Aggregate Device Issues

JoeP · 03-20-2013, 08:27 PM

I have been working all day trying to get an aggregate device working. The devices include a Focusrite 2i2, an Audio Technica 2020 USB mic, and the MacBook Pro built in output.
I think I finally have it working but I have no idea why. It seems like many combinations of clock source, resample selections, and perhaps even the order of the devices in the aggregate result in gross latency, noise, and distortion.
I also had to move Reaper back onto the computer from a usb drive because the aggregate would not work well with devices going through a hub.

Are there any solid guidlines as to how to set up an aggregate device for use with REAPER?

Thanks,
joe

AnyOtherCity · 03-21-2013, 11:03 AM

I had a whole heap of issues documented here http://forum.cockos.com/showthread.php?t=118419

In summary, the answer to your question is no. People seem to say that Apple changed something somewhere along the way and basically if you can't run an external clock then you can never get it to run.

Mine works perfectly sometimes, other times it goes horrible after a few minutes even with exactly the same settings.

Is there any reason why you need the MacBook output? If you used the output from the Focusrite then it would be one less device and maybe less likely to go wrong, just a thought

serr · 03-21-2013, 11:43 AM

Nothing has changed.

Running multiple interfaces together as an aggregate device has ALWAYS required word clock sync between devices.

The problem is that you are trying to sync a device that doesn't have a word clock connection. It looks for all the world like Apple intended to add this functionality with core audio (when OSX first came about) but it just hasn't been finished or even addressed since.

With free running clocks, you might get 20 minutes or so before Heisenburg takes over and you lose sync.

Now, this feature will work if you are only using the built-in audio interface and virtual devices (eg. Soundflower). But that's because there's only one hardware clock running everything (the built-in interface's clock).

FYI I'm still running 10.6.8 at the moment. Testing this with 10.8 is actually on my list of things to do just in case they added this feature. But I've heard nothing about them doing that so I'd be pretty surprised if this suddenly worked with 10.8.

JoeP · 03-21-2013, 08:33 PM

Ok,after about two days of fiddling with it, and almost returning an interface to amazon, here's the setup that seems to be working. At least it's worked for several hours and through two experimental re-boots of the mac. If it doesn't work tomorrow when I try it, I'll report back.

FIRST, WHAT DID NOT WORK!
HAVING ANY DEVICE CONNECTED THROUGH A USB HUB WAS A 100% FAILURE! This was very disappointing because the macbook pro I'm using only has two usb ports. So not only am I limited to only two usb devices, but I also cannot run REAPER on a thumb drive! I had spent several hours setting things up to run of a thumb drive that I could transfer back and forth between macbook and imac, hence my disappointment.

NOW, WHAT WORKED!
This is an older macbook pro, 2.33 GHz Intel Core 2 duo.
Audio Interfaces:
1) Focusrite 2i2 with the latest drivers installed on the mac. There are two condenser mics connected to the 2i2
2) AudioTechnical AT2020 USB Mic.
3) Built In Audio Output.

The Aggregate Device configuration that seems to work:
A) The AT2020 and the 2i2 each plugged into one of the 2 USB ports on the mac.
B) In the Aggregate device, the 2i2 is the first item and is the clock source.
C) The AT2020 and Built In Audio Out are set to resample.
D) The 2i2 sample rate is set to 44100 in the Audio and Midi control to match the AT2020.

Before trying it in REAPER, I found that I had to turn the gain down on the 2i2. Otherwise it would go into some sort of oscillation.

In REAPER, I set the audio device to be the aggregate device. I created a track with the stereo 2i2 and another track for the AT2020 (mono or stereo).

I recorded from both devices simultaneously with very little latency and their tracks matched perfectly. I left it running for several hours and tried it again with the same result.
I quit reaper, unplugged everything, plugged it back in, started reaper (after making sure the aggregate was still set up or re-setting it) and recorded again with same good results.
I tried rebooting and restarting everything and it all worked.
joe

JoeP · 03-21-2013, 08:40 PM

FYI, Once I do a couple of "side-by-side" simultaneous recordings, I think I'm going to abandon the aggregate device approach and go back to recording off one device at a time. It is just too valuable to me to be able to run off the thumb drive.

JoeP · 03-22-2013, 08:09 PM

I ended up sending the FocusRite 2i2 back to Amazon today. It was just too fickle to have spent the money on it. It was completely unusable through a HUB, even though the AT2020 and an ART DualPre work fine. And, the fact that I had to take up both USB ports just to have two devices in an aggregate was too much of a constraint. Add to that the fact that the 2i2 was unstable and would often go into some sort of oscillation, and it was just too much pain and too little pleasure.

I now have several devices hooked up through a USB hub and while it's a bit awkward switching from one device to another, at least everything seems stable and reliable.