MQA creator Bob Stuart answers questions.

[SIY]

I don't know if this has been proofed by proper DBTs.

It hasn't.

The big flaw in distortion cancelation of the sort flung out from the lint pile is that it's level-dependent.

 

[Sergei]

It would seem that this path is not that expensive, and doesn't require 192/24. For example, some of the inexpensive DACs from Topping measure extremely well. And whatever is missing from 44-16, is difficult for the most sensitive well trained listeners to discern, and requires critical listening under controlled conditions with top notch equipment.
I'm not saying 44-16 is perfectly transparent so we're done, but whatever gap 44-16 has is quite thin, and that I'm skeptical that MQA does anything to fill that gap.

Agreed on the DACs. Some parts of the delivery chain remain expensive though, for instance low-distortion speakers.

 

[LTig]

Depends on the definition of timing. Timing of (A) detecting a peak of a sinusoid with frequency below the Nyquist? Or (B) detecting vs not detecting a short pulse with duration comparable to the sampling interval?

With (A), if the peak of the sinusoid happens to arrive in between the samples, it will be still reconstructed to the analog output.

With (B), if the pulse happens to fit entirely between the samples, nothing will be captured. Then there is nothing to reconstruct to the analog output.

I really had hoped, that this red herring has eventually been layed to rest, but you are still running in circles and seemingly learned nothing.

 

[SIY]

I really had hoped, that this red herring has eventually been layed to rest, but you are still running in circles and seemingly learned nothing.

If you keep repeating a lie, it becomes true.

 

[Sergei]

Keep adding distortions until they perceptually cancel each other.
Do you have any evidence this is actually the case ?

As I mentioned, you may want to study contemporary mobile bluetooth speakers, especially those made by JBL and Bose. Some of them seemingly violate laws of acoustics, by producing what is perceived as substantial bass, from 2" speakers, and playing that way for hours, using a tiny battery. The first distortion (dropped bone-fide bass frequencies) is perceptually cancelled by another (added higher frequencies not present in the original signal).

 

[LTig]

As I mentioned, you may want to study contemporary mobile bluetooth speakers, especially those made by JBL and Bose. Some of them seemingly violate laws of acoustics, by producing what is perceived as substantial bass, from 2" speakers, and playing that way for hours, using a tiny battery. The first distortion (dropped bone-fide bass frequencies) is perceptually cancelled by another (added higher frequencies not present in the original signal).

Roll off is not distortion!!!

 

[Sergei]

Otherwise adding distortion just leads to more distortion, and I really would like to see the scientific background how this improves perceptual sound quality. I remember that somewhere Nelson Pass has said that adding 2nd order THD in an amplifier such that it is higher than 3rd order THD from the source improves perceptual sound quality. I don't know if this has been proofed by proper DBTs.

Some of the Nelson Pass amps are good examples. Measurements show that they are highly distorting. Yet some people keep raving about how the amps perceptually improve certain types of music, captured on certain types of media.

DBTs are kinda funny to apply here - the distortions are so obvious and high. It is not about being able to differentiate, it is about preferences, in the context of specific music, recording media, and individuals.

 

[SIY]

Some of the Nelson Pass amps are good examples. Measurements show that they are highly distorting. Yet some people keep raving about how the amps perceptually improve certain types of music, captured on certain types of media.

DBTs are kinda funny to apply here - the distortions are so obvious and high. It is not about being able to differentiate, it is about preferences, in the context of specific music, recording media, and individuals.

Eventually, we'll run out of red ink.

 

[Sergei]

Roll off is not distortion!!!

So, you disagree with https://en.wikipedia.org/wiki/Distortion?

"Distortion is the alteration of the original shape (or other characteristic) of something. In communications and electronics it means the alteration of the waveform of an information-bearing signal, such as an audio signal representing sound or a video signal representing images, in an electronic device or communication channel."

 

[Sergei]

I really had hoped, that this red herring has eventually been layed to rest, but you are still running in circles and seemingly learned nothing.

Tell that to the war veterans, or industrial workers, who lost their hearing because they weren't provided with protection from acoustic events that weren't captured by then-common sound dosimeters, which included a 20 KHz low-pass filter before their measurement circuits. "If you can't hear it, you can't be hurt by it", right?

 

[SIY]

We’re going to need a bigger bottle of red ink.

 

[LTig]

So, you disagree with https://en.wikipedia.org/wiki/Distortion?

