Bit-identical playback CAN sound different

[fas42]

Thanks for that - yes, it's obvious ... a simple tell: listen to the quality of the "ss'es" in the vocal, between the two. Transients are much better defined, in one of them.

[fas42]

What's amusing, of course, as Peter points out, is that the differences could be due to all those little electrical doodahs going on - which we will have to eliminate to try and make the measurement correlate ... but, of course(!!), our subjective hearing abilities can't possibly be picking this up, can they now ... ??

 

It's really very funny, 😁 ...

 

[fas42]

Had a look myself using DeltaWave - there definitely appears to be something going on; in the high frequency content, there is a regular mismatch of the waveform, the difference waveform shows this quite clearly.

 

But to be more sure of this, a controlled recording of something like 3 successive versions needs to be done, in quick succession: setting 1; then setting 2, then setting 1 again. This would hopefully rule out changes in the environment over time, any warm up variations; and, show consistency of the playback, recording chain.

[fas42]

Just now, jabbr said:

If we accept that a difference in any electronic circuit causes a difference in SQ, then we need to realize that software in fact modifies the electronic circuit in the playback chain. This should be entirely uncontroversial actually. I'm surprised that this debate continues....

 

The electronic circuit is not modified, in most situations, but the pattern of electrical activity over a certain time period varies, because of software changing the way the circuit operates. Therefore, if there is any breakthrough of electrical noise from the digital to the analogue side causing audible SQ changes, then changing the spectrum of that noise, by changing the nature of the activity, is highly likely to be audible.

[fas42]

22 minutes ago, jabbr said:

Sorry you just don't understand how computers work if you don't understand how software forms part of the electronic circuit. 

 

There is a hardware level - the physical bits of silicon, etc, on the board - and the software level - the instructions that drive the physical bits ... I would class changing the electrical circuit something like software activating a set of relays activating and deactivating two mainframes next to each; so one took over from the other, and the latter had its power cut.

[fas42]

10 hours ago, manisandher said:

I took 6 new mic captures, with two different bit-identical settings, A and B. The recording sequence was A, B, A, B, A, B. I then reduced each recording down to a 2-second snippet with a strong guitar pluck. So, we have 15 differences: three A vs. A, three B vs. B and nine A vs. B.

 

There's not a lot to take away from this, but here are the results from DeltaWave for completeness:

 

A vs. A and B vs. B (6 samples)

Average correlated null depth = 37.93dB (SD=8.40dB)

Average PK Metric (max) = -38.20dB (SD=3.78dB)

 

A vs. B (9 samples)

Average correlated null depth = 35.26dB (SD=2.45dB)

Average PK Metric (max) = -38.03dB (SD=5.20dB)

 

As I and many others have already speculated, there are just too many uncontrolled variables to get any meaningful results. And I would have to take a whole load more mic captures to get more accurate SDs.

 

I haven't totally given up... yet. I've been using my office system to date, because all the recording equipment is already set up for virtual meetings - all I have to do is swing the mic boom into position and hit record and play. But my home office looks out onto a main and usually noisy road. So, I'll switch to using my main system going forward... when I muster enough enthusiasm to do so 🙂.

 

Mani.

 

I would be curious as to what I could see in them, Mani ... would it be possible to post up a couple of versions of A, and a couple of B, please?

 

Thanks!

[fas42]

3 minutes ago, John Dyson said:

When talking about this kind of stuff, I'd rather look at the big picture...   What is the drive to 'tweak' or be worried about impairments that are a small portion of the actually controllable damage to the recordings?   Is it from frustration, and starting an OCD type process because of deep frustration about the quality?

Even if people don't directly perceive the impairments in the recordings, even with accommodation, there should be something 'subconscious' that hears the damage against the sound...

 

 

The reason for being fussy, about digital, is that very subtle impairments do major damage to the subjective perception of the sound. Which is why it's been a long drawn out process, getting it to the point where rusted on analogue fans grudgingly accept that it can actually be OK to listen to, 🤥.

 

SQ, with digital, is far more a "snap into focus" situation than analogue ... it either 'works', or it doesn't 'work', as a satisfying listening experience ... things are getting better, but we're a long way still from getting on top of it.

[fas42]

On 3/29/2021 at 8:33 AM, fas42 said:

 

I would be curious as to what I could see in them, Mani ... would it be possible to post up a couple of versions of A, and a couple of B, please?

 

Thanks!

 

Mani, I would again request, if it would be possible to upload several versions of A, and several of B.

 

Thanks very much ...

