What is the "Tube Sound"?

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#381
andyjevans said:
I’m getting the impression that much of the failure to communicate and understand views effectively on this thread comes from the fact that we are talking about a number of different and distinct processes.

If we assume that the “subject” under consideration is the typical DIY Audio amplifier builder and that “acoustical” in this case refers to “that which is listened to” (from akoustos: "heard, audible") then we have these processes:

Process 1. Acoustical input > memory > acoustical output.
Here the subject is motivated to re-create a listening experience which is compared to the memory of the original listening experience. This has poor reliability because each stage is highly fallible, but it has good face validity. Face validity here is “subjectively viewed as covering the concept it purports to measure”. Listener experiences would be of the kind that subjectively states “to me it sounds real”.

Process 2. Acoustical input > acoustical output.
Here the subject listens to live instruments (in a DBT test if you like) and compares them with a recorded reproduction of the same instruments in the same space. Though this has eliminated the memory stage, this still has poor reliability but again good face validity.

Process 3. Electronic input > acoustical output.
Here the subject listens to a recorded reproduction which is compared with measurements of the electronic input to the amplification system. In this case we have dramatically improved reliability on the input end which permits a number of inferences to be made. But though we have improved reliability we now have poor face validity. For the subject under test this is not “subjectively viewed as covering the concept it purports to measure”.

In none of these processes do we have both high reliability and high face validity, which may explain why nobody has answered the original question posed – how do we get a mathematical model of what a listener perceives as “tube sound”. We have any number of inferences based on mathematical models of electronic inputs and outputs but these remain on the level of inferences.
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Fiction based opinion again. 🙄 Why? Do you think if you repeat 1+1=1.5 many times, it will become the right answer?
 
#382
cnpope said:
I think the debates only become theological because some people are intent upon blurring the lines between what is measurable and quantifiable on the one hand, and what is subjective opinion and preference on the other.

You say "the notion that we can achieve wire with gain is laughably deluded." In the sense that there is no such thing as a "perfect" amplifier, you are, in a rather trivial sense, correct. But what really matters is whether the amplifier can be made accurate enough that for all practical purposes it behaves as a "wire with gain." Measurements can be made with great enough accuracy that this can be an answerable question. If, for example, measurements show that the output, driving into the loudspeaker load, is simply a pure constant multiple of the input voltage to within an error of X nanovolts, and if the threshold of human hearing would correspond to a signal level of 1000X nanovolts, then it is safe to assert that the amplifier is behaving, for all practical purposes, as a pure "wire with gain," in the sense that it would not be humanly possibly to hear the difference.

It seems to me that you are trying to hide behind the "nothing in this world is absolute, so therefore we can never actually say anything" kind of thinking. This is just a lazy excuse for not confronting the difference between decidable questions and undecidable ones.

Another example concerns what we hear. If you say "I prefer listening to this particular amplifier, because it makes me feel more in touch with the music," then that is fine, and no one can argue against it. But if you say "I can hear a clear difference between amplifier A and amplifier B," then that becomes an objectively testable assertion. It can be tested by means of double-blind comparisons. If these confirm that you can reliably distinguish A from B, then your assertion is validated. If on the other hand you fail to be able to discriminate between A and B in the tests, then your assertion is proven false.

The topic of this thread concerns whether there is a distinctive "tube sound." Interpretations of what this actually means differ as to whether a distinctive difference that is merely the result of "trivial" and easily quantifiable effects like output impedance and frequency response count as "tube sound" or not. But it is a perfectly reasonable question to ask whether a solid state amplifier with a few resistors and capacitors added in order to match the output impedance and frequency repsonse of a tube amplifier will be distinguishable or not. And this is a perfectly decidable question, that can be settled by means of double-blind testing.

Chris
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Thank you for the well written explanation. I'm afraid it will be in vein though. I mean, the conclusion has been reached on 3rd page of this thread but look at the tirade still coming through.
 
#384
Evenharmonics said:
I didn't expect to see a forum moderator play spin.
and you've been spinning it ever since.
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Again, I don't know what you mean. You seem frustrated with me because I'm not answering your questions the way you want. Is that spin? But honestly, I simply don't understand much of what you are asking. Like the sound waves thru and amp and such - I just don't know what you mean. 😕

What I've tried to do is express my point of view and my experience. I've tried to explain that they may be different from yours. If your only definition of Hi-Fi is no alteration to the signal, OK, I understand, it's a common one. It's not the only one tho, that's my point.

