Which one to choose between two 80K$ tube amps?


There are two interesting 80K$ tube amps on sale at Audiogon.

https://www.audiogon.com/listings/lis9jhj0-david-berning-co-211-845-otl-tube

The first one is David Berning OTL design with output of 60 Watts.

it looks beautiful. But I had never used OTL amp yet.

I am curious how it sounds with high efficiency speaker.

https://www.audiogon.com/listings/lisa27ii-jadis-ja800-flagship-tube-amplifier-six-chassis-best-ever-made-nos-new-old-stock-tube

The second one is Jadis JA800 with 6 pieces and 400watts.

I had used JA500  (only 4 pieces with 350 Watts) from 2000 to 2002 to drive B&W Notilus 801 with utmost authority and unbelievable slam.

It was kind of lifetime experience to own this beautiful and overbearing monster.

But I could not use it during summer time in modest size room.

Thus I let it go and got Silbatone 300B SET amp to drive efficient full range speaker.

350 Watt to 8 Watt

If you have money or hit the Jackpot, which one will you go for?




shkong78

The sound of amplifiers is FAR more than the topology employed, the tubes running in the amp, the parts chosen, etc.  The designer voices their gear for a particular sound, and then there is the matter of how the gear plays with the rest of the system.  I have not heard this very upscale Berning amp, but I've heard many other amps of theirs.  I appreciate what they do very well--clarity, great dynamics, vivid sound, but for my personal taste, his gear sounds a bit too lean.  It is certainly NOT in the same camp as original Western Electric if that is what you are trying to achieve. 

Some of the highly sought after Western Electric amps, such as their 300B SET amp, their pushpull 300B amp have crossed the $100k boundary for a pair.  Their 252 amp has probably crossed $300k for a pair (these sound fantastic).  But, one can still find their 350B amps, like the model 124, or their 349 tube amp (model 133) for less than $100k.  Clones of the 124 amp using genuine Western Electric parts can achieve truly great sound.

A very interesting practice that is more common in Japan is using booster amps between the linestage and the power amp.  These booster amps typically have a 600 ohm output transformer.  The gain of the downstream amp has to be modified to work well with the booster, but, when this is done correctly, the sound is amazing--very vivid, the soundstage becomes very big, particularly front to back (the sound is enveloping), and dynamics is much improved.  When placed in the right system and done correctly, a booster amp does more than anything else I know of to improve the sound.  In particular, they seem to give a lot of kick to otherwise somewhat polite 300B amps.  I have heard BIG improvements with boosters as low priced as $6,000, but the best boosters I've heard were clones of Western Electric 133 amps that utilize genuine Western Electric 618 input transformers and 171C output transformers (pricey combination).  Use of booster amps was also a common practice of Western Electric and some of their best amplifiers had booster stages built into the amp itself (like the model 59 that runs the 252 tube).

The designer voices their gear for a particular sound

@larryi I hear audiophiles talk about this, but I've yet to come across a designer who actually does that. If they do, I would regard them as incompetent. As far as I know they don't; I certainly don't!

Most SETs are something called 'series fed' which is to say the output transformer is in series with the output tube and power supply. This arrangement causes a DC magnetic field to be present in the output transformer; if left to its own devices this would cause excessive distortion since the core of the output transformer would be saturated. 

So a gap is introduced to the core, which mostly eliminates the DC saturation problem thus eliminating the distortion it would otherwise cause, but it comes at a price. That price is the inductance (the property that makes any transformer work the way it does) is reduced at lower frequencies in the audio band. 

This is the 'bass problem' most SETs have. To combat this, most SETs have much larger output transformers than they would normally need for the power they make, in an effort to keep the inductance up. But there's a limit because larger output transformers can't do highs as well. The lack of inductance at lower frequencies causes the amp to make a lot of distortion (as essentially it clips at those frequencies) and also heats up the power tube unnecessarily (IOW its hard on the power tube). 

Western Electric solved this problem before WW2 by designing something called a 'parallel feed' circuit (often known as 'parafeed' as opposed to series fed). In this circuit the plate load of the power tube is a choke that won't allow audio frequencies through it. The audio is then passed through a coupling capacitor to the output transformer. Since it does not have to deal with DC current, that output transformer can be much smaller and yet will allow the amp to make full power at 20Hz, something most SETs have no prayer for.

Western Electric's new SET is a parafeed. 

Of course the Berning amplifier side steps this problem as well. 

I know several builders who do voice their amps by the choice of parts and do not necessarily choose the parts with the best specifications.  One electrical engineer who, as a hobby, has been building all sorts of tube gear, including his own design for OTL amps recently began building for a local dealer.  The dealer supplied the parts, but he substituted the “crappy” carbon composition resistors for better modern alternatives and did the same with some capacitors.  The results were disappointing to the shop owner (and to me), but fortunately, easily fixed by using the parts supplied by the shop owner.  The engineer told me he had to adjust his way of thinking and agrees that the sound is much better even though the parts aren’t don’t measure as well.  He also discovered that the pushpull design he had been asked to build had slightly different gain between the two phases which introduced second order distortion; when he corrected this, the amp sounded not as good and he had to make another adjustment to his way of thinking.  
 

Musical electronic instrument makers constantly chase different parts and tubes to achieve the sound they want.  
 

If it were only a matter of sound engineering, as determined by measured performance, practical perfection has been achieved a long time ago; we would all be buying Halcro amps and loving that dry, dead, and analytical sound.