Brian,
You really got me going on this one... Once upon a time, I did a lot of research into mathematical structure of sound produced by musical instruments. I started out with basic FFT and standard spectral techniques to "tear apart" digital streams of recorded sounds. I then took these spectral distributions and recreated sounds mathematcally... they did not sound the same.
I ultimately realized that FFT wasn't going to do it for me... amplitude was fine, but the frequency resolution just wasn't "there". I continued to use FFT as a means to "rough out" where the spectral data was, but I eventually used a more laborious technique to hone in on the fine points.
In your case, steady state waveforms would suffice and greatly simplify the analysis. It goes something like this:
1) Gather 3 fundamental cycles of your waveform in digital.
2) Perform an FFT to get the lay of the land.
3) Create a weighting mask so that only the center third of data has full influence on your results.
4) Starting with your fundamental, use least sum of squares to fit sine waves to your data... fitting for both phase and amplitude. This is where steady-state is your friend... imagine doing this on decaying sines... it gets ugly fast.
5) Subtract the fitted sine from your original data (without the center weighting), lather, rinse well, repeat. At this point you may choose to "re-window" your data or divide the original data into several overlapping "sub-windows"
This is laborious as hell... I was eventually able to kluge together enough code to automate things some what.
Now I can't say much about I learned... let's just say that harmonics in complex waveforms (on an instantaneous basis) are not always the pure integer multiples of the fundamental that we assume them to be. Consider the harmonics in a guitar string when the fundamental is at a peak and the tension in the string is increased... well... enough said. Look at an electric guitar on a scope... why does the waveform "roll"? An FFT won't tell you why(as you have pointed out).
Not that my findings would bear any direct consequence on yours, although there similar things at play... the blurry line between PM, FM, AM, IM, and other evil parasitic modulators. But maybe the measurement strategy would help?
Go for it...
You really got me going on this one... Once upon a time, I did a lot of research into mathematical structure of sound produced by musical instruments. I started out with basic FFT and standard spectral techniques to "tear apart" digital streams of recorded sounds. I then took these spectral distributions and recreated sounds mathematcally... they did not sound the same.
I ultimately realized that FFT wasn't going to do it for me... amplitude was fine, but the frequency resolution just wasn't "there". I continued to use FFT as a means to "rough out" where the spectral data was, but I eventually used a more laborious technique to hone in on the fine points.
In your case, steady state waveforms would suffice and greatly simplify the analysis. It goes something like this:
1) Gather 3 fundamental cycles of your waveform in digital.
2) Perform an FFT to get the lay of the land.
3) Create a weighting mask so that only the center third of data has full influence on your results.
4) Starting with your fundamental, use least sum of squares to fit sine waves to your data... fitting for both phase and amplitude. This is where steady-state is your friend... imagine doing this on decaying sines... it gets ugly fast.
5) Subtract the fitted sine from your original data (without the center weighting), lather, rinse well, repeat. At this point you may choose to "re-window" your data or divide the original data into several overlapping "sub-windows"
This is laborious as hell... I was eventually able to kluge together enough code to automate things some what.
Now I can't say much about I learned... let's just say that harmonics in complex waveforms (on an instantaneous basis) are not always the pure integer multiples of the fundamental that we assume them to be. Consider the harmonics in a guitar string when the fundamental is at a peak and the tension in the string is increased... well... enough said. Look at an electric guitar on a scope... why does the waveform "roll"? An FFT won't tell you why(as you have pointed out).
Not that my findings would bear any direct consequence on yours, although there similar things at play... the blurry line between PM, FM, AM, IM, and other evil parasitic modulators. But maybe the measurement strategy would help?
Go for it...
Measurement vs. auditioning
So just to keep lively the objectivist – subjectivist burning fire, here we go.
Not to simply duck behind the comfortable bastions of established technology and in doing so simply dismiss any attempt to posit “unknown” magnitudes proposed by hard core audiophiles as nonsense, I am more than ready to retract, as soon as well presented, substantiated and repeatable theories are brought forward.
