June 5, 2005

Sending Sound Out to a Different Device Than It Comes In  [ Edit ] 

A reader recently asked me how to send Logic’s output to the internal sound card of his Mac, while accepting input from his external M-Audio sound card. He uses Logic Express 7.0.1, like I do, so I tried to figure it out. I learned today how to do it — it’s actually quite easy once you know what you’re doing. You must have Mac OS X 10.4 or greater.

Up through Logic 7.0.1 at least (I don’t have 7.1 yet), you do not have the option, from within Logic, to send your inputs and outputs to different audio interfaces. You can choose one, and only one. I think other software might offer this capability, but Logic does not.

Mac OS X has included, since 10.2 I think, an application called Audio MIDI Setup. It lets you configure the internal sound system, CoreAudio, to send system input and output to any of the various devices connected to your Mac. That, in and of itself, would seem to be the solution. The problem is that Logic doesn’t listen to Audio MIDI Setup for its sound requirements. It might use the MIDI configuration, but it doesn’t pay any attention to the audio settings. Logic has its own internal system, and that’s what it uses. GarageBand appears to respect Audio MIDI Setup, and although it shares some internals with Logic, in this respect it is a better citizen in the Mac OS X community than Logic.

In Mac OS X 10.4, released in late April, Apple introduced Aggregate Devices, which let you create a virtual audio interface that combines inputs and outputs from your various available audio interfaces into one. With this new feature, Logic can do what we want.

Here are the steps to follow. Make sure, before you start, that your extra audio interface is plugged in and running.

  1. If Logic is running, quit it.
  2. Launch Audio MIDI Setup. It’s found in your Applications/Utilities folder.
  3. In the Audio menu, choose Open Aggregate Device Editor.
  4. The editor sheet appears. Click the plus sign under the Aggregate Devices pane at the top.
  5. Click the checkboxes next to Built-in Audio and your other device, so they are checked. Your aggregate device will probably show 4 (or more) inputs and outputs available.
  6. Click Done.
  7. Relaunch Logic. In its Audio Driver preferences, choose your Aggregate Device. Logic will prompt you to restart or try relaunching CoreAudio. Do the relaunch of CoreAudio (it always works for me).
  8. At this point, you can set your individual tracks in the Arrange window to use any of the four available outputs or inputs. You can send audio out through your internal speakers (or the built-in line out/headphone jack) or out through your audio interface. Inputs and outputs are set in the channel strips for your audio objects (or tracks).

    Here are a couple pictures showing where this is done in Logic 7 and 8 (your outputs may vary):

    Logic7OutputChange.jpg Logic8OutputChange.jpg

If I’ve missed something, or these steps are somehow unclear or incorrect, let me know. I hope that eventually Logic will just use the Audio MIDI Setup configuration the way GarageBand does. Now that Apple controls it, there’s no real reason to have this separate setup, adding an additional layer of confusion.

Posted by Joe

hear is a questiomn i am stuck on what aare the main differences between sounds

Posted by: matty at January 16, 2006 8:56 AM

Sorry, matty, I need more than that to tell you anything. :)

Posted by: Joe at February 21, 2006 5:21 PM

Thanks for posting about this. I'm coming from Garageband and am surprised by the tedious things I have to do just to get my MobilePre USB to work.

I used your directions and was able to get a signal, though it took a lot of switching inputs and outputs. That's just 'cause I'm new to this though.

Anyways, I did have a real problem. When I begin to record my signal, which sounded fine a moment ago, now sounds about twice as loud. Er?

I assume I'll figure this out after some sleep, but thought I might run this by you. Here's to hoping Apple changes things a bit in a future update.

Posted by: Josiah at January 15, 2007 6:49 AM


The first thing that comes to mind is your setting for direct monitoring on your mobilepre. If you have that turned on while Software Monitoring is also turned on in Logic, you'll hear both, and it will sound weird.

