than 30 years and have hundreds of them, with examples of all of the above.
So what is my personal preference , what is the Holy Grail of 6SN7's?
Well maybe surprisingly I'm not that keen on old NOS tubes, mostly because most of them are not NEW OLD STOCK.
The only way you can be sure that a tube from the period 1930- 1980 is a genuine NOS tube is if it comes in a sealed box that has not been opened .
Anything you buy from ebay is suspect, even genuine tube sellers really have no way of knowing if a tube has ever been used or not, or how many hours, and under what sort of operating conditions a tube has been used.
They like to assert quality by using a tube tester and give some vague measurement that really doesn't mean anything.
Quite often the tube tester is more than 50 years old and long past its use by date.
The only way to tell if a NOS tube will give optimum service is to actually measure it in the circuit it is being used in.
Gain and channel balance can be checked and if its a highly sophisticated circuit like the Supratek, the operating parameters can be adjusted for perfect performance. On the proviso that the tubes were in excellent condition to start with.
New production tubes aren't that exciting, the current Sovtek and Chinese 6SN7's aren't bad, but they aren't quite as good as the tubes made when cost cutting wasn't more important than quality.
The tubes I use in my preamps are Russian military NOS tubes with OTK certification.
I buy them in boxes of hundred , never used and they have what I value the most, near identical parameters and performance. They are constant and I know they will work as they are intended to.
You get the occasional bad one, but it would be less than 1 in a 100. And they are all checked in circuit to ensure the preamp has identical performance in each channel.
This is very important for phase response and resultant sound-staging.
Ever wondered where the imaging and sound-staging went with that pair of warm sounding NOS 6SN7 you bought off ebay?
Most likely the tubes are operating quite differently from each other and there is a mis-match between channels.
NOS 6SN7, particulary the early ones from 1930 on are usually microphonic, sometimes quite badly .
Some of the 6SN7 derivatives like the CV181 and the ECC33 aren't really 6SN7s. They have different plate resistances and will give quite different electrical voltages in a circuit designed for 6SN7's.
This can result in different operating points and distortion figures , which might sound "warmer" or "romantic" .
Nothing wrong with that if it is pleasing to the ear, but it is not what the preamp was designed for.
So playing around with NOS 6SN7's can be a minefield, sometimes you'll get a blast you like, sometimes your shooting yourself in the foot.
I've been buying 6SN7's for more than 30 years and have hundreds of them, with examples of all of the above.
So what is my personal preference , what is the Holy Grail of 6SN7's?
Well maybe surprisingly I'm not that keen on old NOS tubes, mostly because most of them are not NEW OLD STOCK.
The only way you can be sure that a tube from the period 1930- 1980 is a genuine NOS tube is if it comes in a sealed box that has not been opened .
Anything you buy from ebay is suspect, even genuine tube sellers really have no way of knowing if a tube has ever been used or not, or how many hours, and under what sort of operating conditions a tube has been used.
They like to assert quality by using a tube tester and give some vague measurement that really doesn't mean anything.
Quite often the tube tester is more than 50 years old and long past its use by date.
The only way to tell if a NOS tube will give optimum service is to actually measure it in the circuit it is being used in.
Gain and channel balance can be checked and if its a highly sophisticated circuit like the Supratek, the operating parameters can be adjusted for perfect performance. On the proviso that the tubes were in excellent condition to start with.
New production tubes aren't that exciting, the current Sovtek and Chinese 6SN7's aren't bad, but they aren't quite as good as the tubes made when cost cutting wasn't more important than quality.
The tubes I use in my preamps are Russian military NOS tubes with OTK certification.
I buy them in boxes of hundred , never used and they have what I value the most, near identical parameters and performance. They are constant and I know they will work as they are intended to.
You get the occasional bad one, but it would be less than 1 in a 100. And they are all checked in circuit to ensure the preamp has identical performance in each channel.
This is very important for phase response and resultant sound-staging.
Ever wondered where the imaging and sound-staging went with that pair of warm sounding NOS 6SN7 you bought off ebay?
Most likely the tubes are operating quite differently from each other and there is a mis-match between channels.
NOS 6SN7, particulary the early ones from 1930 on are usually microphonic, sometimes quite badly .
Some of the 6SN7 derivatives like the CV181 and the ECC33 aren't really 6SN7s. They have different plate resistances and will give quite different electrical voltages in a circuit designed for 6SN7's.
This can result in different operating points and distortion figures , which might sound "warmer" or "romantic" .
Nothing wrong with that if it is pleasing to the ear, but it is not what the preamp was designed for.
So playing around with NOS 6SN7's can be a minefield, sometimes you'll get a blast you like, sometimes your shooting yourself in the foot.
Wednesday, December 6, 2017
Lyrics
Howard got it- Jane Siberry's "At the Beginning of Time"
An otherworldly , spiritual artist that really got to me a long time ago.
Not so much into her now, and I do wish her splendid works were better recorded, but I do still very much like this song.
Here's the complete song, I've never been much into classical poetry , but this is nice.
Tomorrow I'll talk about the NOS 6SN7 tubes I'm sending Howard.
An otherworldly , spiritual artist that really got to me a long time ago.
Not so much into her now, and I do wish her splendid works were better recorded, but I do still very much like this song.
Here's the complete song, I've never been much into classical poetry , but this is nice.
Tomorrow I'll talk about the NOS 6SN7 tubes I'm sending Howard.
At the beginning of time
Before there were waves
We'd sit in our boats
We'd float there all day
And there weren't any waves
'cause there wasn't any wind
'cause there wasn't any sun
We were waiting for the world to begin
We were waiting in the darkness
Each in our own boat
Each in our own thoughts
Sometimes you could hear people
Talking amongst themselves but...
