So.... comparing Schiit Modi 3 over USB to anything else is a pain in the behind because my AP software can no longer control it. I have sent email to Schiit asking them if they have an ASIO driver for it. Until then, I can only run a couple of tests "open" loop. One is the Dashboard which I have already shown. Here I will compare that to Topping D30 which I have not shown before (but is updated here):
This is a few db better than before. Not sure what explains it but as a way of comparison, is valid because everything is the same now.
Putting Modi 3, Topping D30 and D50 we now get this for SINAD:
So all three are in the same class and category.
Next test I can run is J-test. Here, I am running the full resolution version of it instead of letting AP software dither it. J-Test has an embedded 250 Hz square wave in it that was designed to aggravate the S/PDIF cable signal. In the case of USB, that aspect is not useful. What may be useful is the fact that the 250 Hz square wave is designed in a way that causes all the bits to toggle at once. If there is lack of isolation in the device between digital and analog, this could show something. And it did here.
First, let's compare Schiit Modi 3 to Topping D30:
As we see, the 250 square wave in J-test is causing jitter in the clock for Modi 3, causing those symmetrical spikes. The skirt, or random low frequency jitter is also more visible in Modi 3 (blue) than Topping D30.
Topping D30 on the other hand (red), has a few dB higher noise floor but doesn't have this issue at all (see the inset measurements for better clarity).
Perceptually, random noise is preferred to correlated ones so the higher noise floor of D30 is less troublesome than the spikes in Modi 3. That said, hard to make a case for audibility in Modi 3 either due the fact that we don't have 0 dB 12 Khz tones in our music.
Here is the comparison to D50:
D50 betters the Modi 3 (and Topping D30) in noise floor but as I have reported before, suffers from 1 kHz packet timing of USB. They are not nearly as "loud" as the 250 Hz spikes in Modi 3 but nonetheless they show up.
Conclusions
Topping D30 sells for nearly the same money as Modi 3. It has the same three inputs just the same. I like its larger USB input jack and the on/off switch in the front. Aesthetically I say it is better than Modi 3 but this is a personal thing and you can decide that. From distortion+noise point of view, it is neck and neck with Modi 3. It is more well behaved in jitter test/sensitive to USB data than Modi 3. I give it a slight nod in this regard. The gap is small enough that I say let your preferences otherwise guide you.
Topping 50 has lower noise floor and less jitter than Modi 3. Importantly (for me), it has a beautiful OLED display withe volume control which I love to see in DACs. It would have for example told me the issue with Modi 3 ASIO truncating to 16 bits. Its build quality is also in another class completely. While it retails for quite a bit more than Modi 3 at $249, it frequently is discounted on Massdrop (Schiit is the only source for the product and as such, is never offered for discount on Massdrop). So if you can afford the extra cost, my recommendation would be for D50.
I think bottom line is the same as before: Schiit has made a massive improvement in their budget DAC implementation, substantially erasing any advantage Topping products used to have. Some vestiges of old problems such as jitter remain but they are small enough to be ignored.