300B Dual Cabernet

Just finished this 300B Dual Cabernet, and very happy with this one. I haven't built a 300B preamp for quite a while, and incorporating some new design ideas and the features of the "dual" preamp with the iconic 300B tube turned out very nice indeed.

I don't think many people "get" the concept of the DUAL CABERNET so I've copied some of the text from user manual that explains further. Its from the 4P1L manual but also applies to 300B or any DHT tube used.

"The Dual Cabernet has two separate line stages, one utilising a Directly Heated Triode tube – the 4P1L , and the other line stage utilises a two stage tube design , using one half of the dual triode 6H8C/6SN7 and a 6N6/6H30. These two tubes are Indirectly Heated Triodes, which means they have a separate heater , rather than the directly heated filament of the DHT tubes.

Both stages can be used independently , or together. The gain of the 4P1L has two settings, and the gain of the 6N6 circuit can be set with it’s own adjustable level control.

Overall gain is set by the master volume control on front panel.

Both circuits, the DHT and the IDHT are state of the art designs, with high bandwidth, very accurate frequency response, and excellent drive ability.

The 4P1L has all the attributes of DHT tubes, a sense of “tube euphonics” , some microphonics (not a bad thing) and a pleasing, elegant musicality.

This stage also has the option of switching in the other half of the 6H8C/6SN7 triode, which will give higher gain, useful for using with low sensitivity amplifiers, or very low efficiency speakers.  You may find a greater sense of dynamics when this driver stage is switched in, depending on your system and requirements.

The Dual Cabernet’s 4P1L line-stage has a switchable output to choose either transformer or direct output. The transformer output, with switch towards rear has lower gain and because of it’s lower output impedance more drive, handy when driving multiple amplifiers , or a difficult load.

The 6H8C/6N6 circuit is simply one of the most technically advanced tube circuits available. It has very high bandwidth, extremely low distortion, very low output impedance, which enables it to drive any amplifier. It is a “state of the art” design using some of the best audio tubes ever produced.

With both of these circuits you have the very best of both the DHT and IDHT worlds, with this preamplifier you are sure to be able to find a combination that finds the perfect synergy for your system and tastes.

One way to use this dual preamp is with bi-ampable speakers, with separate connetions for bass and mid/treble.

The 4P1L linestage would be connected to the amplifier driving mid/treble and the 6N6 linestage connected to amplifier driving bass. Or the opposite, depending on your requirements, taste etc.

The 6N6 level control can then be set to give the best balance of bass and mid/treble to get exactly the tone preferred for your room and system."

The 6SN7/6H30 IDHT line-stage  alone would cost far more than the total cost of a DUAL CABERNET if purchased from a mass produced high-end audio company, but with the DUAL you get a world class DHT line-stage as well, and a preamp that is custom hand made , tested , tuned and run for at least 3 days before sent to owner.

There's nothing else like it in uniqueness and sound quality in this world.

6SN7/6H8C/6F8G

I've been using the double triode 6SN7 tube for as long as I can remember, I have a collection of about 500 NOS 6SN7's , about the same of the single triode version the 6J5.
The older NOS tubes sound damn nice , but they are frequently microphonic, and although I don't think that is necessarily a bad thing, with a high gain preamp that can be a problem.

NOS 6SN7's 

For at least 10 years I've been using the Russian 6H8C version of the 6SN7, it is a well manufactured, sturdy version that sounds very good, and is not too microphonic.

Russian 6H8C

Another earlier version of the 6SN7, made around the 1930's is the 6F8G. This has a top cap for one of the grids, which is a bit inconvenient as a hole has to be made in the chassis for the top cap connection.  Although it uses the same octal socket as 6SN7, the pin connections are quite different.
But its a fine sounding tube, and I built a few preamps and power amps that used it.
I built one power amp with 6F8G and 807 , both using top caps which gives an "antique" look.
Recently there have been some convertors available on Ebay which allows one to use the 6F8G in place of 6SN7 without any re-wiring of circuit.
One of my Russian customers asked if it was worthwhile, so I bought a pair to give it a try.
They look kind of stupid, but there is something about the 1930's period tube sound  that is very nice, it's different rather than better, but it is a enjoyable alternative , and the 6F8G tubes are relatively inexpensive, or they were when I last bought some many years ago.
A fun experiment for those of you with 6SN7/6H8C preamps.

