This seems to be a religious topic so my apologies ahead of time. 
My streamer / DAC support both digital coax (SPDIF) and USB connections.
I’m curious what most folks are using and why.
I’ve heard and read from good sources that USB can provide a superior sound quality if the equipment supports a good USB implementation.
The functions of SPDIF and USB inputs are completely different on Naim streamers and DACs, so you can’t really compare their sound quality.
SPDIF is used to connect external transports such as streamers or CD players, whereas USB is for hard drive storage, and connecting iOS devices on older streamers.
You may get some comments regarding comparisons on non-Naim DACs, but with the majority here using Naim streamers you won’t get any meaningful comparisons.
He does, whether he realises it or not! I’m just pointing out that this may not be the best place to ask given that the large majority here will be using a Naim streamer, a Naim DAC, or both.
Apologies Chris, I re read your post and deleted mine as a result.
No worries, I’m sure he’ll get some opinions from Naim streamer users too!
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You have streamers that have both and dac that have both, sometimes one is preferred to the other one.
I might be wrong, but as far as I was aware, DSD can only be sent via USB.
USB into dac v1 for roon based streaming.
Optical for my minidisc
Coax digital for my occasionally used “dvd as cd” transport
The usb input on the dac v1 is allegedly the better of all its inputs, so that gets priority.
and the dac v1 has an asynchronous usb input supporting up to 32/384.
With USB, clocking is at the DAC side, done by the DAC’s built-in clock. With SPDIF, clocking is at the source and DAC needs to reconstruct the clock from the data stream using PLL.
USB inputs are not inherently noisy! USB is an excellent choice for a DAC input, as long as the USB SOURCE is designed to be low noise (meaning a purpose built streamer/renderer designed for high end audio use). In fact, wired Ethernet sources have a lot of network noise on them. Just as is the case with USB, an Ethernet input on a DAC needs to be very carefully implemented to not produce noise which gets to the DAC clock circuit and analog circuitry.
A well implemented USB input can perform as well as, or better than, any other DAC input.
So technically speaking, USB should sound better. However, if your experience is the other way round, but as always, your ears tell you what you like best.
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That’s not what happens with the ndac.
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Yes, ndac is an exception, you are right.
Well my tv sound connects via spdif to my ndx2, and thence ultimately to my proac d30s. Best tv sound for miles😂
USB for me. I’ve no choice as it’s the only option out from Innuos Zenith MK3 as a music player direct to DAC. It’s a rabbit hole but I’ve found different USB cables can have a very significant effect on the sound.
Would be interested to know your experience about the USB cables.
Sure… I’ve tried lots over the years. I found the cheaper ones the difference is a little bit harder to discern. But despite being sceptical initially, the first cable that open my eyes that they could have an effect was one that degraded the sound quite significantly by really rounding off the higher frequencies and making everything sound ‘blunted’… that was a ‘Supra USB’ which was apparently an award winning cable. After that I even experimented with a few different very basic cables that were used for printers in my house after that and found they all sounded slightly different.
Although I’ve changed DAC’s and source a few times as well so it’s difficult to fully compare, I found a Vertere D-Fi USB didn’t seem to make any difference compared to my stock Chord Hugo MK1 USB cable. The same was true of a Chord Company Signature USB against my stock Chord Hugo TT2. The game changed a bit though when I tried a Wireworld Platinum Starlight 7 into my Hugo TT2 which was a real step up. Because of this I couldn’t resist demoing a Wireworld Platinum Starlight 8 cable which although expensive, I think is an amazing cable and worth the cost. I had that cable for a good few years.
Finally I’ve more recently switch to a Tara Labs ‘The Artist’ USB which is a bit more pricey but it just added more of everything for me and demonstrated how even the Wireworld Platinum Starlight 8 was perhaps a little bit closed in and not as expressive in the upper frequencies as I thought.
I was always under the impression that they shouldn’t make a difference but they often have done for me, and I suppose it’s also dependent on the rest of your system!
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Nice, but a bit expensive. I am using the Supra USB, but I’ve found it the same as any cheapie USB cables.
I use a cheap Kabeldirekt toslink between an Innous Pulse and Chord Dave. When I say cheap, its cheap about £6 - £8 with no urge to change this cable.
Generally I think at the lower end, USB can outperform coax but after a certain level, the electrical SPDIF interface on good DACs starts to outside USB, so from that perspective, I’m not sure there is a good blanket statement that holds true between any products.
It is also important to note that not all USB interfaces support the same protocols for audio. Off the shelf, nearly everything with USB input will support ASIO which is probably what 99% of people are using when they connect a USB transport to a DAC. However, there are more esoteric protocols like Bulk Pet which are really in another league for incurring less noise at the DAC end. It’s very much the USB equivalent of jumbo frames and results in about a quarter of the processing required for ASIO because it is unpacking far fewer (but larger) datagrams. As far as I know, only Luxman and a few others support it. On my old PC transport into a Luxman DAC I did compare regular ASIO USB to USB from the same PC but via the Bulk Pet driver and the difference was fairly stark. A level of noise and grain I did not even know was there just vanished.
I’ve since moved to a different dedicated transport that doesn’t have Bulk Pet and on that SPDIF over coax is clearly superior to USB. Until a dedicated transport comes along that supports Bulk Pet out, it will be hard to make a direct comparison.
With my Bricasti Dac and Streamer, Aes/Ebu is also far superior to Usb ( i had an Audioquest Diamond Usb before which is sold now). So much more calm, spatial and immersive, it is amazing. Never experienced this with Usb before. Also the Aes/Ebu connection is recommended by Bricasti over USB.