Rob Watts
Member of the Trade: Chord Electronics
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- Apr 1, 2014
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Correct - no user volume control on Qutest.
And no Chord DAC implements Roon controlled volume via USB commands.
I doubt very much that Roon would decimate whilst doing something simple like adding a volume control.
Volume control function involves taking the data, multiplying it by a coefficient; if your data is 24 bits, and the coefficient is say 24 bits then the result is 48 bits. But we need to get it back to 24 bits (or 32 for USB) and this is where the problems start. Normally, you truncate by using dither - just truncating by discarding the unused bits creates distortion so don't do that - but dither isn't perfect. The best from a transparency POV is Gaussian dither, which is better than the usual triangular dither - you get noticeable better sense of depth and detail resolution from Gaussian. The only way of completely maintaining full transparency when truncating is to use 11th order noise shaping, and this only at 705/768 kHz.
Having said all that, you would be better off using Roon to do the volume control than using a pre-amp or a passive volume control, as these all add distortion and degrade small signal accuracy too.
Yes keep your source bit perfect (apart from when you have to do volume control with Qutest) is the best approach.
And no Chord DAC implements Roon controlled volume via USB commands.
I doubt very much that Roon would decimate whilst doing something simple like adding a volume control.
Volume control function involves taking the data, multiplying it by a coefficient; if your data is 24 bits, and the coefficient is say 24 bits then the result is 48 bits. But we need to get it back to 24 bits (or 32 for USB) and this is where the problems start. Normally, you truncate by using dither - just truncating by discarding the unused bits creates distortion so don't do that - but dither isn't perfect. The best from a transparency POV is Gaussian dither, which is better than the usual triangular dither - you get noticeable better sense of depth and detail resolution from Gaussian. The only way of completely maintaining full transparency when truncating is to use 11th order noise shaping, and this only at 705/768 kHz.
Having said all that, you would be better off using Roon to do the volume control than using a pre-amp or a passive volume control, as these all add distortion and degrade small signal accuracy too.
Yes keep your source bit perfect (apart from when you have to do volume control with Qutest) is the best approach.
