A pure sine wave is a very challenging signal to amplify/reproduce cleanly, but it doesn't show the resulting intermodulation distortion.
That's why we have (standardized) IMD/multitone tests. See the measurements I've posted in #1742.
In the single singe/THD test the Pass amp has an audiophool-approved harmonic distortion spectrum. And in the IMD tests you see the resulting extremely poor performance.
Meanwhile, the Hypex amp doesn't always follow this distortion spectrum, sometimes the 3rd is higher relative to the 2nd and so on. But the relative spectrum doesn't matter if its so low in an absolute sense. This reflects in clean IMD results as well.
Same for the TIM measurements.
But this is not a matter of opinion.
See my previous post. Now it's a crazy comparison, yes, but it shows that the spectrum doesn't matter necessarily.
One is a linear & nonlinear distortion FX box with amp despite the "good" distortion spectrum and the other one is just an amp.
This is why blanket statements such as "it's the distortions spectrum that are important, not the lowest distortion numbers" are not helpful. To the contrary. It's just perpetuating an audiophile myth that is simply wrong.
Last edited:
This is like saying "remedies" based on a watered down water and sugar beads are sold by the billions because of <insert positive adjectives> vs. <insert negative adjectives> for medicine.
While science has shown times and times again that all they trigger is a placebo response.
So people either enjoy or are misled to buy 1000x overpriced placebos.
Was that your argument?
How are you not embarrassed posting this? Ever heard of strawmanning?
Last edited:
Both camps, from time to time, claim: "Aha! We finally nailed it! But the issue is still open, as it was 50 years ago. Probably it will remain open for another 50 years.
No, pfb does not do that. Pfb on itself worsens distortion and almost any other parameter, but it does increase gain which enables nfb to use that excess gain as loop gain to improve the amp.
That is clearly explained in the article I linked to.
Jan
Hard to have a discussion when NFB is used for both local and global feedback. Audiophool amp designers are told by the marketing department to not use global feedback because thats what audiophools want. The good designers know what the marketing dept. and there clients dont, ( and most people replying on this thread), global and local feedback do the same thing ( read The F-word ). So they design using local instead of global to sell there amps. You can make good amps either way, and a combination of the 2 is probably the best.
Feel free to dumb it down for the rest of us and throw out the names of designs open to DIY that "do feedback right" or have more than whatever BP's magical feedback threshold is (35dB?).
I agree on sine wave hard to reproduce. Else I agree to not underestimate it's own power. Of course, there is a stable margin as cells multiply, you may always regenerate. But for some that die faster than live, yet do it more lively than anything from this structural void, feedback seems basically invalid. Believe me, since aingularity has been publically approved, everyone has rights to listen what they prefer, because everyone behaves differently. Peace is an order! 😉
I'm not sure what you're talking about. What I've observed, however, is that one side clings to very naive and simple views like "(global) negative feedback is bad" and "the distortion spectrum is more important than low numbers" but also creates the counter-positions like "negative feedback is always good" ... which are not only strawmen but also similarly naive and simple.
Reality is a bit more complex. But the science has been known for a long time. The measurements and tests of audibility of distortion also are nothing new. (This is also easy and cheap to make fun of. See the "hearing test" comments.)
But I can see the appeal to belonging to the former group. It's easy on the intellect. That seems to be the most important point.
It's also fun to make fun of the evil science that cannot be true because that would mean a waste of lots of time and money and admitting that cognitive bias/distortion are real ... by attacking self-made naive strawmen that are easy to make fun of. (So effectively they're making fun of themselves.)
Reminds me of flat earth groups.
Last edited:
Never seen a Schmitt trigger in the signal path of an audio amplifier 🙄.
The tube amplifier designs I was referring to did implement both voltage NFB as well as current PFB, if we can agree that current FB means sending back a signal that is proportional to the amp's output current.
Best regards!
Not just opinion. I have that article on my website for 15 years.
Anyway, if you do the math, it becomes very quickly clear that pfb increases distortion, worsens the freq response, and deteriorates the output impedance.
Which you would have known too, had you taken the trouble to read the article.
Jan
Attachments
Last edited:
Hi Jan,
May want to give up, it took centuries for some to mostly be convinced that the earth is not flat. People believe what they want to and can rationalize it to incredible lengths.
Pretty much a lost cause convincing those who are true believers.
May want to give up, it took centuries for some to mostly be convinced that the earth is not flat. People believe what they want to and can rationalize it to incredible lengths.
Pretty much a lost cause convincing those who are true believers.