2011

Another year gone by, and over the course of my 35 years in audio this has been one of the interesting ones.
The upsurge and improvement in digital playback has been relentless, and even the most diehard flat-earthers are admitting that CD was a big mistake and a rather silly waste of 20 years.
But I guess all ventures have to find the best way through the maze of compromises and 16bit/44.1Khz was certainly a big compromise in sound quality.
At least the quality of the latest dacs is bringing decent sound with 16 bit, and excellent sound with 24 bit and higher sampling rates. And the increasing refinement of up sampling even helps to bring 44.1 KHz to life. Currently I'm limited to an upper limit of 384Khz but expect to be listening to 768Khz up sampling soon. There is at least one dac capable of 768 playback , but as far as I know only the XXHighEnd program is capable of 768Khz upsampling, although JRiver has released 384Khz upsampling this year, so it must be just a matter of evolution .
It's going to be another interesting year in 2012 to see where this takes us.
At the moment I'd say that a well recorded 60's analog vinyl recording played back on a very high quality vinyl set up would still sound better then the digitized version of it, but it is so close. These recordings are very rare though, and when the high complexity , low sound quality mixing desks started to be used in the late 60's and absolute sound quality slipped, vinyls advantages were nullified by these poorer recording techniques.
Of course there are no generalizations here - I'm talking about very high quality recordings, and very high quality systems optimized for the playback required.
A 60's recording straight into tube mics, tube tape decks and then transferred straight to a master disc and played back on a high quality tube based system is something pretty special, but so is a modern recording with good mics,384Khz sampling rate and minimal processing at the master desk.
Early on in 2011 I was almost completely focused on digital/solid state with active electrostatic speakers driven by solid state high power amps and DEQX digital crossover/equalization - the only tube gear was a tube preamp.
However the demand for the Supratek Mondeuse and Malbec tube amplifiers remained constant and I built more than I would have expected, and all were tested on Tannoy and Lipinski monitor speakers.
The new digital technology is exciting , but there is still something about tube amplification that is " just right" . Especially when tube design is done correctly and the design is capable of accurate and dynamic reproduction. There seem to be more tube manufacturers using positive feedback this year, its nothing new, but the Supratek amps are about 5 years ahead of the pack in re-discovering this design feature which gives a modern accurate sound that really compliments the advantages of the new digital playback technologies. The positive feedback amps are not "warm and romantic" and "soggy" like many of the traditional sounding tube amps, but still retain that slight touch of euphonics that make listening a non-fatiguing ,enjoyable experience.
I put my stats away as I really need to do some deep research and learn how to get the best from the DEQX digital equalization , and went back to all tube amplification.
Bi-amping the Lipinskis with 100 watt Mondeuse on the woofer/midrange and 50 watt Malbecs on the tweeters.
My Tannoy Golds were born to be used with tube amps, and as they are a relatively easy load they just require a touch of positive feedback and almost no negative feedback to sing with the Supratek tube amps-they do like a bit of power though and come alive around 50 watts.
However no one is going to say that Tannoy Golds are accurate, despite their "monitor" tag. It may have been true back in the 70's but today's definition of accurate is much tighter.
The Tannoy Golds are usually used in large ,slightly lossy boxes that give a pleasing warmth in the upper bass region but although initially happy I found the inaccuracy a hinderance to evaluating and enjoying modern digital music.
I'm one of those guys that prefers to hear the recording rather than a "beautified" version of it.
With a very rigid cabinet that contains a very thick high density cardboard tube the Tannoys lose nearly all the resonances that colour the frequency response.
And to my surprise the answer to removing the last bit of the Tannoys inaccuracy lay in the digital domain. The Tannoys are used in a system with windows7 OS for the computer digital playback and I use JRivers Media Centre 17 as I like it's ease of use and up sampling capabilities.
It also has a great DSP (digital sound processing)function with octave and parametric EQ.
I've always been suspicious and unsatisfied with the audio quality of most EQ functions, a legacy from the old days of serious compression and distortion usually associated with octave EQ, but I can't fault the 64 bit processing of the JRiver process. Ive only used a maximum of 1.8dB on one of the bands and even less on the other bands , this has resulted in subtle but very advantageous solutions to bring the Tannoys to a very respectable level of accuracy.
Media Centre 17 also has a Sound Field  function that "stimulates a wider, more submersive sound stage" . Yes it sounds tacky, but with medium enhancement it provides a subtle yet very worthwhile improvement I find surprisingly addictive.
So now we have another tool in our armory thanks to the refinement and evolution of DSP.
In retrospect,  2011 was a year of looking forward and yet still enjoying the best of what we have created in the past. Digital and tubes can exist together , and the very best of both worlds creates the present state of the art, to my ears.
Looking forward to 2012, cheers to all.

Lots of lovely tubes!

Tannoys, tubes and computer digital in the 21st century!

DacAttack

Digital computer audio is evolving so quickly it is hard to keep up with it.
At present I'm using two computer systems- on my Tannoy Gold system driven by 6EM7-300B-6C33C-B Single Ended amps /JBL active subs from a 6SN7-71A preamp, the digital system is windows7/JRiver media16/Emperical Audio OffRamp4 usb-spdif convertor into a Eastern Electric Minidac with Sabre chips and ECC99 tube output stage. All files are upsampled to the dacs upper limit of 192KHz.
Very nice musical system.

