[a_t48]

I had a 1971 Marshall tube amp land in my lap, for free. I'm not a guitar player, but wanted to get it fixed it up before either selling it or learning guitar. There's a lot of "magic" there - the amp guy asked if I wanted to swap the tubes for some "more authentic" tubes that were used in England at the time. Pro tip - don't ask the internet for advice for making your tube amp sound nice, you'll get every opinion possible.

[smitty1110]

Guitar amps are all about getting the right kind of harmonic distortion, so of course the guy had opinions. But tube rolling is madness, avoid it at all costs.

[kazinator]

There is a whole range of useable distortions, so a lot of the opinions mainly boils down to genre bias.

E.g. to a metalhead, any tone that doesn't "chug" is useless, including something useable to a jazz fusion player.

[a_t48]

In this case it was a very common swap, 6550->EL34 for Marshall JMP 50W. I ended up going for it (the existing tubes were damaged), it sounds great.

[cluckindan]

You don’t even need to ask! Generally speaking, you don’t want a guitar amp to sound nice, you want it to sound good, good being a function of many things.

For clean sound, use compatible radio preamp tubes and bias the power tubes conservatively.

For distorted sound, use the lowest overhead preamp tubes you can find, and bias the power tubes as hot as you dare without them breaking within the hour. You can always change them after a gig, or between sets. :-)

[kragen]

Goodness, I hope you weren't injured.