Scored an old JMP. Metro Loop anyone?

[Chris6870]

Saw this 78 JMP pop up on Facebook marketplace in my town so I went and checked it out. Recently recapped and retubed. Real clean and looks to be stock. Sounds great and the price was fair.

It has the four output jacks on the back, so supposedly the Metro Zero Loss Loop can be installed using the extra set of jacks without drilling any extra holes. Who has installed one? Any issues?

 

[SpiderWars]

The instructions make it very easy, just plan out all your grounds (for everything including shielding for cables) before you start.

 

[psychodave]

I’ve done a bunch of them in JMP’s. It’s easy. FWIW, I wire them as always on to prevent drilling a hole for the switch. However, you could use a push pull pot and swap out a pot in front of the amp.

 

[Rick Lee]

Put some miles on it with the pedal outfront first. They take pedals well; less so with a lot of pre-master gain, but I just don't feel the need for a loop in any of my Marshalls, except for reverb or a delay.

 

[SpiderWars]

Put some miles on it with the pedal outfront first. They take pedals well; less so with a lot of pre-master gain, but I just don't feel the need for a loop in any of my Marshalls, except for reverb or a delay.

For me, delay is pretty much the whole reason for wanting a loop. A clean volume boost pedal in the loop is nice too but I really just want delay. If I want to do Adam Jones type delay then I put it in front but I usually want delay in the loop.

 

[psychodave]

Put some miles on it with the pedal outfront first. They take pedals well; less so with a lot of pre-master gain, but I just don't feel the need for a loop in any of my Marshalls, except for reverb or a delay.

For me, delay is pretty much the whole reason for wanting a loop. A clean volume boost pedal in the loop is nice too but I really just want delay. If I want to do Adam Jones type delay then I put it in front but I usually want delay in the loop.

Agreed. I love delay and reverb.

I also like to put an EQ in the loop on occasion for a totally different tonal change.

 

[JTyson]

Nice score, its in great shape

 

[ChurchHill]

Killer amp! Those JMP 2203s are monsters! Really clean, too. Nice!!

 

[Kapo_Polenton]

Another vote for the metro loop. You could also just get a Suhr iso line out and feed another cheap solid state amp for your delay and effects though...that would give you a wet/dry sort of deal and actually sounds better than in the loop but if you only want one amp, the metro is the way to go!

 

[Chris6870]

I'm a delay addict and like it to be in the loop. Also I can then run my AX8 4CM essentially giving me a clean channel.I already have the Metro loop.Just Not sure if I want to do the install or not. The tech I use is great but busy so probably a 3 week turnaround.

Here's a few gut shots.

 

[ChurchHill]

Hey, a "Shirley!" I've got three from the same era ('78-'80) that were all signed by Shirley. Doesn't mean anything, but, well, I think it's cool.

That PCB is so clean (unless I'm really missing something). As long as you can uninstall the loop and completely restore it if/when you or a potential future owner might want you to, why not? I wouldn't drill any holes in it for sure, and I wouldn't want to do anything that wasn't quickly, easily, and completely reversible.

Honestly, I'm with Kapo_Polenton in that I'd just grab a line level between the amp and the speaker and use a separate amp to power another cabinet or two. That way, you'd end up with a great W/D/W rig. That's what I do.

What about something like a Fryette PowerStation? It's a loadbox with an effects loop before it's internal power amp. That would get you a loop without having to change anything in the Marshall. Anyway, just a thought.

 

[RedPlated]

I have a Metro loop in my 1980 JMP. I used the extra speaker holes so no drilling. Mine is wired always on. Sounds fantastic. I’ve got el34’s in it, which I prefer to the 6550’s.

By the way, the filter caps nor bias caps appear to have been changed in your amp, based on the pics. Those Daly caps are original.

I just recapped mine myself with F&T filter caps and Sprague Atom bias caps. Made a huge improvement. Tighter, punchier, more gain.

 

[psychodave]

I have a Metro loop in my 1980 JMP. I used the extra speaker holes so no drilling. Mine is wired always on. Sounds fantastic. I’ve got el34’s in it, which I prefer to the 6550’s.

By the way, the filter caps nor bias caps appear to have been changed in your amp, based on the pics. Those Daly caps are original.

I just recapped mine myself with F&T filter caps and Sprague Atom bias caps. Made a huge improvement. Tighter, punchier, more gain.

Do you have a picture of the insides? I know the 1980 Marshall’s have slightly closer output jacks...so the stock Metro loops need to be slightly modified to fit in the stock holes. I’m curious to see what was done.

 

[Chris6870]

By the way, the filter caps nor bias caps appear to have been changed in your amp, based on the pics. Those Daly caps are original.

I assumed they were changed because they are so clean Does everything else look original? Beautiful amp by the way.

 

[RedPlated]

Do you have a picture of the insides? I know the 1980 Marshall’s have slightly closer output jacks...so the stock Metro loops need to be slightly modified to fit in the stock holes. I’m curious to see what was done.

Yes, one jack had to be separated from the board and extended due to the mounting hole distance.

I took this pic after I changed the caps. And yes, I fixed that crusty power switch wiring. Someone had some bad soldering skills at some point...

 

[psychodave]

I was going to add a metro loop to my 1980 JMP but have been lazy due to those close jacks. I didn’t feel like tinkering to make it fit.

 

[Kapo_Polenton]

Hey, a "Shirley!" I've got three from the same era ('78-'80) that were all signed by Shirley. Doesn't mean anything, but, well, I think it's cool.

That PCB is so clean (unless I'm really missing something). As long as you can uninstall the loop and completely restore it if/when you or a potential future owner might want you to, why not? I wouldn't drill any holes in it for sure, and I wouldn't want to do anything that wasn't quickly, easily, and completely reversible.

Honestly, I'm with Kapo_Polenton in that I'd just grab a line level between the amp and the speaker and use a separate amp to power another cabinet or two. That way, you'd end up with a great W/D/W rig. That's what I do.

What about something like a Fryette PowerStation? It's a loadbox with an effects loop before it's internal power amp. That would get you a loop without having to change anything in the Marshall. Anyway, just a thought.

Yeah, once I ran my amp with a wet signal through another speaker it was night and day. Delay sounds great in the metro loop but that spatial separation is godly.the advantage of a loop though is maybe if you want to feed a diff preamp into the output section of your amp. This is probably why the pros have such huge sounding rigs. They run W/D or W/D/W

 

[itsme]

Get a Badcat Unleash. Effects loop, second master volume for leads, Attenuator, and you get to keep that beauty the way God intended it. Win, win, win, win

 

[LP Freak]

All of those attenuaters alter the tone and/or the feel....all of them. Some are better than others though.