Yes..but is it just the speaker? I think it could very well be the amplifier as well..generally transistor or pushpull amplifiers often sound worst when not working hard..(maybe because the crossover distortion has more of an influence when playing at lower levels?) and actually sound better when it is really working hard.
Whereas your typical SE tube amp sounds best at low volumes but worse when asked to do hard duty.
There is anecdotal evidence (which is as good as no evidence..but I find it to be true) that CD's also sound crappy at low levels and better when louder. Whereas this is less evident with LP's.
What's it all about,.............................. Alfie? 🙂
Why do different circuit topologies sound different, even when the same tube is used and the circuits measure similarly?
The more iron I put in my preamp, the better it sounds. Why?
Actually, I don't care, and probably wouldn't understand the explanations that anyone here would have to offer - but it brings up the point that, with a little research and a bit of copying, a fool such as myself can build a tube-based phono and linestage that would be prohibitively expensive to purchase as a commercial product.
That's why I find myself here... reading this thread.
Why do different circuit topologies sound different, even when the same tube is used and the circuits measure similarly?
The more iron I put in my preamp, the better it sounds. Why?
Actually, I don't care, and probably wouldn't understand the explanations that anyone here would have to offer - but it brings up the point that, with a little research and a bit of copying, a fool such as myself can build a tube-based phono and linestage that would be prohibitively expensive to purchase as a commercial product.
That's why I find myself here... reading this thread.
Geddes's papers don't quite say that. What they say (and what I agree with fully) is that there's no correlation below a certain threshold , and that a more sophisticated metric is necessary. Gordon Holt said the same thing 40 years ago...
We tend to measure amplifiers in a relatively sterile environment. We use steady state signals and non-inductive resistive loads. We would not get much listening satisfaction from 1KHz sinusoids. The distortion characteristics of an amplifier will be different with real music and real speakers. We are just beginning to learn how to measure distortion under these conditions. I suspect we will discover all sorts of time variant effects that are dependent on the amplifier, the speaker, and the test signal.
Exactly Sy. The differing views over Geddes itself is a perfect example of where imperfect knowledge is the cause of the "problem", not the knowledge itself.
For example:
"THD" is not the problem. Measuring THD at only one data point (1kHz), and then using it to compare and rate amps is the problem. We don't need another metric.
"Frequency response" is not the problem. Measuring frequency response at 100mW output into a resistor, and then using it to compare and rate amps is the problem. We don't need another metric.
I could go on for all the other measurements, but you get the idea. A fundamental understanding of the test itself, its limitations and relevance, is necessary before any conclusions can be drawn from its results.
I'm reminded of Tomer's book, where he shows failure curves for the same batch of tubes put through several styles of tube tester. They're of course wildly different. Imagine the tube testers are all black boxes. Imagine the arguments.
Joel
Exactly...
The folks who use THD to point at the "distortion" of tubes, most definately need another metric, because it just does not compute.
People who don't like SE tube amps because the don't rock on their dynaudio speakers...now they is talking sense.
But to be fair, Bas, engineering, numbers-oriented guys look beyond that single number, at least they have since the days of Chevys with tail-fins. JAES papers bristle with sophisticated measurements. Even The Audio Critic, which routinely criticizes tube technology, uses a pretty broad measurement palette, including one that hardly anyone else bothers with, overload performance with varying complex loads. Their criticism of tubes (justifiably) goes well byond simple single-frequency THD; they cite broadband THD, IM, overload performance, noise, stability, source impedance, slew rate, bandwidth, phase shift, efficiency, reliability... And they're right. Nonetheless, with reasonable care, it's not hard to make tube electronics whose output cannot be audibly distinguished from input in a controlled listening test, so I can't buy the argument of "added distortion" as a universal (though in many cases, especially the SET craze, that IS one of the reasons).
Now, as a rather hard-nosed rationalist, I have to ask myself, why do I use tubes? Why do other hard-nosed rationalists (like the poor guy who started the thread) continue to use tubes? What's the special quality that well-engineered tube designs have that well-engineered solid state amps don't?
