I was just playing with my amp a second ago, and I realised that the distortion channel is now suddenly VERY quiet. It's a Laney LC30.

The clean channel sounds the same as always, no change in volume whatsoever. On the distortion channel however, with the gain all the way up, I used to only be able to turn the master volume to 1 before it became way too loud. Just now however, I was able to turn it all the way up to 7.

What could be wrong? It seems like it could be some sort of valve issue. But I only changed my pre-amp valves last week. Is it possible I've done something wrong? Or is is that the power amp valves are going?
if it is on the disti channel only my hunch is that it is the preamp valves.

what did you put in?
what was there before?

Also ask in the Laney thread or the Tubes sticky.

Are you sure they are all pushed down and seated real well?