801A/10/10Y DHT Preamp

One of the oldest DHT tubes is the 10 , with near identical substitutes the 10Y and 801A.
Although not rare, it is sometimes difficult to get good NOS matched pairs.

It's perhaps one of the finest DHT tubes to use in a preamp, it has a lovely tone and very balanced sound.

I've built a few 10 preamps for myself over the years, but never sold one as I was worried about tube replacement.

I've just finished building this "copper finish" preamp (all the Supratek preamps have copper chassis which is usually chrome-plated or powder-coated).

It was built to be used at an upcoming hi-fi show, but I've decided to use a production preamp with more available tube (4P1L or 300B) instead.

The 801A is conservatively run and they last 10's of thousands of hours, I'm still using the same tubes in the first 801A preamp I built around 10 years ago.

This is a DUAL CABERNET preamp with two line stages. The 6SN7/801A is the DHT output and it also has a 6SN7/6H30 line stage with volume control to be used in active systems, for example driving the bass amplifier , while the DHT section drives the mid/treble amplifier.
Or either stage can be used on their own. The 6SN7 driver stage can also be switched out when a low gain preamp is required.

The 6SN7/6H30 stage is a wide bandwidth , state of the art
design with outstanding technical specifications, which also sounds excellent.

The 6SN7/801A linestage has all of the Supratek DHT qualities , reinforced by the use of  perhaps the best DHT preamp tube ever made.

The finest components have been used- Mundorf capacitors, Magnequest output transformer etc.

Speakers

In the last post I talked about finding a speaker that will give maximum enjoyment and satisfaction.

I believe it is vitally important to consider the speaker the most important component in any system, it is vital to get this component suited exactly to your taste.

There should be absolutely no doubt that it provides the sound you enjoy, you should have no qualms about it at all.  It should be a 10/10 , and something you could live with over a very long term.

Forget about the dac of the month, find the speaker that speaks to you and everything else will fall into place.

I've had many speakers over 40 years and here follows a description of the 3 speakers I simply could not live without ( ok I could choose one above the others, but I dont have to!)

AR-LST


LST stands for Laboratory Sound Transducer and Acoustic Research meant this design to be a genuine studio monitor.

Released in 1972 its very hard to find a pair in good condition now, But despite their age,they can surpass the best of modern speakers in accuracy and musicality.

With 9 drivers per side- a 10" bass, 4 tweeters and 4 midranges they  throw a large and realistic soundstage. Almost ribbon like tonality,but with very much increased dynamics .

They require some modfication to crossover bring them up to modern standards . I replaced the electrolytic caps with polys and removed a tone shifting network consisting of a stepped transformer and large electrolytic cap.

I also separated the 3 crossover sections so they could be individually actively driven. This requires 3 amps per side but is required if speaker is to be driven by tubes, as the total load is quite difficult .

This also provides the ability to adjust levels of bass,midrange and treble independently so as to adjust tone to suit room and taste.

Back in 1972 there were very few high current amps available that were able to drive the high current requirements of the AR-LST.

I used the speakers for quite a few years with 6 tube amps and was very happy with sound.

But recently I used a modern solid state amp capable of 1000 watts into 1 ohm , with bass, mid and treble paralleled and was very pleased with sound.

Of course a state of the art tube preamp is necessary to get a nice synergy with all that power.
Because this power amp has high gain, I'm using my DHT preamp switched to low gain/high drive.

The midrange of the LST is very good, but probably so because of the excellent integration of the bass and treble units, its a complete sound proficient in all areas.


Supravox 215/ Eminence Alpha/Raal ribbon tweeter. Open Baffle

I've only had this speaker system for a short time time but I can see me living with it for an extended time.
I've already described it in previous posts so will just give a short summation.

Field Coil Drivers are different, The Raal ribbon tweeter is different . Open baffle with the Eminence Alpha 15" drivers is different.

All up this is a great speaker that sounds different (surprise) from anything else. It seems to have the best of everything , with very few vices. Maybe the bass isn't as deep as it could be, but it is so tuneful and articulate .

The music comes out with real ease and vitality , very expansive sound-stage with every instrument clearly audible at its particular level ,and clearly defined.

The drivers aren't cheap , but this is an affordable speaker that anybody would be impressed with.

Its particularly demanding of preamps, nothing but the best for this speaker as it demonstrates the very best (and worst) of all.

I'm using a DHT preamp with 3 outputs and low output impedance in order to be able to drive all 3 outputs.

