Bob Katz: "Adventures in Distortion" Nuvista, Hypex

[watchnerd]

In many ways aligned with Nelson Pass's recent writings.

Bob is coming at it from a recording engineering perspective, but reaches much of the same conclusions, also making a 'dial a distortion' box:

https://www.innerfidelity.com/content/katzs-corner-episode-25-adventures-distortion

 

[watchnerd]

Would also love to get @Ethan Winer 's opinions on what Bob has written.

 

[Blumlein 88]

His description matches my anecdotal subjective experience of triode tube power amps. There are designers who think a little distortion of the right kind smooths the sound, adds apparent detail, and gives a 3D quality. @Cosmik will disagree with us.

Now his level of 2nd harmonic would appear to fall under the masking thresholds and not be heard. The noise level probably is audible at times depending upon the signal. The tube power amps I used in triode had more 2nd and 3rd harmonic than this. And they had other effects on FR from going thru transformers.

The obvious thing to do is get some level matched recordings with and without and see if people hear it in a blind presentation. People like Bob Katz (not necessarily Mr. Katz himself) will at this point tell you how they have to trust what they hear or they couldn't function in their job. They have experience producing and hearing such things and such is not needed to know it was something really heard. I'm not so sure. Our brain is very tricky.

I've done a little recording and am in no way as qualified or experienced as Mr. Katz. The following experience comes to mind however. I was mixing in a recording. I had miked each instrument. I wanted to take an instrument, cause it to waver grow in apparent size and slide from one side to the other snapping back in focus over a few seconds time. As the instrument covered the range where we hear position mostly by time delay and from side to side intensity I thought I might change the phase in one channel vs the other as I panned it the opposite direction or something like that. I tried it and the result was something close to what I wanted. I adjust some things and had it doing very close to my vision for the effect. I switched back and forth between that and simply panning a dozen or more times. Easy to hear the difference. Then the phone rang.

So after a 20 minute conversation about an important matter I'm back to this mixing. I play the track again figuring after the break I'll know if I'm finished with it or not. I don't hear the effect. I figure I was on the track and swap. I still don't hear the effect. I check and make sure I'm listening to the right version and okay there it is. Clearly wavering a bit and then moving over. After a minute it occurs to me maybe I'm only hearing it when I know which track it is. I select a few seconds of each version and put it in foobar. I don't hear nothing different.

Okay, I play it for three other people without telling them much about it. Just asking which of these two mixes do you like. They say they sound the same. I don't hear it foobar. I can convince myself when I know which is which I hear it. Your mind is tricky. I know thinking about such could cause a neurotic episode for mixing and mastering people if they took it as a serious possible problem. However, the measured levels of distortion vs masking curves makes me think Mr. Katz's device won't be heard unless it is the noise level.

So if any of you post there, maybe ask him make a few tracks available that have gone thru his device clean, and for which he has tuned for a better result.

 

[watchnerd]

His description matches my anecdotal subjective experience of triode tube power amps. There are designers who think a little distortion of the right kind smooths the sound, adds apparent detail, and gives a 3D quality. @Cosmik will disagree with us.

Now his level of 2nd harmonic would appear to fall under the masking thresholds and not be heard. The noise level probably is audible at times depending upon the signal. The tube power amps I used in triode had more 2nd and 3rd harmonic than this. And they had other effects on FR from going thru transformers.

The obvious thing to do is get some level matched recordings with and without and see if people hear it in a blind presentation. People like Bob Katz (not necessarily Mr. Katz himself) will at this point tell you how they have to trust what they hear or they couldn't function in their job. They have experience producing and hearing such things and such is not needed to know it was something really heard. I'm not so sure. Our brain is very tricky.

I've done a little recording and am in no way as qualified or experienced as Mr. Katz. The following experience comes to mind however. I was mixing in a recording. I had miked each instrument. I wanted to take an instrument, cause it to waver grow in apparent size and slide from one side to the other snapping back in focus over a few seconds time. As the instrument covered the range where we hear position mostly by time delay and from side to side intensity I thought I might change the phase in one channel vs the other as I panned it the opposite direction or something like that. I tried it and the result was something close to what I wanted. I adjust some things and had it doing very close to my vision for the effect. I switched back and forth between that and simply panning a dozen or more times. Easy to hear the difference. Then the phone rang.

