1978 JMP 2203 adding a loop?

[Dmann]

In a Nutshell, My current set up consists of;

JVM210H
Serial Loop ---> (left)mono in G-Major 2 Effects -->(left)Mono out back to the JVM

What I want to do is use my old JMP as a 2nd head, feeding it from the G-major 2, and run a stereo setup between 2 full stacks, as the G-Major 2 sounds so much more amazing when run in stereo.

I have tried using my 1978 JMP 2203 and feeding it from the right output of the G-Major 2, but even on the low sensetiviy and lowest settings, the preamp input is clipping and sounds like complete shit.

Exploring my options, I was considering selling the JMP, but many people have told me to just get a loop modded in, and that I should just buy a loop kit, but I am not really sure on all the options out there, or if this is even the proper way to add a poweramp insert to turn the JMP into a slave.

So I am calling on all you marshall guru's in the know to help me out here.

 

[Jonathan Wilder]

Get the Zero Loss FX Loop kit from MetroAmp. 100% tonally transparent and it maintains an even gain structure as well due to being located before the master volume as opposed to after the master like most other amps. They were designed specifically with the 2203/2204 amps in mind. The ONLY loop I will ever recommend for these amps -

Zero-Loss FX Loop Kit - $95.00 : MetroAmp, Amplifier Kits and Parts Online Store

 

[Dmann]

Get the Zero Loss FX Loop kit from MetroAmp. 100% tonally transparent and it maintains an even gain structure as well due to being located before the master volume as opposed to after the master like most other amps. They were designed specifically with the 2203/2204 amps in mind. The ONLY loop I will ever recommend for these amps -

Zero-Loss FX Loop Kit - $95.00 : MetroAmp, Amplifier Kits and Parts Online Store

Thanks man, yeah thats one of the ones I was looking at, I just wanted to be sure that this is the proper way to accomplish my goal before going forward.

 

[Dmann]

Ok I just ordered that one, thanks again!

 

[Wycked Lester]

my buddy, and fellow forum member new religion just installed one of the zero loss loops in his 1980 JMP 2203 and he swears its the cats ass. I'm sure he can tell you all about it too. I going to order one for my 82 2203 in a couple weeks..... CANT WAIT!

 

[JCarno]

Dmann, Please keep us updated on your progress. I'm considering putting one in my 4104. Thanks!

 

[NewReligion]

my buddy, and fellow forum member new religion just installed one of the zero loss loops in his 1980 JMP 2203 and he swears its the cats ass. I'm sure he can tell you all about it too. I going to order one for my 82 2203 in a couple weeks..... CANT WAIT!

You will enjoy it Lester.

I installed the Zero Loss in my 2203 & 1987. Great circuit IMO.

 

[JCarno]

David, Any chance for some pics of it installed in the 2203? Thanks!

 

[shooto]

I just put one in my '78 JMP 2204...had one in a MIG Midget 50 as well...really made for these amps

 

[NewReligion]

David, Any chance for some pics of it installed in the 2203? Thanks!

No problem. When I get home off of the IPhone I will post a couple tonight.

 

[JCarno]

I just put one in my '78 JMP 2204...had one in a MIG Midget 50 as well...really made for these amps

That's it......my mind's made up.......ordering one!

 

[Billyblades]

you can also get a marshall effects loop like the ones they put on the new amps from marshall direct from marshall. easy to install too

 

[JCarno]

Although I've never seen one I can't imagine it being much easier than the Zero Loss.

 

[Jonathan Wilder]

The ones direct from Marshall will not install before the master volume. The signal level at that point in the circuit is too great for them to handle without clipping. Moreover, since they run from a low voltage supply, they don't have the headroom to re-amplify the return signal back up to post-tone stack levels without clipping either.

The ZL loop runs from the main B+ line, which gives it the headroom to deal with the post-tone stack levels and reamplify the signal back to post-tone stack level upon returning.

It is important for effects to be installed prior to the master volume as this is proper gain structure. This makes the send levels independent of the master setting. The master setting controls the overall volume of the preamp sound + effects rather than altering the signal level that the loop effects get to play with, keeping your tone consistent at any master setting.

 

[charveldan]

A JMP doesn't need a loop IMO.

And Wilder ur Metro link locked up my computer and apparently has a virus ...

 

[Alabama Thunderpussy]

Oh good Dan is here with his opinion.

 

[JCarno]

And Wilder ur Metro link locked up my computer and apparently has a virus ...

Not mine.

 

[NewReligion]

No butchery on my JMP as I removed 2 of the 4 speaker outs and the loop board is in place with little filing. The bypass switch is secured inside the chassis so the mod is reversible. Depending on which decoupling resistor you use that is provided you should be able to match the voltage at the Phase Inverter. I personally opted for a bit higher value but I caution as does metro stay within the guidance provided to prevent damage.

Delay and chorus in addition to reverb sound very professional through this metro loop. Great stuff.

 

[Jonathan Wilder]

You have to drop the value of the dropping resistor(s) between the choke and PI node to compensate the PI voltage to keep it stock when installing the loop. My target voltage at the PI is usually in the realm of 330-340V.

On a 100 watter I usually end up with a 10K and a 4K7 in serles between the choke and PI node when installing the ZL loop.

 

[NewReligion]

You have to drop the value of the dropping resistor(s) between the choke and PI node to compensate the PI voltage to keep it stock when installing the loop. My target voltage at the PI is usually in the realm of 330-340V.

On a 100 watter I usually end up with a 10K and a 4K7 in serles between the choke and PI node when installing the ZL loop.

I have to look again on my 2203 but I believe I am at about 297v with a 56k + stock 10k. There is still plenty of pick attack and articulation, feels great.