The other system is a bit more complicated as it is a fully active 3 way electrostatic/ribbon /12" bass driver with DEQX digital crossover , DHT preamp, blah blah blah.
The exciting bit is the digital componentry which is the EXA U2I usb-i2s convertor, a Buffalo2 Sabre dac and my own very evolved (and accurate) tube output stage. 384Khz capable throughout, and i'm using a macmini installed with PureMusic to upsample all my computer files to 352.8 or 384Khz playback.
192KHz upsampling can often give good results, but the magic really starts to happen at 384Khz and I was quite stunned by how good this computer audio system is . Even lowly 44.1Khz files are much better sounding when upsampled to 352..8Khz.
768Khz will probably be even better, but a few years away yet. In the meantime I'm building a couple of these very special dacs for my friends. They are expensive- the digital components alone cost  in excess of $1200, so from a mainstream manufacturer expect a minimum total  cost of around $5000.
Spectacular sound.

High Power Push Pull Amplifier Design

The Supratek push pull tube power amps have been continually evolving since I started to prefer them to the Single-Ended amps I built for such a long time in the 90's and early 00's.
SE can sound exceptional with the right speaker, but a high efficiency speaker that is reasonably accurate is so damn rare, a push pull amp is much more practical and suitable for the majority of purposes.
But becoming used to the purity and clarity, and especially the vividness of SE amps, most of the push pull amps I'd heard and built after the SE's left me cold. Sure they had better power and  control, but they all sounded veiled, constricted and lifeless .
So all my design efforts from then on concentrated on building a push pull amp with control and power AND with the immediacy and vividness of a good SE amp.
Fortunately I had Kevin Covi and his amazing computer simulations to do all the hard nitty gritty tube operating point work while I concentrated on fine-tuning the sound to find that elusive magic I was chasing.
I believe the biggest mistake manufacturers make is the overuse of electrolytic capacitors-these are poison to sound quality, and the least you can use the better. The alternative is plastic caps, but when they are 20 or 30 times the size of a comparable electro and many times more expensive, most manufacturers baulk at the idea of using them.
Thet Supratek Monduese amp uses a couple of electros after a set of high speed hexfred rectifiers- the HT voltage is then pushed through a parallel pair of 5AR4 tube rectifiers, used as tube dampers in order to get a nice soft start on turn on, and for some "tube" sound. On each side of the 5AR4 is a polyprop cap with a choke to make a nice CLC(capacitor-inductor-capacitor) filter.With this approach we get the solidity and speed of a solid state power supply combined with the slow turn on features and sound of a tubed CLC . Again, too bulky and expensive for most manufacturers.
The approx 500V HT voltage is sent to the output tubes, and to a tube regulator using a 6H30 tube to shunt regulate the voltage for the input and driver stages.
Surprising to some, we use a single 6H8C/6SN7 for the input and phase splitter/driver. This results in a low gain/sensitivity amplifier circuit, but this is exactly what we are trying to achieve.
The purpose of a power amplifier is to turn the signal voltage from the preamp into current to drive a loudspeaker-it should be nothing more, but these days most power amplifiers are in effect integrated amps, with quite high gain. This seems to have evolved from a desire to use the typical 2V output from a CD player directly into a power amp.
However there are all sorts of problems with this approach- firstly the impedance matching between the source and the power amp may not be optimum and a flat ,boring, un-involving sound is often the result.
A high quality preamp before the power amp will provide much better matching and will give real tangible benefits to the sound. Let the preamp do the signal gain work and the power amp provide the power is our approach.
The second problem with high gain power amps is that of noise- if they are used with a high gain source or a preamp with voltage gain, the power amp will amplify the noise floor of the preamp and the noise will become audible.
A properly designed preamp and power amp, designed to work in conjunction with each other, will be very quiet, even with very high efficiency horn speakers with outputs of 100+dB.
10 years ago I sold quite a few SE Merlolt amps to Avantegard horn owners as they were one of the very few SE amplifiers quiet with horn drivers.
Back to the Mondeuse- the single 6H8C/6SN7 input tube circuit is based on the classic Williamson circuit, with the input tube direct coupled to the phase splitter and then cap-coupled to the output tubes via a pair of polyprop caps .  Very simple, very effective circuit, the only concession to modernism is a Constant Current Source(CCS) loading of the input tubes plate.
There is a  total of 13 capacitors in the Mondeuse amplifier- compare that to a typical amplifier with maybe 50 ,usually all of them electrolytic- capacitors are bad-mmmk?
At the grids of the output tube , instead of using grid resistors we use grid chokes, which do the opposite of "choking" and provide a real improvement in sound quality. The difference between grid resistor loading and choke loading is quite profound, the soundstage is bigger, imaging takes on a more 3D presentation.
There is a bit of fine tuning to be done as the inductance of the chokes does give some subsonic accentuation, but this gives us a great opportunity to tune for flat deep bass. This is done with a compensation filter that is non-obstrusive. Again, too bulky, expensive for mainstream manufacturers.
Biasing of output tubes is usually done by either fixed bias or cathode bias- both have advantages and disadvantage, but we do something different (again)