(someone had a boat with wheels and I said
You're a bit early but I know how you feel)
But mostly it was just silence
And the silence only broken by
The absence of the clinking of the masts
And every now and then a bird would not fly by
And someone would look up and say
What wasn't that ?
We were waiting in the darkness
And one night (or was it day?)
I was awoken from a dream
I was dreaming of someplace like I'd never been
And I heard someone say
Someone's fallen in and they can't swim
So I leaned out and I pulled them in
And he was holding his head
And it was huge and shaped like a fish
And he slid down to the crook of the keel
And when I was sure he'd fallen asleep
I fell back to my reverie
We were waiting waiting waiting
Waiting in the darkness
And you know what I miss most about that time?
It was the quality of blackness
It was soft somehow
In the absence of fear
You could take it into your mouth
And send it out through your teeth
My dear
But the silence...
Oh, if I could go back to those times
I'd take that silence there
I'd take it into myself and bring it back to you
And this is what I'd say
Waiting in the darkness
At the beginning of time
Before there were waves
We'd sit in our boats
We'd float there all day
(or was it night?)
And there weren't any waves
'cause there wasn't any wind
'cause there wasn't any sun
We were waiting for the world to begin
We were waiting for the world to begin
Now?
No.
Before there were waves
We'd sit in our boats
We'd float there all day
And there weren't any waves
'cause there wasn't any wind
'cause there wasn't any sun
We were waiting for the world to begin
We were waiting in the darkness
Each in our own boat
Each in our own thoughts
Sometimes you could hear people
Talking amongst themselves but...
(someone had a boat with wheels and I said
You're a bit early but I know how you feel)
But mostly it was just silence
And the silence only broken by
The absence of the clinking of the masts
And every now and then a bird would not fly by
And someone would look up and say
What wasn't that ?
We were waiting in the darkness
And one night (or was it day?)
I was awoken from a dream
I was dreaming of someplace like I'd never been
And I heard someone say
Someone's fallen in and they can't swim
So I leaned out and I pulled them in
And he was holding his head
And it was huge and shaped like a fish
And he slid down to the crook of the keel
And when I was sure he'd fallen asleep
I fell back to my reverie
We were waiting waiting waiting
Waiting in the darkness
And you know what I miss most about that time?
It was the quality of blackness
It was soft somehow
In the absence of fear
You could take it into your mouth
And send it out through your teeth
My dear
But the silence...
Oh, if I could go back to those times
I'd take that silence there
I'd take it into myself and bring it back to you
And this is what I'd say
Waiting in the darkness
At the beginning of time
Before there were waves
We'd sit in our boats
We'd float there all day
(or was it night?)
And there weren't any waves
'cause there wasn't any wind
'cause there wasn't any sun
We were waiting for the world to begin
We were waiting for the world to begin
Now?
No.
Tuesday, December 5, 2017
And now for something completely different....
First person to name the song and Artist from these lyrics gets a pair of NOS 6SN7 tubes from my stash .
Email me at supra@supratek.com.au if you know the answer.
"And the silence was only broken by
The absence of the clinking of the masts
And every now and then a bird would not fly by
And someone would look up and say - what wasn't that?"
Email me at supra@supratek.com.au if you know the answer.
"And the silence was only broken by
The absence of the clinking of the masts
And every now and then a bird would not fly by
And someone would look up and say - what wasn't that?"
Sunday, December 3, 2017
Preamp Gain
All the Supratek preamps have high , greater then 20dB, gain.
There's a pretty simple reason for this, it simply sounds very much more dynamic and realistic than a low gain preamp.
The 6SN7 triode tube is a dual triode, it has two separate sections, independent of each other, except for the heater.
In the Supratek preamps the two sections are cascaded, the first section is the input, the second section is the output.
This results in more gain than a single section, although the total gain is reduced by a step down output transformer, and the circuit design.
I've never heard a single section with the dynamics and ease of a cadcaded design.
The high gain can be a nuisance with many of todays power amps, as they often have high gain themselves, a power amp should just convert gain into current , but too many power amps are designed more as integrated amps than dedicated power amps.
This is usually so they can be used directly with a CD player , and no preamp, just about the worst sound quality you can get.
So with a high gain power amp and a high gain power amp, there will be a lot of gain, with the volume control at 9 o'clock or less.
There may also be a problem with noise as with such high gain the noise floor will be amplified.
I still would rather put up with a bit of noise (which you wont hear when the music is playing anyway) than listen to the dull and boring sound of a low gain preamp.
Obviously the best way is with a high gain preamp and a power amp with reasonable gain structure, avoid those high gain power amps, which are just integrated amps anyway!
Recent models of the Cortese preamp have a gain control to fine tune the gain if necessary. It is switchable and can be completely switched out of circuit , but handy if you do need to use a high gain power amp.
There's a pretty simple reason for this, it simply sounds very much more dynamic and realistic than a low gain preamp.
The 6SN7 triode tube is a dual triode, it has two separate sections, independent of each other, except for the heater.
In the Supratek preamps the two sections are cascaded, the first section is the input, the second section is the output.
This results in more gain than a single section, although the total gain is reduced by a step down output transformer, and the circuit design.
I've never heard a single section with the dynamics and ease of a cadcaded design.
The high gain can be a nuisance with many of todays power amps, as they often have high gain themselves, a power amp should just convert gain into current , but too many power amps are designed more as integrated amps than dedicated power amps.
This is usually so they can be used directly with a CD player , and no preamp, just about the worst sound quality you can get.
So with a high gain power amp and a high gain power amp, there will be a lot of gain, with the volume control at 9 o'clock or less.
There may also be a problem with noise as with such high gain the noise floor will be amplified.
I still would rather put up with a bit of noise (which you wont hear when the music is playing anyway) than listen to the dull and boring sound of a low gain preamp.
Obviously the best way is with a high gain preamp and a power amp with reasonable gain structure, avoid those high gain power amps, which are just integrated amps anyway!
