Sounds like, in this hybrid mode, the clock is being recovered from AES source and is being used to drive the data to the PC, where it is picked up by the driver and convolver and then pushed back out to the dac on the output USB channel. That output from PC to the DAC over USB is presumably asynchronous? It's not clear to me.
For this hybrid mode, my gut tells me the
DAC is
asynchronous whereas the
PC is
synchronous due to this unique signal path:
AES -> USB Host (Input) -> PC
PC -> USB Host (Output) -> DAC
What is happening here is the DAC is both outputting the AES signal via USB to the PC and simultaneously receiving a USB audio input from the PC. As far as I can tell, those two processes are independent from one another.
With the DAC's output stage, the clock from the AES is being fed to the PC and PC's job is to stay in sync with the AES input's clock that is being looped into the PC via USB. The manual states that in order to get any input, the caveat is you have to ensure you set your PC's input sampling rate to match the AES input's sampling rate. So the PC is synchronous with the AES input.
Meanwhile, with its input stage, the only source that is visible to the DAC is the USB audio which means the DAC drives the clock, not vice versa. Once the PC receives the AES input, it can be processed, recorded, and/or sent back in whatever form you wish to the DAC presumably with any supported sampling rate. That is because the DAC input is insulated from the AES by the PC. For all intents and purposes, you could send white noise back to the DAC while recording the AES input via USB and the DAC wouldn't be the wiser. So the DAC is asynchronous.
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By the way, that would mean the DAC8 Pro would be an ideal (if not
the ideal) candidate for studio and broadcast. Link up all your microphone and instrument inputs at your AES interface, link into the DAC8 Pro via AES, watch the DAC8 Pro send it via USB into your workstation for processing and recording, and then your PC sends it back to the DAC for playback in whatever form you want. The applications extend
far beyond mere room and crossover calibrations.
For example, if you were running a studio, you could even set up a reference quality headphone station for your artists/producers/sound engineers with 4 independent stereo pairs linking up to 4 separate headphone amplifiers (the best candidate here would be the Geshelli Labs Archel2.5 Pro, which features XLR inputs). The artist(s) could hear the individual track, the producer(s) could hear the complete track, and the sound engineer(s) could hear whatever combination of elements they want.
Judging by these features in addition to the already world-leading measured performance, the DAC8 Pro is highly underrated as not only the definitive multichannel DAC in the audiophile market but a largely undiscovered giant killer in the pro audio market.