So after a 20 minute conversation about an important matter I'm back to this mixing. I play the track again figuring after the break I'll know if I'm finished with it or not. I don't hear the effect. I figure I was on the track and swap. I still don't hear the effect. I check and make sure I'm listening to the right version and okay there it is. Clearly wavering a bit and then moving over. After a minute it occurs to me maybe I'm only hearing it when I know which track it is. I select a few seconds of each version and put it in foobar. I don't hear nothing different.

Okay, I play it for three other people without telling them much about it. Just asking which of these two mixes do you like. They say they sound the same. I don't hear it foobar. I can convince myself when I know which is which I hear it. Your mind is tricky. I know thinking about such could cause a neurotic episode for mixing and mastering people if they took it as a serious possible problem. However, the measured levels of distortion vs masking curves makes me think Mr. Katz's device won't be heard unless it is the noise level.

So if any of you post there, maybe ask him make a few tracks available that have gone thru his device clean, and for which he has tuned for a better result.

Great write up. This brings up a few things:

1. Psychoacoustically, I'm wondering if dither, in a digital chain, is performing an analogous role to the low-level 2nd & 3rd harmonic distortion he refers to?

2. The extra angle he didn't get into: the 'soft clipping' of tubes and tape may be kinder to the ear and closer to what we hear often in real life. Nobody hears digital distortion / clipping in 'normal' musical life.

3. Subjectively, I find myself agreeing with Katz....I find myself often liking just a teensy smidge of distortion. But I want it defeatable..I don't want it hard-wired by default no matter the source.

 

[Blumlein 88]

Great write up. This brings up a few things:

1. Psychoacoustically, I'm wondering if dither, in a digital chain, is performing an analogous role to the low-level 2nd & 3rd harmonic distortion he refers to?

2. The extra angle he didn't get into: the 'soft clipping' of tubes and tape may be kinder to the ear and closer to what we hear often in real life. Nobody hears digital distortion / clipping in 'normal' musical life.

3. Subjectively, I find myself agreeing with Katz....I find myself often liking just a teensy smidge of distortion. But I want it defeatable..I don't want it hard-wired by default no matter the source.

I need to look at my old hard drive. There is a guy who developed some of the top Sony studio gear from England. He spent lots of time with dither. He found it audible (tested blind) because synthetic dither would repeat the pattern too often. He described various versions as effecting the perceived soundstage. The guy was not some subjectivist sound engineer. He was very hard nosed and objectively based in his ideas. His name escapes me currently, but I'll think of it. Current dither in current good gear is no problem. Some other sound guy at Abby road originally brought it to his attention.

I owned a McIntosh 752 amp connected to Acoustat speakers for a time. Fairly capable 75 wpc amp, but that isn't really enough for those power hungry speakers. It had an optically operated Powerguard system on it. Lights would light upon detecting clipping and guarantee distortion never reached 1%. In effect it was a low distortion compressor when pushed. You could crank it up until the lights were lighting regularly on peaks. It never got nasty. It would get some bloom if you pushed it enough. And it sounded lightly compressed. Soft clipping of sorts. I've always thought triode amps pushed were compressing just a bit.

 

[hvbias]

I somehow missed that article by Bob Katz when it was written.

"Let's cut to the chase, it was the increasing use of negative feedback that engendered ever-lowering distortion figures. Negative feedback is a perfectly good mathematical technique that works very well. But the designer has to realize that the circuit may not sound good even if its measured THD (total harmonic distortion) is very low. If the designer pays attention solely to the THD value, he may not realize that sometimes the "good-sounding, lower harmonics" get suppressed at the expense of the "bad-sounding, higher harmonics". Research by Norman Crowhurst points out that feedback mostly reduces the level of the 2nd and 3rd harmonics, leaving the upper harmonics more or less alone, or sometimes at higher level than before feedback. It doesn't take very much level of a 5th, 7th, or 9th harmonic to make the sound "bitter", "dry", "clinical", "cold" "small" "dynamically limited" or "harsh". This is all part of the psychoacoustics of distortion and masking"

From measurements I have seen from amps that use a lot of negative feedback it looks like all the harmonics are suppressed, I'll have to look into some more measurements.

From my rather non scientific listening I have to say I do like the sound of the FirstWatt amps I've owned and I was planning to use one of their SIT amps with my midrange/treble controlled directivity horn. I do not think these amps sound like tube or SET amps (these are not for me), they simply sound very transparent without sounding harsh at active concert listening levels, unless the harshness is in the recording.

