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Does the volume coming into a DAC matter?

Help me out I can't quite wrap my brain around this one. I've got a number of DACs, some are in integrated amp components other stand alone. When hooked up to my laptop I noticed that with some, but not all of them, changing the volume on my laptop changes the signal strength. But, I thought we were just passing data over USB to the DAC to interpret and create an analog signal from. Therefore my assumption is that the volume is just another piece of data, and it's not actually changing the signal strength. So is there an optimal volume to set the inbound signal to a DAC? Or does it really not matter?
designtaylor

Showing 2 responses by erik_squires

erik_squires
16,733 posts
 
The biggest issue I know of is usually with how much a laptop's' mixer will alter the bits unless it is using exclusive mode, and sometimes even then you still require special drivers. What is the point of having a super expensive DAC if the data it is being fed has been significantly altered already by a less than careful process?

Yes, in general, if you can feed your preamp full-range signal, you are going to end up with less noise and distortion than if you feed it a small signal you have to amplify.

Having said that, I do use Roon's EQ features a great deal, but it is relatively careful, uses 32 bit math, and I do the volume control in my integrated amp.
erik_squires
16,733 posts
 
If you are using analog outputs, then you are right, the signal strength ( peak to peak of the voltage) is varying.

If you are using USB it will not. The stream of data is conveyed in the difference between two lines, and must be 200 mV or greater to convey a 0 or 1. More here:

https://www.quora.com/What-is-the-exact-voltage-of-a-standard-USB-data-signal-in-either-data-wire-Id...

Altering the volume in a digital stream is altering the stream of 0s and 1s, but the peak to peak or differential of the voltages remains the same.

Best,

E
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