Kevin Covi came up with a couple of different ideas to improve the traditional biasing methods and which have the extra bonus of eliminating crossover distortion which is a problem with traditional Class AB biasing methods. After much evolution, a  CCS is used under each of the output tubes and is adjusted to give constant, unwavering current through each tube that mimics pure Class A operation, with close to the power of Class AB. Another advantage is the CCS devices are bolted to the copper chassis which acts as a heatsink and keeps the heat out of the chassis interior.
As each tube is adjusted for constant current with a small pot on each tube, different tubes can be set up with the amp- KT88 are standard on the Mondeuse, but 6550, KT120,KT90, EL34 can also be used, although some technical knowledge is required to do the adjustment.
However, once done no other tube adjustment is required.
Output transformers are oversized and optimally chosen for the circuit operation- the device we use is a high bandwidth transformer that does not require feedback to give this high bandwidth response.
Feedback- another contentious issue. The Supratek push pull amps use both negative and positive feedback.
There is nothing wrong with a sensible amount of negative feedback, as long as it used properly and not as a cure-all for design faults or poor quality output transformers. Some speakers really benefit from a touch of negative feedback which lowers the amplifiers output impedance and can drive the speaker easier.
Go too far with excessive feedback though and the sound degradation is very obvious- veiling and a loss of 3D presentation is usually the result.
The Supratek amplifiers have adjustable feedback via a 6 position switch- the first position is no negative feedback and the next 5 positions give an increasing amount to a final sensible,but not excessive amount of feedback. Using my Tannoy Golds with an EL34 Mondeuse I might use the first or second position, but driving ribbons or stats requires the higher positions.
Positive feedback. Kevin uses Wolcott amps on his Soundlab stat speakers.  The Cotters are maybe the most technically proficient tube amps available and maybe the only tube amp capable of driving difficult speakers like the Soundlabs accurately. The Wolcotts use positive feedback to lower the output impedance of the amplifier quite drastically, to achieve the same damping factor as the biggest, meanest solid state amps.
However, imo the amps are very complex and whilst I wanted to investigate positive feedback I wanted something a little less complicated.
Positive feedback is nothing new, it was used on quite a few amps back in the "golden age" of tube design, but was less appreciated then as speakers were relatively easy to drive.
However my stat speakers are definitely not easy to drive and Kevin and I spent a lot of time getting a positive feedback system to work with the Mondeuse and Malbec amplifiers.
The result is quite pleasing- in theory the positive feedback can be adjusted to give extremely high damping factors, and while it still cant drive the most difficult speakers it does make the 100 watt tube amplifier a formidable weapon to drive all but the most difficult speaker.
It's greatest potential though is the sheer adaptability of the amplifier- with both adjustable and switchable negative and positive feedback the combinations of different sound perspectives is greatly enhanced. From romantic lush to master tape accuracy the choice is yours.
The Mondeuse and Malbec amps have a negative feedback switch and adjustment on back panel and positive feedback switch and adjustment knob on front of amp.
Setting both positive and negative for best speaker performance can be tricky at first, but with a bit of experience it becomes relatively easy. With my Tannoy Golds, which are a easy load for most amps,  I use very lttle, if any, positive feedback and maybe none or 1 click of the negative feedback .
With my hybrid stats/ribbons it is a different approach. These speakers are a difficult load and the best way to do this is to start with the 2nd position of negative feedback and slowly raise the positive feedback while listening. Then try the 3rd position of neg feedback and raise the positive feedback. You'll soon find the spot where the amps have combined with your speakers and are close to infinite damping and  thus very accurate sound. You can choose to use this or back off for a less damped sound- the choice is yours.
Sometimes the gain of these low gain/sensitivity amplifiers is too low, for example with a preamp with low or no gain (I cant see the point, but there are quite a few available)
BTW sensitivity has nothing to do with power- sensitivity is the amount of volume required to reach full power- a 5 watt amp can be built to have much more gain than a 100 watt amp, but it will not be able to drive most speakers. The 5 watt amp will be distorting at 9 o'clock while the 100 watt amp will be clean and have power in reserve at 11 or even 3 o'clock. (depending on preamp gain)
Another example of when the gain of the Supratek amp could be too low is when an additional device is inserted between preamp and power amp - I have a DEQX digital crossover in one of my systems that soaks up gain and requires higher sensitivity power amps.
In this situation I use an optional switchable input step up transformer. The advantage of this method is that we get the required gain, but dont have the disadvantage of extra input noise, hum etc that would result if we used an extra tube for more gain.
Again it is switchable so it is there when needed and out of circuit if it is of no advantage.
The Supratek push pull amps are basically simple in concept- the basic design of all tube amps has remained the same for over half a century, but there are some very clever design variations in the different stages- the low gain input/driver stage to reduce noise and component count, and minimise phase issues. Minimal use of  capacitors - less is more with capacitors. CCS devices used for constant reliable operation of output tube bias/current. Voltage shunt regulation of driver/phase splitter stages using tube regulator. Grid chokes.
Switchable and adjustable negative and positive feedback. Optional higher gain if needed.
High quality power supply using hexfred diodes and tube rectifiers.
All of these improvements make a very sophisticated amplifier that is very reliable and sturdy with a choice of adjustments that make it possible to fine tune the sound to get the best out of your speaker.

