What do you guys like as a high gain JCM800?

[anomaly]

That's interesting because I've always felt like the Mark series do not sound good with overdrives, and I didn't know it was because they were already so tight sounding from the already built in boost.

They do if you set them right. Try lowering your treble to about 5 and bring the bass up a bit, like 2 or 3. Throw a boost in front and let us know how it works for you. The problem is they get over boosted and too tight and compressed so the settings need adjustment.

 

[Speeddemon]

They do if you set them right. Try lowering your treble to about 5 and bring the bass up a bit, like 2 or 3. Throw a boost in front and let us know how it works for you. The problem is they get over boosted and too tight and compressed so the settings need adjustment.

+1. Set up your Mark's unboosted tone for more of a 70's hard rock meets sludge rock tone (so, a bit more flabby or loose, not too gained) and then the tightening of the boost (be it an SD-1, TS-9, etc. as long as it adds volume and cuts low-end) will do the rest.
The same goes for my Caliber 50+; I set it up like I'm playing Thin Lizzy and then hit it with a boost, BAM, thrash away!

 

[JackBootedThug]

A rectifier…..