Jump to content

Marshall JMP-1 Tube MIDI Guitar Preamp

Sound Quality


General Comments

after reading some other posts regarding this unit. and the fact that it supposably uses diodes to get its distorted tones. i contacted marshall and asked them about wether the jmp-1 is a tube preamp or a solid state preamp that uses tubes to just warm up the sound a bit. here is the respones i got from them.



The JMP-1 preamp is built around 2 ECC83 tubes (4 tube gain stages) and the sound is largely based on the tubes themselves. There are a lot of programmable parameters built into the JMP-1 which require control circuits comprised of IC's as well as some IC's used as buffers or as a part of those controlled stages. There is one solid-state clipping circuit comprised of BR3 which is a diode bridge, but that only kicks in if the signal level is over 1.2 Volts and it's found just before the first tube which is quite early in the signal path. You can have it removed by a qualified tech but you'll see that it contributes to a somewhat overall "roundness" of the tone for lack of a better term. It levels off some harmonic spikes and generally doesn't affect the fundamentals unless the input is extremely hot or has been insanely boosted by another pedal or preamp. As far as the so-called 'experts' are concerned, yes, if you bypass the tubes and max out all the gain you will still get some clipping. However, the overall QUALITY of the tone in the JMP-1 does come from the tubes alone. I hope this answers your question.


Unfortunately for the JFX-1, sadly the numbers requested for production were no longer there and it was discontinued. I can't say now if there will be a re-issue but if there is enough demand then yes, it's always possible.


Thanks for contacting Marshall on the web and if you have any other technical questions, please don't hesitate to contact me directly.


well there ya go the damn thing is a tube preamp.dont listen to these BOZO's who say different. it sounds KILLER. and it has to use some diodes in order to replicate all the various marshall tones. I even went out and started lookin at the Triaxis because of these bozos rantings . the Triaxis didnt sound anywhere near as good as the JMP-1. and it cost waaay more $$$$. the marshall is alot more versatile. lending itself to clean and moderate stones type distortions and all the way to mettalica type metal. the triaxis couldnt cut it for the real metal type of tones. it did have a nice blusey tone to it. but seemed to fall flat when asked to really juice it up as far as saturated tones were concerned. the Triaxis clean channels were also very nice. this is the one area of the JMP-1, i think could use recalibrating. marshall should actually use diodes and convert to a solid state for clean tones. this is what the ADA MP-1 does. It sounds killer also. i wish i could have the clean from the ADA and the distorted from the JMP-1 in one unit.oh well, maybe one day. so i give the JMP-1 a rating of 10 for an all around great preamp that doesnt cost huge $$$$!!!!!


  • Create New...