More Thoughts on Single Ended/High Efficiency Speakers

I've been very critical of SET amplifiers (single ended triode) because of their inability to drive speakers accurately. To briefly recap SET amps have high output impedance, low damping factors and depending on the plate resistance of the tube, amount of feedback,etc can have varying abilities of producing accurate response from a speaker. Variations of more than 10dB "mistakes" either side of flat response can be quite common, and indeed these misrepresentations are often what some people find so appealing about SE operation.
I was building SE amps back in the early 90's when the SE resurgence had just started, back in the good old Sound Practices days with the joelist , and had a lot of fun trying just about every DHT tube known to us then.
Of all those amps i've kept one pair of 300B amps, one pair of 211/845 amps and my favorite SE amps - the technically challenging and innovative 6EM7-300B-6c33C-B .
( I see they are now cheaply built copies of my Cabernet preamp available, at twice the price - watch this design get copied too)
I've also had a long standing 10 year project to complete a 310-10-212E SE pair of monoblocks  that has been in partially  built mode for too long. (Will do a blog on this interesting design soon)
Recently I purchased a pair of Tannoy Gold 15" monitors and tried my 100 watt KT88 push pull amps with them with very pleasing results, so much so that I modified another pair of amps to use triode connected EL34 tubes for 50 watts of  musical power.  (using a big Peerless output trans built for me by Mike Lefevre)
Very nice sound, reasonably accurate. And beyond that to extremely satisfying, almost jaw-dropping sound when placed into a large, very good sounding room.
And with room to eventually end up with half a dozen amps, 3 preamps, various dacs and digital playback equipment and a Micro-Seiki RX-5000 turntable (with another sore back from lifting the almost impossibly heavy plinth)
Much fun, and eventually I couldn't resist to lug the big 6EM7-300B-6C33C-B SE amps into the room to try with the Tannoys, even though I expected the same old midrange prominent, SE sound.
I was very surprised to hear a  sound very similar to the big push pull tube amp sound, and with that touch of euphonics you get with SE sound, but certainly not the soggy bass, lucious but too promiment midrange- instead it was just incredibly natural sounding and very enjoyable.
So what's going on- are all my beliefs about the weakness's of SE amps completely wrong? Am I a goose?
Then I remembered - it had been so long since I used these amps I had forgotten the output stage was configured as a cathode follower . Instead of the usual practice of connecting the output transformer to the anode the output tran was connected between the cathode and earth.
Those of you familiar with cathode followers will know they are commonly used in preamps to provide a low output impedance, and often used as buffers on the end of dacs etc. They aren't my choice to use in preamps- the disadvantage of them is they are a feedback device and the disadvantage of the veiled sound they produce is too high to outweigh any advantages.
The cathode follower principle is rarely used in power amps, but again has the advantage of drastically lowering output impedance. The 6C33C-B tube is a low plate resistance tube, it's Rp is 100 ohms, compare that to a 211 with a plate resistance of around 4000 ohms! The 6C33C-B in SE operation has the lowest output impedance of any tube  and when used in cathode follower configuration is further drastically lowered .
Another advantage is that distortion is lowered- the clipping characteristics with cathode follower mode is symmetrical and clean. Whereas typical SE operation with anode connection is very much higher distortion and with the 6C33C-B quite an asymmetrical clipping character.
Here is the circuit- you can see the output trans under the cathode of 6C33C-b tube.

The disadvantages of cathode follower operation; a closed in,veiled sound doesn't seem to have the same degree of effect when used with power amps- it is audible, but the advantages of that clean power balance out the disadvantages to some degree.
Initially I had the amp set up with a switch so i could toggle between cathode follower and anode follower mode. Both methods sounded very good, but with the conventional speakers I was using I prefered the more balanced, accurate and clean sound of the cathode follower.
As much as I enjoyed the sound of these amps, I valued them mainly because of their technical ability and with the speakers I use preferd the big push pull or solid-state amps for my listening.
So they sat on a shelf for a couple of years till they were paired up with the Tannoys.
It would be very interesting to investigate just exactly what sort of load the Tannoy Golds and their crossovers present to a SE amp- I suspect it would be a very easy load, as others report that even 211 and 845 amps work well with them.
I'm not convinced a 211 or 845 would get anywhere close to the accuracy of a 6C33C-B SE amp in either anode or cathode follower configuration however and I'm astounded how good the combination with the Tannoy Golds is, especially in a big room where the sound is glorious and magnificent.
Reference quality in terms of accuracy and reproduction? No. 
Emotionally and musically satisfying? Yes , and in a big way.

For those of you interested in the effects of output impedance on speaker response this is an interesting page-

http://www.stereophile.com/content/primaluna-dialogue-seven-power-amplifier-measurements

http://www.stereophile.com/reference/60

4 Speaker Systems

double click to enlarge pix
I have 4 sound systems in use- that probably sounds a bit excessive but as a passionate audio enthusiast/manufacturer that specialises in preamps and power amps it is necessary to have a range of speaker/systems  that generally covers the type of sounds my customers listen to.

