Of course they apply to my system. You’re stating the obvious. My point is they don’t apply only to my system, and that’s what makes them relevant.
Sure…but most of what you say says that it applies to all systems when it certainly does not.
Great to see someone else repeating the testing!
Mainly, galvanic isolation is used to eliminate ground loops. If you don’t have them the isolation won’t change things. What you’re really demonstrating is that modern PCs aren’t noisy. There are specifications they have to follow about how clean various signals are, including data lines on USB cables.
USB-powered DACs (and any USB-powered peripheral) are another kettle of fish, entirely. A crappy power supply in the computer may bleed noise into that power, and if your DAC doesn’t properly filter the power input (which it should do), you can see noise.
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I’m sure I didn’t say “all”. I would think though that in a typical home environment and with due precautions, getting a significantly different result may indicate some kind of fault somewhere.
That’s a very good point. The D70 has its own power source. I do have the USB-powered FiiO E10 DAC, so I’ll measure that too. (I need to build some cables first, since the Cosmos has balanced inputs and the FiiO has a mini TRS line output.) Not an audiophile DAC per se, but I’m curious to see how it handles the USB power.
An excellent presentation in the main. Jitter does matter. Jitter can be deterministic or random. Presenter covered the difference in aural presentation between the two.
As the presenter mentioned, jitter appears as a blurry soundstage more than as audible hiss or tonals. I experienced the change in focus personally when I moved from an AirPort Express to a Google Chromecast Audio digital endpoint. Suddenly, there was a soundstage. Later updates to the DAC sharpened the focus.
Dave and Mike Moffat at Schiit are all over jitter and will do the best they can within the the price constraints on the product. Schiit Unison USB is an in-house minimalist implementation of USB Audio 2 stripped to the essentials for PCM audio reception. Schiit is a USB consortium member and Unison has been compliance tested and is USB trademarked.
Most current Schiit DACS (2022) are Unison USB devices. The older ones use the C-Media USB receiver. Modular products that are pre-Unison can be upgraded to Unison USB receivers. Most require return to Schiit to update the firmware. Mike and Dave have expressed a preference for Unison USB over SPDIF. They keep TOSlink around for TV applications.
There are other considerations than jitter in choosing a DAC interconnect. TOSlink is very good for sending TV audio to a DAC. Glass does not introduce ground loops. I use a Schiit Modius TOSlink input for TV audio. TOSlink is perfectly acceptable for this preference. Mike Moffat is not keen on TOSlink but keeps it around for TV audio. Mike currently prefers Unison USB to SPDIF giving a slight edge in presentation to Unison.
I got the graphs for the headphone output of FiiO E10 on my PC:
I get the same regardless of load. This looks clean enough to me. THD+N is 0.0032%; the spec says <0.004%. This is about -90dB, which is not bad at all for a $75 portable DAC. While the noise floor is higher than the Topping’s, it’s still below -120dB, so at least for the headphones output, power noise doesn’t seem to be an issue.
The line output is a different though, and not in a good way:
THD+N is now about 0.01% (-80dB) and low-frequency noise increases to about -100dB. I wouldn’t call this horrible, but it seems the line out is an afterthought, just to check a box. If you get this device, most probably you’re using it with headphones.
Once again, if a tiny $75 device can do this, then either USB power noise on generic PCs is not an issue, or devices can do a very good job of filtering it, even at the bottom of the price scale. Take your pick.