Are your gain settings labeled someway?

If they're labeled in volts you might actually be doing the opposite of what you think/we meant here...

If they're labeled like 0.25V - 8V (or something like that), that refers to input voltage needed to get full signal out. The higher setting (8V) here actually means you get less output for a given signal, and the "lower" setting (0.25V) means that you get much more output for the same given signal...

I'll try to keep the following neutral from up/down etc...

For a given volume setting on the empeg, say -30db, turn the gain knob so that you get minimal output from the amp (should be at one of the ends of the knobs range). Then turn up the volume on the empeg until you start to hear distortion or you're as loud as you ever want to be - but don't go past 0db into the + range!
If you're at 0db at not as loud as you want it and don't have distortion, turn the gain away from the end it was set to until you start to hear distortion or you're as loud as you ever want to be. If you stop due to distortion, turn the gain setting back a little bit (and consider upgrading your speakers :-)

(If you couldn't turn up the empeg all the way to 0db with the "lowest" gain setting, then your amp probably can't handle the 4V output from the empeg - but most newer amps should...)

The above should maximise the signal from the empeg compared to any external noise entering the amp. If you still have noise; follow the procedures in the resources linked in the FAQs trouble shooting part.

/Michael