Well here we are in 2009 and this piece of gear i still find to be very valuable and effective. I bought mine used and obtained it in very near mint condition in 2004 - it has been serving me well ever since. I have an eight space Grundorf cab loaded with a Mesa Boogie 20/20 power amp - the JMP-1 - TC M300 - BBE 482i - Furman power conditioner. Let me first clarify that the addition of the BBE or EQ relative equivilint is mucho needed to acquire the very best tones you can create using the JMP-1 ... it's simply a must have. As a stand alone unit without the addition of added EQ or Aural enhancing , the resident tones are a bit dull and lifeless. For my own needs the BBE works a great singular magic adding spank and life back to the tone. I use a Lopo 2x12 cab loaded with a pair of WGS ET-65 speakers to run it all in stereo. I love these speakers! Read my review of them here at HC. Okay , now for the details. You really have to twiddle with the various parameter settings to bring this thing to it's best offerings. There's a lot of hidden treasure in these units just waiting to be unearthed. You'll read other reviews knocking the effects loop - don't believe it! The effects loop in particular is probably the most careful parameter settings to make per patch. There's a range of 0 to 12 resident to the effects loop. The key is to get your effect from your unit dialed in first (all its parameters) and then to balance the input / output ratio using the range control on the JMP-1. Each patch according to the effect being used will yield a different range value - that's the deal. You've heard about the cleans not being too clean - forget about it! Again, the BBE brings the clean and the sheen into the mix. The trick is to twiddle the EQ and especially the gain settings resident to the JMP-1. I have dialed up a beautiful assortment of clean tones - my faves include a bit-o-grit when rolled up at the guitar volume and then fades out rolling down the guitar volume. The resident distortion patches on the JMP-1 are generally dark sounding to my ears - but again , the BBE changes all that. I really dig the variance of grit to grind to shred i can dial up with this unit. For my own taste , i don't use a gain setting over 15 even though a total value of 20 is available. I also use a pedalboard equipped with various dirt boxes and phase,chorus, and delay units that i send straight into the front end of the unit to get further tonal options. When using the pedalboard dirt tones i use a clean patch i created within the JMP-1. Don't use dirt boxes into the front end feeding a distortion patch - things can get out of control at that point and you'll find that you just end up wrecking a better dirt tone resident to the unit along with a lot of unwanted noise. I have found that the JMP-1 is a great versatile tone shaping preamp - with just a little added help. Of course , your power amp and speakers are the final stamp on your sound so be mindful of that. I forgot to mention up top that i use the Rolls Midi Buddy to make patch changes to the JMP-1 and TC M300 - there's a bit of latency between the switching but i myself can tolerate it as i don't do a lot of constant real time patch switching during a tune - moving from verse to chorus to solo patches has been just fine even though the lag is present as a very micro blip in time. It's no wonder these units have regained some popularity as more and more players are rediscovering the hidden riches these beauties hold. I can't think of a more fundamental preamp to be without ... the JMP-1 is a must have in my opinion.
For myself , the JMP-1 is my choice as the go-to rack preamp. It allows me to cover a lot of stylistic tonal soundscape. You must use something like the BBE or equivilint to get the best out of it. I use a McCarty, Strat , Tele , SG , and JEM through it - each with great success. The pups on my Strat and Tele are humcancelling i should point out. I've been playing since my teens and i am ... well, a classic rock age player to say the least. What i like most about the JMP-1 is its one space configuration and flexibility and its famous heritage tones we all cut our teeth upon at some time or another. I tried other preamps and i won't name them out of respect for others who may like that product - but for me , the JMP-1 fits my needs best while yielding a variety of useful tones with careful editing.