[ebuddy]

Okay here's my setup and let me know if I've got something fundamentally wrong here;

- Analog mixer L & R OUT via 1/4", IN to Tascam US-122 audio interface.

- Tascam IN to dual 2gig G5 via USB.

- Out of G5 to Tascam (of course via same USB cable)

- OUT of Tascam US-122 L & R 1/4" back IN to analog mixer

Noisier than a 90HP outboard motor. Some humming, and cyclical drive noises. I downloaded CHUD tools and have disabled "nap-mode". This has eliminated a considerable amount of noise, but w/ headphones on I can still hear way too much of it. I'm running a home studio using Digital Performer 4.12 ( I can't afford to upgrade the OS and DP). Here's what I'm thinking; why can't I have something exactly like the Tascam, but with optical in and out instead of the USB? In other words could I go like this;

- Analog mixer L & R OUT via 1/4" cords to optical interface

- optical interface IN to G5 via toslink (A/D conversion)

- Out of G5 via toslink IN to optical interface (D/A conversion)

- Out of optical interface via 1/4" cords back IN to analog mixer

The problem with this is that I'm seeing analog IN L&R and analog OUT L&R, but then to computer using not toslink, but RCA/ Spdif. The G5 is spdif, but it's optical. I'm not finding a product that can do all this. The Midiman Flying Cow comes really close, but then uses RCA. Is this type of interfacing possible? Will I still get a bunch of noise??? I've been told AD/DA is the way to go to eliminate unwanted processor/drive noise, but I'm wondering why I'm not seeing my needed application in action?

[tooki]

It's HIGHLY unlikely that it's CPU/drive noise. It sounds to me like a ground loop problem.

tooki

[analogika]

The humming might be a ground loop.

Are both the G5 and the mixer hooked up to the same power strip? If so, does it still hum when nothing at all is connected to the mixer except for the US-122/G5?

Also, the G5s DO have a nasty known issue where the power supply will produce weird interference on audio interfaces connected via Firewire or USB. This is pretty much catastrophic and could account for the cyclical noise.

You can get the PSU of the G5 replaced under warranty, but chances are about 4:1 that the replacement will have the same issue.

[ebuddy]

Originally Posted by tooki

It's HIGHLY unlikely that it's CPU/drive noise. It sounds to me like a ground loop problem.

tooki

You guys are great! Yeah, after I typed the above question I went to the Apple support site (for which I'm almost sure I found nothing a few weeks ago) and found then saying the same thing. They recommended some "direct boxes" or transformers if you will. I called one of the suggested manufacturers at the bottom of Apple's support article and that guy (Pro Co Sound) was very helpful and gave me several ideas up to and including;

- Try putting all of the gear on one outlet
- Try stereo (TRS) 1/4" cords from mixer to TASCAM and from TASCAM back to mixer. He says sometimes interfaces have issues with balance/unbalance cord anomalies though I'm almost certain that shouldn't be the case with this bad boy.

Analogika; I hope you're wrong on the power supply bit. I reeeaaalllly do.

I'm going to try these things although I'm a little curious about the load here considering I'm running 2000 watts worth of heads, a keyboard, a Roland V-Session drumkit, midi interface, rack mixer, headphone amp, crossover, etc...

Thanx all!!! I appreciate the info!!!