Recent models of the Cortese preamp have a gain control to fine tune the gain if necessary. It is switchable and can be completely switched out of circuit , but handy if you do need to use a high gain power amp.
Thursday, November 30, 2017
6SN7 NOS
An interesting article about the origins of the 6SN7 .
I dont agree with some of the comments , but some good info here, especially the historical content.
Double click to expand page.
Wednesday, November 29, 2017
FAQ -DHT PREAMP
What happened to the Directly Heated Triode preamps you were building ?
Yes I built DHT preamps for quite a long time , I built the first commercially available 300B preamp, and built quite a few different models, using different DHT tubes over the years. 45, PX4, 33, 101D, 4P1L and a bunch of obscure tubes.
I still very much like the lush, slightly warmer sound of DHT , and I still have a DHT preamp in one of my systems.
In the right system, or to cater to a certain subjective taste they can be very enjoyable, and I will still custom build them if required.
Its a bit of a shame that the best DHT preamp tubes are NOS from the 1930-50 period, I really like the 71A, 10/10Y/801A , but buying them now is a bit of a lottery as to what you will get.
And DHT tubes, because the filament is in the signal path, are usually very microphonic. Some are worse than others, the 300B isn't too bad , the 4P1L can be quite "ringy".
It doesn't particulary worry me, I even think a little microphonics can be a good thing, but it drives most audiophiles crazy, as they think that something is "wrong" with the tube.
All the time I was building DHT tubes , around 10+ years, I still had 6SN7 preamps, and continued to work on them .
The octal 6SN7 tube was designed for applications such as preamps, and is maybe the ultimate preamp tube.
Everyone uses 12AX7,12AU7, 12AT7 etc, but these tubes were designed for TV purposes and to my ears aren't a patch on the 6SN7 and its Russian equivalent the 6H8C.
The 6SN7, in the right circuit, which lowers the output impedance to an optimum level , without any side effect degradation , is just about perfect in every way.
Its accurate, has a big soundstage and sounds natural and full of ease. Clean solid bass and lots of air.
Most other tubes sound closed in, strained and brittle in comparism.
A couple of years ago I found a combination of componentry and circuit which gave the 6SN7 preamp a performance that I thought gave all the advantages of DHT without any disadvantages.
Its since been fine-tuned and is my number 1 product .
Tomorrow I'll talk about different 6SN7 tubes and the pitfalls and advantages of NOS.
Yes I built DHT preamps for quite a long time , I built the first commercially available 300B preamp, and built quite a few different models, using different DHT tubes over the years. 45, PX4, 33, 101D, 4P1L and a bunch of obscure tubes.
I still very much like the lush, slightly warmer sound of DHT , and I still have a DHT preamp in one of my systems.
In the right system, or to cater to a certain subjective taste they can be very enjoyable, and I will still custom build them if required.
Its a bit of a shame that the best DHT preamp tubes are NOS from the 1930-50 period, I really like the 71A, 10/10Y/801A , but buying them now is a bit of a lottery as to what you will get.
And DHT tubes, because the filament is in the signal path, are usually very microphonic. Some are worse than others, the 300B isn't too bad , the 4P1L can be quite "ringy".
It doesn't particulary worry me, I even think a little microphonics can be a good thing, but it drives most audiophiles crazy, as they think that something is "wrong" with the tube.
All the time I was building DHT tubes , around 10+ years, I still had 6SN7 preamps, and continued to work on them .
The octal 6SN7 tube was designed for applications such as preamps, and is maybe the ultimate preamp tube.
Everyone uses 12AX7,12AU7, 12AT7 etc, but these tubes were designed for TV purposes and to my ears aren't a patch on the 6SN7 and its Russian equivalent the 6H8C.
The 6SN7, in the right circuit, which lowers the output impedance to an optimum level , without any side effect degradation , is just about perfect in every way.
Its accurate, has a big soundstage and sounds natural and full of ease. Clean solid bass and lots of air.
Most other tubes sound closed in, strained and brittle in comparism.
A couple of years ago I found a combination of componentry and circuit which gave the 6SN7 preamp a performance that I thought gave all the advantages of DHT without any disadvantages.
Its since been fine-tuned and is my number 1 product .
Tomorrow I'll talk about different 6SN7 tubes and the pitfalls and advantages of NOS.
Tuesday, November 28, 2017
That's not a tube, THIS is a tube!
Apologies to Crocodile Dundee.
211 on the left V1505/212E on the right.
I built quite a lot of SE amps 20 years ago, the V1505 is the most impressive tube , sounds pretty good too, like a giant 300B.
211 on the left V1505/212E on the right.
I built quite a lot of SE amps 20 years ago, the V1505 is the most impressive tube , sounds pretty good too, like a giant 300B.
Monday, November 27, 2017
Sunday, November 26, 2017
6SN7 Preamp specs
Someone asked for specs of 6SN7 preamp, specs don't really tell you how a preamp will sound, but here they are, in approx order of importance:
Output Impedance 1300 ohms.
Gain 0-26 dB adjustable.
Tube Compliment 6SN7 linestage 5881 5AR4 power supply
6688 6H23 phono preamp.
Power supply 300VA transformer, CLCRC shunt regulated
Copper chassis chrome plated
Remote volume
Lundahl, Magnequest amphorous input and output transformers
Output Impedance 1300 ohms.
Gain 0-26 dB adjustable.
Tube Compliment 6SN7 linestage 5881 5AR4 power supply
6688 6H23 phono preamp.
Power supply 300VA transformer, CLCRC shunt regulated
Copper chassis chrome plated
Remote volume
Lundahl, Magnequest amphorous input and output transformers
What Makes a good Tube Preamp- Pt3 Power Supply
A tube power amp can get away with a good solid power supply (PS) that consists of a big transformer , rectifier and a simple capacitor /inductor/capacitor bank.