[fas42]

13 hours ago, manisandher said:

 

I've been experiencing these sorts of things for over two decades now - change this, the sound changes; change that, the sound changes. 3 years ago, I 'proved' it with my 9/10 score in a blind ABX. And I'm not the only one - there must be literally thousands of people who hear bit-identical changes as sounding different, mostly through different USB cables I suspect.

 

Once a system is working well enough, and once one's hearing is tuned into the subtleties of the changes, it's trivially easy to hear what's going on. Doesn't have to be someone who understands the "audiophile thing" - Bev regularly draws my attention to the fact that the SQ is sub-par, when my focus is elsewhere.

 

13 hours ago, manisandher said:

 

I totally agree that this opens up the opportunity for profiteers to take advantage of those of us who are on the OCD spectrum (all audiophiles perhaps?). This is where one's judgment comes in. Who's selling what? How credible are they? How trustworthy? Etc.

 

If no-one "in authority" fixes the thing, then you leave the door wide open for the shonks, etc, to walk right in ... the industry has reaped from what it's sown ...

 

13 hours ago, manisandher said:

 

It seems to me that there's something fundamental at play here that is not well-established and accepted. I believe that if we can explore it with an open mind, there may be something really fruitful at the other end.

 

Mani.

 

Not accepted, by the industry, is the problem. There is a fervent belief by the designers, etc, that one doesn't have to worry about a lack of overall integrity of the system - so long as your own box of tricks does magic things with measurable numbers, and sells well, all is good in heaven, 🙃. Which leaves the poor sod of a consumer in the poo, with a system which doesn't sound, "quite right" - and the crazy dance begins ... 🙄.

[fas42]

Peter's philosophy is very different from mine ... and that's fine. He wants to fix the noise at the source end; I want to block all noise, no matter how bad it is, from getting to the sensitive areas of the analogue circuitry - meaning, I should be able to have the 'worst' CPU activity happening, right next to the rig - and it makes no difference to the SQ ... the advantage of my approach, as I see it, is that using excellent levels of isolation ensures that the sound is always working well, so matter what the situation, electrically, is like around it.

[fas42]

35 minutes ago, manisandher said:

 

Happy to do that Frank, but I'd rather wait until I've got decent mic captures from my main system, if that's OK.

 

Mani.

 

Thanks!! ... There is definitely something going in what you've already posted - so, I'll take a closer look at that in the meantime, and see if i can pick a pattern ...

[fas42]

Does foobar ABX still do what it used to do? ... Never actually play the files you specify, but instead resample them, and write new versions of them to some temp directory which is 'unknown', for use in the test. Not exactly useful if the nature of the storage is what you're aiming to test, 😉 ...

[fas42]

What all these procedures do is optimise the electrical environment for the cleanest playback. Which varies per machine. And the version of the player software.

 

Previous laptop sounded a dog with foobar200 - so I checked other players around, and subjectively Media Monkey (MM) was a very good fit - for that PC! Allowed lots of fine tuning, did excellent buffering at start - easy to hear the improvements.

 

Current laptop, very different ... foobar was actually the best when I compared it with MM - so, what had changed? Obviously the m/c, but perhaps the latest foobar was just enough altered, and a better fit, for the new situation ...

[fas42]

The first time I tried the foobar software ABX comparator, I thought, "Hey, why does the playback sound much poorer than when using foobar directly!" ... which led me to work out what the comparator was doing. Right! It was making those temp copies ... so, its functionality as a comparison tool was inherently broken ...

 

It seem some people are incapable of understanding that circuitry that's reading and processing the track data are capable of generating electrical noise that by some route interferes with the analogue areas of the replay system. So long as one has faith that areas marked, Digital, and others marked, Analogue, are by magical means kept 100% apart, under all circumstances, then the gap of understanding will never be crossed ...

[fas42]

10 minutes ago, March Audio said:

There is no direct relationship between the data on the hard disk and what enters the dac chip.  The data has been copied and moved multiple times.

 

The issue is not the data per se, but electrical processes which by whatever means enable a copy of that data to be presented to the DAC input.

 

Quote

 

The real area of concern ground currents flowing from the computer to the dac along the USB shield and noise on the power lines.

 

This is neatly avoided by galvanic isolation which is incorporated into some dacs.  Otherwise buy a proper galvanic isolator (maybe the Intona devices) and the job is done.  There is no physical connection between computer and dac.

 

And that's the nub of it. Using the term "neatly avoided" doesn't mean that such is the case in the majority of rigs out there. That a well implemented solution is indeed possible is no guarantee that such is in place. And we still haven't worked out precisely what needs to be done to guarantee that RF noise, and noise fed between the two via their mains power leads is not having an impact