True all valve distortion

[jagermike66]

Ok firstly, any tube change should be accompanied by a bias tweak. Even if the tube is in the same family or indeed the same type of tube, there will still be differences. Most companies who sell tubes claim to balance all their matched sets evenly, but it still helps to tweak the bias. Its not gonna hurt it if you do a straight swap with EL34/KT77/6AC7 but its like air pressure in a tire. Needs to be just right for the amp to run as well as it can.

Phano36 has pretty much said all the things I would say. I will stress again that EL34 to 6L6GC is a far more complicated switch and could require a new output transformer amongst other stuff! If the tubes are in the same family then it should be safe to swap between them.

As for having the amp cranked, I play alot of hi gain stuff (I use a tube screamer in front of the amp most of the time, so lots of pre amp distortion), and it always sounds better cranked (therefore introducing power amp distortion). You don't have to crank it to get it sounding good....but in my experience it always sounds better if you do, even if power amp distortion isnt your main goal....seems to just be the way tube amps work :).....and rightly so!

[ArtyPaul]

First off - thank you everyone - what a wealth of information...

...and from this, I think I'll do the following: not much just yet.

I'm actually pretty happy with the sound I'm already getting, so much so that I've actually now taken my EQ out of the effects loop. I might like to fine tune things, but my first move will be to play with different 12AX7s, and even that may not happen for a while. I like quite a sharp sound, so I'm happy with the level of presence I've got, and certainly wouldn't want any less. Also, I've only had the amp for a week and a half, so I'd rather get to know it as well as I can before I start trying to tweak it. I think I've just got really excited by the potential it has!

What's great about the MA is that I wouldn't be scared to tweak it, whereas if I'd paid three times as much for a JVM I'd probably be much more hesitant. And the strange thing is that whatever amp I play, I still seem to find a way of sounding sort of like me - the MA is organic enough for me to play with the guitar's volume and have real fun trying to sound like Jeff Beck playing with James Hetfield (OK - in my dreams, but you get the idea). It's great fun. And at the end of the day that's all I want from an amp - tons of fun.

What a great forum though - thank you again for all the amazing input

Paul.