If its big enough and of sufficient quality thats all that's really needed.
A preamp though is a different story- its a gain device and if the PS isn't clean, fast and powerful the good (the signal) will get amplified along with the bad (noise and distortion) .
A really good PS for a preamp will have 0.0mV of noise at the voltage output of the PS feeding into the loads of the triode tubes used for gain.
So for example, a Supratek will have 300V DC at the loads and will measure 0.0mV AC with no signal.
There's not many preamps that can achieve this and it takes an evolved and sophisticated design to do this competently and reliably.
Personally , I dont really take a PS for a preamp seriously unless it is regulated.
This means the voltage will always remain constant no matter what the mains voltage is or regardless of the demands of the circuit to produce distortionless amplification.
There's simple and more sophisticated ways of doing regulation, a good solid state regulator can be made with a handful of transistors and components, but being a died in the wool tube guy, I prefer a tube based regulator.
These come in either series or shunt versions, series is simpler.
Tube shunt regulators bleed off a portion of current to earth to maintain a constant current through the preamp circuitry, and from a sonic perspective are superior to series regs.
I've been using shunt regulators in my preamps forever, and they are a big determinant in the sonic signature of the Supratek preamps.
They provide a "blackness" around the amplified signal, with zero noise and distortion.
There's no strain with complex or dynamics passages as the voltage to the circuit is always constant and uninterrupted.
In contrast, an unregulated PS will "sag" with the demands of voltage peaks.
Component choices are also a big factor in performance. Once again, you will hear me say how detrimental electrolytic capacitors are to audio quality, and how so many audio devices these days are filled with them. Its not uncommon for a modern preamplifier to have 50 or more electros in them, with a maximum lifetime of 10,000 hours.
There are 2 electro caps in a Supratek linestage, one for the tube heaters, and one for the remote volume.
Polyprop caps are much better, or even better again, minimal or no cap designs simplify design, performance and reliability.
There is no substitute for transformer size, you can definitely have too small a transformer, but its hard to go too big!
The Supratek preamps have a seperate power supply chassis simply because the PS is too big to fit in one chassis, and there are advantages in getting the transformer and inductors away from the circuitry.
I also use 1.2mm copper chassis for both preamp and PS, its expensive but if you live with a copper chassis for a while you will hear that a steel chassis does have a "sound" that is less neutral than copper. It's almost intangible , but it's there.
There's a good reason the hyper expensive Japanese AudioNote gear is copper chassis based.
Power supply on the left. The middle tube is rectifier, the outside tubes are the shunt regulator tubes.
Saturday, November 25, 2017
60 Year old tube amp that kicks arse.
Ok lets get away from the technical stuff for a day and do some reminicising.
A very long time ago I found a pair of Altec-Lansing 604B coxial speakers in a big cabinets on the side of the road.
Turns out they were from the Australian Broadcasting Commission radio station, and in the back of each cabinet was an industrial looking tube amp.
This was back in the day when tube amps were being phased out, solid state was becoming dominant and tubes hadn't had the renaissance they enjoyed a decade later.
But you could still buy replacement tubes in the local electrical shop and I'd heard old guys tales that these old fashioned tube amps actually sounded pretty good.
A new 5Y4G rectifier got it going again , and goddam the 604B and amps sure sounded different to the English amps and speakers we were listening to back then.
The tube amp was an Australian made Trimax A52 , a push pull EL34 design with a 6AU6 input tube and 12AT7 driver.
These were built on commission to the ABC , Trimax was mostly a transformer winding company , who had a very clever and enterprising design dept.
They produced quite a varied range of professional gear for the ABC, including some interesting preamps and mixers.
The A52 was loosely based on the Mullard 5-20 EL34 amp. It put about nearly 30 watts with only a minimal amount of feedback, achievable because of the very high quality of the output transformers.
Its a very elegant design, straight out of the Golden Era of tube design. A fantastic output transformer, that would take the very best winders to match today.
Only one electrolytic capacitor in the entire amp, and that was probably installed later in its life.
Todays electronic components have hundreds of electrolytic capacitors , mostly used because they are very economical- the paper in oil caps used back in the 50's and 60's were much costlier, and can be as good as new 60 years later!
The pair of EL34 tubes put out a solid 30 watts, but its not stressed or working hard to achieve this, so it will keep working reliably year after year.
I dont have the original pair I found 40 years ago, but i do have another 2 sets of amps I bought about 5 years ago.
I have a lot of respect for these amplifiers, they are of a good solid, timeless design, have incredible reliability that comes from over engineering of components, and sound excellent.
There are very few audio devices that can maintain this sort of integrity and quality over a 60 year period.
It may be as ugly as sin, but underneath that exterior is a real beauty.
The Trimax A52 inspires me in my own preamp building, my preamps are very over engineered, with massive power supplies, and a reluctance to use those damn electrolytic capacitors with their limited life.
Suprateks built 25 years ago are still working reliably and I'm even more focused on the latest models being super reliable and long lifed.
This is what makes a classic in the vein of the old tube Marantz , Luxman products. They are simply built to last, something that is sadly not a priority these days.
I was using my Trimax's in an active/passive configuration with my Supraxox field coil speakers, but the Supravox are going back to France for a re-cone and i now have the Trimax's on my AR-LST speakers.
These are another high quality, over engineered product from long ago, a fantastic speaker that was very revolutionary when introduced. It has 9 drivers per speaker, a 10 " bass driver, 4 mid range and 4 tweeters per speaker, kind of like a big Bose .
Despite receiving much praise, the LST's never really took off as they came out at the end of the tube era and they needed high power solid state to work well.
They were just ahead of their time, the high power Crown solid state amps they were partnered with were quite horrible sounding amps.
