Interview with Bruno Putzey

[Matias]

Another interesting part is when he says he can predict subjective performance when things measure well, but when they have distortion is quite difficult to predict how it will sound like subjectively.

 

[March Audio]

I have been looking for a science based alternative point of view or criticism of the work of Toole/Olive, just because I'd prefer to have more authoritative sources and not only one - but let's face it, reality is that there is only their work.

But I don't want to derail this thread into speakers, a positive thing is that regarding amps we know all that needs to be known since decades, certainly there is not shortage of research.

I think one reason for this is that most people who looks into the research in detail find little which makes them say "that can't be right". Or to make them think that something fundamental is missing. Hence why repeat the same work and come to the same conclusion?

 

[tuga]

Quite- but I think what draws the most ire is when an O perceives an S as asserting the poorly measuring but euphonic AND EXPENSIVE bit of kit is "better" than the more humble but better measuring kit, with all the accompanying flowery narrative. Sometimes I think that assertion may not actually be there, the S is just raving about some kit they like.

That is a problem of nomenclature. For an objectivist better means more accurate, for a subjectivist better means more pleasing.

For some more accurate is also more pleasing, for others that does not happen.

 

[Matias]

Look I have only just skimmed that article but if I read correctly this is just some of Bob's personal listening impressions, hardly scientific research

Not scientific but very technical and coming from a well known mastering engineer and audiophile, includes observations by his assistant too.

 

[pkane]

Not scientific but very technical and coming from a well known mastering engineer and audiophile, includes observations by his assistant too.

This test can now be repeated by anyone with a desire and a PC to run my DISTORT app. Add any one or combination of harmonics to any music track and listen through your own system. Archimago recently completed an Internet blind test with various levels of distortion with nearly 70 participants, and the results are public.

 

[carlob]

I think one reason for this is that most people who looks into the research in detail find little which makes them say "that can't be right". Or to make them think that something fundamental is missing. Hence why repeat the same work and come to the same conclusion?

Because in my view there are still things that need to be investigated. Let's talk about in-room FR, to simplify we know that there is consensus that anecoic FR should be flat and that in-room FR should also be flat but sloped down. But how much? Should it be +3dB at 20Hz and -3dB at 20KHz? Or +5 and -5? Now we enter again in the realm of subjectivity, in particular now with all the inexpensive ways we have to EQ our speakers. At the same time we are obsessing about the 0.5dB (audible?) difference between say a Ncore module and a Purifi one at 20KHz so we feed a perfect (within 0,5dB) signal to our loudspeakers and then we EQ their in-room FR to be down 3dB or 5dB at the very same 20KHz and dial in a couple of dB at bass frequencies according to what? To our subjective preference.
Is there anything more subjective that a target curve or a so-called Harman target curve?

 

[Blumlein 88]

Halcro by designer Bruce Candy. Halcro was an offshoot of his Minelab (the best metal detecting technology in the world) company.

View attachment 75678

That is the one I had in mind.

 

[SIY]

Oh, none were inexpensive.
https://www.stereophile.com/content/mbl-reference-9011-monoblock-amplifier-measurements
This is one I had in mind. I seem to recall another from Accuphase just can't remember which model.

Another which was so low in distortion it was not clear the measurement gear was up to it. I recall it stood tall vertically (I think it was Australian). Had tons of power, but was something like $30k. Sorry, I'm drawing a blank on the name, but maybe it will come to me or someone will remember it.

All of which put into context how good the Purifi, Hypex and Benchmark designs are in getting us gobs of power at high fidelity for relatively little money.

The Cambridge Edge W I reviewed had championship distortion measurements.

 

[carlob]

Forgot to mention this: https://www.audiosciencereview.com/...nechoic-measurements-community-project.14929/

Seems to me that there is no science telling me how sloped should be the in-room FR, and if I mess a little bit with Dirac/Audissey/Minidsp/Rew/etc. I can introduce differences in the FR that are in the order of many dBs with a touch...

 

[Matias]

This test can now be repeated by anyone with a desire and a PC to run my DISTORT app. Add any one or combination of harmonics to any music track and listen through your own system. Archimago recently completed an Internet blind test with various levels of distortion with nearly 70 participants, and the results are public.

Yes, but if I recall correctly, Archimago's test was more trying to see how much distortion was noticeable, the less the better, while Bob Katz's is in another direction, how much 2nd harmonic distortion is subjectively "better" to hide/mask other artifacts and "improve" sound. Interesting topic.

 

[Chromatischism]

Forgot to mention this: https://www.audiosciencereview.com/...nechoic-measurements-community-project.14929/

Seems to me that there is no science telling me how sloped should be the in-room FR, and if I mess a little bit with Dirac/Audissey/Minidsp/Rew/etc. I can introduce differences in the FR that are in the order of many dBs with a touch...

I think you'll find this interesting:

 

[pkane]

Yes, but if I recall correctly, Archimago's test was more trying to see how much distortion was noticeable, the less the better, while Bob Katz's is in another direction, how much 2nd harmonic distortion is subjectively "better" to hide/mask other artifacts and "improve" sound. Interesting topic.

Archimago found that about -75dB distortion is preferred to no added distortion. What Bob was testing is a somewhat unnatural distortion consisting of just a very large second harmonic. No device I know of (other than designed for just this purpose) produces just the second harmonic at 1% with no other harmonics added. But my point was that it's just as easy to test just the second harmonic with DISTORT. Or you can mix second and third only, or any number of other harmonics You don't need Bob's blender to do this. Just a PC and way to play WAV audio files.

 

[Matias]

What Bob was testing is a somewhat unnatural distortion consisting of just a very large second harmonic. No device I know of (other than designed for just this purpose) produces just the second harmonic at 1% with no other harmonics added.

