Compatibility question regarding a Chord 2Qute and a PS Audio Perfectwave Transport

I’m doubtful that connecting to the USB interface of the DAC would be practicable or even possible in this case. While of course there are many USB-to-coax adapters that are available, I don’t know of any adapters that convert in the opposite direction. A device providing a USB output would have to either be a computer or somehow emulate a computer’s USB-related functionality. And if there are such devices I would question how well they perform.

Lowrider, as I interpret various statements in the manual for the PWT its XLR output appears to simply be balanced AES/EBU, presumably 110 ohms. I say that despite there being some potentially misleading statements about the signals on that output being "S/PDIF encoded."

I have no first-hand knowledge of either component, but I wouldn’t be surprised if Charles is correct in anticipating that a straight coax link with a good quality 75 ohm digital cable (preferably RCA to BNC, or alternatively RCA to RCA + an RCA to BNC adapter) would work fine.

If you decide to proceed in that manner, it may be a good idea to ask PS Audio if they would recommend a particular length for the digital cable. The optimal length may depend to some extent on the unspecified risetimes and falltimes of the signal provided by the transport, among other variables involving the cable itself and the accuracy of the impedance match between the cable and each of the components.

Regards,
-- Al

Andrew, thanks for providing the link to the Stereomojo review. The reference to "S/PDIF via balanced XLR" in the review should most likely have said "S/PDIF encoded via balanced XLR." That would be consistent with what is said in the PWT manual, which also indicates that the XLR output is AES/EBU compatible (as stated in the excerpt you quoted). AES/EBU compatibility necessitates a nominal impedance of 110 ohms, and various other signal characteristics that differ from coaxial S/PDIF. AES/EBU and S/PDIF **encoding** is very similar, the difference being in certain control (non-data) bits. And surely the encoding that is used on the XLR output of the PWT would have been designed to be compatible with the AES/EBU inputs of consumer-oriented DACs.

Also, regarding the following comment that is stated in the review in support of I2S as being the best performing output...

The PWT uses an asynchronous clock that is completely divorced from pulling data off the optical disk when using I22 [sic]. Normal clocks float with the disk’s output and can introduce artifacts.

... while I wouldn’t quite classify this as techno-gibberish, I’ll say that it is not particularly meaningful and shouldn’t be taken too seriously.

Finally, to add clarification to my earlier comment about there being no coax to USB adapters that I am aware of: There are, of course, adapters that can provide many kinds of non-USB devices with a USB interface. However in all such cases that I am aware of those devices enable a non-USB peripheral to communicate with a computer’s USB "host controller," and would not enable a peripheral (i.e., a non-computer, lacking USB host controller functionality) to communicate with another peripheral, such as the USB interface on a DAC.

Good luck. Regards,
-- Al

Well, I’m not sure what to suggest regarding that cable. On the one hand I would of course consider a recommendation provided by PS Audio for a cable to be used with one of their products to be extremely persuasive. On the other hand I don’t see how a cable employing that kind of construction can maintain an accurate 75 ohm impedance, at frequencies extending far into the MHz (radio frequency) region (those frequencies being very important in the transmission of digital audio signals), and without significant variations in the impedance along its length.  Not to mention the lack of shielding.

BTW, I note that Anti-Cables only offers their digital interconnects in a length of 1.5 meters, and near the bottom of their web pages on those cables they reference the paper by Steve Nugent of Empirical Audio which explains the rationale for that length. That length should be viewed, IMO, as providing the best odds of being optimal (unless an extremely short length is practicable, such as 6 or 8 inches or so), but both technical considerations and anecdotal reports that can be found here and elsewhere suggest that it will not always be optimal. As I mentioned earlier what length will be optimal depends on signal risetimes and falltimes (the amount of time it takes for the signal to transition between its lower and higher voltage states, and vice versa), which is almost never specified, and several other component and cable dependent variables.

Good luck. Regards,
-- Al