Ive split the crossovers on mine so the three bass, midrange and tweeter sections can be each driven by a separate amplifier, with the Trimaxs driving the mid range and tweeters.
This relieves the need for a really high power amp and the 30 watt Trimaxs are adequate for mid and treble, with a high power SS amp on bass.
I've installed level controls on each amp, so tone can be adjusted to suit. Of course a powerful preamp that can drive 3 sets of amps is also required.
LST stands for laboratory standard transducer and that is pretty much what they are, monitor standard with the ability to colour the tone if required.
There's a real satisfaction using products you know are well designed , engineered and constructed to perform at the highest level, and last a lifetime .
The Trimax was probably the highlight of the Australian audio manufacturing of its era, and I feel privelged to own them.
A very long time ago I found a pair of Altec-Lansing 604B coxial speakers in a big cabinets on the side of the road.
Turns out they were from the Australian Broadcasting Commission radio station, and in the back of each cabinet was an industrial looking tube amp.
This was back in the day when tube amps were being phased out, solid state was becoming dominant and tubes hadn't had the renaissance they enjoyed a decade later.
But you could still buy replacement tubes in the local electrical shop and I'd heard old guys tales that these old fashioned tube amps actually sounded pretty good.
A new 5Y4G rectifier got it going again , and goddam the 604B and amps sure sounded different to the English amps and speakers we were listening to back then.
The tube amp was an Australian made Trimax A52 , a push pull EL34 design with a 6AU6 input tube and 12AT7 driver.
These were built on commission to the ABC , Trimax was mostly a transformer winding company , who had a very clever and enterprising design dept.
They produced quite a varied range of professional gear for the ABC, including some interesting preamps and mixers.
The A52 was loosely based on the Mullard 5-20 EL34 amp. It put about nearly 30 watts with only a minimal amount of feedback, achievable because of the very high quality of the output transformers.
Its a very elegant design, straight out of the Golden Era of tube design. A fantastic output transformer, that would take the very best winders to match today.
Only one electrolytic capacitor in the entire amp, and that was probably installed later in its life.
Todays electronic components have hundreds of electrolytic capacitors , mostly used because they are very economical- the paper in oil caps used back in the 50's and 60's were much costlier, and can be as good as new 60 years later!
The pair of EL34 tubes put out a solid 30 watts, but its not stressed or working hard to achieve this, so it will keep working reliably year after year.
I dont have the original pair I found 40 years ago, but i do have another 2 sets of amps I bought about 5 years ago.
I have a lot of respect for these amplifiers, they are of a good solid, timeless design, have incredible reliability that comes from over engineering of components, and sound excellent.
There are very few audio devices that can maintain this sort of integrity and quality over a 60 year period.
It may be as ugly as sin, but underneath that exterior is a real beauty.
The Trimax A52 inspires me in my own preamp building, my preamps are very over engineered, with massive power supplies, and a reluctance to use those damn electrolytic capacitors with their limited life.
Suprateks built 25 years ago are still working reliably and I'm even more focused on the latest models being super reliable and long lifed.
This is what makes a classic in the vein of the old tube Marantz , Luxman products. They are simply built to last, something that is sadly not a priority these days.
I was using my Trimax's in an active/passive configuration with my Supraxox field coil speakers, but the Supravox are going back to France for a re-cone and i now have the Trimax's on my AR-LST speakers.
These are another high quality, over engineered product from long ago, a fantastic speaker that was very revolutionary when introduced. It has 9 drivers per speaker, a 10 " bass driver, 4 mid range and 4 tweeters per speaker, kind of like a big Bose .
Despite receiving much praise, the LST's never really took off as they came out at the end of the tube era and they needed high power solid state to work well.
They were just ahead of their time, the high power Crown solid state amps they were partnered with were quite horrible sounding amps.
Ive split the crossovers on mine so the three bass, midrange and tweeter sections can be each driven by a separate amplifier, with the Trimaxs driving the mid range and tweeters.
This relieves the need for a really high power amp and the 30 watt Trimaxs are adequate for mid and treble, with a high power SS amp on bass.
I've installed level controls on each amp, so tone can be adjusted to suit. Of course a powerful preamp that can drive 3 sets of amps is also required.
LST stands for laboratory standard transducer and that is pretty much what they are, monitor standard with the ability to colour the tone if required.
There's a real satisfaction using products you know are well designed , engineered and constructed to perform at the highest level, and last a lifetime .
The Trimax was probably the highlight of the Australian audio manufacturing of its era, and I feel privelged to own them.
Friday, November 24, 2017
What makes a good tube preamp- Pt2 The Circuit
In todays marketing focused world there's a lot of hype - especially about hyper quality components- exotic capacitors , resistors etc .
But the determinant factor in quality sound reproduction is simply the requirement for a high quality electronic design (or circuit)
Super duper capacitors and resistors wont turn a pig of a circuit into something that sounds wonderful.
A really competent design with bog standard , nothing-fancy parts will rock the socks off a poor design that someone has stuffed with $1000 of hyper parts.
The trick is to use the most advanced, up to date and state of the art design and then carefully choose the componentry to achieve the desired sound signature.
Its a matter of synergy and the experience of knowing what works best in situation.
I've never been a big fan of electrolytic capacitors, but most audio devices have hundreds of them in them.
Eliminating them is difficult and expensive, but the result is very worthwhile, as it results in a superior phase performance, which means more 3D imaging and more expansive sound-staging.
My Supratek preamps have typically no more than 3 or 4 electro caps , and used only where absolutely necessary.
The painfully common direct coupled/cathode follower design is the stalwart of preamplifier design and is employed in the vast majority of low cost preamps on the market.
Cheap to make with 12AU7 or 12AT7 tubes , and with reasonable performance , there must be many thousands of these preamps built over the years.
Its a great way for designers who wish to produce a tube preamp without too much thought or development- its a proven design with just enough "tube" sound to classify as a tube preamp.
