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RE: In theory.....

Posted by cics (A) on January 24, 2008 at 05:42:41

In Reply to: In theory..... posted by ....Theory and practice are the same.... on January 24, 2008 at 01:18:48:

My preference is ladder based analogue VCs as implemented in AA Prestige CDP. I put together a second minimalist setup using foobar's digital VC and was expecting poor volume control. Not so. It sounds good at low levels - no loss of details, harmonics etc.. Hence this analysis.

EMU 1616M is an excellent card.

On digital you comment:

Now lets attenuate the Signal by 24db in the digital domain, AFTER upsampling to 24-Bit (not that this is neccesarily a good idea in itself). You have now barely achieved 16-Bit equivalent but attenuated performance after a lot of math had plenty of time to distort your music more than a good quality analog volume control.

Not sure if I understand you correctly. The math as I'm seeing it (and I could be wrong) gives an effective 20 bit resolution at -24db and not the 16 bits you mention. Likewise, -50db yields highly accurate attenuation using same technique. Also, at 24 bits, rounding error due to integer conversion from 64 bit double precision is factors less than 16 bit.

You mention "the digital domain using the volume control build into the HDCD Digital Filter". Such chip based digital VCs is not my preference.

I'm not religious about VC, just the theory using 64 bit double precision suggests a better alternative. This assumes a high quality DAC (with SNR better than 108db) is used.

I know foobar implements its DSP in double precision and VC is done after DSP processing (otherwise we would experience a lag effect when volume is changed). It would be interesting to know how exactly VC is done. (Any foobar developers here?).

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