No speaker is perfect, but you can find a type that suits you more than another- most people are happy with a well sorted out multi driver moving coil speaker (eg Sonus Faber) Some like to take this a little further with an active version (eg ATC)

Others like the sound of planar drivers either electrostatics (eg Martin Logan)or ribbons (eg Magneplanar)

Although one of the most ancient designs, and very tricky to get right, the sound of horns is very appealing to those dedicated to the principle. (eg Avantegard)

Somewhat related to the horn , the coaxial , or full range  driver is also hard to get right despite the fact it is a beautifully simple concept (eg Tannoy)

There are other exotic types of speaker drivers but these 4 concepts are the most widely used.

I’ve spent close to 40 years building, owning , listening to and enjoying many different versions  of these 4 types of speakers and after all this time I still don’t have a “favourite” type of speaker- there are aspects of all of them I like and dislike. I gave up trying to find the perfect speaker many years ago and have been happy to enjoy the strengths and ignore the weaknesses of all types, and have had a lot of satisfaction getting the best out of each of my many speaker systems over the years.

I’ve found that in my role of amplifier designer and builder that it can be quite perilous to commit to one type of speaker as the designs tend to then hone in on overcoming the weakness of that particular speaker (none are perfect)

You might build a preamp or power amp that is fabulous with a horn speaker but less than that with a moving coil driver, and vice versa.

Eventually the only really successful amplification is that which is accurate under all conditions, into any load- if it appears to be “coloured” or any deviation from flat response it is then the speaker responsible, and recognised as such.

Having an arsenal of 3 or 4 different types of speakers allows one to really come to grips with the strengths and weaknesses of each speaker concept and is invaluable in designing and building amplification that can either specifically suit each type of speaker or find the best design compromises that enable each type of speaker to sound as satisfying as is possible.

In no particular order of merit my speaker/systems are:

ELECTROSTATIC/RIBBON HYBRID

(1) Modified Martin Logan Request electrostatics.  I listen to these the most as they have the best acoustical position in room and are closest to bridging the gap between technical accuracy and subjective listening pleasure. They have a big open sound that is reminiscent of what you would hear if you were in a jazz club or even in a symphonic concert- the sound is very wide with good depth presentation.
 The very high level of accuracy is due to the implementation of these speakers- they have had the passive crossovers removed , and are used as actives with seperate amplifiers directly driving the step-up electrostatic transformers.
They also have multi  line-array ribbon drivers (7 per side) covering the response from 200Hz-500Hz. I use these as I prefer the sound of them to the electrostatics in the range of upper bass- lower midrange. And they help with the integration of the bass- which is always difficult with hybrid ‘stats. If a big bass driver is used it will have good lower bass but struggle to blend seamlessly in around the crossover point, and if a small bass driver is used  it will struggle to do deep tight bass. This has always been a problem with hybrid electrostatics and the ML Requests I use have a 12” bass driver in a sealed cabinet which gives great bass, but has a real problem at the higher frequencies at the crossover point.

The ribbon drivers cover this upper bass to lower midrange region beautifully and seam effortlessly with both the bass driver and the ‘stats. 
A DEQX digital crossover is used with filters of 24dB, amplitude and filter type is easily adjusted at the listening position with Windows7.  The DEQX has the optional Jensen output transformers which  sound very good.  There is a bit of bass eq to compensate for the bass roll off of sealed design, bass is very tight and deep enough for no need of subwoofers.

Power amplification is all solid state- 6 channels of serious power but also load invariant, which means the amps can drive the speakers accurately through the very big impedance swings of the electrostatics.  The amps output 200W/8 ohms and 1000W/1 ohm. Tube amps can drive ML’s but not accurately.

Naturally a Supratek preamp is used for controlling all the inputs and presenting them to the DEQX at the correct level and no negative impedance effects.  A Grange preamp with 6H8C/101D DHT triode linestage and E180F, 7308(6922) and 6E6P phono  stage .
Every system should have some tubes in it and the best way to use them is in a preamp that has low output impedance – with a really good design this results in the all the magic and positive attributes of  tubes  without any negatives (the slow, warm sound of traditional old style tube design)

Sources  are phono from a Luxman PD-444 direct drive turntable , with two arms , a Dynavector DV505 arm and a Ortofon SPU cartridge modified by Expert Stylus in London (fantastico!)and a FR-64 with DL-103 cartridge, again modified by Expert Stylus . They replace the cantilevers and diamonds with the very best available and I cant speak highly enough of their work.

Other source is computer audio based – Windows 7 , JRiver Media Centre , exaU2I usb-I2S convertor, Sabre 32 dac, capable of 32bit/384Khz. Files stored on external hard drive- see other blogs for details.

The sound of this system is very dynamic, it can play at very loud levels and stay clean and distortion free, whilst retaining its ability to resolve micro-dynamics.  It loves concert and live recordings as it expresses the sense of aliveness and “being there” in spades.

It is very capable both as an analytical tool and as a source of listening enjoyment. It surprises most people when they hear it as it doesn’t sound like what they are used to,  and it does take some acclimatising to, but I always find my other speakers lacking it’s sense of life and realism.

And with computer control of just about every parameter it can be changed in a instant to suit any mood or recording.

It’s only fault is a very tight sweet spot that makes it a one person speaker.

