Old 02-16-2013, 03:36 PM   #1
AnyOtherCity
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Default Aggregate device crackling on one device

I've set up an aggregate device with an Apogee One and Emu Tracker Pre. It works perfectly for a while but eventually the tracks from the Emu start crackling, and it gets worse and worse, becoming a horrible distortion so it's unusable.

Anyone encountered this with aggregate devices?
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Old 02-16-2013, 04:30 PM   #2
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In the Aggregate Device settings I would check that you have a proper source for the clock source. Perhaps change the source to the other device, perhaps it would work better.
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Old 02-17-2013, 09:44 AM   #3
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Have tried the clock source from both, but either way it just results in the Emu crackling after about an hour (not an hour of continuous recording, but an hour of use). It works completely fine on its own. Have also tried it with 'resample from this device' ticked and unticked, but still the same. I'm stumped!
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Old 02-17-2013, 11:15 AM   #4
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It sounds like one device is clearly losing sync.

How are you clocking these devices? It's general practice to clock all devices with word clock (as opposed to getting sync from an audio connection like AES-EBU or SPDIF or from the firewire bus).

Have you designated your master interface and are you then clocking the other interface from it? (Master interface word clock out to all other interfaces' word clock in.)
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Old 02-17-2013, 02:11 PM   #5
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Are you using L or ML? I'm getting the impression that they broke some aggregate device functionality and also sync. E.g.

https://discussions.apple.com/thread...art=0&tstart=0

https://discussions.apple.com/thread...art=0&tstart=0

Opposite experience:

http://www.gearslutz.com/board/music...te-device.html

However, AFAIK even with Slow Leopard the aggregate device didn't always work with all interfaces.
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Old 02-18-2013, 03:32 AM   #6
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Ollie: I'm using Lion (too scared to upgrade at this stage!) The issue of mixing different manufacturers could be part of it though. Obviously the One is designed for OSX but the Emu very much isn't (they only released drivers for Lion about a year ago).

Serr: I understand about 10% of what you're saying but I will do some research as that sounds plausible. In aggregate device settings I'd just set one interface as 'Clock Source' - but either way the crackling starts after a while. From what you say it sounds like there is a more complicated procedure that I need to dig into.

Thanks for the input guys
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Old 02-18-2013, 03:47 AM   #7
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While googling for that I saw a post somewhere stating as well that you may need to use physical wordclock connections between the devices instead. It seems aggregate device functionality was already changed in Lion.
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Old 02-18-2013, 08:51 AM   #8
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Ah balls. Can't afford to buy another piece of gear. Might have to say goodbye to recording three things at once until I have more cash.

I will faff about with the settings anyway and report back if I get anywhere. I refuse to give up hope seeing as it seems to work perfectly for about an hour before the crackling starts.

Seems very odd that this really useful function could get worse and worse with each new operating system, but I guess it's not really something that the average consumer uses so Apple probably just doesn't give a toss.
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Old 02-20-2013, 11:56 AM   #9
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So in a possibly misguided refusal to just give up, I digested this lengthy thread from the Avid forum - http://duc.avid.com/archive/index.php/t-289728.html

The overall conclusion seems to be that, yes, you do need an external word clock to get multiple devices to be EXACTLY in sync with no jitter at all.

Obviously this is impossible for those with low-end gear that doesn't have that functionality, like me. Now that I've got a bit of an understanding of what clock and jitter and resampling actually mean I'd experiment with every combination of settings and thought I might as well post here in case other people have the same problem.

From reading the Avid post, it seems like you're supposed to set one interface as Clock Source/Master and then have 'Resampling' selected for the other device, so that in theory that device will resample to the sample rate of the master device.

I tried it set like that (One as Clock Source/Master, Emu as slave with Resampling selected). It started off working fine but after about 4 minutes of recording the jitter was very noticeable on the Emu tracks.

So I changed the settings so that the One is also set to Resample, thinking 'surely this can't make a difference'. Well... (touch wood) I'm now at about 30 minutes of recording with no jitter.

I'm fairly sure that this isn't going to turn out to be rock solid and either the jitter will start soon, or next time I use it it'll jitter after a few minutes. Fact is though, when I record on three inputs at once a 'session' only tends to be 3 or 4 hours, so if I can get that far without it descending into explosions of aural horror then I'll be happy.

Bottom line - if your aggregate device is causing jitter, try every possible combination of master/slave and resampling, as there might just be one that is at least usable.
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Old 02-20-2013, 12:49 PM   #10
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Quote:
Originally Posted by AnyOtherCity View Post
Ah balls. Can't afford to buy another piece of gear.
Pretty sure you can pick up a BNC word clock cable for under $10.

I don't think this is a bug or shortcoming of the aggregate device function. Multiple interfaces were always intended to sync with word clock.

It's not complicated. Just connect a word clock cable from your master devices word clock output to the slave(s) word clock input.
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Old 02-21-2013, 11:19 AM   #11
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Quote:
Originally Posted by serr View Post
It's not complicated. Just connect a word clock cable from your master devices word clock output to the slave(s) word clock input.
I'm sure it wouldn't be complicated but neither of my devices has a word clock input. Cheap-ass gear wasn't designed with this in mind I suppose.
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Old 03-07-2013, 10:55 AM   #12
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Update: Despite all the success in my tests at home, as soon as I tried to actually do some recording properly the jitter started after about five minutes even with the same settings. Weird.
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Old 03-07-2013, 01:32 PM   #13
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Yeah, Apple changed something under the hood in multiple Aggregate Devices at Lion and caught many unawares (and ML fixed some and broke others for some). The gradual clock issue is exactly a Lion symptom I read a lot about on the Metric Halo list and they had to rewrite their driver to deal with it (for the software control panel for their hardware), so I would think there's going to have to be a fix from Apogee or Emu for this to be corrected. Problem is that the general niche of both of these companies' products is with users who don't create multiple devices, so they either don't get much feedback of bugs there or possibly aren't motivated enough to fix them. And ironically it can be fixed with a cable, which doesn't help the boxes which have no hardware clock in or out.

If this is something that is biting you in the butt I'm *pretty sure* it can't be fixed by doing anything different having to do with Apple system or utilities. Not everyone has this issue but there are a lot of reports of it.
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