Recording Problems Making Me Insane :( Options

[cwolfson]

Bear with me here. I am a radio producer; I record my shows to DAT at the radio station then bring the tape home for post-production on my Mac in Peak Pro.

For many years I used a G4 running OS X 10.4.x with M-Audio Audiophile USB, but last year started having all kinds of problems with the recordings. It was usually a jittery, "motorboating" kind of sound, but occasionally there were artifacts from other parts of the recording popping up in inappropriate places or just generalized distortion. (This occurs in varying degrees whether recording into Peak or Quicktime.) When all my troubleshooting failed, I decided the M-Audio was the culprit and bought a Behringer UCA202 USB A/D converter. The problem persisted. I did a clean system install, replaced the logic board. When that didn't work, I gave up and purchased a new iMac 2.4Ghz Dual Core.

The first few recordings I made were OK, but then the problem came back with a vengeance. Here are just some of the other troubleshooting attempts I've made:
Upgraded all software
Changed the cables running from DAT to A/D
Tried using sources other than DAT (ie, a cassette deck)
Switched USB ports
For the hell of it I thought I'd try the M-Audio again, but the latest driver seems to be in be incompatible with Leopard and/or the Intel processor. My recording attempts came out blank.

Last night I contacted Apple. The tech guy I spoke with had never encountered this problem and suggested that USB might be the bottleneck and that I should get a Firewire A/D converter. Frankly, I don't understand why popular USB devices that work for others aren't cooperating with my setup. The Firewire converters I've seen online are very expensive and wa-a-ay overkill, since all I need is something that will accept a stereo analog or SP/DIF input and convert it to 16-bit, 44.1 Mhz. No mixing, no instruments, no midi.

Since this directly affects the way I make my living I HAVE to find a solution before I go totally nuts. I figured that if anyone had ever heard of this or could come up with a solution it would be you folks.

Cary
iMac 2.4 Ghz Intel Core 2 Duo
OS X 10.5.2
4 GB RAM