These designs are really hangovers from the 1950's , state of the art tube design has well and truly moved on from there , but surprisingly few modern designers deviate much from the tried and true.
More innovative and developed designs use a hybrid mix of tube and solid state components, and even iron chokes and transformers in the mix, with sophisticated power supplies to give highly accurate frequency response , the ability to drive any amplifier and superior phase performance to give realistic imaging and sound-staging.
Tommorow- power supplies.
But the determinant factor in quality sound reproduction is simply the requirement for a high quality electronic design (or circuit)
Super duper capacitors and resistors wont turn a pig of a circuit into something that sounds wonderful.
A really competent design with bog standard , nothing-fancy parts will rock the socks off a poor design that someone has stuffed with $1000 of hyper parts.
The trick is to use the most advanced, up to date and state of the art design and then carefully choose the componentry to achieve the desired sound signature.
Its a matter of synergy and the experience of knowing what works best in situation.
I've never been a big fan of electrolytic capacitors, but most audio devices have hundreds of them in them.
Eliminating them is difficult and expensive, but the result is very worthwhile, as it results in a superior phase performance, which means more 3D imaging and more expansive sound-staging.
My Supratek preamps have typically no more than 3 or 4 electro caps , and used only where absolutely necessary.
The painfully common direct coupled/cathode follower design is the stalwart of preamplifier design and is employed in the vast majority of low cost preamps on the market.
Cheap to make with 12AU7 or 12AT7 tubes , and with reasonable performance , there must be many thousands of these preamps built over the years.
Its a great way for designers who wish to produce a tube preamp without too much thought or development- its a proven design with just enough "tube" sound to classify as a tube preamp.
These designs are really hangovers from the 1950's , state of the art tube design has well and truly moved on from there , but surprisingly few modern designers deviate much from the tried and true.
More innovative and developed designs use a hybrid mix of tube and solid state components, and even iron chokes and transformers in the mix, with sophisticated power supplies to give highly accurate frequency response , the ability to drive any amplifier and superior phase performance to give realistic imaging and sound-staging.
Tommorow- power supplies.
Thursday, November 23, 2017
What makes a good tube preamp? PT1 - Output Z
What makes a good tube preamp?
There's quite a few tube preamps available from the cheapest Chinese import to the exotic and expensive, so what makes a tube preamp good?
The most important feature is low output impedance ie the ability to drive loads. A power amplifiers load (input impedance) will vary from typically 5000 ohms (solid state) to 100,000 ohms(tube) and its generally recognised that a ratio of 1:10 is suitable, ie the preamp will have an output impedance 1/10 of the input impedance.
So if a tube preamp is going to sucessfully drive a solid state power amp with an input impedance of 5000 ohms it should have an output impedance of around 500 ohms.
This is just about worst case- 5000 ohms input is quite low, but not uncommon.
What happens if a preamp's output impedance (Z) is too high?
The preamp will not be able to transfer its frequency response in a linear fashion, it will be inaccurate and "sloppy' sounding.
This can happen when an unsuitable high resistance tube is used in a circuit that does not do any "shifting" from high to low output Z.
Tubes like the 12AX7, 6SL7 are often used in simple, minimal preamps but their high resistances require circuits such as the cathode follower to be used , which lower the output Z.
Unfortunately there's a price to pay , as 100% feedback is employed in this circuit, which does introduce a bit of haziness and veiling.
Without the cathode feedback, the high resistance tubes sound slow, warm and so "romantic" they will put you to sleep pronto.
Another way to lower Z is to use a "transformer" a step down device which can drop the ratio by a chosen amount, for example a 4P1L triode tube has a resistance of 1000 ohms, if we use a 4:1 ratio step-down we will end up with a Z of 250 ohms, which is low for a tube preamp, and lower than you will ever need!
Transformers vary tremendously in quality , and they must be carefully matched to each tube and application. Transformers don't work well with high resistance tubes and even with well matched tubes, its quite an art to build a really competent and high performance transformer.
I use the 6SN7 tube in my preamps , with a special circuit and Lundahl or Magnequest output transformers the preamps have an output Z of 1300 ohms , nice and low .
So output Z is important for a preamp in order to control a power amp with accurate frequency response and drive.
Tomorrow I'll talk about something else that's important.
There's quite a few tube preamps available from the cheapest Chinese import to the exotic and expensive, so what makes a tube preamp good?
The most important feature is low output impedance ie the ability to drive loads. A power amplifiers load (input impedance) will vary from typically 5000 ohms (solid state) to 100,000 ohms(tube) and its generally recognised that a ratio of 1:10 is suitable, ie the preamp will have an output impedance 1/10 of the input impedance.
So if a tube preamp is going to sucessfully drive a solid state power amp with an input impedance of 5000 ohms it should have an output impedance of around 500 ohms.
This is just about worst case- 5000 ohms input is quite low, but not uncommon.
What happens if a preamp's output impedance (Z) is too high?
The preamp will not be able to transfer its frequency response in a linear fashion, it will be inaccurate and "sloppy' sounding.
This can happen when an unsuitable high resistance tube is used in a circuit that does not do any "shifting" from high to low output Z.
Tubes like the 12AX7, 6SL7 are often used in simple, minimal preamps but their high resistances require circuits such as the cathode follower to be used , which lower the output Z.
Unfortunately there's a price to pay , as 100% feedback is employed in this circuit, which does introduce a bit of haziness and veiling.
Without the cathode feedback, the high resistance tubes sound slow, warm and so "romantic" they will put you to sleep pronto.
Another way to lower Z is to use a "transformer" a step down device which can drop the ratio by a chosen amount, for example a 4P1L triode tube has a resistance of 1000 ohms, if we use a 4:1 ratio step-down we will end up with a Z of 250 ohms, which is low for a tube preamp, and lower than you will ever need!
