Marshall Jmp 2144 (1980) - Info

[DSharp]

I recently acquired a rare 2144 combo dating back to 1980. It has the footswitchable boost and spring reverb, with two T1221 blackbacks (1979). I got it from its first owner and it's in a very good condition and little play time. Circuit, caps, transformers and preamp tubes still original and work well.

As this is my first experience with a JMP (early JCM) era amp, and to my understanding they are bright and are more of clean amps unless pushed really hard, I am trying to understand how it compares with its regular 2104 or 2204 siblings.

From an output perspective and driven directly by an LP standard (burstbuckers), the Low input is all clean with moderate output, the High input with boost OFF delivers a nice light crunch with preamp all the way up, and it delivers more crunch with boost ON but with more icepicky treble.
The reverb is quite nice up to 8 to 9 o'clock.

Comparing the preamp circuits from downloaded schematics with the 2104, I noticed the following main differences:
- Attenuator before the preamp pot is missing
- Tone stack is driven by the high impedance output of V2A (warm bias) and its output is amplified by V2B (cold bias), as opposed to the usual cathode follower low impedance method
- Boost seems to be a bias modification to V1A
- Additional preamp tube and circuit for the spring reverb

I am planning on validating the downloaded schematic with the actual circuit when I get some free time.

I was wondering if anyone here has some experience with these amps:
- What's the effect of the tone stack method on the amp sound, does it make it less/more Marshally?
- Is it closer to the 2104 with the boost ON or OFF?

Thanks!

 

[DSharp]

apologies for the double posting.

 

[DSharp]

For reference in case anyone is interested, I compared a couple of things between the amp and the schematics:

1- Boost OFF adds a 15k resistor and a 0.47cap to V1A cathode's regular 2k7 resistor and 0.68 cap in series to ground. Boost ON shorts them to ground making this stage similar to JMP 2104. Hence the boost is actually an attenuator to the regular output of the 2104.
Resitor R5 (47k) mentioned on the schematics has a place on the board but never made it there.

2- Load resistor of V1a reads 400k instead of 100k (that was a surprise), did not have the time to measure the B+ voltage. V1b has the usual 100k.

3- Tone stack confirmed not being cathode driven

I am very pleased with the amp sound, Low input is very pedal friendly and the cleans are great even with preamp volume full up. High input needs to be cranked to get to the sweet spot, pure Marshall bliss ...

 

[JCarno]

I'm surprised that none of the "experts" have chimed in yet. I'm definitely not one of them!
I own a 1981 4104 (2204 2x12) that doesn't have the bells and whistles(boost/reverb).
To be quite honest, I didn't even know your amp existed.
I only popped in to ask if you wouldn't mind sharing more pics. The front, back.
It also looks like yours is a Canuk model by the extra fuse board?
Sound clips would really tickle me too. The boost and reverb in action. Especially the boost. Definitely would like to here the difference between on/off.
Congrats on a cool amp!!

 

[Kris Ford]

1980 is still 10000% JMP era, no "early JCM era" about it at all..in fact, quite the opposite...the first JCMs were JMPs with a new look.

If Canadian, it would have black grill cloth..lets see it!!

 

[pleximaster]

Kris is right. first JCMs were just the same as earlier JMPs.

The story goes (Book on Jim Marshall) as Roose Morris, the company that was the sole agent for selling the Marshall amps (apparently limited to the JMP (Jim Marshall Products) name, stock thousands of amps as the contract was running out and they had got the indications that Marshall wanted to distribute their amps themselves. By doing so they thought they could force Marshall into signing a new contract as they planned on pricedumping the amps if Marshall did not comply. Jim then apparently changed the outside design and the renamed the amps to JCM 800 (after his licence plate on his car) making the stock Roose Morris had out of date. As always with these stories, take it with a grain of salt especially when coming from Jim who was a fantastic story teller!

plexi

 

[DSharp]

Thank you JCarno, I will try to record some clips during the weekend, but basically with boost off you get mild crunch and less highs. Photos attached.
Kris yes it's black grill.
What I meant is that as far as I know JMP 2104 circuit should be the same as the JCM 2104.

 

[Kris Ford]

Looks like a ripper!!

 

[Jaguarguy]

Here's some pics of my 2144 from 1979

 

[Jaguarguy]

Here's a video of Aynsley Lister who is using a white 2144 for this cover of Purple Rain

 

[Jaguarguy]

Another one from Aynsley Lister on his white 2144

 

[Jaguarguy]

BTW - as I understand it you are right it is a bit rare. 200 or so made. I got mine a year ago but haven't seen one for sale since.