I think the answer will not come out of work like Geddes', no matter how excellent and useful it otherwise is.
Now, as a rather hard-nosed rationalist, I have to ask myself, why do I use tubes? Why do other hard-nosed rationalists (like the poor guy who started the thread) continue to use tubes? What's the special quality that well-engineered tube designs have that well-engineered solid state amps don't?
I think the answer will not come out of work like Geddes', no matter how excellent and useful it otherwise is.
Ahh, late to the topic again!
Don't want to detract from where the course of this thread is naturally taking itself, but I was interested in the earlier comments about the prevalance/importance of 2nd harmonics.
Mainly because I'm thinking of building the Morgan Jones balanced pre (or variant) at some point. So the cancelation of 2nd harmonics in this instace is obviously bothersome...
Of course reviews (for what they're worth) of balanced tube products (e.g. BAT, Atma-sphere, et. al.) aren't disparaging at all. But I guess that only the building of two similar products with care would be able to tell for sure.
I mightn't have been that clear; my point was that if 2nd harmonic was the tell-all for us tube lovers then we wouldn't expect to find balanced circuits having a following from some fellow tube-o-philes.
Don't want to detract from where the course of this thread is naturally taking itself, but I was interested in the earlier comments about the prevalance/importance of 2nd harmonics.
Mainly because I'm thinking of building the Morgan Jones balanced pre (or variant) at some point. So the cancelation of 2nd harmonics in this instace is obviously bothersome...
Of course reviews (for what they're worth) of balanced tube products (e.g. BAT, Atma-sphere, et. al.) aren't disparaging at all. But I guess that only the building of two similar products with care would be able to tell for sure.
I mightn't have been that clear; my point was that if 2nd harmonic was the tell-all for us tube lovers then we wouldn't expect to find balanced circuits having a following from some fellow tube-o-philes.
Despite my 'newbie designer' status, (*cough*avatar*cough*) I'd have to agree with this too. Unless there is some new kind of 'distortion' we're yet to discover (akin to the 'discovery' of TIM after THD), then if the stedy-state metrics that we know today still aren't telling us the sonic story, then it stands to reason that it's possibly something to do with the plethora of dynamic interactions that are occouring.tubelab.com said:
I agree with everything (apart from the bandwidth and reliability (my 6c41c SET amp went way past 100kHz..not that I think it matters all that much )
everything up to the part where the added distortion is what the SET folks like. Most SET users with sense use efficient loudspeakers. And use less than 1 watt of power..and to use but one 300B amp's specs because they have been measured..(Axiom) 1 Watt = THD 0.042% which is below the "threshold" I just cannot see the sense in the tube colouration argument.
Background: I have the privilege of working in an analytical chemistry laboratory where we routinely run transient laser experiments on nanosecond timescales. Signal amplification, whether it originates from a photomultiplier tube, CCD, photodiode array, or any other device, is an area where my job depends on accurately amplifying data without introducing noise. Based on this experience, I posit that accurate amplification maintains all of the original characteristics of the original signal, boosting only the information contained on that signal. Any addition of harmonics, any deformation of waveforms, any distortion of timescales, or any other augmentation of the original signal in ANY way that does not ACCURATELY mimic the original signal. I would posit that these are DISTORTIONS to the original signal.planet10 said:
Typical signals in my lab must be amplified by factors of 1000 or more to even be detectable on most DAQ cards (often times more). If I use amps for my instrumentation that introduce noise, then my peer-reviewed papers get shot back to me without a second glance. I have at my disposal a large array of measurement equipment which can accurately determine the level of noise introduced into a device by amplification equipment (our in-house electronics shop is rather well equipped!) Without exception, our amplifiers are op-amp based. There has never been a triode, nor any type of vacuum tube in my laboratory since I have worked here. This is not due to durability issues, voltage issues, nor cost issues, rather this is due to the fact that every vacuum tubes are not clean amplifiers when compared to solid state circuitry.