It works very well with an all tube system , a mix of Single Ended and Push Pull amps and responds very favourably to digital EQ/room correction . (that will get the traditional tube die-hards up in arms!)

Accoustat 2+2

Another old design from the 80's. I've had numerous  electrostatic speakers over the years- Quad, Crown, Martin Logan, Nakamichi (Whise), SoundKing) but the one that overawes them in size and sound is the Acoustat 2+2

Electrostatics are famed for their detail and crystalline highs, but the 2+2 has the most majestic tone of all stats. It isn't bright , as most stats can be, but has a very natural tone that most resembles real ,
voices and instruments better than any other speaker I've heard.

It does low bass and although not as "heavy" as a bass driver it is nicely articulated. I use a pair of subs but crossed in low at 50Hz, so they mostly are contributing little to the sound.

Voices, brass instruments are so natural sounding ,its the closest thing to being at a real show!

They do beam,so its a one man show,but in the optimum seating position the soundstage is huge and wide, as you would expect from a speaker this size
.
Like all stats they only really gel with a very powerful set of amplifiers, I'm using two pair of 1000W into 1 ohm solid state amplifiers
'
The designers got this one right and they dont require much modification to surpass any modern day stat.
I did split the crossovers so I could bi-amp, rebuilt the high voltage section with up to date stronger components and did a mild jump in HT joule capacity.

These mods enabled me to use my Supratek Dual Cabernet preamp. The 2+2's have 2 step up transformers and using one of the preamps outputs to drive the amp for speakers bass/mid transformer and the other preamp output to drive the amp for speakers treble transformer , I'm able to make fine adjustments to the speakers blend of bass/mid and treble.

Every speaker/room benefits from the ability to do these adjustments and is the perfect example of how the Dual Cabernet can be utilised.

If I had to choose the 2+2's would be my preferred speaker, and I'm presently building a dedicated (large) listening room to suit them.

There are many other speakers that can make fine music, the trick is to find the the one that suits the way you enjoy your music, and what really sounds like music to you.

Its obvious from my choice of speakers that I like big sound-stages, wide and deep imaging , and speakers that disappear.

Others will value tone or frequency response, it's all subjective but important to find what sounds like the real thing to your ears.

Get the speaker right, then the preamp, power amp/s and finally the sources and everything will fall into place.

Photos above used for illustration only- not my speakers. Photos coming.

Finally-Beautiful Digital Sound 2

My Finally Beautiful Digital Sound post from March 2014 created a lot of interest and still gets quite a few visits.

These days I'm often asked what I'm using for digital in 2016 and I'm pleased to say I'm still using the "old" Philips TDA1541 R2R dac chip.

I still haven't heard a modern dac chip that gives the same ease and musicality - the new delta sigma chips  are much better than the earlier ones, but still don't quite give that overall fatique free listening experience the olde R2R dac chips like the 1541, PCM1702, 1704 etc.

I'm using state of the art FIFO buffering and USB to I2S direct into the 1541. This enables play of hi-res up to 384Khz . So its a combination of the old and new digital process's.

I also use a no-usb approach , which is also FIFO based ,  and I2S direct . IMO this sounds even more natural and organic than the USB approach, although the difference is not startling, just again a more relaxing, emotive and musical sound.

Over the last few years DSD has gained some traction in the audiophile world. Every new dac seems to be DSD capable , and I've spent a fair bit of time playing around with DSD dacs and DSD implementation.

Make no mistake, DSD can sound very good .

But at its essence , any method, whether its the PCM  derivatives - MP3, FLac, AIFF, etc or DSD, SACD, DXD etc are only as good as the original recording .

A good sounding DSD , just like PCM , requires a very good recording technique and equipment , if its a poor recording being DSD wont "fix" it or sound any better.

A very well recorded MP3 file will sound far better than any mediocre DSD recording .

Another method gaining some popularity is up-sampling  PCM to DSD 512 or higher. Again, this can sound very good, but is also dependent on the quality of the original recording .
And this method requires heavy computer power and an almost obsessive dedication to going to all the trouble of doing this.
I did it for a while, but then came to realize I was missing the basis of why I enjoy fooling around with all this- the enjoyment and satisfaction of listening to music.

And it all comes down to the quality of the original recording, so isn't it just as meaningful to concentrate on what really makes a difference rather than concentrating on the small differences between playback methods, whether PCM or DSD etc.

