Usb or Optical

I would invest in a JCAT USB card ($495), though it’s probably more than you want to spend. Alternative, the Matrix Element H USB card ($329) or the SOTM tX-USBexp USB 3.0 card ($350) might be options. That being said, it’s hard to say whether the motherboard USB output would be better or worse than the motherboard optical output. You would just have to test to see.

If you are using an AMD processor, then look into a Pink Faun S/PDIF card ($360). That will likely be better than a USB card, since you are not looking for DSD.

This entire post needs some background info, First of all, all things equal, and for good technical reasons, USB > SPDIF and within SPDIF Electrical > Optical. So an SPDIF card would be pretty much the last choice.

So USB has the most potential, mostyl because it is aysnchronous and allows the DAC to reclock everything. The DAC likely has a better clock than the transport, and there is no long cable to mess it up, so less jitter.

Now, if you are using the solution with the best potential, which is USB, you have the further option of isolating either the sending side or the receiving side. Either works. I dont know enough about he internal design of either to be sure how well isolated one of the other is. Assume the sending device is poorly isolated - all PCs, Macs and laptops are poorly isolated (unless you buy one with a custom card, like an Allo streamer).

Optical (toslink, SPDIF) has one advantage: in a high EMI environment it is immune. That’s why its on TVs.

That said, one of this first posts hit the nail onthe head:  with the equipment you describe the differences are likely academic.

I do appreciate all of the input I just spent $400 on a brand new DAC I'm not dumping another $400 into a USB card to go into my computer that's not going to happen.  I'm running at USB right n. I don't understand why I need another special card just to run sound out of my computer into a DAC anyways I appreciate everybody's input and it probably would make a difference but I'm not spending $400 on a card.

So an SPDIF card would be pretty much the last choice.

I don’t actually completely agree with this. USB is required for DSD. However, USB is a data packet interface. It is true that an upgraded USB audio card will help things, but this is not necessarily superior to S/PDIF card. It really depends how good the USB-to-i2s section is in your DAC.

I had an opportunity to compare USB vs S/PDIF on two different DACS. The music server was a $20,000 Pink Faun 2.16x with both USB and S/PDIF AES/EBU output cards. Both output cards had the OCXO clock upgrades.

When using my friend’s $16,000 DAC, the USB connection just did not sound good. It had a hard solid-state edge and the bass was weak. The DAC actually sounded amazing when using a AES/EBU cable, but it was very apparent that the USB connection sounded like crap.

Now when I put in my modified LKS MH-DA004 dac, the USB vs S/PDIF was a lot closer. The USB input on the LKS dac was significantly better than my friend’s $16k dac. It actually sounded pretty good, but it still was not as good as the balanced SPDIF input (AES/EBU).

to one post above, with the exception of some recent upgrades to the standard that essentially no one implements, optical SPDIF is alwasy limited to 16/44 or 16/48. Its part of the limitation (along with more jitter, lots more).

So an SPDIF card would be pretty much the last choice.

I don’t actually completely agree with this.

You may not agree, but your reply indicate you don't understand the reasoning (despite the fact that i laid it out).  USB is asynchronous. It simply reads bits into abuffer and is then reclocekd with a high quality clock.  If you don't have a high quality clock, you dont have a HQ DAC.

SPDIF, including Toslink, demands that the source clock and the sink derive timing.  Not good and the source clock is likely quite poor anyway

People love re-clockers. Yet a USB interface IS a reclocker. It must be.