roberth:

You could try a line level shifter. Ebtech makes them. You can get one at any pro audio or musical instrument dealer (ok, not a place that sells just brass and strings). They shift the line level from -10dBV to +4dBV or vice-versa. They are primarily used to mate pro with consumer gear. They include a hum eliminator and will also accept and convert balanced and unbalanced inputs/outputs. You can get them in 2 or 8 channel versions. The work great, not sure if it will fully help your problem, not really what they were designed for, but it will boost or cut the line level signal. Generally consumer gear uses –10dBV for both input and output while the pro gear uses +4dbV. Many mixing boards allow you to switch the inputs to match the output of the gear that you are using.

I think this is what you are asking for.

Shifting levels may or may not cause any damage to your system.

Here are a few links:
Ebtech Audio
Interstate Music
Musician's Friend (2ch)
Musicisn's Friend (8ch)

[This message has been edited by Dr.Spike (edited July 23, 2003).]