I think its vitally important to get a speaker and system that really appeals and talks to you.
It should be so good that you would consider it a lifetime choice if needed .
Speakers and preamps count far, far, more in your system than any dac, and have so much more effect to give you the music that you want to listen to.

Get the basics of your system right, find the speaker you can listen to, and enjoy all day long.

When you have that right you will enjoy listening to music and not fretting about whether your missing out on the latest dac of the month.

Eminence Alpha/ Supravox 215-EC/RAAL 70-20XR Pt 3

I used Dirac Live with calibrated mic to measure the 215/Eminence combination and this is the result.
It looks a bit bumpy, but this isn't actually too bad. It's a result of speaker and room.

The Eminence bass level is higher than the Supravox , but I've deliberately set it like this .
I also tried moving the bass crossover frequency up higher, but sonically it sounds best like this.

You can see the 215 rolls off from about 5Khz, it doesn't sound as bad as it looks, indeed I didn't think it needed a tweeter, till I heard one in place.

The orange line is the target for correction , and Dirac does a pretty good job of getting very close to the target.  It cant compensate for the roll-off above 5Khz , but it follows the target to there.

But it does show that for true full range a tweeter is needed. The problem is finding a high efficiency tweeter to match the Supravox.

I've used ribbon tweeters before, with limited success, they can be  thin and metallic sounding , however I've heard very good things about the RAAL ribbon tweeters, some claiming they sound unlike any other ribbon.

I ordered a pair of the 70-20XR from Russel Story at Stones Sound Studio and installed them alongside the Supravox.

Well,  the claims were valid, these are the best sounding ribbons I've heard and match the 215's wonderfully well.  They have quite amazing dynamics , seem completely unhindered and play as though they have much higher efficiency then their 92dB.
Detail is all there, but not in a metallic or tizzy way, its just open and realistic.

They don't sound as though a tweeter has been added, they combine effortlessly with the 215 to give a truly full range , organic and exciting sound.

I simply used a 3.6uF capacitor as passive crossover for the ribbon, and will experiment further with different values and adding an inductor.

Here is measurement of the complete 3 way of Eminence, Supravox and RAAL. Dont forget, this is speaker and room.  A bit of juggling of levels and and the bass's DEQX EQ would get this even better, but I'm going to rely on Dirac to sort it out at this stage.

And here is the corrected response.

And here is the impulse- impressive!

I've had mixed results with Dirac, it doesn't always suit all types of speaker/room correction, sometimes the correction is worse than the problem, but here it has done a superb job with the Eminence/Supravox/RAAL combination.

Building this system is not in-expensive, but frankly I doubt you could get the same exciting , realistic and satisfying sound for  many multiples of the cost.

I've heard very expensive (>$20K)box speakers that cant do what this combination does.

Defined, tonally correct bass, the dynamic vividity of high efficiency near full range field coil , and the ribbon tweeter that sounds like it's not there, yet everything is so correct and beautiful.

And that is the perception of live , real music.

Next is to do a bit of fine tuning and put the drivers onto a nice furniture grade baffle.

Supravox 215-EC Field Coil Driver Pt 2

The first thing to do to get a field coil driver playing is to provide it with a power supply.

The 215-EC uses quite a lot of current - 5A at 12V. This requires a hefty power supply, and if regulation is used, then quite a large heatsink.

Another method is to use one of, or a pair of deep cycle 12V batteries.

With a trickle charger to keep the battery/s topped up, this a quite an effective solution and sounds very good.

However it takes up quite a lot of room space, is a bit ugly, and inconvenient.

I built 3 prototype power supplies , and chose to go with regulation using LT-1083 regulator chips , which are rated for 7.5A,  300VA 2x12V transformers and quite a substantial bank of capacitors for a stiff power supply. More heat-sinking than necessary so as to run cool and reliable.

The first PSU (power supply unit) used a pair of high current chokes to provide a very clean supply to the regulators. This is way over-kill and the next unit did away with the chokes, and no difference in sound quality was noted.

The next unit used a constant current regulator circuit, which provides constant current rather than constant voltage to the field coil.

In theory, this should be the least effective method, but over the long term, I quite liked the sound from the CCS.

The difference is very subtle, but it just sounds a bit smoother and easier to listen to.

I also settled on 10V operation , it seems to be a nice compromise between the more laid back 8V and the dynamic , but forceful 14 V operation.

