Mike M. said:
With all due respect to the suggestion of a Greenback by some of the good folks here, I personally would'nt put one in a Classic 30. I tried one in mine and if you think that amp has a bit too much presence now (I assume you're talking about the gain channel) look out! It will slice your ears off. With a Greenback I found the high end to have way too much sizzle and the bottom end seemed to fade off. Of course were talking about something that is very, very subjective here. I hated it but you may love it. And I'm not saying there isn't a better speaker for this amp either. I just got tired of trying things out.
As a suggestion here's what I did with mine. After trying numerous speaker changes I wound up keeping the stock speaker and installed a Weber Beam Blocker in front of the speaker. In case you don't know about them it's a bar that's about 12 1/2" long and approximatley .030 thick. In the center is a 4" diameter cone and the cone side is towards the speaker. What this does is to diffuse the highs so they're dispursed just as the mids and lows are and it really, really helped tame the sound enormously. That spikey quality that the OD channel can have isn't going straight at your ears now. If you do go this route there is a little trick to installing these, so let me know and I'll give you the scoop.
I also added a 1X12 cabinet as an extension that I made with an Eminence Cannibus Rex and it really, really helped to fill in the sound. I also recentley thought I'd try out one of those new Bad Monkey overdrive pedals by Digitech and I'll tell ya what, I am MOST impressed with this pedal. It's only $40.00 and in my VERY humble opinion it's the best OD pedal (thru that amp) that I've tried out to date. The bass control is what really helps to fill it all out. I'm not saying it's the pedal above all others, no. But again (subjective) it just rocks thru that setup. It sounds great used as a main OD in the clean channel, but I think it shines as a boost in the gain channel. Keep the amps pre-gain at about 9:00, post-gain at about 12:00, set the pedal accordingly and you're flying!
Did'nt mean to go on and on here. Just thought I'd share what seems to work for me.