Pro audio for recording has been shifting to USB over the past few years. They were heavily on Firewire or PCI card formats before, but USB has finally gotten fast enough to do the throughput, and of course it's much cheaper and more standard.

And thus throughput is not enough. In pro audio, we can't afford dropouts or lost data, even when the CPU is under heavy load.

I'm not a pro audio guy, but I think if you want to work with any external audio device and want that connection to be noise-free, your safest bet is still optical.

I have an external DAC/amp, and I had been using optical until I recently upgraded my workstation. Now I am using USB, because the new motherboard doesn't have optical; I assumed USB would be fine, so the lack of optical wasn't something I considered with the purchase.

Unfortunately there's an awful amount of hiss with USB on this DAC. I'm not knowledgeable enough to pinpoint what's causing it, but standard remedies I've found (eliminate ground loop, try ferrite cores, get a usb filter) have not made a difference. It could be the USB interface on the DAC side, I have no idea.

While I don't _need_ an external DAC, I like using one for a few reasons: mine has a low output impedance which is good for some headphones, a convenient switch to toggle between headphone and speaker output, and a big volume knob with really smooth action. I like it. The alternative is to use the motherboard's ports; this motherboard does jack sensing such that the rear line out gets disabled if something is plugged into the front, so switching between headphones and speakers involves plugging/unplugging the headphones all the time. I also don't like adjusting volume through a tray applet.

Since it’s USB, it has to be the DAC generating the hiss. No amount of electrical interference can do anything to the digital audio going Ofer USB.

The electrical interference can't do anything to to the digital audio, but interference on the USB cable can potentially be picked up by the analog amplifier circuitry in the DAC. I had a particular combination of headphone, DAC and amplifier years ago that I could hear electrical noise on when no music was playing.

Absolutely. I work as a sound engineer and have used lots of things of this type, and it's particularly easy to understand how a USB connection to the computer would wreck the sound of a cheap (sub-$1000, not professional) DAC.

Optical digital means perfect isolation from the ground plane of the computer. It's that simple. The DAC can do whatever it needs to manage its own noise levels, but you're pretty much guaranteed a huge difference from entirely decoupling the DAC from the computer's ground plane. That electrical interference can do a surprisingly enormous amount of damage to the analog circuitry of the cheap DAC, which itself is probably not very resilient at rejecting any sort of electrical interference.

But it sounds like its the same DAC, which was hiss free with optical. So it's not the DAC "generating" the hiss. Rather electrical "interference" making it over to the analog side from the digital side.

So it's the DACs fault, but maybe it's fair to say that it's harder to make a good DAC when USB is how the data is being delivered. I'm sure a high end USB DAC doesn't have this issue, but I'm pretty impressed with my cheap offbrand optical DAC that was $11. I'm guessing I would not be so impressed with the $11 USB version.

A higher quality USB DAC either has to do quite a bit of signal clean-up, and may use its own power supply rather than trying to clean up the USB power from the computer.

Optical has the benefit of always being electrically isolated.

I thought so too, but regardless, with this same device there is no hiss when connected via optical. So if I had the option, I'd be using optical vs. USB today, which was what the GP asked.

Logically, it seems like if you had a USB-optical dongle you would have no further trouble. I don't know if there is such a thing, but I do know that in that situation all the 'it's digital, so it should be perfect' talk becomes somewhat true.

You'd be converting from USB to optical, at which point you'd break the ground connection which would be where your hiss is coming from (assuming it's still noiseless when still being used with optical). Then, your concern would be jitter and whether the added conversion is adding lots of jitter to the equation. Your DAC might (or might not) be good at rejecting jitter noise. I've got a Lavry DA10 that's exceptionally good at rejecting jitter (in crystal mode), but that's mastering grade and maybe overkill for you.

It wouldn't add literal noise, but it's also possible for the USB connection to be more jittery than a different computer making the optical connection. That's partly hardware and partly software design (controlling how the data stream is buffered, and associated things that might slightly modulate the audio data clocking). So a change in computer feeding the DAC could also substantially affect the 'sound' of the DAC, as well as the noise issue you observed.