Post #208 presented by Brian Beck. is a good and honest attempt to shed light on the issue, much as I must also say it remains to be seen how the argument is fleshed out with hard data. For one thing, it must be acknowledged there is a vanishingly small amount – if any – of available program material based on analog media and processed only with vacuum tube technology.
Analog media based, but solid state processed material should be contaminated by the posited artifacts that come with for example highly variable and nonlinear device capacitances (this holds as much for power as for low level stages), while digital based program simply cannot be produced – as far as I know – without solid state processing equipment.
So, restricting the reproduction end of the chain to vacuum tube gear, at best only avoids a further insult on an already offended source material, and it defies credibility to attribute to this single fact a perceptible, even overwhelming improvement as so strongly advocated.
On the other hand, if it is argued solid state production gear is so sophisticated as to introduce negligible distortions, please let me note performance levels as gauged for example by THD, are situated in the 0.001% and below. This is the realm of the best commercial solid state devices anybody can also put a hand on, and with which production equipment in the end is built with. This is good but nothing unattainable in turn both by good quality commercial reproduction gear, or good, no compromise designs, without need to resort to exotic or immensely expensive components.
Not willing to extend in a single post beyond an edible span, I will be writing a pdf to post here with longer but unavoidable elaboration on this subject.
Rodolfo
PS. By the way, the Hawksford issue about current drive, some moths back this was treated here and I made a sensitivity analysis proving it was not as clear as presented, for anyone interested I can search and post the link. The fact is is not used at all probably speaks for itself.
So just to keep lively the objectivist – subjectivist burning fire, here we go.
Not to simply duck behind the comfortable bastions of established technology and in doing so simply dismiss any attempt to posit “unknown” magnitudes proposed by hard core audiophiles as nonsense, I am more than ready to retract, as soon as well presented, substantiated and repeatable theories are brought forward.
Post #208 presented by Brian Beck. is a good and honest attempt to shed light on the issue, much as I must also say it remains to be seen how the argument is fleshed out with hard data. For one thing, it must be acknowledged there is a vanishingly small amount – if any – of available program material based on analog media and processed only with vacuum tube technology.
Analog media based, but solid state processed material should be contaminated by the posited artifacts that come with for example highly variable and nonlinear device capacitances (this holds as much for power as for low level stages), while digital based program simply cannot be produced – as far as I know – without solid state processing equipment.
So, restricting the reproduction end of the chain to vacuum tube gear, at best only avoids a further insult on an already offended source material, and it defies credibility to attribute to this single fact a perceptible, even overwhelming improvement as so strongly advocated.
On the other hand, if it is argued solid state production gear is so sophisticated as to introduce negligible distortions, please let me note performance levels as gauged for example by THD, are situated in the 0.001% and below. This is the realm of the best commercial solid state devices anybody can also put a hand on, and with which production equipment in the end is built with. This is good but nothing unattainable in turn both by good quality commercial reproduction gear, or good, no compromise designs, without need to resort to exotic or immensely expensive components.
Not willing to extend in a single post beyond an edible span, I will be writing a pdf to post here with longer but unavoidable elaboration on this subject.
Rodolfo
PS. By the way, the Hawksford issue about current drive, some moths back this was treated here and I made a sensitivity analysis proving it was not as clear as presented, for anyone interested I can search and post the link. The fact is is not used at all probably speaks for itself.
poobah said:
There's something to this and it might partially explain why high order harmonics are so much more objectionable (though my hunch is that it does not, in itself, answer the whole question of this thread, but who knows.)
In a private forum, Steve Schell laid out a very detailed analysis along these lines. Steve is a professional piano tuner and according to him piano tuning is not only subject to the equal temperament that we're all familiar with, but also something called octave stretching; octaves are not tuned to perfect mathematical multiples but are slightly stretched along the keyboard. The consequence is that if middle C is tuned perfectly, then the lowest C on the keyboard will be slightly flat while the highest C will be slightly sharp.
I'll leave it at that and not go beyond my depth to attempt to describe the intricate details of piano tuning. Also, as I said, I read it in a private forum, so it would be wrong for me to provide a link. I'll send Steve an email to see if he'd like to contribute to this thread.
