Just got back from "megtronics", that amp tech place I mentioned in the first post.
Took my amp in, and firstly changed all the EL34's as the old ones had been in there for far too long and were making popping and hissing noises. The guy then rebiased the amp (very easy to do btw!!! Now that I've seen it I could easily do it myself).
The left 2 tubes were running way too hot >120, while the right 2 were ok'ish at 80+.
Anyway, I plugged in. Immediate difference in tone. But still not the growl I wanted.
So he suggested we start pulling the preamp(I think that's what they are??) tubes, and substituting them for 12ax7 one by one.
Change the first, instantly different sort of gain. Change the second, GROWL! Change the next one, no change, but still GROWL! So I told him to change all four.
The ones the 12ax7's were replacing have "Yogoslavia ECC-83" written on them. Are the 12ax7's known to sound growlier?
Switch channels and I can get smooth lead sounds that I couldn't get before with this head.
I'm surprised. I didn't need to get it modified. The tubes in it were just really dead, and I needed the 12ax7's to be in there. I still have the same problem of loudness though. There is no way I can use this amp at bedroom volumes. It only starts to come "on song" with the volume at half-way, which is window shaking loud (even when run through a twin speaker cab).
I had to totally change the amp's EQ section too. I use to run the amp with the deep switch on, bass at 3, mid at 6, treb at 8, presence at 7, and tone switch off. Gain was and is still set at 5 on both channels.
Now I have the deep switch off, bass at 5, mid at 4.5, treb at 7, presence at 7, and tone switch on.
I'm liking the sound I'm getting again from this amp.
*wil wipes his forehead and sighs the sound, "phew"