It *cannot* just be about 1's and 0's - surely?

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23 minutes ago, Mazza said:

What I don't get is *how* the playback volume can increase when all I am doing is shifting 1's and 0's over a 5v/3.6v cable and secondly,

 

Either that cable multiplied all data with 1.258, or it made the individual 1s and 0s 1.258 times heavier.

 

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19 hours ago, Mazza said:

I used three constant test tones/files ..... 100Hz, 1kHz and 2kHz....each 10 secs long and the increase in volume on any file was approx 2dB. So no transients, just constant tones.

 

Did you keep the position of the speakers and the microphone utterly constant between the tests, and your own relative position to them too?

 

At 1-2kHz in-room the slightest deviation may result in significant readout differences.

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5 hours ago, Hugo9000 said:

It would actually be rather cunning of them to sneak an active device into a USB cable. 

 

But still unlikely.

 

Suppose they embedded a processor in the lump that would detect PCM audio formats and sneakily increased the volume with 2dB, whille leaving all other data alone.

 

1) Sooner or later that would be discovered, and AQ would be lynched (*) of forums.

2) It would cause clipping on many recordings, and on some of these this would be audible clipping.

 

(* While the audiophile press would shrug it off.)

 

 

As for the battery bias thing: I remember people theorising about exactly that on forums 20 years ago. And didn't JBL/Infinity have battery bias on speaker crossover caps some time ago? Not very original, then.