MOVING COIL  LOUDSPEAKER-PASSIVE CROSSOVER

I have a friend who has a mastering studio- it’s a relatively small room but built solely to sound good(accurate). It has had a lot of acoustical engineering and he’s a clever guy who can understand the considerable physics involved with acoustical engineering. And he’s pretty good with a computer and programs which is essential these days.

The first time I heard this room I was blown away by the sound- I had never heard such good imaging and clarity of tone. I realized most of the magic was coming from the room, but I also realized how good his studio monitors were and I had to get a pair.

The Lipinski L505 is a curious beast- it is a designed to be a full blown studio monitor, which are usually ruthlessly accurate, but this monitor has none of the aggressiveness usually experienced with studio monitors. It’s fantastic imaging properties really shine through and even though it remains very accurate, it has a 3D imaging ability that simply gives a sense of realism that is quite breathtaking, especially in a near perfect listening room. 

This  quote from the Stereophile review:
"While the Lipinski L-707s displayed excellent imaging, extended dynamic range, and translucent mids and highs, their strongest characteristic was their wide, deep soundstage, with an unusual level of spatial resolution for individual orchestral instruments and choral voices." 

Taken from the Lipinski specs we can look  for clues as to why they sound so good.

L-505 Monitor

1. A sealed enclosure tuned for the best impulse response rather than a low-end extension. We strongly believe that various kinds of vented enclosures always cause coloration that does not deliver reference accuracy.

2. Sturdy enclosure made of 1" (25mm) thick MDF with internal bracing to bring unwanted resonance and box coloration to an almost nonexistent level.

3. Stiff Glass Fiber Cone mid-woofers with low dampening rubber surround, diecast chassis, and a low distortion magnet.

4. Neodymium Ring Radiator - super low distortion tweeters with frequency response up to 40kHz and extra wide dispersion.

5. The absence of a grill in front of the tweeter. Our laboratory and listening tests prove that even the most transparent grill fabric causes high frequency comb filtering.

6. An acoustic, rather than an electronic, time-coherence of tweeters.

7. Unique tweeter surrounding. Perfecting the tweeter environment appeared quite possibly to be the most challenging aspect of the design. The goal was to eliminate the edging effect by carefully shaping the tweeter surrounding with specially designed Belgian foam.

Patent pending.

8. A low-order crossover for the best phase response. We also selected the lowest possible crossover point to deliver the best transient response.

9. Premium quality crossover parts. Foil Inductors wound on a wooden core - with their skin effect conductivity - provide performance unmatched by less expensive wire wound coils, and provide much lower coloration than iron core inductors. We also use non-inductive resistors, premium audiophile grade capacitors and special flat, Super OFC internal wires.

10. Matching internal dampening design. Internal dampening is outsourced and precut to absolutely identical shape and weight for the best speaker-to-speaker consistency.

11. Dual, all-brass, gold-plated posts, which accept banana plugs or up to 2 AWG wires.

12. Magnetic Shielding. All our speakers are magnetically shielded for demanding pro video applications.

13. All parameters perfected in anechoic chamber.

I believe the important points are 1,2,6,7 and 8. My own conclusions about loudspeakers is that phase performance is the key to good imaging, soundstaging and that 3D ability to convey width and depth, that delivers the vividness and coherence of a good recording.

Combined with the Lipinski’s inherent accuracy this totals up to a very good moving coil loudspeaker. Somewhat in the mould of the Dunlavey range of monitors, still very highly regarded- anyone got a Sovereign they want to sell?

Unfortunately the L150 subwoofers I bought with the L505 aren’t up to the same level of performance and they have been replaced with a set of JBL active subs.

Pre-amplification is a Supratek Cabernet DHT preamp with 6H8C and 71A dht triode.

The speakers are bi-amped with either a 4 channel load invariant solid state amp or 4 monoblock KT88 100 watters with adjustable positive feedback.

The solid state amps are used for critical/analytical listening and the tube amps rarely when a more romantic , perhaps “musical" sound is fancied.

Input is a MacMini – either PureMusic,Decibel or Audivarna file players, Audiophilleo1 usb-spdif convertor into a Lavrey DA 10 dac. Files are stored in external hard drive.

MOVING COIL LOUDSPEAKER-FULLY ACTIVE

While the Lipinski could be considered to be state of the art for the early 21^st century the AR-LST was considered state of the art back in the late 20^th century.(Laboratory Standard Transducer)

A very unusual speaker, although designed primarily as a studio monitor it was also used as a very high end audiophile speaker .

With 9 drivers per speaker -4 dome midrange, 4 dome tweeters, and 1 10” bass driver  it is capable of a very dynamic performance with a very wide soundstage , at the cost of very high power requirements.

 I was fortunate in that I was able to purchase 2 pairs and stacked as a D'Appolito configuration the sound is very similar to a big stat or ribbon transducer, with very serious bass. The 10" AR bass driver is a beauty, done properly it is very hard to beat the bass of a sealed box.

The only downfall is that one pair of LST is a serious load for any power amp and two pairs require an amplifier that is unique and not so easily available, and you can forget about tube amps completely.

Most of the problem comes from the  complex passive crossovers in the LST, so to bring these speakers into the 21^st century I decided to remove the passives completely and go all active.