Of course voltage selection will depend on the system the driver is used in. Open baffle is quite different to box operation and a quite different operating voltage could be required.

The Q's or parameters of the 215-EC are changed with different voltages so in reality they are quite different drivers at different voltages.

The drivers are mounted on a flat piece of plywood with solid pine bracing . I placed the 215 between two Eminence Alpha 15" bass drivers, which are designed for open baffle use. 215 is at ear level.

There is no crossover on 215, it is connected to a SE-300B power amp , which is driven by one of my DHT preamps.

The woofers are connected to tube monoblock amps, which are connected to DEQX unit, which is connected to same preamp.

Crossover in DEQX is 250Hz @ 24dB. this might seem a bit high, but in open baffle the 215 rolls off quite high and the Eminence has to be brought up to flatten the curve, as much as possible.

I also have some bass EQ to counter the eminence bass roll-off and give it a bit of oomph.

So how does it sound in this first, basic version?

Ive never been a fan of "box" speakers, the typical 2 or 3 way just doesn't provide enough excitement or realism for me. No matter how expensive or exotic, they always sound like a pair of speakers.

Planar speakers can also have their limitations, however the best do possess an ability to give a big wide sound that does come close to what you would actually hear in a studio or live entertainment venue.

Likewise with horns, the very best have a palpability that is to die for.

I'm not so much into impressive sound with explosive bass and scorching treble, I'd rather listen to something that has a natural musical tone and dynamics that simply sound real.

Music touches me when it gets close to revealing the emotion , ability and performance of the recording.

I don't want to listen to speakers, I want to listen to the recording.

The Supravox can do that, they do a very good job of disappearing and leaving the music in place.
Imaging, sound-staging are near perfect.

I haven't heard a speaker that can throw a big a sound as my modified Accoustat 2+2's , but at 8 foot tall and requiring 4 channels of 1000W , they are bordering on impractical for most situations.

The Supravox come very close and only require low power, preferably a tube power amplifier.

Like all full range drivers they are not monitor studio accurate, but they don't shout or have excessive peaks like Lowthers and the other full range drivers.

They are not perfect, but they are very interesting, and very satisfying drivers. You don't tire of the Supravox sound. Indeed its hard to turn them off!

Like a good tube preamp, they don't scream out their advantages, but take them away, and you soon miss them very much.

The integration with the Eminence bass drivers is good.  Open baffle bass is a very interesting subject , and subjectively, very easy to listen too.

Open baffle cant do very low sub-bass, but what it can do is very articulate and defined bass. There is no boom or overhang . It may sound "light' if you are used to big subwoofers moving lots of air,  but the definition is quite startling once you come to appreciate it.

If you have ever sat next to an acoustic bass you will have noticed there is no boom or lack of definition , you can clearly hear every note - open baffle bass is like that, the bass lines are very easy to follow and enjoy.

All in all a magnificent speaker system, but in Pt 3 I measure them, use digital speaker/room correction to make them damn near perfect, and use them with the amazing RAAL ribbon tweeter.

Supravox 215 Field Coil Driver. Pt1

Quite a while ago I read this on the 6moons website:

"After four years of building a number of different baffles, trying many drivers and fine-tuning passive crossover points, what conclusions have I arrived at? Only one. Anyone reading this can easily and for little cash build a substantially more open, palpable and real-sounding speaker system than they are likely living with at present regardless of cost." 

That's a big claim, but the author seemed a genuine guy with some credibility, and I put it in the back of my mind to investigate further at a later date.

The author was describing an open baffle system, (no box, just a flat panel with drivers mounted on it) with field coil drivers.

 Field coil drivers use an electro-magnet instead of a permanent magnet to generate the magnetic force to move the voice coil.

They require an external DC voltage to energise the electro-magnet. It's how the very earliest speakers were utilised, before permanent magnets were viable .

These days they are expensive and exotic, and one of the best designers and manufacturers is the French company Supravox.

Recently one of my preamp owners asked me to build him a power supply for his Supravox field coil drivers.
Its a little out of my field of expertise, but an interesting challenge.
Bob sent me a pair of Supravox 215-EC's to experiment with ( and then gave them to me- thanks Bob!)

The easiest way to get field coils going is with a car battery, the 215 are happy with 12V so a 12V deep cycle battery minimum 25 AH will last through an extended listening session.

