Setting the Master Volume

[Budda]

A JCM800 sounds best when it is getting its distortion from a combination of preamp and power amp distortion.

+1

And a Tubescreamer!

Or SD-1, or anything adding signal lol. Bay area thrash is SD-1 into JCM800 and its a ton of fun

I had a JCM800 that for some inexplicable reason was manufactured with 6550s. The power amp would never distort. I tried putting a booster in the effects loop, and all it did was clip the effects return. It sounded like shit at any volume, even with a power soak. I absolutely hated that amp. Then I heard one with EL34s, and it dawned on me why everyone else didn't hate them too.

Power amp would definitely distort, just might have needed biasing and a higher level than you ran. Source: running an EL34 2203 opposite a 6550 2203 (mine on 8 his on 4 for equal volume). Iirc 6550 was US import only, or modded. And if yours was modded for them, it may have been done so poorly..

Mine starts filling out at 2 and sounds pretty great at 3-4. That’s running 2 of 4 speakers, gonna let it run free next year. Lunchtimetones on IG to hear it.

I sometimes forget to check the master vs block level when trying new amps in the axe, but also go by if its meant to be a vintage or modern voicing.

Pic for good measure

 

[steadystate]

Mine was a 6550 US import, not modded. I bought it brand new. It would crank insanely loud, but the power amp would not distort, for whatever reason. It made for a useful clean channel, but the distortion channel sounded like garbage at any volume. I was sorry I sold a fender Pro Reverb to buy it, and I celebrated the day I sold it.