Kent S. said:
Guy, although I'm not 100% sure, your post gain shouldn't have anything to do with your fX loop gain ... something sounds wrong or needs repair their ... have it checked out ... Now if it's a preamp output/power amp input arrangement ...well tht would make sense, although most will still drive pedals at 1 (0~10), and racks at about 2.5 to 3. Something doesn't sound right there, but I'll take your word that it's happening ...Yes you can use a pot (preferably the same value and power rating as the post gain pot itself), wired as a volume control (just like you would with a volume pedal) ... and put it after your effects so that you turn the volume down after the effects have gotten the level that they want to see.
Here's is the problem though ... If the problem is after the loop, and turning up the post again (without cutting the volume post FX) is masking it, and making it seem like the loop isn't getting enough send, when it may not be getting enough return. If you've got racks with level led level ladders on them check them and see what they tell you about the level coming into them.