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Progressive Distortion Problem


Larry Lion

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Hello. I am new to Logic Pro, having recently taken the plunge, buying a MacBook and LP9, after being frustrated with aspects Windows and PT9. I use my LP/Mac to record my band practices from a ROland VM7200 system, via an m-Audio Lightbridge, 20 channels simultaneously, set to 44.1KHz, 16 bit. The audio (AIFF) files are dumped directly to an external USB drive. We are running OSX Lion, and the MacBook is a 2008 (intel) model, with 4GB RAM, and nothing else running.

 

Our process is to start recording the session, play for 2-3 hours, then mix and bounce tracks for the band to analyse mistakes, arrangements etc. A very useful tool.

 

I've noticed a progressive distortion happening. The recordings start off fine, then deteriorate after about 30 minutes - first the occasional pop or crackle, then progressively more, until the recording is a wash of ugly digital noise, totally unusable.

 

I've ensure we start the Mac from cold, I religiously kill all other SW running on the Mac, and sometimes, I get pristine recordings. Most of the time, though, it is garbage.

 

What am I doing wrong? Many thanks for your help ...

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Your external USB2 drive could be getting 'hot' and 'slowing down....'

 

This happens with some USB2 ext drives and there is little you can do about it.. other than going to a better quality (and much faster) FW800 ext drive... to record to.. given you have a MBP without USB3

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Thanks Nigel - I have no USB3 on that MacBook, but I can try a different drive, I suppose. I don't think it is the drive, though - I've used it on a new MBP, with no issues whatsoever. I'm convinced I have the preferences/configuration messed up in my inexperience with LP9.
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Have you tried using a larger i/o buffer size in the Logic audio preferences?

 

Are there any guidelines for setting the buffer size I can play with? I seem to think my problem is configuration (preferences), and possibly the template I established. I might have inadvertently caused the tracks to have "monitoring" on, or something equally task-heavy, when all I need is a plain vanilla, record-only setup.

 

Any help on ideal buffer size would be welcomed!

 

Thanks

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