How should I interface a desktop PC and a Marantz PMD560 to the SPDIF out on an LS9-32?

Question

I'm looking to use the coaxial SPDIF out on Yamaha - LS9-32 to record a stereo mix on both a Marantz - PMD560 and a rackmount PC. The PMD560 has unbalanced phono inputs and the PC has USB and motherboard 3.5mm line audio input only. I'm not looking to spend too much on doing this but I do want something robust without too much chance of ground loops. It also important that the Marantz recorder works with the PC off. How should I hook it up?

This will be a permanent install and there's plenty of space at the back of the racks and I may possibly be able to expose 1U of rack space if I have to.

(I know the LS9-32 has lots of other output options but we are using them all for other things).

The desktop PC audio line out is connected to an Behringer ADA8000 which is connected with ADAT and BNC word clock to the LS9-32. With the word clock connection in place we do get some hum on the signal from the PC.

Answer 1

Assuming that your PC and your Marantz recorder (and your mixer) are powered from the same power strip (or whatever) the chances of a ground loop seem low enough that it would certainly be worth trying it.

You could even take advantage of the RCA outputs to supply the recorder, and use the 3.5mm "headphone" output to supply the PC.

If you do have a ground loop problem, you can deal with it as it appears. Don't go looking for trouble where it may not exist.

Answer 2

Currently I'm thinking something like this USB DAC.

Not clear whether that will cause ground loops between the PC and the Marantz.

Answer 3

This is a high end model for your Marantz. JDS Labs

And this is a budget model. Orei

Neither require a computer. The website for your Marantz unit mentions Phono inputs which is inaccurate. They are line inputs as listed and confirmed in the manual. It's a big difference but you have the right one. Only other thing you need is RCA male/male patch cable and coax digital audio for your connection to the DAC.

The Marantz unit has a line output. I would connect this to the PC with an RCA male to 3.5mm male patch cable. I would run a test to see if the unit passes audio through while monitoring / recording.

If it does not in certain modes, then you cannot perform your simultaneous recording in this way. You'd instead need a mixer with multiple outputs to accept the DAC output and split out.