I will readily admit the straw man argument that our signals are very low voltage and current, and that at the higher powers needed to drive speakers the chips I am most familiar with are not used. However, I would make a general statement that the criteria I use for amps in my lab carry over to amps for use in audio amplification. Based on these criteria, I would again posit that tube based amps are not ACCURATE amplification stages.
And I would again add that if you LIKE the distortion, feel it decompresses the music somehow, you like the glow, the nostalgia, I get it!!! I love old furniture that sucks from a practicality standpoint, but I love the craftsmanship, the smell, and the feel of old wood! There is no way that it is practical, nor that it is as technically well made as most of the stuff you can buy today, but it is my preference! I would never try and tell someone that my furniture is perfect, but for some reason we still get hung up on this subject with tube amps!
The issue of harmonic distortion, and the particular harmonic involved, being so contentious... I just can't resist confusing things further.
Walk up to any piano in good tune. Play any note in the middle of the keys and listen (the fundamental). Now strike a note exactly one octave higher and listen (the second harmonic). Now strike both both notes in unison. You will hear. and very clearly in fact, the third harmonic. This percieved note is not produced by the piano. In fact, if you play the third harmonic, a "musical fifth" above the higest note in the octave, you will find the note on the keyboard to be a wee bit flat. This is because pianos are tuned "tempered"; meaning the 3rd harmonic is dialed in at 2.9966 times the fundamental.
The point here is that in the presence of a strong 2nd harmonic, our ears/mind insert the 3rd.
This can be repeated with sine generators as well...
Curiouser and curiouser...
😕 😕
Walk up to any piano in good tune. Play any note in the middle of the keys and listen (the fundamental). Now strike a note exactly one octave higher and listen (the second harmonic). Now strike both both notes in unison. You will hear. and very clearly in fact, the third harmonic. This percieved note is not produced by the piano. In fact, if you play the third harmonic, a "musical fifth" above the higest note in the octave, you will find the note on the keyboard to be a wee bit flat. This is because pianos are tuned "tempered"; meaning the 3rd harmonic is dialed in at 2.9966 times the fundamental.
The point here is that in the presence of a strong 2nd harmonic, our ears/mind insert the 3rd.
This can be repeated with sine generators as well...
Curiouser and curiouser...
😕 😕
I hate to be that guy on the forum that quotes the post and says "mee tooo!!!!!" but I have to say that this statement distills many problems that we are facing within this thread. I have not personally measured the response of many of the "Low THD" amps that sound like crap, but my bet is that if one were to dig and run a few more tests, you could pick out the factors that made the amp sound like crap.Joel said:
dfdye: As someone who knows enough to know that the Pittsburgh Conference isn't held in Pittsburgh, allow me to observe that the job of laboratory electronics and audio electronics is often the same, but often quite different.
At that level, I agree, there shouldn't be audible coloration!Bas Horneman said:
Unfortunately, I don't have speakers efficient enough for that! 🙁
Let's just assume for a minute that a triode could be a clean enough amplifier...then they would still not be in your lab, because of expense...and a host of other reasons. You can't call that proof!
😉 Right about now most people in the so called civilized world are listening to mp3's as their main source of music.. does this mean that LP, CD and SACD do not produce clean enough sound?
An op amp is a wonderful thing..but it could not amplify music satisfactorily without gobs of feedback. The feedback is used to make a non-linear device linear. This does not mean anything ofcourse...because a little opamp based phono stage I built ..the VSPS..sounds suprisingly good to me 😉
My point is...a tube is a perfectly good thing to use as an audio ampflication device...especially if you DIY. Which brings me back to the point tubelab and Pedrovska made..use whatever you like to amplify. But don't dismiss a tube on the basis of THD or the fact that they can't be found in instrumentation amplifiers these days 😀 is what I think.