Other than that, I'd have to hear how everything's connected before I could give any better guesses.

Posted by: Joe at January 15, 2007 10:46 AM

Thanks for your help. I managed to solve the 'twice as loud' problem I was having.

(For the time being, I've chosen the simplest method-- i.e. forgoing the aggregate method. I'm using my MobilePre as a monitor, with the audio driver set to MobliePre. I plug my electric guitar into the first channel, and a condenser mic into the second.)

Asides from the condenser cutting out every once in a while (?) and not trusting the MobilePre to provide decent sound, it's a pretty nice setup for me. Honestly, I'm just thrilled to be able to slowly learn and be able to work in Logic after Garageband.

Thanks again, and I look forward to your future posts.

Posted by: Josiah Wahlrab at January 21, 2007 6:23 AM

Can you advise at all: I bought a floor-demo MobilePre USB for my laptop (OSX10.4.10), & am getting no sound out.
Maybe it's a dud. I realize this web site is more a chronicle of your experience than an advice column, but I would be grateful for any advice.

First, I've recorded before, using iMic, and an M-Audio keyboard, into Garageband and Audacity, so I know the laptop is ok.

I installed the MPre driver (with restarts afterwards). The MobilePre powers up from a main USB hub. The MPre control panel says it's connected.
The main Sound Prefs have it as Input and Output.
Headphones going into the MPre.
I've turned up the gain on the MPre a reasonable amount (inst. input and headphones).

However, the Sound Prefs meters don't 'hear' it, nor do Garageband nor Audacity, nor do my headphones.

I tried a guitar pickup into ch1 inst/line (also tried ch2), and a lapel mic into stereo mic input. Both known good.

LineIn (from Amoeba) is set to route from MobilePre to my headphones. LineIn 'sees' the MobilePre but does not 'hear' inputs.
AudioMIDI recognizes that the MPre is there.

There you have it; if anything leaps out at you, I hope you'll share it. Thanks for your time.

Posted by: Eve at July 8, 2007 2:55 PM


Nothing in particular jumps out at me as a guaranteed problem, but here's what I'd try:

1. If possible, try the mobilepre on another machine. If it's works, at least you know the hardware works, and it's a software deal.

2. Try creating a different user account if you don't already have one, and see if the mobilepre works under that user account. If it does, you definitely have a software issue.

3. Try disabling every extra piece of software that might be messing with your audio. I'd include LineIn in this group, and maybe things like Jack or SoundFlower if you're running them. If there are any lingering drivers from the iMic (which I doubt, I think it's just a CoreAudio device), disable those. Reboot and see if it works.

Posted by: Joe at July 8, 2007 11:07 PM

Thanks for that prompt reply - I will try it and let you know.

Posted by: Eve at July 10, 2007 9:35 PM

I just bought a used MobilePre, downloaded the Tiger driver and installed it, set input in Sound and through Logic to the Mobile Pre. Hooked a mic up to channel one and plugged headphones in. I can hear myself speaking into the mic but when I try to record in Logic, it isn't hearing it and records flatline. Any ideas?

Posted by: Chris at October 16, 2007 8:29 PM

I tried the list of instructions but unfortunately, my external audio device did not come up on the aggregate device editor! It comes up everywhere else as an option for audio in and audio out. Even on the Audio MIDI setup software. Any ideas please?

Posted by: Andrew Snow at January 6, 2008 2:35 AM


That's strange that it's not showing up in the aggregate device editor. Did you try clicking the plus sign button first? It might be that nothing shows up until you do that. Beyond that, I'm at a loss without seeing everything right in front of me.

Posted by: Joe Chellman at January 6, 2008 11:02 PM

Thanks for posting this! Everything worked perfectly until step 8 - but I can't figure out how, in the Arrange window, I select the input/output for each individual track. I would really appreciate any help you can give me on this.

Posted by: Matt B. at January 9, 2008 8:42 PM


Just click the "Output 1-2" button in the channel strip for the track you want to output differently. I added a couple screenshots to step 8 to make this clearer (hopefully).

