Don’t know if that actually makes a difference, though, as long as you avoid sharing root hub ports with other devices (cameras, NICs, storage, …) via hubs.Įither way, as long as the hardware is built properly, and the drivers are solid, I don’t think this is the limiting factor. With lots of channels, and/or extreme sample rates, bandwidth is of course going to matter more.īTW, AFAIK, 1394 explicitly supports realtime devices, whereas USB does not, so 1394 should be better for audio in theory. That said, audio is very low bandwidth by modern standards, so this doesn’t have nearly as big impact as one would think! 24 bit stereo at 48 kHz is just 2.3 Mbps, and even USB 2.0 can handle 480 Mbps, so that’s about 7 microseconds for transferring 64 samples, corresponding to 1.33 ms of audio.

Even if the USB/1394 devices may have DMA on the PCI/PCIe side (meaning they read and write data without CPU intervention), there’s still added buffering and a slower serial connection between the hub and the sound interface, which invariably adds latency.Īlso note that there are HUGE differences in bandwidth between the generations/versions of USB and 1394/FireWire/Thunderbolt, and that directly affects latency, as latency, as we’re talking block transfers here - not sample-by-sample.

That said, it’s normally pretty solid, as long as you don’t have other devices on the same root hub port, and I believe most of the issues are due to driver bugs.Īs for latency yes, there’s definitely a difference, as PCI/PCIe has a high speed connection directly to the computer chipset, rather than via USB or 1394 interfaces, which are a bit like network interfaces.

Well, I just had a harsh reminder of the flaky nature of USB audio the other day… The Scarlett glitched out, resulting in a few BSODs, after which I had to remove and reinstall the driver to get audio working at all again, and then reconfigure all applications, as they suddenly no longer recognized the interface. TL DR: the computer/audio interface communication is only a small part of the problem, and I’m not even sure PCIe is worth the effort, unless you need massive channel counts.

Usb 2 vs usb 3 audio imnterfaces