JCM800 w/ 6550.. leaving me uninspired

[petejt]

How long have those tubes been in there? It might be time for a retube. It won't give you any more gain, or not much if it does, but it may return it to the tone beast it's supposed to be.

Good idea. Reminds me too- I think my JCM 800 is due for a re-valve.

 

[Psionic Audio]

Have a tech redo the bias circuit in your amp. Marshall limited it so it won't really bias much more than warm, at best (my guess is to make the tubes last longer on the guitar shop floor). Usually they are cold, and 6550s will make this worse. Just a matter of changing one resistor so the bias trim pot range is more useful.