Posted by: Joe Chellman at January 10, 2008 12:23 AM

Thanks, Joe - I guess I was looking for something where it listed the actual names of various available inputs/outputs (i.e. "Internal Mic", "Internal Input", "TASCAM-122", etc.). I followed the screenshots and it worked perfectly. You really helped me a lot here - I was very frustrated and couldn't imagine that Logic would have failed to include something so basic, particularly when every other Apple program (including GB) is specifically designed so they can use different inputs/outputs.

Posted by: Matt. B. at January 10, 2008 10:06 AM


Yeah, the inputs aren't listed by their internal name. That would be nice, I agree. There's very little Logic outright can't do (especially if you're using one of the new versions), but it is not always easy to figure out how to do it. Logic is a powerful and complex piece of software, so there's definitely a lot to learn.

Posted by: Joe Chellman at January 10, 2008 11:20 AM

Hey Matt,

I made the the jump to Leopard and GB 8 to Logic Express 8. The Aggregate Devices preference setting worked. Thanks for your help.

Posted by: Dominic Pezen at February 24, 2008 8:36 PM

I know I'm a couple years later, but the correct tool for this job is SoundFlower, a free driver from the guys who make Max.

Aggregate drivers are, by definition, and must crash at some point.



Posted by: Chris at June 3, 2008 10:40 PM

Soundflower is certainly another option, but if one wants to stick with what's built into the operating system, aggregate devices are another "correct" solution. I haven't experienced any crashes using them, but I don't think I'm really stress testing them either. With any of these solutions, one's mileage will vary.

Posted by: Joe Chellman at June 4, 2008 12:29 AM

Hey Joe,
It absolutely depends on what you're doing - what I'm talking about is clock skew that will at some point crash the interface and force you to reinitialize the driver and/or restart your audio application.

This is not a big deal in the studio, but it will kill you live on stage.



PS: I see that I messed up the previous post. What I was trying to say is that aggregate drivers, by definition, are trying to synchronize two separate clocks. (one for each card)

Running at 44100 samples / second even a minute difference will make itself known over time. At some point the clock skew will become so great that one or the other interface will try to clip to a sample ahead of its buffer - i.e., to catch up with the other clock - and the audio driver will shit its pants. Not fun stuff with a room full of people watching that W.T.F.-look come over one's face...

Posted by: Chris at June 5, 2008 10:20 PM

Hi guys...I really hope you can help with this one, here is my system...

Macbook 2.4 Dual Core, 4GB RAM, 160GB HD
Leopard 10.5.6
Logic Pro 8
M-Audio Fast Track Pro

My Fast Track Pro runs very smoothly as the sole audio device when recording and during playback. No problems whatsoever. However for my live setup, I require a click track, so I want more outputs than it offers. I therefore have to setup an aggregate device, consisting of Fast Track Pro (1-2, 3-4 for instruments) and the built in sound card (5-6 for click track).

This is where the problem starts. When selecting the aggregate device inside logic everything seems fine for a few seconds, then it crashes. I have to relaunch logic and try again.......once again it crashes! I cant seem to stabilise Logic long enough to work on my arrangement.

I have uninstalled the Fast Track Pro, reinstalled various drivers. Nothing works. It even crashes Garageband.

Im at the end of the line now, however I really dont want to buy another audio interface just to perform such a simple task. Can anybody help...?!?

I would really appreciate it

Posted by: Nick at January 25, 2009 1:41 PM


Good luck finding the answer. I see you've spammed, I mean posted the same question verbatim, in a whole bunch of other places online, so with any luck you'll get an answer in one of those communities. I don't have a FastTrack, so I can't be much help.

Posted by: Joe Chellman at January 26, 2009 1:44 AM

awesome! thanks a lot

Posted by: Bruno Tozzini at June 6, 2009 12:15 PM
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