Transformers vary tremendously in quality , and they must be carefully matched to each tube and application. Transformers don't work well with high resistance tubes and even with well matched tubes, its quite an art to build a really competent and high performance transformer.
I use the 6SN7 tube in my preamps , with a special circuit and Lundahl or Magnequest output transformers the preamps have an output Z of 1300 ohms , nice and low .
So output Z is important for a preamp in order to control a power amp with accurate frequency response and drive.
Tomorrow I'll talk about something else that's important.
Thursday, September 21, 2017
Sophisticated and Elegant Tube Preamplifier .
Custom Cortese
I've been building preamps for nearly 40 years and to hear an old recording, that I thought I knew every last detail and nuance of, to sound like I'd never heard it before, with a freshness and amazing retrieval of detail and vividness , makes it almost impossible to believe I'm hearing the same recording!
I thought I knew the old Beatles records very well, but I had no idea that so much musical info was there that I'd never heard that way before- a presentation that is like listening to a completely different recording.
What this preamp does so well is the 3D thing, it lets you hear way into the music, the depth and width of the soundstage seems to be much magnified , it sounds less like a recording and simply more lifelike, digital is less digital, and vinyl is more vinyl!
Supratek preamps have always had a reputation for that, but now there is a new standard.
To get such a big step up in sonic gains with a new design is unusual- preamplifier design usually results in little steps over a long timeframe to achieve a remarkable design, which in essence is what I've done when one considers that I've been playing around with the 6SN7 tube for so many years.
What happened over the last couple of years was a very rewarding coming together of a lot of synergy, lots of knowledge and experience that resulted in a mix of design elements being put together , that went KABOOM and resulted in something special.
Not that there was , or is , anything deficient with any of the previous Supratek designs, they are all very highly thought of world class preamps.
And I think there may be some who still prefer the warmer, delicious sound of a Supratek DHT preamp, with its slight emphasis of tone and perhaps a touch of veiling.
But I'm finding the new 6SN7 preamp to be perfect in just about every way, its a magical looking-glass into the heart of the music , its exciting, AND soothing and so damn musical , yet is also so very accurate and transparent- theres no tube shortfall or compromises, its an exciting state of the art design that I'm going to find a real challenge to improve.
I'd like to go into some detail of the design and component elements of this preamp- I don't usually get too technical , but I would like to shed some light on the numerous elements that go together to make this such an extraordinary and incredible value preamplifier.
Everything starts with the power transformer and a big 165VA transformer that is the size normally used in a power amplifier provides plenty of electrical energy comfortably and reliably.
A tube rectifier provides DC voltage into a CLCR filter , designed specifically for use with the tube rectifier (I've lost count of the number of tube preamps I see with inappropriate filter design. Tube rectifiers cannot use the same values as a solid state design, but the wrong component values that suit solid state are all too common)
Electrolytic capacitors are not used in the High Tension voltage supply, electros have limited life, and a thinner , less satisfying sound. They are used extensively in commercial products because they are cheap, and polyprop/oil caps are too bulky to fit in a one chassis design.
The DC voltage is then fed into a tube shunt regulator- one for each channel. I've been using tube shunts for over 20 years and they are part of the reason for the Supratek sound- they keep the voltage of the preamp tubes constant no matter what the current draw is , and help with the definition and "blackness" around all dimensions of the music.
The power supply also contains a solid state rectifier for the tubes heaters- very over-engineered and mounted on a large heatsink for reliabilty.
This is attached internally to the chassis of the power supply, made of 1.2mm copper plate which is an excellent heat transfer .
copper chasis before polishing and plating
Copper plate is also used for the preamp chassis, it has a different sound than the steel chassis's used in virtually all other preamps, its not a sound instantly recognisable, but is a softer , less harsh sound over long term listening.
On to the preamp circuitry.
The first tube preamp I built 40 years ago was a phono stage that used 12AX7 and 12AU7 tubes, which are still very common these days and the first choice today for commercial tube manufacturers - they are readily available and cheap.
They were also designed to be used in televisions.
The 6SL7 and 6SN7 tubes were the lower distortion predecesors of the 12**7 tubes and came from audio applications, but back in the 1970's they were largely unused , and for a decade or so until they came back into vogue , one could buy really nice NOS 6SN7's for peanuts.
The first 6SN7 preamp I built I fell in love with the sound - lush , inviting and so much better than the newer , modern tubes which sound strained and distorted in comparism.
Simple circuits - plate resistor loading , capacitor outputs , highish output impedance that demanded an easy load, preferably a tube amp.
Over the next 40 years I tried just about every possible combination of tube/circuitry/components till I have finally arrived at todays 6SN7 circuit.
Both triode sections of the 6SN7 (It's a double triode with two seperate triode gain sections with a common heater) are cascaded, ie the line inputs are connected to the first section , which is then connected to the second gain stage section, which becomes the output stage. It's not quite as simple as that as there are some design tricks I'm not going to divulge , but that's a basic description.
This results in a high gain circuit, which to my ears always sounds more dynamic and flowing than a low gain circuit, and there are ways to make the gain useable and useful.
6SN7 double triode
Both sections are plate loaded with solid state constant current sources, (CCS) which have been refined over many years to be as transperent and musically coherent as passive devices without the limitations.
The cathodes of both sections also use constant current sources, but in this case its to avoid the use of capacitor/resistor bias devices.
CR filters must introduce phase anomalies , and this affects the imaging and sound-staging of the preamp. By eliminating the CR filters common to almost all other preamps , the Supratek preamp gains a tremendous advantage in realism that preamps with CR filters always degrade.
The CCS's used in the cathodes are discrete solid state devices, mounted on a small PCB with the plate CCS devices.
