I Have been playing hardcore/ metal for years, as well as blues and jazz, and even though the channel switching came in handy, i thought that it lacked any real defining tone. The distorted channels just needed more. It is a decent base sound, thats all. After i added and Aphex aural exciter and a rocktron intellifex my sound came together (The Jmp-1 was running into a 20/20 mesa power amp). the Jmp-1 is the weak link. I am a metal freak, but i want defintion, clairty, and tone in my sound; not just over distorted mush. Adding more digital components almost hurt more than helped, and i never found a sound that lept out at me. I play a PRS custom 22 that sounds great, fat warm tone on the lows, sustain and articulation with the highs; the jmp-1 stifilled its beauty. There is not enough versitility in the four channels. Clean 1 and 2 sound very similar. You can dial up clean 2 on the clean 1 channel if you want, same thing for the distortion. What is the point? what a waste of space! I know marshall is know for its signature "sound" but if all they have is one sound, give it up. If you are going to offer a four channel pre amp, the channels should be distinct.
I used this for many years without a backup (just poor, not stupid)and it never failed at a gig. One day though it decided to blow a fuse and keep on blowing them. I took it to a tech(he knows little about the JMP-1) he replaced the tubes and the fuse. It worked for about three chords and then it blew the fuse again. It may be the battery inside, i have yet to check that. I have had other problems with marshall solid state stuff, as well. I had a 80/80 solid state power amp (garbage) that would blow about every three months. It was under warranty so i got a new one every time this happened. Marshall ended up giving me four amps. The guys at the store i got it from thought it was the way i had things wired... but it turns out that marshall likes to put bad power converters in that amp. Marshall was not going to replace may amp under waranty (they stand by there products HA HA) so with a little pressure i got the store to give me a used Mesa 20/20 power amp. My love afair with tubes begins...
I did have a drunk friend knock my rack off my cab and the only thing that broke on the jmp-1 was the input jack. My guitar was plugged in and the Jmp-1 fell right onto the jack. eight buck in repairs. Atleast you can hit someone with it...
I now play through a Mesa Mark III and i am much happier. It suits my demands much more than any marshall i have played. They have pissed me off. Like someone else said, Marshall rides on its reputation and has given up on producing anything quality. they have become a brand for amatuers. The Jmp-1 is reminicient of that. With a little more work they could have made a great pre amp. Instead they cut corners and tried to sucker people by selling it as a Valve pre. Shame on Marshall. It works, and sounds better than a floor pedal, but if you want something that will push your sound to the next level, this is not it.