This is no small job as the crossovers are quite large and bulky and there was a lot of wiring , however with the crossovers out and a digital active crossover inserted between the preamp and power amps I was keen to see if  I see if I had enhanced or destroyed two pairs of perfectly good speakers.

The first thing I noticed was that the drive requirements were greatly eased- 6 channels of 200 watt each was plenty to drive the two pairs of speakers with the bass, mid and tweeter sections all paralleled . I suspect that 6 channels of strong tube amplification could also work reasonably well.

However replicating the original crossover frequencies and slopes wasn’t entirely satisfactory- 3 way active speakers can take a very long time to dial in as the respective amplitudes, crossover frequencies and filter slopes present a multitude of choices – it can take years  to get it right, and I’m still on the trail to success. 

However it is very apparent that dynamics are much improved, these are explosive speakers  that can output a lot of clean , undistorted power- great for big symphonic recitals.

COAXIAL OR FULL RANGE SPEAKER

Always coloured, only marginally accurate, coaxials tantalise and seduce, but always leave you wondering if there is “more”.  I’ve owned Goodmans Axiom 80’s and Triaxioms, Altec 604, Corals, Lowthers, Fostex, in fact my hi fi enthusiasm started with a pair of Altec 604B and Trimax EL34 UL amps.

I’ve also owned one of the small 10” Tannoy coaxial monitors, but again, like all full range drivers the lack of consistency in the frequency response had me move on to something else.

Recently I heard the 15” Tannoy Gold Monitor drivers and the story of how I finally found a speaker that is happy with tube amps AND is reasonably accurate is here:
http://supratekaudio.blogspot.com/2011/07/3500-for-pair-of-speaker-drivers.html 

HORNS

While I'm here, lets mention horns- like coaxials capable of very good sound, but so damn hard to get right- getting them to seam properly with good integration is very difficult.
This system cost in excess of half a million dollars (and powered by Supratek amps) and is the most impressive system I've heard, not in terms of accuracy, but incredibly dynamic. The bass horn went out the wall and 30 foot long!

Something a bit more affordable for most of us, the best violin reproduction I've heard came from Martin Seddons Azurra horn set up. It seems his horns are just about perfect at the response needed for violins, and you would swear that Nigel Kennedy was in the room. Martin has a very good sounding room, and I think that contributes quite heavily to the sound.
At the end of the day though, horns are just too uneven and disjointed for me, however people with less technical requirements could be very happy with them.

Art Pepper 7 LP Vinyl set

This recording was made using multi-microphones in a straight stereo mix without any noise reduction system, limiting, compression or equalization on either the location or on the transfer of the original master tapes to the lacquers from which the final pressings are made.
Great recording, fantastic conversion to vinyl.
Definitely recommended for both the sound and music performances.
http://www.purepleasurerecords.com

Also enjoying Junior Wells Hoodo Man on Delmark Stereo LP, the sound on this record is extraordinary.

More on Accuracy

So far the response to this blog has been very positive- thanks to those who have appreciated my ramblings thus far.
As I predicted the only negative feedback has been from those who don't value accuracy as the highest aim of "hi-fi", and don't agree with my philosophy on this subject.
The following excerpt is from a review that Jonathon Valin recently did on an expensive Magico speaker.
He is a much more eloquent writer than I am and his piece on accuracy which sets up the review is very interesting. From the Absolute Sound July2011.

Jonathan Valin

If it does nothing else (and it does plenty else), the

Magico Q5—the current top-line, full-range, fourway

dynamic loudspeaker from the Berkeley-based

company that has, over the last four years, shaken up the

status quo in the ultra-high end—cuts straight to the core

of what we mean when we say something is a “highfidelity”

component.

This is the very issue that led to the foundation of this

magazine, and the position that Harry Pearson staked out

almost forty years ago has been a beacon and a bone of

contention ever since. Should “high fidelity” components,

as HP argued, aim to reproduce the sound of acoustic

(i.e., unamplified) instruments as they are heard in life in

a concert or recital hall? Or, in a significant variant of the

absolute sound approach, should they reproduce precisely

what was recorded on the disc, whether that sounds

like the absolute sound (as it ideally should) or not? Or

should they aim at something else again, something far

less prescriptive and more personal? Should they simply

(or perhaps not so simply) consistently please whoever

listens to them?

Although these views aren’t mutually exclusive, over

the years they have typically been cast as if they were,

as if they represented opposing sides in a never-ending

battle between the forces of “realism,” “accuracy,”

and “musicality.” All three positions are rife with

contradictions, all three share certain patches of common

ground, and all three have been “shaped,” like battlefields,

to reflect the prejudices of individual reviewers and

listeners. The absolute sound school, for example, has

trouble dealing with amplified music, such as rock ’n’

roll, which in today’s world makes its proponents seem

old-fogeyish. After all, what is the “absolute sound” of

a Fender Stratocaster or Telecaster? By the same token,

will a speaker that delivers the whomp of a Fender

Precision bass guitar as it sounds at a rock concert via

a Marshall stack also do justice to the pitches, timbres,

and dynamics of an unamplified cello or doublebass? For

that matter, will an “accurate” system tend to make both

Fender bass and cello sound a bit too cold and analytical,

like an unretouched glamour shot?

