A ton of Marshall's in a box! Great crunchy/rock sounds; the best I have ever heard in a MIDI tube pre-amp (have tried several over the years). There is a big volume/tone transition from 6 to 7 on the effects loop. 6 still is still meaty, but there is not enuf of the FX unit at this setting. After 6 the sound kinda thins out a bit. The balance is off, but still OK. I find the clean sounds simply unusable. They are VERY dark, and muddy. If you try to use the EQ to get a nice clean sound by removing the low end or boosting the top end it really sucks the life out of your sound (I use a '77 Strat with Evans pickups and a '77 Les Paul with a Duncan Antiquity humbucker). Trying to overdrive the clean channels doesn't produce very usable sounds at all. The OD1 channel sounds great tho. With my guitars however any gain setting less than 9 sounds real sucky and thin. This is my biggest complaint with the JMP-1: Trying to overdrive the clean channels or cleaning up the distorted channels doesn't work well at all. Getting the Pink Floyd tone (basically clean with just enuf dirt to make the guitar sing) is impossible. Also, I find that it doesn't work well with the guitar volume no-how. The sound will clean up, but becomes very dark; it isn't reacting like a normal amp at all (altho EVERY tube rack pre-amp I've tried behaves like this. No, I ain't gonna start playing with caps or the volume control values on the guitar). The OD1 channel for distorted rock stuff DOES sound really good tho; pure Marshall sound big time! The OD2 channel is great for leads and thick distorted metal type rhythems. I do find OD2 behaves wierdly in the mid part of the spectrum. I can't nail a creamy sound here; I feel that the mid control is lacking on it's own (mebbe a low mid/high mid setup would be in order, but what Marshall has that eheheh?). It either sounds scooped out, or too middy. Fine tuning the mid on this channel is difficult. The overall level between clean and dirty is hard to match well with an external FX device. If you balance the levels so the clean and dirt setting have the same sound level, the clean settings will clip the external FX device, whereas the dirt settings will barely drive it. Using a compressor will help the matching, but I found I must use an overall volume setting on the external FX unit to have the sound levels consistent and drive the external FX unit properly (I use a Replifex which handles this VERY well). One thing that REALLY improved the sound of the JMP-1 wuz changing the stock tubes to Sovtek 12AX7's. There wuz a dramatic change for the better after the switch. The unit warmed up greatly and had a much better overall sound.
The speaker simulator is suberb; it made me a believer that speaker sims could, ah, actually work. I miked my 4x12 with a 58 and patched the speaker sim output to a 4 track. There was almost NO difference in the sound at all. I mike up the cab live and give the spkr sim send to the PA as well for a real good live sound (soundmen like this flexability as well).
I find it a bit noisy on OD2 but tolerable (and much quieter than most tube preamps). I use a MOSVALVE 500 amp with it, and the JMP-1 translate touch and dynamics very well.
The unit sounds 'raw' and unrefined; pure rock all the way! Again, if you wanna ton of Marshall sounds, look no further.
I give it a 10 based on what it is designed to sound like, not an overall sound rating compared to other preamps. Awesome Marshall sound!!!
Broke the input jack slightly (tripped/pulled on cable...doh!)but not enuf to warrant replacement (wish it wuz metal) and the Patch button has lost it's mounting somehow on it's own (you can pull it out of the faceplate just less than 1/4". It still works fine tho). I know several others that have a JMP-1 and use it steady (for years now) without any problems at all. I feel you must take some care in replacing tubes; the 12AX7 PC board and it's mounting to the main PC board seems kinda fragile, and problems may turn up here if you don't use a gentle touch when replacing tubes.
I have gigged without a backup unit for four years without a problem (touch wood). I feel that with any computer based product you should use a power conditioner of some sort, otherwise when the big beer fridge at the bar kicks in you may have problems (this happened once to me without any conditioning and found I had all my presets scrambled!).
Have been playing for 15 years and own numerous tube amps (Fender Twin, a black face Showman, Marshall JCM-800, Marshall SuperLead 100, Gibson's, Supro's, etc.). I love each for their own particular sound but find them impractical (on their own) for live gigging. I want a million sounds at my disposal, so I have been into rack stuff for about 8 years. When I got my JMP-1 it wuz the only real contender on the block at that time; I didn't like the ADA and the Tri-Axis wuz too much. I also tried a TwinTube (mediocre sound, big pain to edit) and a SGX-2000 (crap) at the time so the JMP-1 came out a clear winner.
I feel this preamp is an excellent one if you need/like the Marshall sound only! The tone controls can alter the character of the sounds but it is still voiced for the Marshall sound, and you cannot get away from it (well, duh!). It is not very flexible with regards to getting a wide variety of sounds; it doesn't cover enuf bases for the styles I play (rock, blues, pop).
After playing with many tube racks over the years, I have come the the realization that these units are not gonna cut it for overall flexability and quality of sound. I have tried solid state/tube hybrids but haven't found any that sound all that great to my ears. I now am looking seriously at DSP preamps like the Yamaha DG-1000. I think that they sound and feel like a tube preamp (I wuz EXTREMELY skeptical of these amps till I tried some recently, and wuz, well, blown away). DSP amps have really shown me the limitations of tube preamps. They do everything that I wish the JMP-1 did. I am not completly sold on DSP amps yet tho. If I wuz to consider another tube preamp it would be the Rocktron Piranha hands down (they weren't out when I bought the JMP-1). They are MUCH more flexable than the JMP-1, and you can make a Piranha sound like a Marshall.
I give an overall rating of 10, again based on what Marshall set out to do with this unit.