I agree, that should work. I haven't seen USB-optical devices that weren't straight media converters though. Everything that converts USB to spdif is advertised as a DAC, so I'd have two DACs.

This isn't a huge issue for me, it's just an example of where I'd prefer to use optical. If it ends up bothering me such that I need to fix something, I'll 'fix' the motherboard.

> Unfortunately there's an awful amount of hiss with USB on this DAC.

If you used optical before, it can be reasonable to use USB->optical. A lot of USB audio interfaces already have this. I'm not making use of it, but the USB interface I have on my Mini has an optical out.

I bought a soundbar for my TV a couple months ago. Recent Samsung model. Has optical. I beleive the only other option was 3.5mm jack.

Interesting. I bought a pretty cheap soundbar this year (from Yamaha) and I think it had optical as an option (along with 3.5mm and Bluetooth) but the main interface was HDMI-ARC.

And it works great over ARC! The TV remote's volume buttons get passed through automatically, and it turns itself off and on along with the TV. I don't even know where the soundbar's own remote is anymore.

The easy answer is: same thing I was using it for 10 and 20 years ago. Audio equipment doesn't age nearly as quickly as personal computers. I'm not going to replace my entertainment system just because there's a new Mac.

Also, I've had compatibility problems with HDMI between my old Mac Mini and my receiver. I don't know how to troubleshoot those sorts of issues. I do know that optical audio always works perfectly with every device I've ever used it with, though.

Shockingly, I need optical for a $300 set of gaming headphones I purchased within the last year (Astro A50). Maybe it’s the only way they can do pass through, dunno.

Headphones are stereo (okay, there are some exceptions), and optical S/PDIF can do stereo PCM, so there's no quality downside. But for home theater audio, you can't do any lossless multi-channel formats over optical S/PDIF, so the vast majority of enthusiasts will use HDMI.

It’s (likely) because they don’t want to add a secondary hdmi output for audio like a lot of other high end gear uses.

Never would have guessed that for headphones! I guess they have some kind of a dock?

Wireless (non-Bluetooth) Sennheiser headphones also take optical input (as well as 3.5mm). Since they're only doing stereo, and require a digital-to-analog conversion on the headphone side, makes sense to avoid an additional analog-to-digital on the transmitter side.

I'm probably in a tiny niche but I use it so that I can have optical out to my speakers and analogue out to an extension cord with a plug next to my keyboard that I plug my headphones into. This means I can swap between audio devices without touching cables or plugging things in to go headphones -> speakers depending on whether I want to annoy my wife with my music or not.

I have the same setup actually! But my speakers only take analog in so I use a cheap USB sound card.

Sonos, which might be one of the most hyped average user audio things in the last years, only offers optical inputs for their soundbars. Imho it's a pretty huge limitation on Sonos side, but maybe they did it because HDMI ARC is still flaky in many setups and they prefer ease of use. Or simply because of cost savings.

I've got a pre-ARC TV, so use optical for my home theatre. Am hell-bent against smart TVs, so my next display will probably be either a digital signage display or a projector still without ARC.

I want to smash a Sony engineer with a hammer because my goddamned $5000 smart TV keeps insisting on switching from tv audio to external audio to tv audio to external audio to tv audio to external audio.

It doesn't matter that I have my audio preference set to "prefer external audio" because the effing thing decides to switch back and forth between 2 and 30 times on startup, and maybe 80% of the time it settles (properly) on the receiver, and 20% of the time it tries to use the TV speakers, which are off, and of that 20% of the time, at least half of the time I HAVE to power everything down and start all over again. The other half of the time I can go through the menu with the slow-ass on-screen menu, and manually toggle back to receiver.

I just want an effing option that says "never in hell try to use the fucking TV speakers, for the love of god".

My (very low-end) Samsumg soundbar only has optical and 3.5mm in. I think a lot of cheap equipment still uses optical.

Still pretty popular in the 2-channel audio world... audiophiles, in other words.