Regarding the quality of the DAC conversion - for me it`s important to check if the volume control is implemented by slicing bits from the samples (mul/div by 2/4/8/16/32/etc) or there is analog hardware potentiometers with digital control. Cheapest usb devices usually do not have analog potentiometers. Software volume control reduces the samples resolution especially in 16-bit mode. It can make your DAC to utilize 14 or less bits. If we want to prevent it, we need to set the volume to 100% on the software PCM and master controls and have potentiometers in our amplifiers - one for each channel. Since the analog potentiometers are noisy things and for 5.1 one would need a lot (6) of them, a digitally controlled analog solution is needed. Something like MCP41010. But note - the digital potentiometers add harmonic distortions (~0.05%) and have capacitance.
AFAIK X-FI HD ust like SB 1090 does NOT have harware volume control, so it slices bits (Software volume control). IMO creative is not a good design sold at not so low price. It doesn`t support usb asynchronous transfers (with precise clock to DAC) also.
I still have X-FI SB 1090 and have found several major design flaws (LDO selection for analog circuits, lack of muting circuit, relatively powerful processor that`s not used even to do software volume control, doesn`t support usb audio class 2 standard, doesn`t get detected as Hi-Speed USB2.0 w/o drivers, doesn`t support usb async operation, software volume control, turns off & on the analog power of the DAC and amplifier ICs during usb bus resets which (in combination with very fast ramp-up LDO regulator) causes irritating spikes when it`s directly connected to a powerful amplifier). I bought it because I thought that it`s something that it isn`t.
But did "Creative" fixed `em all in X-FI HD ?
How/where do you control the volume ?
more information about asynchronous and other usb DAC solutions here: USB
Edited by Gele - 5/19/12 at 11:11am