Question about Coaxial and Toslink outputs from PC to external DAC

[Rodster]

I have perhaps what is a very stupid question, but here goes.

 

For years I output music from my Windows via a sound card, which contained a DAC chip. At first I used Creative Soundblaster cards, and later when I dabbled with Computer music creation I upgraded to M-Audio sound cards, and finally I got a RME Hammerfall sound card. This card has analog and digital out, and its DAC can handle 24/196 samples.

 

Fine.

 

Recently I got interested in outboard DACs for listening to music through headphones. I've done a lot of research on these DACs and have used a couple. Now, I understand outputting digital music through USB 2.0 to these DACS from my PC or other sources, such as an Android phone or Raspberry Pi, and that is what I have been doing up to now because USB was the only input to the DAC that handles DSD and sample rates greater than 192.

 

Lately I'eve been considering using my DAC as a substitute for my sound card in the PC I use for dabbling in music creation. And I've seen some people on various forums saying that with such-a-such DAC, the digital (be it coaxial or optical) input was (for whatever reason particular to that DAC) superior to its USB input. And I further see that many people use a digital output from a DAP such as a Astell & Kerns 120 or similar unit to stream music to a standalone DAC, such as the Chord HUGO, through a coaxial digital cable.

 

Now the point of my post is not to open up any debate about the relative merits of USB vs. coaxial or optical digital inputs or cables, but rather is a more basic question. To my knowledge, most computers or other front-ends for computer music do not come with coaxial or toslink outputs in and of themselves--these outputs are associated with some kind of sound reproducing system -- in other words, with a DAC. (Contrasted, of course, to USB which does exist independently of any particular function in the PC).

 

So, here is my question: Whenever you use a coaxial or toslink digital output from a PC or a DAP or whatever to send a music stream to a outboard DAC, is that stream going through the DAC of the PC or DAP before it goes to the external DAC? Or is it just a pure digital stream (akin to the stream that goes through the PC's USB output) that is in no way processed or affected by the DAC belonging to the PC's sound card (in my case the RME Hammerfall) or the DAP's DAC?

 

In any event, when using the coaxial or optical output of a PC's sound card, are there settings in the sound card software or in Windows that need to be set to avoid any conflict with the external DAC in terms of sample rate or the clock settings (forgive my ignorance, before now I've never had to worry about syncing with external clocks or the like, because the PC sound card was the only digital input or output in my system).

 

I hope this question makes sense. I'm basically trying to understand the different pathways that can be used between a PC and an external DAC, and what I need to worry about when using any of them. USB seems pretty straightforward, since I can simply bypass the PC sound card and output through the external DAC drivers. But when using a coaxial output, I have to send the stream through my sound card, and I want to make sure I do it so that the sound card really doesn't affect the stream in any meaningful way or in any way conflicts with it.

 

Thanks very much.

Rod

[toddrhodes]

Hello Rod. It is my understanding that when using things like WASAPI or Kernel Streaming, in conjunction with ANY digital output (USB, SPDIF, Toslink), the digital stream is passed directly from RAM/SSD/HDD to the DAC. I believe this to be true as I am using my internal sound card TOSLink to output to my DAC, a Schiit Gungnir. Having A/B'd USB vs. the onboard Toslink (aka optical out), the Toslink is far favorable relative to my current USB setup. I'm limited in what I can output thanks to the crappy Realtek Toslink implementation I'm saddled with but even considering that, it sounds better than USB. I'm hoping a better USB cable (Supra) and a Regen will get me back to using USB out to my DAC.

 

By using WASAPI or Kernel Streaming or ASIO, which I left out in my initial statement, you are bypassing all of the internal mixers and processing within your PC to arrive at a direct digital stream to your DAC.

 

I hope this helps!

[Rodster]

Thanks very much for your reply! That's exactly what I wanted to know--the the digital stream is untouched by the internal sound card DAC on its way to the external DAC. So if I understand correctly, by selecting the ASIO driver that belongs to the external DAC as the output source, the digital stream will bypass the DAC of the internal sound card.

 

Thanks again.