After a warm up I was impressed enough to go further with open baffle and field coils.

I should mention that my friend Martin Seddon of Azura Horns has been using field coil drivers for some time now, specifically the Line Magnetic LM555W , which is a clone of the Western Electric 555 compression driver.

The realism of his system  is extremely impressive , and initially piqued my interest in field coil drivers, hopefully I could pull the same palpable sound from the Supravox.

As you know, i'm a big fan of active speaker/amplification, ie using a seperate amplifier for each driver with either passive or active crossovers.

The Supravox is essentially full range , in the same vein as the Lowther , Coral, Feastrex full range drivers , but the Supravox doesn't have the shouty upper midrange accentuation of these drivers.

However these drivers are known for their dynamics and ease of portrayal of micro-dynamics, they are very revealing, but in an easy, almost relaxed way.

They tend to be in-accurate, but the excitement they display tends to forgive their sins over the short time.

The 215 are reasonably accurate, so don't suffer from the same fatigue, they can be taken very seriously as a transducer of the highest quality.

But, like all full range drivers, they're not really full range and have roll-off at bass and treble extremes.

Eminence make a 15" bass driver designed for open baffle. They cant do deep sub-woofer bass on an open baffle, but these days we have some great tools to coax reasonably flat bass response from these drivers.

However, there's a real problem integrating other drivers into use with full range drivers.

The beauty of full range drivers is that they dont use crossovers, they are used "full-range" and this lack of crossovers preserves the phase response of the driver.

Crossovers ALWAYS do some damage to phase coherence, which leads to a diminishing of openess, soundstaging and imaging - the big 3 when it comes to realism.

Of course no full range driver can do 20Hz- 20Khz , so if the frequency extremes are required , bass woofers and treble tweeters can be added, although crossovers, whether active or passive , will be required.

What I like about the Supravox is it has a nice roll of at the bass and treble points, quite smooth, and this enables us to blend in bass drivers and treble tweeters with crossovers just on these drivers.
We can get away with no crossover on the 215 at all, and this preserves the phase character of it, the magic remains even with the bass and treble crossovers, as they are not effecting the 215 at all.

I used two Eminence Alpha 15" bass drivers per speaker with a DEQX digital crossover with a steep 24dB crossover at 200-250Hz.  I also used the DEQX equaliser function to counteract the open baffle bass roll-off,  to a certain degree.

In part 2 I will go further into the implementation, power supply and sound quality of this splendid speaker.

Forums

I've stopped contributing to, and even reading internet forums.

When I first started building tube gear back in the 70's there was no internet, and indeed there was not much interest in tube gear. Solid state pretty much ruled and there were only a few commercial tube amplifier manufacturers and tube diy enthusiasts.

Tube design knowledge came mostly from libraries, I used to spend many afternoons in the State library, requesting electronic design books from the bowels of the archive basement.
Most of these books are lost now, although there are still some references available - The Radiotron Designers Handbook by Langford-Smith , The Mullard Design "green" book, the GE book, Morgan Jones work, etc.

I also had some mentors who were building amplifiers and were happy to show me their work.
But mostly my knowledge of how to build tube preamps, and what makes them work really well came from building many hundreds, perhaps in the thousand , of actual circuits.

Only from this approach does true knowledge and experience come, its called hands on, and a few electric shocks through those hands over the years!

Today,  there's more talk than hands on, the internet forums are full of gurus and experts . You can get an opinion on just about any audio topic.

But its just OPINION. Anyone can digest a terabyte or two of digital audio and then re-sprout it as hard gained knowledge , but its not realized or experienced knowledge, its just re-hashed opinion.

Im my opinion (!!) 80% of what you read on audio forums these days is merely opinion, there's very little actual knowledge , and extreme caution should be exercised in believing what you read.

The internet is a wonderful device and a source of great knowledge, but discrimination and common sense is needed to sort the chaff (opinion) from the wheat (knowledge).

Enough said, I found this pix on an old hard drive the other day when looking for an old preamp design .
It featured in a Singaporean book "Marques of Distinction" . "A collection of the most beautiful photographs of audio products in one volume"

double click to enlarge.

UPDATE!!!

Hard to believe its's been over a year and a half since my last blog.

So what is happening with Supratek? We'll I'm still here and I'm still busily building preamps, although lately it has been mostly custom builds for long term customers.

I've also been busy upgrading older Supratek preamps to my latest DHT designs, and from the happy responses, the upgrades are very worthwhile.