As for moderators, please remember that we are forum members too. If you don't see the cop hat, we are simply posting as forum members, just like anyone else. (That is sorta explained on the Rules page).
 
#385
hpeter said:
this is answer from person which continuously argues on many threads about precise numbers and precise measurements?
i am disappoint...🙂
don´t tell me we´re back to "wire with gain" again
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That is because it has been established by tests-by-the-hundred what most normal folks are capable of hearing and what not. That is the purpose of 'modelling' something not directly and repeatedly available when required, so that one is able to base one's further research/test results on reality.

Where such a model has become established/available, one then does use numbers and measurements to check one's work. Why do you find this disappointing when it is the basis of all scientific work?
 
#387
I would also agree with Chris Pope's post #374, without repeating the contents here. (On the previous 'page'.)
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andyjevans said:
I see amplifiers as being on a similar scale. NONE are identical to the original sound, therefore they are ALL on a scale of "effects-ness" somewhere, however small the distortions.
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Andy,

Not singling you out here, just using your statement of what others have also contended, pointing to me to some of the problems we have here. (I re-affirm my respect and envy for the line of work you are involved in and what you have achieved.)

We will be forever rowing about in this sea with many very laudable thoughts, if we do not limit the subject to what is relevant here and agree on some phrases, however incomplete in their content. (In the latter context I really think we should no longer quote equalisations as 'distorting' the signal? It is hopefully agreed on what is meant by 'distortion'?)

Back to the 'identicalness' of an amplifier's rendering of an output to the input: "All on a scale of effects-ness somewhere, however small the distortions." Oh sure - if you mean that the output of an amplifier with distortion of 0,000005% is different from the input .....

We have to do with audibility of effects-ness, not perfection. And I do hope that by now folks are in agreement about the effect of magnitudes of various harmonics etc. etc. (If not, that is another subject, if still necessary.) In that sense it is simply possible to design valve and ss amplifiers that are 'blameless', which as a concept I accept is by now understood.

But whether such were the models various individuals based their judgment on? That is the question (as the worthy Shakespear said). I cannot condemn specific models; my purse is sadly incapable of supporting the purchase of umpteen amplifiers and comparison of the same. It is clear from analyses, a.o. by 'Stereophile', that there exist many amplifiers which cannot be classified as blameless. That can only compromise honest assertions of what is experienced.

Then I detect some misconceptions in beliefs:

1. 'Valve amplifiers are under-damped, ss ones over-damped.' Not necessarily. This concept is due to the invalidity of the term 'damping factor' as a measure of loudspeaker control - it can be easily shown that a d.f. of some > 20 has little if any effect on response. It is also possible for any half-decent valve amplifier to have a d.f. (per the definition) of > 20. (The Williamson and Leak is over 30; my own 40W valve design has a d.f of >100 ....)

2. 'The output transformer is the weak point of any valve amplifier'. No, many good OPTs have lower distortion than the power valves and bandwidths of better than 30Hz - 40kHz.)

3. The 'pure class A' fallacy, vs. 'cross-over distortion inherent in class AB operation". No; it can be shown that proper class AB design is as 'pure' as class A; the latter is not necessarily distortion-free. And the cross-over phenomenon has been cured decades ago; it should no longer exist.

Etc. - I am way off-topic, but I read arguments based on the above in some comments on this thread. My point: Unless we come closer to what constitues reality, the arguments can all be informative (as has been the case up to now - for me at least ....) - but the 'real-world' scene (a phrase repeatedly used here) will not emerge. That is, whether an amplifier of whatever topology must necessarily have an audible character/footprint, whether there is necessarily tube-sound and transistor-sound, or whether these exist (and I have no doubt that they do) because in some small way practical amplifiers have not succeeded in eliminating such.

Whether valve sound (or any 'sound' for that matter) can be modelled ... Yes, by way of what can be measured and judged to be of meaning in the light of existing knowledge. What is appealing: As said by many, that is everybody's preference and right to such; only that answer would include a multitude of variations.
 