There is no single answer to these (and a zillion other)

questions that will satisfy all music lovers, which is

precisely why I try to take the biases of different kinds

of listeners into account whenever I write a review. The

way I see it most of us fall into one of three basic groups:

what I call the “absolute sound” listeners (who prefer

music played by acoustical instruments recorded in a real

space, and gear that makes those instruments—no matter

how well or poorly they were recorded—sound more like

“the real thing”); the “fidelity to mastertapes” listeners

(who want their music, acoustical or electronic, to sound

exactly as good or as bad, as lifelike or as phony as the

recording, engineering, and mastering allow); and the “as

you like it” listeners (who care less about the absolute

sound of acoustical instruments in a real space or about

fidelity to mastertapes and simply want their music to

sound some form of “good,” which is to say exciting,

beautiful, forgiving, non-fatiguing). Though I think these

groupings are valid, I also think that no listener is purely

one type or another, i.e., the fidelity to mastertapes listener

also wants his music to sound like the real thing, when the

recording allows; the absolute sound listener wants his music

to sound beautiful, when the music or orchestration allows; the

“as you like it” listener puts excitement and beauty ahead

of fidelity to sources, but is not at all unhappy when those

sources also sound like the real thing as he defines it. What

I haven’t been as clear about, perhaps, is where I stand in

this triumvirate—and why.

I stated my opinion on this crucial topic about twenty

years ago when I wrote a book about RCA recordings,

and in spite of occasional forays into other kinds of

listening I haven’t really changed my mind. Since The

RCA Bible has been out of print for a very long time, let

me quote what I had to say way back when:

“How much of the ‘absolute sound’ of an orchestra

does a microphone really capture? Well, it’s a fact that

microphones differ significantly from the response

of the human ear. Throughout the fifties and into the

sixties Mercury Records, for instance, used German

microphones (Telefunken 201’s and Neumann M 50’s)

with a rising high end. Are Mercury’s ‘living presence’

recordings [from Watford Town Hall] actual transcriptions

of the sound of the LSO with Dorati at the helm, or

are they the products of hot mikes—ones that added a

little upper-midrange sheen and bite to the LSO strings,

winds, and brass—or are they some incalculable blend

of both?

 “Well, you’d have to have been at the Watford Town Hall to

know for sure. And even then, you’d have to have been sitting

where the microphones were placed. And since you don’t hear

in three channels mixed down to two and your chair’s not tall

enough to put you where the mike heads were located and your

ears have a different frequency balance and directional pattern

than mikes, you’d be hearing sounds that were different from

those which the microphones recorded. How different? The

question is unanswerable. On the basis of a recording we can

never know what the LSO ‘really’ sounded like on a particular

afternoon, on a particular piece of music. All we can know is

what the tape heads recorded.”

Twenty years on, I stand by what I wrote. For me high fidelity

means fidelity not to the absolute sound and not to some idealized

sound but to the sound of the mastertapes, which still seems to

me to be the one and only “truth” we’ve got. That this truth is

inevitably a compromise that will be further compromised in

playback is simply the way the recording/playback process works.

To achieve high fidelity as I define it means that the

loudspeakers and everything else in the playback chain need to

“disappear” as sound sources. To accomplish this, they must

be neutral, transparent, high in resolution, seamless in top-tobottom

coherence, low in distortion, and capable of a high degree

of realism rather than romance. As beguiling as such things can

sometimes sound, pieces of gear that impose a beauteous or

exciting or forgiving sonic template on the presentation—and,

thus, don’t disappear—are, in spite of any other virtues, finally

not for me. This doesn’t mean that they aren’t or shouldn’t be for

you. I have no argument with friends and colleagues who prefer

a less “neutral” component, either because they think a more

bespoke presentation makes music more like the real thing (as,

for example, those “absolute sound” types who eq their systems

to roll off the treble and/or boost the bass—or who prefer

equipment that effectively does the same thing because of builtin

dips and boosts in frequency response) or because they think

a romantic presentation makes recorded music more attractive

and, well, “musical.”

What I do have an argument with is calling such presentations

“high fidelity.” By my lights anything that makes you more aware

of the way sources are being colored and distorted by your system

is, ipso facto, less of a true high-fidelity component and more of

a tone control. I don’t want to hear my equipment automatically

adding virtues or subtracting flaws from every record (even

from records that benefit by such additions and subtractions); I

want to hear what is on the recording, good, bad, or indifferent,

because, as I just argued, the recording is the one indisputable

truth that stereo systems can be faithful to. The way I see it,

if you’re unhappy with the sound of the LPs and CDs you’re

playing back, then don’t try to correct the problems with your

stereo system. Instead, go out and buy better records.

My position has had certain undeniable consequences when

it comes to the kind of playback gear I prefer and how I set

it up. While as a reviewer I’ve recommended any number of

different kinds of loudspeakers for different kinds of listeners

(and was sincere in these recommendations), as a civilian I’ve

always owned electrostats, planars, and (occasionally) twoways.

Why? Because they were (and in many respects still are)

the lowest-distortion, lowest-coloration, highest-resolution,

most transparent-to-sources, least-present-in-their-own-right

transducers—the “highest-fidelity” speakers, if you will, by my

standard of high fidelity.