There have been so many of these debates, but it seems that the overall lesson never gets learned. That lesson is: LISTEN TO WHAT YOUR EARS TELL YOU. Why would people purchase early solid state or early CD? Because they weren't LISTENING. For whatever reason, be it some audio reviewer, a salesman or some "authority" - sold them a bill of goods and the "great leap forward" that was promised had nothing to do with the enjoyment of music and everything to do with pushing product and increasing profits.
I've heard one of those early Harmon Kardon receivers. Frankly, I'm amazed that they sold any at all, but they sold a lot of them. Why? I think it's because for some people, it's not about the music. Simple as that. Most people want aural wallpaper, background noise with a monotonous beat and insipid lyrics that they can hum along to. They didn't care because they weren't really listening anyway.
I don't understand why any "objectivists" would bother with vacuum tubes at all. I mean, what's the allure? Is it the adrenaline rush of playing with lethal voltages? Is it the sheer joy of wasting electricity on an inefficient means of amplification? Is it the "aesthetic" of working with an obsolete technology? I read Bruce Rosenblitt's book "Audio Reality" and while he had quite a few good points, I never quite understood why he isn't a solid state amp designer. He doesn't want to deal with output transformers, his basic thesis is that the circuit design is what matters most of all, but yet uses a technology that is far more inefficient, inconvenient and dangerous than the alternative. I just don't get it.
Then we hear the stories about people that have perfectly good stereo systems bringing home garage sale tube dinosaurs on a lark, only to have them replace the more "accurate" solid state gear. The myth of accuracy is such a lie, it's one of the worst tricks that audio writers have played on the listening public. I've seen what the "accuracy uber alles" mindset gets you. It gets you about ten to twenty audiophile approved recordings and 10K plus worth of audio gear that constantly changes. I've known these guys, they sit there, remote in hand, going back and forth and never hearing a track in its entirety, much less an entire CD. They read all the audio magazines, and comb Audiogon for new gear to buy to "improve" this or that aspect of their systems. It's one of the most pathetic things I've ever seen, and there's a lot of them out there, chasing some high end audio weenie version of the holy grail, "accuracy". Feh.
Here's my rule: If you do something to your system and it makes you want to listen to music more often, or makes you enjoy it more, it's GOOD. If it makes you want to turn the system off, or prevents you from listening to music you like because it "sounds bad", it's BAD.
Screw accuracy. Or at least what audiophile "authorities" deem it to be. I listen to music, not test tones.
Tubes are better because they sound better.
I've heard one of those early Harmon Kardon receivers. Frankly, I'm amazed that they sold any at all, but they sold a lot of them. Why? I think it's because for some people, it's not about the music. Simple as that. Most people want aural wallpaper, background noise with a monotonous beat and insipid lyrics that they can hum along to. They didn't care because they weren't really listening anyway.
I don't understand why any "objectivists" would bother with vacuum tubes at all. I mean, what's the allure? Is it the adrenaline rush of playing with lethal voltages? Is it the sheer joy of wasting electricity on an inefficient means of amplification? Is it the "aesthetic" of working with an obsolete technology? I read Bruce Rosenblitt's book "Audio Reality" and while he had quite a few good points, I never quite understood why he isn't a solid state amp designer. He doesn't want to deal with output transformers, his basic thesis is that the circuit design is what matters most of all, but yet uses a technology that is far more inefficient, inconvenient and dangerous than the alternative. I just don't get it.
Then we hear the stories about people that have perfectly good stereo systems bringing home garage sale tube dinosaurs on a lark, only to have them replace the more "accurate" solid state gear. The myth of accuracy is such a lie, it's one of the worst tricks that audio writers have played on the listening public. I've seen what the "accuracy uber alles" mindset gets you. It gets you about ten to twenty audiophile approved recordings and 10K plus worth of audio gear that constantly changes. I've known these guys, they sit there, remote in hand, going back and forth and never hearing a track in its entirety, much less an entire CD. They read all the audio magazines, and comb Audiogon for new gear to buy to "improve" this or that aspect of their systems. It's one of the most pathetic things I've ever seen, and there's a lot of them out there, chasing some high end audio weenie version of the holy grail, "accuracy". Feh.
