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Two Logic Pros & Radial SW8 (unsynced) - backing tracks LIVE

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Hi guys,


I'm getting together stuff we need for our first live shows with backing tracks. We're running two Macs into our own rack unit - based on Radial SW8 (which works perfectly well). "Master" one is described below in my signature, "slave" is a newer one from 2012 with 500 GB HDD and original 4 GB RAM only.


Now . . . I might not have a good audio interface for this purpose YET. I'm definitely planning to buy two identical pieces of something better though. Hopefully sometimes soon.


At first I was freaking happy that I could sync two Logics via MIDI and it worked! But as soon as I found out that once "master" goes down, "slave" obviously stops playing as well. So I started doing a research and Dave from Devin Townsend Project was kind enough to tweet me back that he just hits two spacebars at the same time.


Unfortunately I didn't get a chance to test two identical audio interfaces (expect from cheap Fast Track Pros). But the point is - what I found out is that when I run Macs WITH these interfaces (any combination I've tried), one is playing slightly faster than the other one. At one moment - the delay between two USB Fast Track Pros was longer than between RME 400 (firewire) and my M-Audio FireWire 410. Macbooks WITHOUT any audio interfaces were running precisely - just like synced.


Here are the steps I did:

1. I turned on the SYNC on "slave" Mac.

2. I hit the spacebar on "master" Mac. Now both of them are running together.

3. I turned off the SYNC on "slave" Mac.

4. I waited for a while, maybe left the room, made a coffee, came back... and suddenly one click track was like 60 ms in front of the other one. The longer I let them play unsynced, the more milliseconds it was.


Now what might be the possible solution?

1. Some sort of external time clock? (I don't really like this idea)

2. Maybe better audio interfaces will cause a smaller delay?


It doesn't have to be (and it probably won't be) like synced. I'm just worried that when our SW8-like machine switches from A (master) to B (slave) at the point where backing tracks are playing for too long (like 15 minutes or so), it might cause a big jump and confuse a band AND people.


Now that was a lot of text! Thank you for ANY advice!


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  • 1 month later...



are you trying to sync via MTC?

if so it will never work properly as MTC is only 1 part of syncing, you need to have both sound cards clocked together as well as sending MTC.

word clock out of 1 soundcard into the other or both from a separate word clock generator + MTC is one solution.

MTC tells your computers what time the tracks are at, and the word clock keeps the sample rates identical, so no drifting and ultimately no crash.

i use 2 motu travellers started from a midi controller and no sync and have not experienced as much drift as you.

i would imagine keeping to the same manufacturer might help the cards stay together?

apart from the simplicity of this system, there is less likely hood of a syncing glitch which might take both soundcards out.



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