http://www.stereophile.com/content/ayre-acoustics-qa-9-usb-ad-converter
ADC chip inside is a sigma-delta type (Arda Tech), so any claims of this being a 'zero feedback' design are rather thrown to the wind. Note on the measurements page significant noise modulation (characteristic of S-D type converters) is visible at the higher frequencies - the FFT noise 'floor' shows a rise towards 20kHz. Fig3 shows around -140dB, with just 5dB input level reduction this falls to around -145dB. We might expect this to be audible as a change in the background noise 'colour' with signal level.
JA in his review says it sounds transparent (to an LP source) at 192k, not at 44k1 due to surface noise getting integrated with the music but then he's using S-D type DACs (dCS, Benchmark, Metric Halo are listed) to listen to the redbook.
ADC chip inside is a sigma-delta type (Arda Tech), so any claims of this being a 'zero feedback' design are rather thrown to the wind. Note on the measurements page significant noise modulation (characteristic of S-D type converters) is visible at the higher frequencies - the FFT noise 'floor' shows a rise towards 20kHz. Fig3 shows around -140dB, with just 5dB input level reduction this falls to around -145dB. We might expect this to be audible as a change in the background noise 'colour' with signal level.
JA in his review says it sounds transparent (to an LP source) at 192k, not at 44k1 due to surface noise getting integrated with the music but then he's using S-D type DACs (dCS, Benchmark, Metric Halo are listed) to listen to the redbook.