Traditionalists could argue that passive loading use transformers or steel/nickel/wire chokes sound more "tube like" . I did use metal/wire chokes and transformers for these purposes for quite a few years, but I was always aware of the severe limitations the resonances and frequency anomalies of the devices brings to the sound when using them for plate or cathode loading.
I like a preamp to sound beguiling and interesting, but there's no reason it cant be accurate and technically proficient as well.
However, there is a place for transformers and chokes in a well designed preamp , as long as they are very well made and used accordingly.
I use Lundahl and Magnequest input and output transformers and grid chokes - these are expensive , high quality products that are the result of many years experience with transformer winding techniques.
The use of transformers for the output stage has two distinct advantages. Its a step down transformer which transforms the high gain of the circuit into a lower gain , and also lowers the output impedance
of the circuit. This 6SN7 circuit has an output impedance of around 1500 ohms, which will drive any solid state or tube amp.
It also has a centre tapped winding which allows the use of balanced or unbalanced output switching.
This is by far the best way to achieve a balanced output. We can use a Single Ended Class A circuit throughout the preamp and then get a perfectly symmetrical fully balanced or unbalanced output signal.
(I'm sorry but if you think an all balanced preamp, with double the components working in push pull sounds better, then you need to get new speakers. 😊 (but not as critical with balanced power amps which have their uses)
People like to talk about the use of super expensive and exotic capacitors. I do use very high quality caps in my preamps, but the overall determination to the sound is the correct value of a high quality cap, rather than some exotic all-talk device designed to make money.
Using high quality film capacitors rather than electrolytic caps has far more effect than replacing a capable film cap for an exotic one.
My line stages have no electrolytic caps , and the phono stages have only a couple of Elna Silmics electro caps in them.
The result of this circuit design, high quality components and dedicated handmade craftsmanship is a preamp that is sophisticated and elegant.
It is technologically state of the art design , but is also an instrument of music - its purpose is to convey the music in as pure a form as it can.
It will startle you and calm you, it will enchant and beguile you.
It is the result of my dedication to the art of the tube preamplifier over a very long period and a lot of hard work, combined with a lot of joy taken from the amazing and heart lifting world of music.
Custom Cortese. Power supply on left with tube shunt regulators and tube rectifier.
Saturday, June 24, 2017
New Design and Preamp.
New Supratek design and preamp!!!
There hasn't been a" new" Supratek preamp for quite some time.
The DHT models have been the mainstay of the product range for a long time, starting with the 101D, 300B/45/PX4, and lately the 4P1L versions.
I also did some custom preamps with the rare 71A and 801A tubes
.
A long time ago (30 years!) Supratek preamps were based around the the 6SN7 tube, a triode which could arguably be called the perfect preamplifier tube
.
Despite gravitating towards the DHT tube's I continued to have had a very soft spot for this tube, and have always had a 6SN7 preamp in my arsenal , and continued through the years to build 6SN7 preamps, alongside the DHT preamps, for those who wanted them.
There is nothing really new in preamp design, we have better components to use, we can mix tube technology with solid state design, but in essence all the claims for "new" designs are just variations on a theme.
Breakthroughs in sound quality now come from finding the right combinations of all the available design and component choices. Its a little like alchemy , find the right synergy of all the combinations and you might make gold!
I couldn't say how many 6SN7 circuits I have built over the years. In conjunction with my friend Kevin Covi's design and simulation skill , and my own design and building experience, I'd say it would possibly be over a hundred circuits.
It's hard to build a bad 6SN7 circuit, it's a very good tube with a lovely sound .In its most basic preamp configuration, it has high-ish output impedance , which restricts drive ability, and can give a tone which some call "tube or valve" sound.
The Supratek preamps have always used designs which give low output impedance , and with the in-built power supply regulators, can drive most power amplifiers, even multiples of amps in active systems.
Supratek preamps are always designed to be very accurate, fast and clean. Even the DHT preamps , while having the DHT sense of musicality were always accurate.
Many tube preamps these days are designed with conventional, 1950's style circuits that are are more tone control than accurate preamp.
This last year I've put together a 6SN7 preamp that achieves every goal I've wanted - its very accurate, has lots of drive , is amazingly transperant and as resolving as anyone could wish for.
It truly is a window into the music , so many times I've sat down to listen for a little while, and a complete album later gratified to hear and enjoy it as if for the first time.
It has the musical tone of a DHT preamp, with the resolution and accuarcy of the very best , and very expensive, solid state preamplifier.
I built this pre using all of my experience and knowledge of 6SN7 tubes, design technique and component choice.
It uses very high tech solid state anode loading, Magnequset and Lundahl transformers and chokes.
With the Supratek immense power supply , copper chassis, tube regulators and all the tricks o f 30 years of preamplifier construction, I have built a preamplifier that is simply the best I have heard.
Somehow it seems to make the very best DHT preamp sound a little veiled and un-exciting.
Now sound quality is very subjective and some will still prefer the sound of a well designed DHT preamp, but the compromises of DHT- microphonics, noise levels do not exist in this new 6SN7 design.
I have half a dozen preamps, both 6SN7 based and DHT , and whilst I enjoy all of them, I find it very hard to listen the DHT preamps now.
No mistake, the DHT preamps are excellent preamps of the highest sound quality. The new 6SN7 design is simply better.
I addition to 6SN7 tubes, this pre can use Russian 6H8C , CV181, and with a convertor base the 6F8G/VT99 tubes.
As of the 1st July 2017 Supratek will be returning to full time production of preamps, and I expect to be building mostly the 6SN7 preamp.
The preamp pictured is a Dual Cabernet . It has the new 6SN7 circuit ( in this case CV181 tubes at back) and a 6H8C/6H30 circuit, both independent but working off a master volume. Useful for bi-amplifying, or active application.
Also available as Single Cabernet- just the 6SN7 circuit.
Also the Cortese- 6SN7 circuit with tube phono stage.
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