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Multiple Audio Interfaces

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Multiple Audio Interfaces

Postby gallaman » Tue Oct 22, 2019 6:57 pm

Hi -

Due to units that failed, were replaced, and then mysteriously sprung back to life, I have ended up with three good (what I consider good) audio interfaces: an EMU 1616m (PCIe card interface), a Focusrite Scarlett 18i6 (USB), and a Focusrite Scarlett 18i8 (USB). My question is how can I use all of these for a total of 20 concurrent audio inputs on my Win 10 system?

My limited understanding is that ASIO is the best driver protocol to use for a number of reasons but it will only talk to one interface. I am currently compensating for this by connecting the ADAT output of the 1616m to the ADAT input of the 18i8, which is connected to my Win 10 desktop by USB, and this works well. I have all 14 channels available using ASIO. But this seems like a kluge. Unfortunately neither of the Scarletts has an ADAT output for some reason, so this is the only configuration that works with ASIO. Is there a better one? In my DAW I see WDM/KS, WASAPI Exclusive, WASAPI Shared, and MME(32-bit) protocols also available.

I tried to set up ASIO4ALL a few times in Win XP ages ago and could not get it to work with my interfaces. In addition, I have heard that it uses the relatively underperfoming WDM protocol to connect to the interfaces while using ASIO to connect to the DAW, so even if it did work I believe I would be left with the higher latency and lower performance of WDM. Wouldn't this yield the same problems as connecting all three interfaces using WDM only (without ASIO4ALL)?

Is it really true that you can't stack interfaces without using a dated and underperforming protocol? This seems wrong. Is this my punishment for not using an Mac? :roll: Would I have this limitation on a Mac?

Thanks for any advice you can offer!

Setup: Cakewalk Sonar Professional on Win 10 PC
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Re: Multiple Audio Interfaces

Postby CS70 » Tue Oct 22, 2019 9:37 pm

Have a look at this recent thread about the same issue:

https://www.soundonsound.com/forum/view ... p?p=618542

ADAT as you are doing is the way to go (or other digital connections which allow daisy chaining).

About ASIO4All, you can also have a look at my blog here
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Re: Multiple Audio Interfaces

Postby gallaman » Tue Oct 22, 2019 11:34 pm

Thanks so much! Those two resources really do finally answer my question. Realistically I am unfortunately limited to one device in Windows if I use ASIO.

But your very well written blog raises another question. "Recent versions of the Windows Audio subsystem allow for just as much efficiency as ASIO." If this is true then is there any advantage to using ASIO over WDM or WASAPI, which do allow for multiple interfaces?

That said I cannot seem to get either of these Windows protocols to work with my Focusrite Scarlett 18i8.
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Re: Multiple Audio Interfaces

Postby The Elf » Wed Oct 23, 2019 12:11 am

Put simply - on a PC you can only use one ASIO driver at a time, which typically means only one audio device.

Some manufacturers (e.g. RME) allow you to use more than one hardware device within a single driver instance, but it isn't a common feature.

ASIO4ALL reportedly allows some form of aggregation, but I've never seen it working.
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Re: Multiple Audio Interfaces

Postby ef37a » Wed Oct 23, 2019 6:48 am

Try Samplitude and WDM drivers, if you are just tracking you might not need low latency?

One possible downside is that the various sources may not keep in time with each other but there might be a fix for that in Sam? I.e. you can lock all sources to "System Clock"?

Costs nothing but time to try!

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Re: Multiple Audio Interfaces

Postby Wonks » Wed Oct 23, 2019 8:13 am

Other way round, Dave. When tracking, unless everything is recorded live in one take, then you really do need very low latency, especially if recording vocals using headphones, otherwise you get a very off-putting delay. When just mixing, the latency can be much higher.

You can use an interface's direct monitoring system (if it has one) to avoid processing latency issues, but that often leaves you without the ability to add reverb when tracking, which can be important in getting good vocal takes.

If you are using a control surface to automate a mix, then low latency becomes that bit more important when just mixing.
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Re: Multiple Audio Interfaces

Postby ef37a » Wed Oct 23, 2019 12:22 pm

Wonks wrote:Other way round, Dave. When tracking, unless everything is recorded live in one take, then you really do need very low latency, especially if recording vocals using headphones, otherwise you get a very off-putting delay. When just mixing, the latency can be much higher.

You can use an interface's direct monitoring system (if it has one) to avoid processing latency issues, but that often leaves you without the ability to add reverb when tracking, which can be important in getting good vocal takes.

If you are using a control surface to automate a mix, then low latency becomes that bit more important when just mixing.

Ho kay but I did say "might not need low latency".

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Re: Multiple Audio Interfaces

Postby Wonks » Wed Oct 23, 2019 12:35 pm

But when the OP is trying to get 20 concurrent audio inputs working all at once, I'd say it's pretty likely that low latency will also be a requirement.
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Re: Multiple Audio Interfaces

Postby CS70 » Wed Oct 23, 2019 1:41 pm

gallaman wrote:Thanks so much! Those two resources really do finally answer my question. Realistically I am unfortunately limited to one device in Windows if I use ASIO.

