Annoying feedback problem. help please.

[ffud]

So I'm trying to hook the line out from my hotplate power attenuator for my guitar amp to one of the inputs on my Mbox. I don't care about the quality being super good I'd mic it if I was trying to do serious recording work, but I just want to be able to record little ideas, jams, and demos. For some reason making this connection causes my amp to give me terrible feedback. I need help figuring out how to get this to go away.

Heres what I know:

Not the power attenuator:
I tried the line out on my amp and had the same result.

Not a ground loop between my amp and computer:
I plugged my amp and pedalboard and everything into an extension chord, ran it down the hall to outlet on a different circuit. This ha solved grounding problems for me in the past, but it didn't fix this.

Not the Mbox:
I've also hooked the line out of my bass amp into the other input on the Mbox and I haven't had any issues.


Any Ideas what going on?

Help would be greatly appreciated. Thanks.

 

[mjbphotos]

Unless you have the Mbox output or computer output plugged into your amp, the amp has a problem.
Do you get the feedback if you plug the cable into the amp out with the other end of the cable NOT plugged in to the Mbox? If not, how about if you short out the open end of the cable - does it do it then? It's supposed to be output only, so if the feedback occurs, there is something shorting the amp output to the amp input in there!

 

[ffud]

Unless you have the Mbox output or computer output plugged into your amp, the amp has a problem.
Do you get the feedback if you plug the cable into the amp out with the other end of the cable NOT plugged in to the Mbox? If not, how about if you short out the open end of the cable - does it do it then? It's supposed to be output only, so if the feedback occurs, there is something shorting the amp output to the amp input in there!

It doesn't do it if the cable is not plugged into the mbox. I'll try shorting the open end of the cable and see what happens, but I'm a little skeptical it's just the amps fault since I have used the line out at a show before and had no issues.

Thanks, I'll keep messing with it.

 

[ffud]

never mind. It had to do with a pedal I was using. fail.

thanks anyway.