Maybe I can explain what I mean by stationary or not. Let's say we have an ideal voltage amplifier. Its voltage transfer function is a straight, diagonal line. A stationary nonlinear amplifier has a voltage transfer function that is not a straight line, rather there is some curvature. A nonstationary nonlinear amplifier has a voltage transfer function that is not only not a straight line, its curvature is not constant over time.
I'm sure someone will realize that an amplifier that measures a bit different distortion at 10Hz, 1kH, and 20kH is in reality a nonstationary nonlinear system. However, most of the time we want to use the simplest model that is good enough for our purposes. Its a basic principle of engineering.
The reason I described something like a high end audio amp the way I did was because I don't think what the distortion is doing for a listener that likes the sound can be gleaned from looking at distortion measurements taken using stationary sine waves. That just gives a snapshot of the system nonlinearity in one fixed state. Its too hard to mentally extrapolate from that how it is that a sane person could like the sound of it. (Sure, we know about some audiophiles that are pretty neurotic, but not all are.)
I'm sure someone will realize that an amplifier that measures a bit different distortion at 10Hz, 1kH, and 20kH is in reality a nonstationary nonlinear system. However, most of the time we want to use the simplest model that is good enough for our purposes. Its a basic principle of engineering.
The reason I described something like a high end audio amp the way I did was because I don't think what the distortion is doing for a listener that likes the sound can be gleaned from looking at distortion measurements taken using stationary sine waves. That just gives a snapshot of the system nonlinearity in one fixed state. Its too hard to mentally extrapolate from that how it is that a sane person could like the sound of it. (Sure, we know about some audiophiles that are pretty neurotic, but not all are.)
I asked myself several times and always got techno babble (if anything). Which makes “stationary/non stationary distortion” an ingredient in the word salad we are served on a daily basis.
Curvature shape could vary depending something about the history of the signal being amplified, say. In the digital domain, curvature could change depending on something about the future of a signal. Obviously I hope, we need to keep such changes very small not to have them be overbearing. They can be very subtle, but nice. They can also be ugly sounding, so be careful about that.
If done intentionally, is it technically an effect? Yes, I think so. But, it can sound more real perceptually if done correctly.
Also, some of the people designing that way don't even know what subtlety is occurring, or why it is some circuit just sounds good, they just perceive it sounds better to them, more real, so they use it.
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Did you see Rob Watt's dac master class video on youtube? I think that was one where he said something about everything moving around, everything changing, time, frequency, blah, blah, blah. Whatever it was, but to similar effect.
I wondered how he could be talking about anything he was really doing. Was it all BS? Maybe. Now I'm starting wonder if he found some subtle perceptual DSP algorithm.
I wondered how he could be talking about anything he was really doing. Was it all BS? Maybe. Now I'm starting wonder if he found some subtle perceptual DSP algorithm.
Bill: I have some experimental evidence and I know of some applicable preexisting theory. However, I am not going to lay it all out right now.
What I would like to do is get people thinking about why some people like really good hi-fi tube preamps, or whatever. Tube circuits are simple and there are subtle effects as things interact. Taken to an gross extreme you have a guitar amp, and even guitarists get bored with stationary distortion.
That's very different from a opamp based preamp with high loop gain to suppress any nonlinearities.
What I would like to do is get people thinking about why some people like really good hi-fi tube preamps, or whatever. Tube circuits are simple and there are subtle effects as things interact. Taken to an gross extreme you have a guitar amp, and even guitarists get bored with stationary distortion.
That's very different from a opamp based preamp with high loop gain to suppress any nonlinearities.
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There is this too: RMAF17: DAC Design Masterclass - YouTube
Between the interview and the video, I wonder might kind of DSP he might be writing to make his dac sound more 'musical.'
Even though he is obviously promoting his products, marketing stories are often based on a certain amount of truth.
I wouldn't give it another thought except I know of people who own one of the $100,000 DCS dacs and a Chord DAVE who like the sound of the DAVE better, think it sounds more 'real.' The Chord DAVE and the Hugo TT2 dacs have reputations as some of the best sounding dac available.
If you don't care, no problem.
Between the interview and the video, I wonder might kind of DSP he might be writing to make his dac sound more 'musical.'
Even though he is obviously promoting his products, marketing stories are often based on a certain amount of truth.
I wouldn't give it another thought except I know of people who own one of the $100,000 DCS dacs and a Chord DAVE who like the sound of the DAVE better, think it sounds more 'real.' The Chord DAVE and the Hugo TT2 dacs have reputations as some of the best sounding dac available.
If you don't care, no problem.
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