As we dive further off topic, what would you use? I would personally like MDF/asphalt/MDF sandwiches, but that is overkill for my speakers.planet10 said:
As for MDF being "not good," it is directionally stable, doesn't warp, is resistant to expansion/contraction due to changes in heat or humidity, it’s dense, sturdy and doesn't add much resonance if properly machined and assembled. I'm not sure what else you want out of a cabinet material. (Other than something that doesn't make so damn much dust that gets in EVERY crevice in my shop!!!! 😀 )
dfdye said:
If it's noise specifically you mean, I can post test results of a tube headphone amp I'm prototyping with noise performance better than the 24-bit limit of my measurement system in all respects save hum. Then again, it's still a bunch of parts on a piece of plywood and I expect improvements once shielded.
This post comes a bit late from the threads current topic but i have grown sceptical over the claim that even order distortion components are preferable over odd and that "pleasantness" of amplifier's tone should be measured with such a simple logic. IMO there are couple of points why this way of thinking sounds unlogical:
1. There is no relation between amplitude and frequency. Will it sound equally good to have a same amount of odd and even harmonics at, say 1 kHz or at 180 Hz? In order to make these measurements count at any way they should be performed at many frequencies instead of only a few.
2. My involvement with guitar distortion effect circuits have many times proven that a pleasing tone requires both (even and odd harmonics). One can create a distortion figure that is dominated by even harmonics just by clipping another halfwave of the (audio) signal but usually the result sounds like a broken radio and is far from being pleasing to ear.
3. The measurement is based on deformations in sine wave but it is not dependent on deformations in it's amplitude: What's a difference of 1V rms pure sine wave and 10V rms pure sine wave in THD? See: These figures cannot tell anything about compressed music.
Teemu K
1. There is no relation between amplitude and frequency. Will it sound equally good to have a same amount of odd and even harmonics at, say 1 kHz or at 180 Hz? In order to make these measurements count at any way they should be performed at many frequencies instead of only a few.
2. My involvement with guitar distortion effect circuits have many times proven that a pleasing tone requires both (even and odd harmonics). One can create a distortion figure that is dominated by even harmonics just by clipping another halfwave of the (audio) signal but usually the result sounds like a broken radio and is far from being pleasing to ear.
3. The measurement is based on deformations in sine wave but it is not dependent on deformations in it's amplitude: What's a difference of 1V rms pure sine wave and 10V rms pure sine wave in THD? See: These figures cannot tell anything about compressed music.
Teemu K
LOL!!! And if it were held in Pittsburgh, nobody would go! 😀SY said:
As for lab electronics and audio electronics often having different purposes, I whole heartedly agree, but my argument is simply that distortion in both systems is analogous.
That being said, I wonder if I could find a chipamp that could run on the 240V rails
of my Ar+ ion laser. . . . Hmmmmm . . . . . .
SY said:
Got to pick a bone on this.......I use tubes because (hiding my tube amp behind a screen) everyone says the adorned thing sounds so natural.....So what's "under the chassis " that does the trick ? I still use the old carbon resistors for grid stoppers but the rest are met film types and ICW p'prop caps.. Some years ago I put a couple of Maplin MOS kit amps under the chassis and kept some old tubes above"just glow'in" ....Would it fool everyone ? I botched up soft start to keep some authenticity...and some did spot the sound difference. Those Maplin MOS amps had only 3-4 stages.....actually performed darned well and again comparing those kit amps to reacdy built stuff, again most spotted the differences. So as been mentioned several years prev, the basic mosfet amp can sound close to a tube amp, BUT not quite. The Mos amp has lower thd, way higher global feedback 70-100dB and a far better frequency response.
Some pointed out that triodes as the most linear devices have got to produce "close to" the perfect reproduction. Okay point made, but in defence of p-p UL topology and using feedback we arrive at the results a triode can give but at much greater pout and the Mos linearity isn't brilliant either. So can anyone put their finger on the magic stuff that does the trick ?
richj
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