Re: [ARSCLIST] Stereo records.

[phillip holmes <insuranceman@xxxxxxxxxx>]

Several reputable engineers have proven that a triode tube is inherently 
more linear than a transistor.  That is, a triode is much more acceptable 
without feedback than a transistor without feedback. They tested tubes like 
the 6sn7, 37, 101, and the like.  Transformer coupled, they produce very low 
distortion of any kind, can last 20,000 hours and have very few parts.  The 
reason you don't see much transformer coupled designs like this is that they 
were very expensive to build.  Good input and interstage transformers have 
always been hard to produce.  But that doesn't mean in the real world you're 
going to use archaic single ended circuits with zero feedback.

Tubes produce more even order harmonic distortion.  On the other hand, if 
you have push-pull tubes, the even order harmonic distortion is often 
canceled out more than the odd harmonic distortion, subjectively a less 
pleasing sound.  Psychoacoustic research has shown that people will accept 
even ordered distortion much more so than odd ordered harmonics.  I don't 
much mind harmonic distortion as much as IM/TIM distortion and the problems 
associated with too much overall loop feedback.  I've heard class A single 
ended transistor amps that sound like tube amps (but with drive!).  They had 
zero feedback, fewer stages, and predominantly 2nd, 3rd and 4th harmonic 
distortion.  The measured harmonic distortion was close to .5%, but 
SUBJECTIVELY, the sound was cleaner than that of the transistor amp with 
more stages, tons of feedback, push-pull complimentary, bells and whistles. 
I think the single ended class A transistor amp also clips and compresses 
more naturally than does a complicated amp.  Feedback can only do so much 
before it falls apart.  With a simple circuit, it just compresses and 
saturates.  But none of this can hold a candle to the awful distortion when 
you screw up digital.

Those field coil power supplies cost more than most transistor amps.  The 
permalloy and nickel cores are 'spensive!
Phillip

I wonder what some of you will think of this: 
http://cygnus.ipal.org/mirror/www.passlabs.com/seclassa.htm
----- Original Message ----- 
From: "steven c" > Two thoughts...
> 1) The whole point of using tube amplifiers is the fact that what 
> distortion
> they do create is much more pleasant to listen to than the distortion
> of solid-state amplifiers (in fact, it may be that tube amps need to
> be driven slightly into distortion to produce their desired sound!).
> As a blues harmonica player, I WANT an overdriven, distorted sound...
> and, as a result, have to use small tube amps (I can overdrive my
> only solid-state amp, but the results grate on my nerves!). I would
> assume this is because an overdriven tube amp produces a distorted
> waveform, but NOT one resembling a square wave (tubes approach
> cut-off gradually)...while an overdriven tranistor simply goes
> so far and no farther, producing pseudo-square wave output?!
>
> 2) It would seem to me that if field coils are being used as they
> once were (they were also the filter chokes for the B+ supply)...
> using them would lead to problems with audible hum? Of course, for
> $15,000 they could afford to provide a filtered-DC supply for the
> field coil(s)...
>
> Steven C. Barr