Interesting that you mentioned it, I was just re-reading this review about the Qutest yesterday.

PS: not that I chase this, my systems are all the lower distortion the better, but I try to keep an open mind on people wanting to add flavours of distortion, specially tube preamps.

 

[pkane]

Interesting that you mentioned it, I was just re-reading this review about the Qutest yesterday.

View attachment 75685

PS: not that I chase this, my systems are all the lower distortion the better, but I try to keep an open mind on people wanting to add flavours of distortion, specially tube preamps.

That's hardly a 1% second harmonic, more like 0.0001%

 

[Matias]

That's hardly a 1% second harmonic, more like 0.0001%

True, his "recommendation" was:

"I recommend a maximum level of second harmonic no higher than 60 dB below the fundamental at nominal level (mezzo forte), typically -20 dBFS. The sound of -60 dB second harmonic is pleasant to the ear and enjoyable to many listeners, but perceived as a bit thick sounding with some loss of detail. Probably -66 dB second harmonic is the ideal setting, as in our listening it produces an attractive, warm, three dimensional quality with no apparent loss of detail or other side effects on any amplifier we tried. With some musical sources and some listeners, we may have to further lower second harmonic."​

So about -20 -66 = -86dB full scale (0.004%), right? Chord did not go fully on this but possibly half way. Point is: some people do like added distortion.
Anyway this is getting off topic. Bruno is a zero distortion oriented designer.

 

[GXAlan]

@March Audio
Examples of euphoric distortion can include things like all channel stereo or even surround upmixing. It’s not harmonic distortion but if you measure the actual distortion off test tones at the listening position, you will see that distortion goes up from all the room interactions, yet it sounds better/different and deviates from trans

Another example of euphoric distortion is listening to vinyl. Improved dynamic range due to differences in mastering plays a role for sure, but the popularity of vinyl today is another good example.

That said, I agree with you that amps and dacs should be as transparent as possible with as minimal artifacts as possible.
https://www.stereophile.com/reference/406howard/index.html

Supports your view on that distortion is hard to hear, transparency is best. — but it also does suggest that patterns of distortion may be preferable to others if you are forced to have distortion.

Since distortion can be added electronically but never taken away, I personally say that minimizing distortion makes the most sense if you have a single system and if you have multiple listening rooms, to consider building them around vintage/era so that the rooms that have higher distortion products reflect the way the recording engineers or artists may have been working.

 

[pkane]

True, his "recommendation" was:

"I recommend a maximum level of second harmonic no higher than 60 dB below the fundamental at nominal level (mezzo forte), typically -20 dBFS. The sound of -60 dB second harmonic is pleasant to the ear and enjoyable to many listeners, but perceived as a bit thick sounding with some loss of detail. Probably -66 dB second harmonic is the ideal setting, as in our listening it produces an attractive, warm, three dimensional quality with no apparent loss of detail or other side effects on any amplifier we tried. With some musical sources and some listeners, we may have to further lower second harmonic."​

So about -20 -66 = -88dB full scale (0.004%), right? Chord did not go fully on this but possibly half way. Point is: some people do like added distortion.
Anyway this is getting off topic. Bruno is a zero distortion oriented designer.

-60dB is 0.1% (Bob has it incorrectly stated in his article, saying -66dB is 0.1%). -66dB is 0.05% THD.

I don't doubt that some people like some level of distortion. My point was that it's not hard to figure out for yourself if you like it or not. You don't need to take someone's (Bob's) claims for what he hears or prefers.

 

[March Audio]

Not scientific but very technical and coming from a well known mastering engineer and audiophile, includes observations by his assistant too.

That's just an appeal to authority. Doesn't really provide us with any further weight of evidence. It's just an opinion of one guy, nothing more.

 

[March Audio]

Because in my view there are still things that need to be investigated. Let's talk about in-room FR, to simplify we know that there is consensus that anecoic FR should be flat and that in-room FR should also be flat but sloped down. But how much? Should it be +3dB at 20Hz and -3dB at 20KHz? Or +5 and -5? Now we enter again in the realm of subjectivity, in particular now with all the inexpensive ways we have to EQ our speakers. At the same time we are obsessing about the 0.5dB (audible?) difference between say a Ncore module and a Purifi one at 20KHz so we feed a perfect (within 0,5dB) signal to our loudspeakers and then we EQ their in-room FR to be down 3dB or 5dB at the very same 20KHz and dial in a couple of dB at bass frequencies according to what? To our subjective preference.
Is there anything more subjective that a target curve or a so-called Harman target curve?

Sure we shouldn't stop investigating. WRT frequency response the important bit is that the speaker is flat in the first place - anechoicly so that on axis is good. Remember what you measure in room is not what you hear. Sure different rooms will change the sound in different ways but people still recognise the "good" speakers regardless.

Is there a Harman target curve for speakers? Or is it just the fact that in room measurement of an anechoicly flat speaker will show a downward sloping response?

You don't Eq a speaker to be this way and wouldn't need to if it had a fundamentally good frequency response, it's just what a speaker actually does when you put it in a room.

 

[carlob]

Is there a Harman target curve for speakers? Or is it just the fact that in room measurement of an anechoicly flat speaker will show a downward sloping response?

There is. I don't know if you have played with Dirac, I have recently got a Minidsp SHD with Dirac and it works with a default target curve, once you make the initial measurements it presents you with a target curve which is a "Harman" one and if you don't change anything it corrects to that target. Obviously you have the option to correct only below the transition frequency, or full range. You can change the slope, you can change any point of the target curve but still it has a default target curve embedded in the software. You can load different third party targets like Harman 4dB, Harman 6dB etc: https://mehlau.net/audio/dirac-live-2/
Audissey works pretty much the same, corrects to a target curve. All of this is very subjective.