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RE-JMP-1 Rack-Ears for the Marshall JMP-1

I got an e-mail from Lenton Engineering this morning, informing me that a whole bunch of stuff I asked them to do for me, was now done and ready to collect. Amongst all the bits 'n' pieces were a pair my RE-JMP-1 replacement rack-ears for the Marshall JMP-1. Oh, I was so excited!!!! 😀

Lenton Engineering is in Watford so only ten miles away but did I race there or what?!?!? Then... I raced back to the lab!

I have three Marshall JMP-1s in at the moment but decided to try these on my own test JMP-1 first, the one I use to test Eclipses before they get sent out.

RE-JMP-1 replacement rack-ears for the Marshall JMP-1 fit perfectly
RE-JMP-1 replacement rack-ears for the Marshall JMP-1 fit perfectly.

Oh man, these things fitted like a glove. Why was I so excited about a couple of bits of metal? Well, these have been in the making for a couple of years, that's why. In fact, looking at my very first drawing, I see that it's dated 5th February 2021. That's three years ago, almost to the day!

I only had original rack-ear reinforcements to work from and measuring, remeasuring and remeasuring again, I wasn't even sure if they were designed with metric or Imperial units. Anyway, now I don't give a damn because the Lenton boys have have done it again. What a great job, guys!

RE-JMP-1 Rack-Ears for the Marshall JMP-1 includes screws
My RE-JMP-1 rack-ears for the Marshall JMP-1 includes screws.

The Marshall JMP-1 is an awesome early MIDI controllable valve pre-amp. Now accredited with 'vintage' status' and adorning a 'classic' badge, the humble Marshall JMP-1 continues to be used by many named artists like Phil Collen (Def Leppard), Billy Gibbons (ZZ Top) and Trent Reznor (Nine Inch Nails), to name but a few.

One thing that makes the JMP-1 unique amongst guitar pre-amps of the time, is the fact that it's analogue. Yeah, I know what you're thinking; "How can that be when it's got MIDI and presets?" Well, just like many early MIDI synthesisers, the audio is all analogue. In the JMP-1 specifically, the audio signal (the output from your guitar) passes through analogue circuitry only but some of it is digitally controlled, thanks to the use of voltage controlled amplifiers (VCAs). A preset comprises a whole load of noughts and ones which are converted to analogue control voltages which in turn, are used to set the gain of those VCAs, hence provide variable gain, volume, tone controls, etc.

Toshiba TC9176L VCA in Marshall JMP-1
Highlighted in red is half of one of the Toshiba TC9176L VCAs that's used to control parameters (such as volume) in the Marshall JMP-1.

Anyway, I digress. So... finding a really nice JMP-1 is becoming increasingly more challenging and buyers are often forced to compromise. Joining my arsenal of JMP-1 peripherals, I'm rather hoping that my RE-JMP-1 replacement rack-ears for the Marshall JMP-1 will help out a few users. I currently have three JMP-1s in for service. Pictured below, the bottom unit which belongs to a lovely gentleman called Tim, doesn't have rack-ear reinforcement brackets so I know there's going to be at least one happy JMP-1 owner very soon! 😀

Marshall JMP-1s in for service at Plasma Music Limited
Hmm... I tend to regularly have a small collection of customer JMP-1s in now-a-days.

Supplied with six black Phillips crosshead screws, my RE-JMP-1 replacement rack-ears for the Marshall JMP-1 can be installed in a few minutes. Yes, you read correctly; Phillips crosshead. I often replace the original hex heads, which in my humble opinion, are crap anyway, with Philips crosshead screws. In fact, all the screws in my screw kit for the Marshall JMP-1 are crosshead types, which makes maintenance of your Marshall JMP-1 a little easier and reduces the risk of messing up a screw head.

UPDATE - 9th February 2024

Marshall JMP-1 stuff at Plasma Music

With so many bits 'n' pieces available for the JMP-1 and always thinking of new stuff to make for our favourite MIDI valve pre-map, I decided to make a category just for the Marshall JMP-1 in my on-line store. You can check it out here.

Marshall JMP-1 Service
Marshall JMP-1 Needs Attention
Eclipse Marshall JMP-1 Data Encoder Fix
Marshall JMP-1 Nuts, Knobs and Bezels
PML-TX01 replacement transformer for the Marshall JMP-1
CR2031 battery adapter for Marshall JMP-1
RE-JMP-1 replacement rack-ear reinforcement brackets
Screw Kit for the Marshall JMP-1
Oracle Battery Eliminator for the Marshall JMP-1