Here's my rule: If you do something to your system and it makes you want to listen to music more often, or makes you enjoy it more, it's GOOD. If it makes you want to turn the system off, or prevents you from listening to music you like because it "sounds bad", it's BAD.
Screw accuracy. Or at least what audiophile "authorities" deem it to be. I listen to music, not test tones.
Tubes are better because they sound better.
Objectivists bother/study tubes because they are pragmatic enough (or smart enough) to respect those, such as yourself, that are proponents of tubes.
If tubes are better, some of would like to know why. I have yet to listen to a system that was totally transparent... tube or otherwise. I would like to and it shouldn't be deemed as impossible or worthless to try.
There will always be the kids that put $300-a-pop tires on their car and then park. Doesn't matter, you can try to discourage them; but they will follow and buy the amp de jour anyway. And your right; they don't want to listen to music. They want to brag and stress over their next purchase... they are their own victims.
The most recent posts are just about what might be the root cause of the "debate" in the first place.
If tubes are better, some of would like to know why. I have yet to listen to a system that was totally transparent... tube or otherwise. I would like to and it shouldn't be deemed as impossible or worthless to try.
There will always be the kids that put $300-a-pop tires on their car and then park. Doesn't matter, you can try to discourage them; but they will follow and buy the amp de jour anyway. And your right; they don't want to listen to music. They want to brag and stress over their next purchase... they are their own victims.
The most recent posts are just about what might be the root cause of the "debate" in the first place.
Measurement vs. auditioning
Some posts back I mentioned I was going to put toghether some reflections regarding the never ending objective - subjective issue.
Out of necessity, this cannot be solved (I mean the writing down, not the controversy!) in a few lines, so attached is a pdf.
I strongly urge well meant enthusiasts to read and comment, whatever the reaction may be. I am more than willing to get criticism and to change oppinion, as long as arguments are solid and equally sincere, in pursue of a better understanding of a shared passion, the enjoyment of music.
Rodolfo
Some posts back I mentioned I was going to put toghether some reflections regarding the never ending objective - subjective issue.
Out of necessity, this cannot be solved (I mean the writing down, not the controversy!) in a few lines, so attached is a pdf.
I strongly urge well meant enthusiasts to read and comment, whatever the reaction may be. I am more than willing to get criticism and to change oppinion, as long as arguments are solid and equally sincere, in pursue of a better understanding of a shared passion, the enjoyment of music.
Rodolfo
A method to check phase intermodulation distortion from an earlier SS thread on this:
http://www.diyaudio.com/forums/showthread.php?postid=419158#post419158
Don
http://www.diyaudio.com/forums/showthread.php?postid=419158#post419158
Don
Critisism fair's fair....Another bash of on a subject that's been aired so many times. > Another reconditioning after 35 years without major acheivement ? Sorry I don't swallow the comments. By the laws of physics we will never get acoustics and all related perfect and we all will just simply have to accept that...
It is wrong that we try to design perfect sounding equipment to a specification which most simply don't fathom all the jargon so long it sounds good. I've seen many go in HiFi shops to buy equipment ...go home...listen to it, then realising its a load of rubbbish. People buy LSpeakers because to them it sounds good v.s size, even though the distortion produced may be through the roof. So what ?
I built my hi fi system from scratch and everyone says it sounds brill, expansive, balanced, deep and one feels it too.
After I've mucked the cows out I'll grab my coat and put my skis on.
richj
It is wrong that we try to design perfect sounding equipment to a specification which most simply don't fathom all the jargon so long it sounds good. I've seen many go in HiFi shops to buy equipment ...go home...listen to it, then realising its a load of rubbbish. People buy LSpeakers because to them it sounds good v.s size, even though the distortion produced may be through the roof. So what ?
I built my hi fi system from scratch and everyone says it sounds brill, expansive, balanced, deep and one feels it too.
After I've mucked the cows out I'll grab my coat and put my skis on.
richj
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.