 

[andreasmaaan]

I somehow missed that article by Bob Katz when it was written.

"Let's cut to the chase, it was the increasing use of negative feedback that engendered ever-lowering distortion figures. Negative feedback is a perfectly good mathematical technique that works very well. But the designer has to realize that the circuit may not sound good even if its measured THD (total harmonic distortion) is very low. If the designer pays attention solely to the THD value, he may not realize that sometimes the "good-sounding, lower harmonics" get suppressed at the expense of the "bad-sounding, higher harmonics". Research by Norman Crowhurst points out that feedback mostly reduces the level of the 2nd and 3rd harmonics, leaving the upper harmonics more or less alone, or sometimes at higher level than before feedback. It doesn't take very much level of a 5th, 7th, or 9th harmonic to make the sound "bitter", "dry", "clinical", "cold" "small" "dynamically limited" or "harsh". This is all part of the psychoacoustics of distortion and masking"

From measurements I have seen from amps that use a lot of negative feedback it looks like all the harmonics are suppressed, I'll have to look into some more measurements.

From my rather non scientific listening I have to say I do like the sound of the FirstWatt amps I've owned and I was planning to use one of their SIT amps with my midrange/treble controlled directivity horn. I do not think these amps sound like tube or SET amps (these are not for me), they simply sound very transparent without sounding harsh at active concert listening levels, unless the harshness is in the recording.

Others here will know more about this than I do, but in general it is correct that a small amount of negative feedback will reduce lower order harmonics while raising or failing to reduce higher order harmonics. But enough negative feedback will effectively suppress both lower and higher order harmonics.

See for example: https://linearaudio.net/sites/linearaudio.net/files/volume1bp.pdf

 

[L5730]

I had a similar experience to @Blumlein 88 . I was messing with some EQ, tweaking and sculpting a track to make it just so. After spending some good time listening, looping and adjusting this EQ curve, I rendered out. Dropped the original and my EQ'd version onto the same time line, and I couldn't hear a difference. I thought, subtle is good, but I should hear something at least. Did a null test - it cancelled out, there was no change!
Loaded up the project, it turns out I was playing with an EQ plugin on a track with nothing in it - I think this is akin to adjusting the "producer's dial".

Didn't Mr. Katz make another box with a couple of little tiny square 'tubes', which were more like some kind of strange glowing hybrid square thing. It looked cool, if nothing else.

 

[Cosmik]

I had a similar experience to @Blumlein 88 . I was messing with some EQ, tweaking and sculpting a track to make it just so. After spending some good time listening, looping and adjusting this EQ curve, I rendered out. Dropped the original and my EQ'd version onto the same time line, and I couldn't hear a difference. I thought, subtle is good, but I should hear something at least. Did a null test - it cancelled out, there was no change!
Loaded up the project, it turns out I was playing with an EQ plugin on a track with nothing in it - I think this is akin to adjusting the "producer's dial".

Didn't Mr. Katz make another box with a couple of little tiny square 'tubes', which were more like some kind of strange glowing hybrid square thing. It looked cool, if nothing else.

As you point out, all music production decisions are based on sighted listening tests - which everyone round here says are useless due to a human's inability to suppress their biases and imaginations when assessing what they hear. Ironic?

In fact, the entire creative world is based on 'sighted judgements', whether it's designing a building, a car or a company logo.

I don't think it's a conundrum, though. I suspect that users (listeners) adapt easily to 'straight' design. It's no coincidence that scandinavian-style minimalism is regarded as good or that "form follows function" is regarded as an important idea. The best designers are simply being led by the requirements of the project rather than the other way round.

In music production, I have long suspected that the first 'rough mix' is probably better to listen to than the one where people dynamically fiddle about with faders, or even worse, EQ, compression, distortion, etc. If the music is any good, and the production isn't required to be a major part of the performance, then simply committing it to tape as straight as possible will produce the most satisfying results. Listeners will adapt to the recording with a fairly wide latitude when it comes to precise levels and balances, I think.

There are too many albums of fairly basic music (and nothing wrong with that) that have been fiddled about with, including muddy 'cassette saturation plugins' and so on which probably reflect the producer's biases and expectations more than any improvement to the production.