But your very well written blog raises another question. "Recent versions of the Windows Audio subsystem allow for just as much efficiency as ASIO." If this is true then is there any advantage to using ASIO over WDM or WASAPI, which do allow for multiple interfaces?

That said I cannot seem to get either of these Windows protocols to work with my Focusrite Scarlett 18i8.

WASAPI exclusive mode would theoretically allow you to have latencies nearer to ASIO.

Essentially, if your DAW can open a sound device in exclusive mode, it will not be accessible by other applications (say your browser), therefore bypassing the Windows sound mixer; and also bypassing the Windows effects engine - becoming much nearer to the "I am only a data exchange buffer" approach of ASIO. It also allows for higher sample rates and sample word length than WDM, and crucially, allows you to set the buffer size (as ASIO).

Nor all DAWs support it yet - but some do - I just opened the Cakewalk version I have on my laptop and you can indeed select WASAPI Exclusive and set the buffer size (wasn't an option with previous versions of Sonar). Haven't tried it tough.
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Re: Multiple Audio Interfaces

Postby CS70 » Wed Oct 23, 2019 1:46 pm

The Elf wrote:Put simply - on a PC you can only use one ASIO driver at a time, which typically means only one audio device.

Some manufacturers (e.g. RME) allow you to use more than one hardware device within a single driver instance, but it isn't a common feature.

ASIO4ALL reportedly allows some form of aggregation, but I've never seen it working.

ASIO4All works for playback, it's pretty pointless for any type of recording which depends on low latency.

For playback, you can probably aggregate devices and happily send data to more than one interface, but of course there's few cases when that's useful.
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Re: Multiple Audio Interfaces

Postby The Elf » Wed Oct 23, 2019 2:13 pm

CS70 wrote:
The Elf wrote:Put simply - on a PC you can only use one ASIO driver at a time, which typically means only one audio device.

Some manufacturers (e.g. RME) allow you to use more than one hardware device within a single driver instance, but it isn't a common feature.

ASIO4ALL reportedly allows some form of aggregation, but I've never seen it working.

ASIO4All works for playback, it's pretty pointless for any type of recording which depends on low latency.

For playback, you can probably aggregate devices and happily send data to more than one interface, but of course there's few cases when that's useful.
I would like to see aggregation working in ASIO4ALL - how do you set it up?


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Re: Multiple Audio Interfaces

Postby gallaman » Wed Oct 23, 2019 5:50 pm

Sounds like WASAPI Exclusive is the way to go if it were supported. I can select it in SONAR with my interfaces connected, implying that there are drivers and it should work, but when I try to playback I get an error message that the devices aren't compatible, implying that there is no WASAPI driver for them, and Googling Scarlett/WASAPI yields nothing. Also there is no mention of WASAPI on the Focusrite site. So I would say that practically ASIO is all there is on Windows.
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Re: Multiple Audio Interfaces

Postby The Elf » Wed Oct 23, 2019 9:48 pm

There's still host software that has no knowlege of WASAPI, and even when it does it still has poorer latency than ASIO IME.
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Re: Multiple Audio Interfaces

Postby CS70 » Wed Oct 23, 2019 11:14 pm

The Elf wrote:I would like to see aggregation working in ASIO4ALL - how do you set it up?

I install it very seldom, only when for some reason I have a pc with a DAW but no interface, and de-install it after use.

Next time I do I'll give it a try, should only be an issue of switching to advanced mode and enabling the various device pins - "pin" is the name that WDM kernel streaming gives to I/O sockets on the (virtual) device.

But my guess us that it is a bit hit and miss, which is why I used "probably". And if it works for me it may well not work for you.

That's because of a couple things. First issue is clocking: USB devices can get their clocking in different ways (asynchronous, synchronous and adaptive - this last one is the most likely to work and the asynchronous will almost never work). No common clocking, no joy (and much drift). Then there's the device latency, which which "traditional" WDM (pre-Windows 10) you can only guess at application level... so the various frames may be reassembled at the wrong positions.

That said, if USB device latency is similar and the two devices happen to use the same clocking, it may work for playback. But your AC97/HD Audio motherboard sound card and an USB audio interface will almost never use the same clock, so my money is that won't ever work.

As a side note, Windows 10 has vastly improved WDM also outside the ASIO-like exclusive mode - much reducing the audio engine inherent latency (which they say is now little more than 1ms vs 12 or 6 before), and allowing the driver to query the device latency and to set a buffer size - instead of being fixed to 10ms as it was before. It also apparently manipulates the thread priorities for both audio engine, driver interrupts and DPC and even client threads (the DAW) and callbacks making them more real-time, besides introducing "AudioGraph"s which are a bit better models of actual devices as we think of them and easier to use for developers. So Audio4All will be faster with Windows 10 than Windows 8 could be.
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