Hm, apparently there is also an option to use an optical (S/PDIF) cable, to connect motherboard digital S/PDIF output to the DAC, then there is no need to use the DP at all I suppose.

Last edited by Shmerl on 4 Dec 2019 at 2:32 am UTC

Just get a good USB DAC :) there are plenty to be found.

I myself for example use Focusrite Scarlett 2i2 for the last 5 years or more. Works amazingly

Looks like using SPDIF can reduce interference, which is the reason I really wanted an external DAC in the first place.

Quoting: ShmerlI've never really used DisplayPort audio capabilities, but supposedly it could provide a better result, if you can get the digital output from there, and combine with good quality DAC that's better than what you get on common motherboards.

The question is, how can it be done, when DP is connected to a monitor? I.e. I don't want to use monitor's built in DAC which is likely very low quality, but want to find a high quality external one. How can such setup be organized? Can one DP output go to the monitor, and another to DAC for example?

And a question about DACs. I'm not an expert, and searching around I found the ODAC project which is described as one of the best DAC designs:

https://nwavguy.blogspot.com/2012/04/odac-released.html

There are hardware implementations, like JDS Labs DACs: https://jdslabs.com/shop/?category=featured

But they are using USB for input. How DP can be used in such case, or I'd need to find a DAC that takes DP in somehow? Or it's done on the audio driver level, and the signal from the video card's built in audio can be routed to the USB?

currently pulseaudio will allow you to route audio to any audio channel you prefer; DP, HDMI, USB, onboard audio, etc.

I currently have 2x 40in TVs attached to my rig, one via HDMI and the other via DP. in the audio setti gs i can choose which device i wish audio to be processed by. in my case, HDMI, DP, onboard audio. If i pair my bluetooth headset, i can route audio to that as well. You can also route audio from apps to certain devices, ergo, i can route game audio to HDMI and voice comms to the headset.

it is possible to purchase a HDMI/DP audio extractor and attach that to an output such as a home theatre system if you'd like.

I'm not sure how the sound quality would compare to SPDIF as I've never used SPDIF so i have no point of reference.

I also found some comments, that DP can be useful for surround sound, which is supposedly not going to work over USB or SPDIF? Though I didn't really find any standalone DACs that take DP input, so such setup will require some converter.

I'll probably go with USB or SPDIF for now.

Last edited by Shmerl on 4 Dec 2019 at 10:05 pm UTC

One review of JDS labs amplifier + DAC combo: https://www.themasterswitch.com/review-jds-labs-objective2



From all the sources, it looks quite solid.

Quoting: ShmerlI also found some comments, that DP can be useful for surround sound, which is supposedly not going to work over USB or SPDIF? Though I didn't really find any standalone DACs that take DP input, so such setup will require some converter.

I'll probably go with USB or SPDIF for now.

SPDIF doesn't support uncompressed audio with more than 2 channels. That said, it's rock solid 80's technology usually implemented in pure hardware on the DAC side. TOSLINK can give you optical isolation, but I don't think any digital audio (DP, HDMI, SPDIF over RCA) implementation worth anything would leak significant interference to the analog side. It would still protect your DAC from voltage spikes should something terrible happen to your PC. One possible future problem is that fewer and fewer motherboards come with optical out these days and the situation is probably only going to get worse. I remember watching some MB comparison video where an SPDIF connector was derisively called "obsolete". The guy probably thinks the same about 3.5mm jacks...

AFAIK you could put pretty much anything through USB as long as you have the appropriate hardware and drivers. Multichannel is supported in the standard, but I don't know how useful/used it is in practice. As usual there is plenty of proprietary BS going on with these devices.

Since you seem to be looking at headphone amps, you probably won't need to transfer multichannel audio anyway. That JDS DAC doesn't support 192kHz sample rate so remember not to feed it that. Qualitywise 96kHz will sound exactly the same. Supposing you can even find material on that quality level.

Quoting: NonjuffoSPDIF doesn't support uncompressed audio with more than 2 channels. That said, it's rock solid 80's technology usually implemented in pure hardware on the DAC side. TOSLINK can give you optical isolation, but I don't think any digital audio (DP, HDMI, SPDIF over RCA) implementation worth anything would leak significant interference to the analog side. It would still protect your DAC from voltage spikes should something terrible happen to your PC. One possible future problem is that fewer and fewer motherboards come with optical out these days and the situation is probably only going to get worse. I remember watching some MB comparison video where an SPDIF connector was derisively called "obsolete". The guy probably thinks the same about 3.5mm jacks...

Interesting. I've never used SPDIF before, but actually mostly high end motherboards support it. Asrock X570 Taichi has it. Hopefully they aren't planning to drop it any time soon. It's for sure not any more "obsolete" than a regular 3.5 mm audio jack.

