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Recording D.I, Very annoying problem.

I recently purchased an M Box 2 bundled with Pro Tools LE7 as well as a Behringer B2 Pro Mic. Ideally I'm trying to record two channels, one DI and one mic. My problem occurs without the mic or the bass even in the picture.

My setup would usually go as follows;
I plug my bass into my amp, my amp has an XLR D.I output which I then run into the Mic input of the M box. In theory this should all work ok right?

The problem is that my amp lets out this really high pitched whining sound. Its not incredibly loud but its just annoying, it shouldnt happen. Now this occurs with or without the bass plugged in and it only happens when pro tools is open.

It is definitely not the leads or proximity to any other devices as I have checked this.

Any help for this annoying problem would be very much appreciated as I have spent a lot of money on this gear (well for me at least is was a lot).


zemlin Mon, 07/03/2006 - 18:37
I'd expect the DI out of your bass amp tol be a high impedance output. I'm no electronics whiz so I won't venture to guess what that impedance is. The mic input on your audio interface will be a low impedance input that feeds into the mic preamp. The line input likely bypasses the mic preamp and is a high (or at least higher) impedance input.

Again, I only know enough to think I know what I'm talking about - I don't know what about an impedance mismatch would cause the noise you're hearing, but it's something to try.

Pro Audio Guest Mon, 07/03/2006 - 20:16
Damn, i'll still try anyway, thanks.

My other thought is to buy a D.I splitter like this one,

I'm thinking I run my bass into input 1 and there is a mode in which both outputs run from input 1, therefore I could have one output running to my amp for miking, and the other to the D.I on my M Box.

Using this method my amp won't be communicating with my mbox, therefore no interference right? Also remember that if i run my bass straight into the D.I on my M Box there is no problem at all.

Anybody see anything wrong with this idea?