Why is only one USB audio path allowed?

[This Wreckage]

This is no doubt an uninformed (aka stupid) question, but why is only one USB audio path available at one time? I have several synths and a mixer with USB audio outputs but I cannot combine them in my Windows PC. I have to choose which one to use. Clearly, this is not like an SP/DIF digital audio stream. Perhaps someone could explain...

[Hugh Robjohns]

It's because, under Windows, each USB audio connection requires its own driver and there is no facility to synchronise the digital audio sample rates coming from multiple sources through multiple drivers.

[Wonks]

It's a Windows thing.

[Drew Stephenson]

Isn't it technically an ASIO thing rather than a Windows thing?

[The Elf]

Each time this topic comes up I find it incredulous that this one hasn't been solved after all this time.

[This Wreckage]

Each time this topic comes up I find it incredulous that this one hasn't been solved after all this time.

If a solution were to be found, who would provide it? Microsoft? Does Apple architecture allow multiple USB audio streams?

[BigRedX]

Probably not the answer you want to hear but on the Mac it's built-in at system level:

Create an Aggregate Device to combine multiple audio interfaces

[Hugh Robjohns]

It's a handy feature.... but I wonder if anyone has done any performance testing on the 'drift correction' function which is a software asynchronous sample rate converter?

[Jimmy B]

A partial solution might be to use Asio4all to combine the usb inputs.
I say "partial" because I've got it working here on Reaper with a Fender Mustang amplifer (usb output) and a Focusrite audio interface but it seems a bit flaky, with excessive latency and little control of where the audio output goes. However, I can successfully record via both devices at the same time. If you just wanted to record, and monitor using the speakers in the synth, it might be OK.

[resistorman]

Even with a Mac, it's probably better for Ye to use an AI with a lot of I/O

[N i g e l]

Each time this topic comes up I find it incredulous that this one hasn't been solved after all this time.

If a solution were to be found, who would provide it? Microsoft? Does Apple architecture allow multiple USB audio streams?

YAMAHA [as in YAMAHA Steinberg ASIO driver]

I believe Apple handles multiple AI because devices are USB class compliant and dont need drivers.

Windows can handle multiple drivers if they are different but it cant handle multiple asio driver instances.

So for instance, I cant use Yamaha USB synth outputs at the same time as a Yamaha guitar amp or Yamaha audio interface.



Is this a nail in the coffin of USB microphones ?

In a multitracking scenario, I would only be using 1 device at a time and would be happy to press a hot key to select which driver is in use i.e. which driver is the timing master.

[resistorman]

Is this a nail in the coffin of USB microphones ?

It's a distinct disadvantage I'd be interested in hearing from Mac users that use aggregate USB devices in their everyday workflow. It seems to me that having a single interface with multiple analog inputs or networked digital devices would be the best way to do production?

[The Elf]

I can only speak for myself and Cubase, but switching ASIO drivers is a load of hassle.

[Drew Stephenson]

It's pretty straightforward on Reaper; plug in your two interfaces, go to the options list and select the one you want and confirm the number of inputs and outputs.
Never had any glitches off the back of it.

[ef37a]

You can use multiple audio sources in Windows (W7 anyway) I did it some years ago but you have to use mme drivers and the tracks are not sync'ed. They don't even start recording together, quite. I was using Samplitude SE8 and that makes it very easy to slide tracks to sample accuracy. They don't of course STAY together but over a 3 minute song, close enough.

Hmm? Switching USB interfaces is easy enough in Sam I think? Won't be a one button hack though. I shall rig my M4 and the KA6 later and have a do! Mind you, both those interfaces have very solid, well behaved drivers.

Dave.

[Johnsy]

To get some idea of what's involved in syncing interfaces in the absence of a common clock, take a look at this:

https://www.youtube.com/watch?v=8jHLusUVa2Y

[The Elf]

It's pretty straightforward on Reaper; plug in your two interfaces, go to the options list and select the one you want and confirm the number of inputs and outputs.

I don't even have to do that in Cubase - it sorts all that out itself, but... Cubase loses all of my External Instrument/FX assignments, and I have to re-allocate all of the Control Room I/O. It's not an experience I want to repeat.

I once did it to record a TR-8S's separate outputs over USB - never, ever again. I could have recorded separate passes in far less time.

[Drew Stephenson]

It's pretty straightforward on Reaper; plug in your two interfaces, go to the options list and select the one you want and confirm the number of inputs and outputs.

I don't even have to do that in Cubase - it sorts all that out itself, but... Cubase loses all of my External Instrument/FX assignments, and I have to re-allocate all of the Control Room I/O. It's not an experience I want to repeat.

I once did it to record a TR-8S's separate outputs over USB - never, ever again. I could have recorded separate passes in far less time.

I think, given the options, I'd prefer Reaper's manual switching!

[The Elf]

With Reaper I don't create external links to hardware, so it's a non-issue, but then I don't have the same level of flexibility and speed (e.g. 'Render In Place' for hardware synths).

(Hint: 96 inputs and outputs!)

[merlyn]

The OP could try Voicemeeter Potato :

https://vb-audio.com/Voicemeeter/potato.htm

Potato is working along the lines of the video Johnsy posted above. (Good video BTW).

... I believe Apple handles multiple AI because devices are USB class compliant and dont need drivers.

Windows can handle multiple drivers if they are different but it cant handle multiple asio driver instances.

All devices need a driver. Mice, keyboards, graphics, even if the driver doesn't have to be installed. There's still a driver, it just came with the OS.

Class compliant devices have a driver -- all devices of that class e.g. USB audio use the same driver.

A key concept with Windows is 'third party'. To be of any use Windows needs third party software, third party drivers ... ASIO is a third party sound stack. Back in the day Steinberg decided that what was built into Windows wasn't up to snuff, and re-wrote it from scratch.

[Guest]

Aggregate devices on a Mac work will all audio interfaces, they do not have to be class compliant.

The best solution is to actually use a hardware clock connection between the devices and then you don't need to turn drift (resample) on at all. This all works perfectly.

I use drift (resample) occasionally for testing and as long as the clocks are not too far out of kilter it seems to handle it well, I'm not sure I would rely on it in a professional setting though. Lots of I/O and a few patchbays seems a better choice.

[MarkOne]

I understand that those clever boys and girls in Redmond did solve this for windows in the form of Direct X

But by the time they did ASIO ruled the world, and it’s much easier to develop your own driver for your own device and only test that combination, rather than the hassle of having to dig into a system level feature you don’t control.