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Does Foobar really leave original music bits unchanged when paired with a DAC

post #1 of 3
Thread Starter 

Hi, this has puzzled me for a few hours, I hope somebody can figure this out.

When Foobar2000 player application is paired with an external DAC and the necessary settings have been made in the playback settings (namely changing playback output to channel the bits to the DAC via WASAPI, as well as changes to the Playback preference turning off any ReplayGain), I found that although the main sound control of my PC loses control of my DAC music volume (which I suppose is understandable because the computer sound card mixer and internal DAC loses control of the music channeling to the external DAC), the puzzle is that Foobar volume control can still control the volume of the music going out to the external DAC.

If Foobar really left the bits untouched, then I think Foobar should be unable to change the volume, because theoretically a change of volume will involve some sort of digital bits multiplication to increase the weight of the bits going out to the DAC.

Can someone set me straight here please?

post #2 of 3

Think of WASAPI as making a direct link between the DAC and Foobar. It skips your PC's volume control, but Foobar's volume control happens "before" WASAPI. The bits coming out of Foobar are untouched, but Foobar can still touch them before they leave. If you set the output to 24 bits (same part of the Foobar menu where you select WASAPI and turn off ReplayGain), then you can mess with the digital volume considerably without affecting the sound. This is because the digital volume control acts on the extra 8 bits added by playing a 16 bit with 24 bits of headspace. I've read you get about 20 Db of play in the digital volume before you start affecting the original 16 bits of the signal. Assuming you are playing 16 bit music, anyway.

post #3 of 3
Thread Starter 
Quote:
Originally Posted by manbear View Post
 

Think of WASAPI as making a direct link between the DAC and Foobar. It skips your PC's volume control, but Foobar's volume control happens "before" WASAPI. The bits coming out of Foobar are untouched, but Foobar can still touch them before they leave. If you set the output to 24 bits (same part of the Foobar menu where you select WASAPI and turn off ReplayGain), then you can mess with the digital volume considerably without affecting the sound. This is because the digital volume control acts on the extra 8 bits added by playing a 16 bit with 24 bits of headspace. I've read you get about 20 Db of play in the digital volume before you start affecting the original 16 bits of the signal. Assuming you are playing 16 bit music, anyway.

 

O I see, that explains why it makes sense to use a 24bits DAC even if my library are 16bits 44.1KHz CD quality FLAC files .

Thanks manbear, pretty good information.

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