Jump to content

Marshall JMP-1 Tube MIDI Guitar Preamp

Sound Quality

Distortions are GREAT albeit limited to the few sounds you can get out of the unit. The bottom line is either you like the gritty Marshall somewhat tube somewhat solid state sound or you don't. If you play STP, Van Halen, ZZ Top, or straight up rock you are really in business with this unit. As for the clean channels they are extremely limited and you really have to "build" a solution to make them work. If you want glassy cleans and sparkly clean/dirty sounds a la Toad the Wet Sprocket or cleans like on all those old 80's tunes (INXS, etc.) I had great luck with switching to active pickups. Not just any, I got Seymour Duncan classic livewires. These are not as harsh as EMG's and since they use 2 batteries have much higher headroom from what I understand. They turn a extremely mediocre clean into a very usable one. I suggest if you have a guitar with a humbucker in the bridge and singles in the neck and middle you modify that guitar. Get a push pull put and make it so that the neck pickup comes on when you pull it. This gives you some great Romantics type distorted sounds because you are playing the bridge humbucker and neck single at the same time. Anyway, this is a preamp review, so I'll get off my high horse regarding pickups. The bottom line here is finding the right combination of preamp, guitar, power amp, etc. to get you the sound you are looking for. This unit would be worthless to me without the rest of the tools. You don't just have a hammer in your toolbox do you? If you do then you are probably using this unit all by itself to no avail.


Very reiable, no problems, there IS solid state aiding the distortion sound, cleans are all tube and as discussed before anemic unless you try and remedy the situation. Have two of them and just changed the tubes on both after 10 years to Mesa Boogie stock 12ax 7's, not a huge difference but doubtful you'll get one with so few tubes to work with and since they are in parallel the unit only uses both tubes for clean 2 and OD1 not for the others. What do you know, OD2 sounds better...and you thought just the tube overdrive was the way to go. The battery backup is something I think sucks. Rocktron and others use technology that doesn't require you to change anything. We'll write down your presets or back them up because when you try and change the battery you will lose them. I have never had to change the battery but after ten years I am a little nervous that it may be going. I found someones post that changed the battery and it seems like a HUGE pain in the ass, here is the excerpt on how they did it: . The problem seemed that my unit obviously been sitting on a shelf for a few years and the back-up battery CR3032 was going dead. To change it out I would have to send it to Marshall for repair. Guitar Center had no more in stock so I couldn't exchange it. I figured that I would do this myself. Well let me tell you that they do not use a standard battery, it is a CR3032 but it has two legs/connectors soldered to it. It was a test of patience and cordination with a desolder and soldering iron. After about 1-1/2 hours and a trip to Radio shack I was in business. This is a key thing to remember because if you have you customized programs in this unit you better back them up or at least right them down so you can replace them when the battery dies your up the creek impaled on the paddle. I have used it on gig without back-up. The tube looks to be mounted in a very delicate manner, you can easy rip the tube socket right of the motherboard. The tube socket should have been molded to engage with circuitboard or chasis so the stress of the tube is not transmitted to the board. A similiar arrangement as to the lamp end sockets of a flourescent light fixture would work. I don't know if there is any telltale sign to when your battery is going to die so reliability is somewhat of an issue. Most preamps that are programmable at least you can dump in the factory programs via system reset and finish a gig, but not on the JMP-1.

General Comments

I give this a 8 overall. I love the unit but it is far from perfect. If there are any sites dedicated to JMP1 lovers please drop me a line, I would love to check it out.

  • Create New...