[eugovector]

If you have the desk space, you might consider a mixer instead.

 

[eugovector]

Feedback destroyer is a totally different piece of equipment. If I'm understanding correctly, have a single stereo source (your laptop) with a -10dbm output that you want to convert to +4dbm, and if it can incorporate a single volume control and be rackmountable, all the better?

If that's what you're looking for, the MX882 is exactly what you want. I'd look to get a replacement.

 

[eugovector]

Hmm...try switching out your cables, and doing some general trouble shooting just to verify that it is in fact the behringer that's causing the problem 2 bad units seems very unlikely.

Also, the manual seems to indicate that the XLR's may not like unbalanced signals. Try using just the 1/4"

 

[eugovector]

Aren't the in's on 5 and 6 1/4"?