Quoting: NonjuffoAFAIK you could put pretty much anything through USB as long as you have the appropriate hardware and drivers. Multichannel is supported in the standard, but I don't know how useful/used it is in practice. As usual there is plenty of proprietary BS going on with these devices.

So USB can also drive surround, using regular open standards? That's good.

Quoting: NonjuffoSince you seem to be looking at headphone amps, you probably won't need to transfer multichannel audio anyway. That JDS DAC doesn't support 192kHz sample rate so remember not to feed it that. Qualitywise 96kHz will sound exactly the same. Supposing you can even find material on that quality level.

Yes, regarding surround that was just in theory, right now I plan to make a setup for headphones, that's why I was looking at that DAC and amplifier. As you said, SPDIF / TOSLINK should be good enough for that. I'll take a look at frequency that's fed to the output. Is that something that's configured on the ALSA level?

Last edited by Shmerl on 6 Dec 2019 at 1:00 am UTC

Some interesting details here: https://alsa.opensrc.org/DigitalOut

Quoting: ShmerlSo USB can also drive surround, using regular open standards? That's good.

In theory yes, but it depends on the USB device. I have no experience of these so I can't say what the market is like.

Yes, regarding surround that was just in theory, right now I plan to make a setup for headphones, that's why I was looking at that DAC and amplifier. As you said, SPDIF / TOSLINK should be good enough for that. I'll take a look at frequency that's fed to the output. Is that something that's configured on the ALSA level?

You need to tinker away with pulseaudio / ALSA to enable the better bitdepths and sample rates. By default you probably only get 44.1/48 kHz @ 16-bits. Meaning that everything else is sampled to one of those. Coincidentally I'm personally fine with the defaults. All my music goes out in its native 44.1/16b resolution when it's the only source playing. I'm not so picky about other audio. For mixing multiple audio sources a better bit depth could theoretically help, but I don't really see the point.

I think [this write-up](https://people.xiph.org/~xiphmont/demo/neil-young.html) explains the realities of digital audio playback much better than I can.

Quoting: NonjuffoI think [this write-up](https://people.xiph.org/~xiphmont/demo/neil-young.html) explains the realities of digital audio playback much better than I can.

Yes, I've read that before actually.

I noticed that SPDIF outputs are shown without volume bars in ALSA mixer. Does it mean that software volume control (like in KDE) will have no effect on such setup, and using the hardware volume dial on the amplifier is the expected method? I.e. SPDIF is supposed to be just a pure signal, and the rest handled by external hardware? Or PulseAudio volume control will still have an effect on it?

Last edited by Shmerl on 9 Dec 2019 at 3:57 am UTC

I can’t check right this second, but I’m sure Pulse lets you adjust the volume of digital signals. I know for a fact that I can adjust the volume of audio sent via HDMI. This isn’t possible on e.g. my Mac, which forces me to use the monitor’s controls and that’s less than ideal.

You can adjust SPDIF output volume with pulseaudio controls, but pulse often seems to bundle the volume settings in unintuitive ways. For me its easier to just set SPDIF out to 100% and use application/amplifier controls instead. You can test yourself with pavucontrol what the controls actually do. You don't even need to connect anything (unless you actually want to hear something).

Setting player/SPDIF less than 100% means you start losing detail depending on the material. There is a limited number of bits after all (unless you pad with larger bit depth). I don't know if pulse forces some additional signal processing, but this should be the "purest" setup.

Just got my DAC and amplifier, and set them up over optical SPDIF from the motherboard output on the back. The sound is very clean! JDS Labs did a good job with it. Even on max amplification - there is no noise.

Last edited by Shmerl on 12 Dec 2019 at 11:37 pm UTC

Is there any tool that visualizes current audio output in Pulse or ALSA?

ProjectM? ..or what you mean exactly by that

I mean something similar to how Audacity displays audio graph.

Last edited by Shmerl on 19 Dec 2019 at 6:38 pm UTC

GLava, cli-visualizer, cava, spek, spectrum3D etc

some links also:

https://github.com/karlstav/cava
https://github.com/dpayne/cli-visualizer
http://spek.cc
https://github.com/jarcode-foss/glava

edit: ohh wait, you mean just the peaks of left and right channel?
that i dunno if there are any.

Last edited by Xpander on 19 Dec 2019 at 8:04 pm UTC

I mean simply the waveform graph: https://en.wikipedia.org/wiki/Waveform

That's what Audacity displays for audio by default:



Realtime audio visualizer can display it by storing some amount of history of what was played before I suppose.

Last edited by Shmerl on 19 Dec 2019 at 8:30 pm UTC