Despite the increase in digital sound quality over the last 5 years,  a very high quality tube preamp is still the best way to get the most from your system, especially if you value realistic sound-staging and imaging, the most important attributes for realism and musicality in your system.

The Supratek designs are leading edge tube technology- I'm happy to use a blend of tube and solid state componentry  to ensure that performance is not only objectively superior on the test bench, but subjective sound quality must also be very pleasing to the ear.

The real test of an electronic audio device is its long term adaption in a system. It is most pleasing to me that most of the Supratek preamps are still with their original owners, some going back more than 25 years.

Audio can be a fickle pastime, but there is something about a good tube preamp that is ultimately very satisfying , and very hard to live without, once the realisation of the transformational character of these rare devices has pervaded the senses.

I build mostly Directly Heated Triode preamps these days.

Supratek released the first commercially available DHT preamp (with 300B tubes) many years ago,
I've used 45, PX4, 101D and many other DHT triodes in the Supratek line-up.

The last 5 years I've mostly used the Russian 4P1L triode connected, as it perhaps one of the finest tolerance directly heated tubes ever made. No need to match these tubes, they are all eerily within the closest specs, and sound very good.
Lately, I see other commercial builders are starting to use this tube - you cant keep a good tube down!

The DHT sound is one of vividness and immediacy and  musicality.

Of course, all the Supratek preamps have remarkable technical performance , with excellent test bench performance .
There is no tube "romance" or "lushness" with a Supratek preamp , which is essentially coloration from poor design and componentry which results in the  inabilty of the preamp to drive the following power amplifier with accuracy and "life".

Its quite difficult to build a preamplifier to match all the different types of power amplifiers available.
There is a huge variance in topologies (tube and solid state), gain structures  and drive requirements.
A tube power amp is relatively easy to drive, a 3 way active solid state system not so . (and one of my favourite ways to drive a speaker) .

All the Supratek preamps now have a wide range of adjustments to ensure that they will drive any power amplifier to its finest performance.

They are unique, and always have been, but now are even more adaptable to any system and ears.

I'm now building The Supratek preamps in the same or similar configurations I use in my own custom systems, it's different to what's available commercially, but these configurations can be used for any
system configuration, from a simple Single Ended line stage to a complex fully active 3 way system.
Transperancy, musicality is never compromised.

Starting at the output,  the tube output stage can be switched to either capacitor or transformer coupling.

Transformer coupling "transforms" the tubes output impedance , and it's level of "drive" (or power) , lowering the output impedance  and increasing the drive, usually by a level of 4 or more.
Have an active system that uses 3 solid state amps?  A typical tube preamp will not like this at all, no problem for a Supratek.
The gain is also lowered , which can be useful for signal to noise ratios.

Capacitor coupling is simpler,  has more gain and can suit some systems and ears as well as , sometimes better, than transformer coupling.

Most of the  Supratek preamps use a 6SN7 driver stage ahead of the DHT. DHT's are typically low gain  so it's useful to have extra gain available if needed, and the 6SN7 and it's Russian namesake the 6H8C are one of the best IDHT (indirectly heated triode) tubes available.

The 6SN7 gain stage is switchable , so it can be switched in and out, while the preamp is playing , to find the best gain structure and sonics to suit the system. And used in conjunction with the trans/cap switch you have a range of gain/ drive structures to suit any system.
In essence a Supratek preamp can be 3 preamps in one , its a heap of fun being able to have a different sonic flavour when the need or mood arises.

There is no other preamplifier like the Supratek DHT , and it will transform your system.

Here's some pix of a 2005 Supratek preamp just modified to use the DHT 4P1L tube.
The 6L6 regulator tubes have been moved to the power supply and the 6SN7/4P1L tubes go on the preamp chassis.
The 4 phono tubes and phono stage remains unchanged.

This worked out very well, and I'm sure the owner will be very pleased.

Later. And this is what he said: "...it's like you are much more in touch with the music (like a ESL speaker), it's much more direct.

Images, depth of image, dynamics and speed are all improved but still musical and natural sounding."

I'm planning to contribute to this blog a bit more regularly.
Keep a lookout for a post on vintage speakers, and the amazing Supravox 215 field coil fullrange speaker system.
I'm also planning to do something about my other passions - motorcycling and it's obscure relationship to audio, and men's health- healthy body,  healthy mind.