#388
fas42 said:
Interesting that all amplifiers are the 'same', but all speakers are 'very different' ... 😉.
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No, it's not. It may be factual and utterly obvious to the non-deaf, but it is not particularly interesting that loudspeakers can be very different from one another. Nor is it particularly interesting that when amps are different from one another, the difference rarely boils down to anything but mismatched levels, noise, or source impedance. It's just common sense at this point.

fas42 said:
Well, I have listened to hundreds of "real" speakers over the years, and on the basis of what they sounded like at that moment and on the 'assumption' that all the SQ issues I could hear are solely due to the speakers misbehaving, then for the vast majority I would be happy to biff them into the rubbish bin by the back door ... 🙂
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Yes, in the real world the quality of the speakers and/or their setup in the room accounts and/or your listening position accounts for most of that.

fas42 said:
And, the behaviour of an amplifier is a multi-dimensional thing ... which is the 'subtle' point I was trying to make ... 🙂
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"Wrong" and "subtle" are not synonyms.

TiMBoZ said:
*** it reminded me 'sonically' of an old Marshall stack.
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That might partially be the amps if they're very low power and/or the speakers are inefficient and you're playing the system loudly.

I hear the same thing in my car with the system loud. Yet the amps are solid state (Class H) low output impedance devices with flat FR from about 5-40k Hz!

Then why does it sound like an old Marshall stack? Because the 2" widebanders I use from 800Hz up (Aura Whispers) have a distortion profile quite similar to a slightly overdriven tube amp when pushed hard.

It's a lovely effect with the top down, hands on the wood steering wheel, shoes dancing between three pedals, and the wind in my hair!

cliffforrest said:
"I say, go listen to your amps ...."

Why not go listen (sic) to some music?
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Indeed!

I always wonder how people "listen" to their amps. Do they strike them with a mallet or a pair of drumsticks? Drop them on a gong? Whip them with their magic freeze-dried (sorry "cryo-treated") wires?

Newsflash: if an amp makes sound on its own, it's either broken or a POS to start with.
 
#389
*** it reminded me 'sonically' of an old Marshall stack.
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The sound, the 'presentation' of the PP mono blocks was similarly lean, and a bit 'glassy/edgy/forward' in the trebles. There was an underlying 'vibe' that was reminiscent of my experience with the Marshall SL 100 - it was a beast

It occurred to me at the time I was listening to the hi-fi amps.

I have no interest, there's no logic in making any connection. So why did it occur to me?...'Hey these sound (have a flavour) a bit like that old Marshall. WTF?'

If that isn't an example of 'tube sound' I dunno what is.
 
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#391
Ok here's another audiophile imagining..

My everyday, integrated amp, has a 6922 tube buffer or driver on the input, but you can bi-pass this and go straight into the S.S power stage also.

Listening via the tube buffer, and volume control - the amp has a fraction more upper bass, BUT also suffers a slight loss of immediacy (relative to inputting directly into the power stage from DAC). This slight loss of immediacy also translates into a sense of the amp being a bit more laid back, more relaxed, more docile. Generally speaking, I prefer the tube bi-passed.

NOTE: You hear 'the amp has a fraction more upper bass, BUT also suffers a slight loss of immediacy' in the 1st minute after switching over

But you don't hear the amp 'being a bit more laid back, more relaxed, more docile, a vaguely organic vibe that seems to align nicely, most notably with reggae music' until after about a week or two

With the tube bi-pased the reggae music has a sense of being 'mechanical' 'automated' 'synthetic'

Tube sound
 
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#392
You're talking there of the dilemma between getting more of the recording through with the possibility, or more typically the likelihood, of extra distortion artifacts being generated and audible, versus discarding elements of the sound entirely, making it 'simpler' and less prone to being audibly disturbing in some way.

A tired car analogy: 50's boulevarde cruiser with marshmallow suspension compared with an Italian sports machine from the same era ...
 
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#394
TiMBoZ said:
My everyday, integrated amp, has a 6922 tube buffer or driver on the input, but you can bi-pass this and go straight into the S.S power stage also.

Listening via the tube buffer, and volume control - the amp has a fraction more upper bass, BUT also suffers a slight loss of immediacy (relative to inputting directly into the power stage from DAC). This slight loss of immediacy also translates into a sense of the amp being a bit more laid back, more relaxed, more docile. Generally speaking, I prefer the tube bi-passed.
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Don't tell me, let me guess: the tube buffer stage (cathode follower?) is run from quite a low supply rail, even for a 6922, or at a poor bias point? Hence its main function is to add a little low order distortion.
 
#400
gk7 said:
Just google it. As long as the amplifiers under test are not faulty or driven into clipping they sound all the same in a DBT this has been shown numerous times.
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No, that's not correct, but at least you've added some of the necessary qualifiers. Different output impedance, different noise, different frequency response, different stability, all those (and probably a few more mundane parameters) can absolutely make an audible difference under ears-only conditions.
 
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