[Mr Rick]

I sure there have been many tests done on the subject. Can someone point me to a couple of the best?

 

[Speedskater]

We can divide tube amplifiers into two groups:
a] Those with an accurate output.
b] Those with euphonic coloration.
 
The accurate tube amplifiers when playing into reasonable loudspeakers under reasonable conditions will sound just like accurate SS amplifiers.
The euphonic tube amplifiers will sound - well they will sound euphonic.

 

[limpidglitch]

One of my favourites, The Carver Challenge.

 

[Mr Rick]

Thanks guys. I've also found the 'myths busting ' thread. That should keep me busy. LOL

 

[Vernon D]

Some may remember the work done by Peter Walker of QUAD in establishing that there is no measurable or perceptible difference between well- designed and manufactured valve and solid state amplifiers.
 
Here is a link to another forum where his work is discussed , as well as scans of some of the articles from that time.
 
(There are probably better sources for this information elsewhere)
 
http://www.vintage-radio.net/forum/showthread.php?t=65423
 
Yet we still see people ascribing the visual aspects of their equipment to the auditory performance of the equipment- valves "sound" spacious and "sound" warm - reflecting the physical volume of the valves and the glow of their internal components. 

 

[davidsh]

Same thing with cables. That screechy silver sure needs some gold for mellowing the highs. But copper is overly warm and closed in etc. etc.

 

[Mr Rick]

I love this quote from a recent review of the Cavalli Liquid Crimson Headphone Amplifier.
 
Eric Neff asked the question of designer Alex Cavalli.
 
 
"EN: What is your design philosophy? How would you describe the Cavalli Audio sound?
 
AC: My amps have similar character. I actually try to build amps that sound like nothing. My amps are designed to pass the signal through as transparently as possible. No Color. What typically happens to my amps is people realize that their system chain may not be as solid as they had thought. These amps will expose any weakness. Given a great recording and equipment chain you will get what you are seeking."
 

 

[441879]

I have been reading a lot of threads on tube amps and headphone pairing. Per various reviews, tubes can add euphoric coloration which can work well with the right headphone. I was intrigued, but Not enough to spend $300 up on a tube amp without hearing the sound. To get some insight, I loaded some tube amp plug ins into VST and played around with the sound. So far I haven't found a sound I like better than just straight through with no effect. The main problem is that noticeable tube coloration is accompnied with noticeable distortion. Is this the case with real tube amps too?

 

[Pio2001]

Hi,
There was such a blind test published by Sound and Vision mag. It was available as a file named ampspeakerinterface.pdf, but it doesn't seem to be online anymore.
 
The result of the blind test was that the listeners could distinguish the transistor amplifier from the valve amplifier if the test was done with speakers whose impedance varies significantly across the frequency range, for example 3 to 20 ohms.
The listeners could not distinguish the two same amplifiers on speakers whose impedance remains high over the whole frequency range (with a minimum above 6 ohms or more).
 
The test came with measurements showing the frequency response of both amplifiers. The frequency response of the valve amplifier was significantly altered when the low impedance speaker was connected. Much less when the high impedance speaker was connected, and not at all with a pure resistance of 8 ohms. The transistor amplifier had a flat frequency response in all cases.
 
Thus, the results of the blind test matched the measurements.

 

[jcx]

you can read a bit on the history, "hi fidelity" tube amps of the 50's were push-pull with power Pentodes with considerable loop gain, explicitly applied negative feedback
 
but the Audiophile storied modern tube amp is Single Ended Triode - often with no audio frequency negative feedback beyond that built into Triodes (internal negative feedback from the Plate V is responsible for low Plate Resistance and the internal negative feedback is why Triodes have low mu, Voltage Amplification factor - but you should see antifeedback SET lovers sputter when this is pointed out)
 
properly designed and biased, Push-Pull amps cancel even harmonic distortion even before the explicit negative feedgback further reduces distortion
 
SET often have 2nd harmonic distortion dominating
 
so there is a big divide even among "Tube Amps"
 
 
more locally, interesting read is http://www.head-fi.org/t/701900/schiit-happened-the-story-of-the-worlds-most-improbable-start-up/9000#post_12153256
 
of course I read it a bit differently than I think intended
 
the 1st issue is why the "engineer" never thought what any in my experience would about the Marketing "requirements"
 
hm, this guy sez he "needs" a tube, discrete hybrid to sell at a price point - what happened to the Audio Performance Spec? don't his customers actually care about "The Sound"
 
while skeptical that there is a "formula" - lets play along - shouldn't Marketing be asking for a circuit, (at a price point is inevitable and a legit input to Engineering) that sounds as much as possible like some specific tube amp, or has some identifiable "tube sound"?
 
 
what makes it a fun read is the engineering commentary on all the detailed compromises needed to make it cheap, and have a tube - in fact explaining why it won't "sound like" a Audiophile revered 80's Japanese SET with 845 or 300B tube running at 400+ V, 80 mA with exotic output transformers that alone would cost the finished price point asked for
 
but it will have a tube that can be "rolled", and apparently its possible to get away with discrete SS parts in the Marketing Story without losing too many of the marks
 
it "Sounds" to me like "The Story", a tube, tube rolling, discrete SS are all that really matters - whether it in fact it actually has any "sound" character in common with those storied Japanese SET loudspeaker amps is never addressed

 

[Frihed89]

I have 4 different speaker amps (12V6/1626 SET, 45 SET, 300B SET, Class A triode wired pentode PP and 2 1 SS and 1 2A3 SET) headphone amps.  If my wife ties me to chair and plays the same music for 5 minutes on each of the 4 and 2, I can't tell the difference.  But from years of listening, I can tell you exactly which amp i prefer on specific music and why.
 
I am not the only one to come to this conclusion.

 

[watchnerd]

  I sure there have been many tests done on the subject. Can someone point me to a couple of the best?

 
Many tests have been done.
 
Which specific question are you trying to ask?

 

[Baxide]

  Some may remember the work done by Peter Walker of QUAD in establishing that there is no measurable or perceptible difference between well- designed and manufactured valve and solid state amplifiers.

There is a difference between measurable difference and audible difference. Measurements are also generally taken from a repeating sinewave, which is consistent in its distortion figures due to the feedback correction within the amp under test. But to get a far better idea of differences, you have to use waveforms that are not constant and even in nature. Like a pulse of 1K at say  1 second intervals. By observing what happens at the output of the amp between the period when no signal is supposed to be present, the differences start to show up on a scope.

 

[sinesweep]

You can make a SS amp distort like a Tube amp. The 2 are different in their distortion characteristics and noise floor. Given a certain volume level (tolerance), it is near impossible to distinguish in a double blind test. You can immediately tell when they reach their boundary conditions since Noise floor and distortion levels of a TUBE amp will reveal itself. 

 

[FunkyMonkey909]

I highly recommend Stephan Micus, the visionary multi-instrumentalist recording for ECM records. Start with "The Garden of Mirrors" album (very accessible imo), you will be amazed.