Bit-identical playback CAN sound different

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On 3/22/2021 at 2:24 PM, PeterSt said:

 

You realize that it is all about exactly that, right ?

(but the taming of it by various means and in various base states (statuses))

Perhaps we can explain this this way:

 

I think most people would accept that it is uncontroversial that playing back a bit identical stream through two different DACs will sound different? Right? I hope so because there are only those with a somewhat extreme view that believe the sound of the music is determined solely by the bit stream.

 

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....

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14 minutes ago, March Audio said:

Well my point still stands; that every room and its effects on the sound is different.  So why should we assume that any particular playback software will result in a noticeably different or better sound?

 

It should be fairly obvious that playback software which converts/upsamples and filters the bits might certainly affect the playback. All software provides some type of transform. It should be entirely uncontroversial that software might affect SQ, what is the argument here? This should be entirely uncontroversial.

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4 minutes ago, fas42 said:

 

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.

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

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3 minutes ago, March Audio said:

However we are talking about "bit perfect" software which does not modify the data.

As the digital stream enters the DAC it ceases to be entirely digital and becomes an analog signal. No one is saying that the analog streams are identical. 

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7 minutes ago, PeterSt said:

Jonathan, sure. But this time it is not about those phenomena. Just different buffer settings, for example. Your DAC's driver could do it. Both output the same (net) data (both as bit perfect). Both will sound different.

 

"bit perfect" playback has the implication to many people that the unmodified "pure" bitstream enters the DAC.

 

1) The computer becomes essentially the input filtering stage of the DAC in taking over the upsampling/conversion function which otherwise is typically done my the DAC. Your PCM1704 was often used with an 8x digital interpolation filter (on a separate chip). The connection between the computer and DAC should be seen as forming part of the DAC circuit.

2) at some point the analog characteristics of the digital signal become audible.

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4 minutes ago, March Audio said:

Those changes will be the same if two players feed the same data.

faulty assumption

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41 minutes ago, March Audio said:

Not an assumption, its based on testing.

 

Anyway please take part in the forthcoming test.

Yeah yeah this is a oermathread — show me the data please. 

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2 minutes ago, March Audio said:

This wont be a "measurement" test, its a subjective test about what you can hear.

Not interested, I’m happy with what I can hear.

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3 minutes ago, March Audio said:

Well thats a shame, its what this thread is about.

We were just talking about electrical changes and you switched it to subjective hearing tests — your methodology is irrelevant to me.

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14 hours ago, PeterSt said:

 

And so do I. Just set it to do that. Don't let the software upsample / filter. I suppose any software can still do that. :-)

In XXHighEnd that can be done too.

 

Ok, but I suspect we are in overall agreement about this issue. I know I am explaining it in an entirely different way than you are.

 

I am saying that the computer and it’s software firm an electronic circuit along with the DAC. Software changes the electrical “signature” if you will, of the computer, and the computer is electrically connected with the DAC. 
 

Depending on the details of the software and details of the DAC (not just yours but generally) certain processing can occur in either the computer or the DAC — regardless of the bits being identical. So the SQ might change, that’s all.

Quote

 

 

Totally unrelated because it is not about that situation whatsoever.

 

 

Following the above other two quotes ? No. It is not about that.

 

Apparently it is not easy to follow what's attested here:

 

1. Play back with one piece of software and one set of upsampling/filtering (hence do-not-change-that-ever);

2. Change a "buffer" of any type (numerous are in there).

--> The two files Mani uploaded are about #2. At the digital input of the DAC they would be equal (same checksums etc.). After loop-back to a digital capture, they would be equal (same checksum, but also the 100% same samples throughout). But they sound vastly different. Read Jud's quotes again. Or trust mine (I said the very same in advance of that).

3. Capture the sound of the two playbacks by microphone. Look at the diff files of it, might you be able to do something with that.

 

 

Well ok, but I am not questioning the possibility that this might occur. I don’t need to listen. I’m convinced that the SQ **might** be different, because the electrical stream might be different.

 

Here is a **different** concrete example:

1) a software setting modulates the rise time of the USB signal. 
2) the bits are identical 

3) it is well known that too fast a rise time causes electrical ringing in the USB receiver (Google folks) and consequently electrical changes **might** occur in a DAC.

 

Im not saying this *is* the case rather that it might be so I’m not at all surprised that bit identical playback might sound different. 

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55 minutes ago, March Audio said:

Ok that's a theory but we need some evidence to support it.

 

The data coming into a dac is not directly "coupled" to the dac chip.  It's buffered a clocked out locally.  So the potential ringing has to produce some secondary effect which influences the dac output.  It's not in the data.

 

As an example you could suggest it causes jitter in the clock.  Well we can easily measure that in the dac output.

 

To be audible any effect will be measurable yet it isxseemingly not possible to do so.  Hence I would look for different causes for what people claim to perceive.

I will defer to @PeterSt to give technical details about how his software couples to his DAC and how the software settings affect the electrical activity in the DAC — I can only speculate.