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Ron Choma

Marshall JMP-1 Tube MIDI Guitar Preamp

Sound Quality

This preamp is the shit! Nothing nails a Plexi like this unit or, a Plexi. I have mine setup Ch1 Clean Gain 8 Cln1, Ch2 blues-like Gain 8 OD1, Ch3 Gain 13 OD1, Ch 4 Gain 12 OD2. It goes from clean to scream. You can blend in effects whether they be stomp box or rack effects through the effects loop. I use it with a Guyatone WR3 auto wah, Maxon CP101 compressor, MXR Micro Amp (for solos) Boss NS-2, MXR EVH Phaser, Visual Sound H20 (chorus/delay) and, DigiTech DigiVerb. My guitars (7) vary but, all of them are humbuckers. You can go direct to board or mixer (as I do) with phenominal results. My sound guy is very happy. I gave it a 9, only because the clean is not absolutely sparkly Roland JC-120 clean. With humbuckers you have to use the Clean 1 setting or you will get unwanted distortion. My PRS CE22 with dragon 1 pickups does that. It works out well on Clean 1 with the gain around 8. This unit consistantly sounds great. I can do everything I need to get done with it. The OD/Dist stompbox thing never held a candle to the JMP-1 for me anyway. This unit has a very good "chime" on some settings and a wonderful Marshall "Kerranggggg" too. It also sustains very well. I like the fact that as far as volume goes, it is again, consistant from gig to gig. Once it's dialed in, minor adjustment are always few and far between. I set the output dial on mine at 3 o'clock. It's a keeper. I've been through some serious crap over the years. This is the unit I always come back to. By the way, it marries up extremely well with the Marshall EL84 rackmount 20/20 amp. A great combination ! Even a Tech 21 Power Engine 60 or, a Fender 1270P powered monitor for us "direct" players.


Not one serious problem with it ever since 1995. My output pot is currently a little scratchy. Some of that liquid gold contact cleaner should quiet that down.

General Comments

I play Rock. 60's, 70's, 80's, and a little 90's. It is perfect for what I'm doing. 100 midi channels total available if I need more presets. Been playing since October 1964. I would buy it again if the CURRENT build quality was the same as my 1995 unit. [i mean,...look what Roland did to the JC-120. That was a very well put together amp at one time. I think it is cheaply made now. Metal parts and switches became plastic. I'd hope Marshall wouldn't bastardize the JMP-1 by currently making it cheap and unreliable.


Mine is just shy of 10 years old and it just keeps going. It's a Marshall and in MY book, that is, the sound of Rock. :-)

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