I've been using an unmodified Blues Junior for gigs. 15w has been plenty because although it's a large band (with brass, woodwind, backing singers etc), we play relatively gentle gigs and try to keep the back-line sound in control to give the singers a chance.
I normally set the gain pretty high so that with the volume up on the guitar I get a crunchy sound for solos and keep the guitar backed off for rhythm playing.
Yesterday we played an outdoor gig in the Brimingham Botanical Gardens and in the break a couple of people said I was too quiet in the mix, so I turned the master volume up for the second half, leaving the gain at about 80%. Here's the weird bit - this seemed to clean the sound up and I struggled to get a comfortable sound at all - the volume pots went super-sensitive and much above about 3 the volume just went right up but I had lost the crunch I was expecting and just got a not-very-musical toppy sound that was too loud for everyone else on stage.
Am I expecting too much from a 1x12 15w combo and what's with the cleaning up? Do the preamp volume and the power amp volume interract more than I realised?
Here's the scene of the crime......