"Distortion is the alteration of the original shape (or other characteristic) of something. In communications and electronics it means the alteration of the waveform of an information-bearing signal, such as an audio signal representing sound or a video signal representing images, in an electronic device or communication channel."

Point taken - I thought of harmonic distortion, since you wrote of added higher frequencies not present in the original signal (aka harmonic distortion) which cancels bass roll off. In audio we talk about harmonic and nonharmonic distortion and both means adding frequencies, not weakening or strenghtening existing frequencies.

Actually the simplest way to let a small speaker sound bigger than it is is to have a bump in the frequency response of +6 dB at 100 Hz. This increases the loudness of the second harmonics of frequencies around 50 Hz. Have a look at typical hifi speakers and you find this bump almost everýwhere.

 

[PierreV]

I sense this paper landing soon

https://royalsocietypublishing.org/doi/full/10.1098/rspa.2015.0624#d3e4088

 

[LTig]

Tell that to the war veterans, or industrial workers, who lost their hearing because they weren't provided with protection from acoustic events that weren't captured by then-common sound dosimeters, which included a 20 KHz low-pass filter before their measurement circuits. "If you can't hear it, you can't be hurt by it", right?

I can't see what that has to do with timing resolution in digital audio? Anyway, I'm glad that my speakers do not emit a lot of SPL above 20 kHz so I cannot lose my hearing when playing hires audio.

 

[LTig]

Some of the Nelson Pass amps are good examples. Measurements show that they are highly distorting. Yet some people keep raving about how the amps perceptually improve certain types of music, captured on certain types of media.

DBTs are kinda funny to apply here - the distortions are so obvious and high. It is not about being able to differentiate, it is about preferences, in the context of specific music, recording media, and individuals.

Don't get me wrong - I have absolutely no problem when people prefer a specific sound. I just don't buy it when they say that this sound is true fidelity, especially when measurements show that it's clearly not the case.

 

[SIY]

I can't see what that has to do with timing resolution in digital audio? .

It doesn’t, of course. But every time I think his arguments can’t possibly get more mendacious, he proves me wrong.

 

[MRC01]

You may be able to design circuits where distortion in one part cancels distortion in another part, e.g adding them if they are 180 degree out of phase. ...

Indeed, that's one way to intuitively visualize how negative feedback reduces distortion. Though negative feedback is inverted, not phase shifted.

 

[MRC01]

... Some parts of the delivery chain remain expensive though, for instance low-distortion speakers.

You can have low distortion (clean), wide bandwith (full), or high amplitude (loud). Pick any two. If you want all three, it ain't gonna be cheap.

That's always been the case, and probably always will be. No matter how much cheaper, faster and better computers, software and signal processing gets, making actual sound (changing air pressure in a room) requires a physically large and carefully engineered mechanical device.

 

[Cosmik]

I am glad that most people working in audio pay no attention to this idea that 'harmonic' distortion might have magical perceptual qualities. The distortion of a bent transfer function is only harmonic in the sense that it generates harmonics when stimulated by a single tone, and even then it will not be constant with level. It would be better analysed as a bent transfer function rather than a "Signal-dependent complex harmonic synthesiser with proprietary analogue lookup table function".

People have a fantasy that a box containing a couple of resistors, a transistor or two and a PP3 is going to transform their recordings, or that their favourite circuit's drawbacks might, in fact, be found to have magical properties. Wishful thinking.

It belongs in the realm of listening to a system rather than through the system - which some people no doubt do, but establishing which of those two they are for your listening test may be tricky. I suspect most of us may switch between the two modes of listening depending on just how good or bad the system is. Even I can appreciate the 'warm tone' of an old valve radio, but I am certainly not listening through it.

 

[Blumlein 88]

Point taken - I thought of harmonic distortion, since you wrote of added higher frequencies not present in the original signal (aka harmonic distortion) which cancels bass roll off. In audio we talk about harmonic and nonharmonic distortion and both means adding frequencies, not weakening or strenghtening existing frequencies.

Actually the simplest way to let a small speaker sound bigger than it is is to have a bump in the frequency response of +6 dB at 100 Hz. This increases the loudness of the second harmonics of frequencies around 50 Hz. Have a look at typical hifi speakers and you find this bump almost everýwhere.

I assume he was referring to the missing fundamental principal. You can get the ear to sort of hear a fundamental with the harmonics present and no actual fundamental. So it sounds deeper than it is.