You're going to want something with asynchronous USB then. The JKMK3 converter would be a good choice, it's 100% battery powered, so you can use the Empirical Short Block with it. That will cut the Vbus line from the USB cable, and should eliminate any difference (or at least most of the difference) from running the MacBook on battery power vs. the SMPS.

If I connect a very low jitter transport (says audiophilleo 2, 2.6ps listed spec) to a middling receiver chip (say CS8412, max 200ps listed spec), would the resulting jitter be somewhere in between, same as the transport or same as the receiver? Or it's more complicated than that?

If I connect a very low jitter transport (says audiophilleo 2, 2.6ps listed spec) to a middling receiver chip (say CS8412, max 200ps listed spec), would the resulting jitter be somewhere in between, same as the transport or same as the receiver? Or it's more complicated than that?

Once the inherent jitter of the source gets low enough, you're going to run into the limitations of the receiver chip. There's nothing you can really do about that, if you just love the sound of a PCM63P-K DAC you're just going to have to put up with the sucky digital receivers that go along with them.

The input stages of these DACs are not good at rejecting high levels of source jitter. When you add that on top of the mediocre performance of the CS8412, the results are very disappointing. I had that experience with my now departed EAD DAC.

You'd want to use a DAC with a USB receiver that is self powered. Many of them use the Vbus line to power the USB input, and with a notebook running on a SMPS that means lots of DC ripple and a very noisy ground. The AQVOX or a Vaunix Lab Brick are better than nothing, but the best way to do it is to have a self powered USB input and cut the Vbus line entirely.

You'd want to use a DAC with a USB receiver that is self powered. Many of them use the Vbus line to power the USB input, and with a notebook running on a SMPS that means lots of DC ripple and a very noisy ground. The AQVOX or a Vaunix Lab Brick are better than nothing, but the best way to do it is to have a self powered USB input and cut the Vbus line entirely.

Fair enough, so the Dacport LX wouldn't be good (bus powered)?