Guitar Gear Forum

I fancy trying the one wire mod on a JMP marshall does anyone know how to do this mod or know where I can find the mod online
thanks

1-wire for the 2203? I thought the 1-wire was for the Super Lead only, no? Isn't that the mod to cascade the gain on volumes I and II?
If so, the 2203 already does that by default.

The other possibility is that I am just talking out of my ass It wouldn't be the first time lol

But IIRC the 1-wire is not a 2203 mod.

GuitarBilly wrote:1-wire for the 2203? I thought the 1-wire was for the Super Lead only, no? Isn't that the mod to cascade the gain on volumes I and II?
If so, the 2203 already does that by default.

The other possibility is that I am just talking out of my ass It wouldn't be the first time lol

But IIRC the 1-wire is not a 2203 mod.

Hi , I am always talking out of my ass in fact I make a very good living out of doing it

I have been given to understand that the one wire mod is a different style master volume to the one that marshall uses on the 2203/2204 and I also think you are right that it would be used on a super lead non master volume amp but...
I believe that the one wire mod can be added as a second master volume to a 2203 so you would then have two master volumes that when used in conjuction can yield a different tonal result
I know that the randy rhoads signature amp that marshall did used the one wire mod on a superlead and apparently a pre phase inverter master volume can be added to that amp so I would guess that means both can be used in conjunction , I know that the Lar/mar can also be added to a 2203 and I think that the lar/mar is a variation of the one wire mod
But I dont have the first clue how to do the one wire mod...
I am also of the opinion that I could also be talking out of my ass...

just to continue the talking out of your assness - wouldn't a master volume require a bit more than 1-wire??

mamberg wrote:just to continue the talking out of your assness - wouldn't a master volume require a bit more than 1-wire??

I believe that one wire mod is just the name that was given to the mod
I dont think it actually means that just one wire is used , I had a marshall with the mod when I was younger and I am sure it involved a pot but it was a long time ago and I was not really an amp techie then and I am not now
I can do basic mods if I am given painting by numbers type instruction with pics or line drawing instructions but thats about the extent of my abilities.

Found this on metro. About 5th post down on my browser.

http://forum.metroamp.com/viewtopic.php?p=180449

GmN wrote:Found this on metro. About 5th post down on my browser.

http://forum.metroamp.com/viewtopic.php?p=180449

Nice one , thanks for that

If you have a JMP 2203/4 the you can do the "one-wire mod" to cascade V1a and V1b, thus adding an extra gain stage to the amp. If you have a JCM800 2203/4 then the mod is affectibly already in the stock circuit, for the low input you go straight into V1b and on the high input you go into V1a then cascaded into V1b.

liam5150 wrote:If you have a JMP 2203/4 the you can do the "one-wire mod" to cascade V1a and V1b, thus adding an extra gain stage to the amp. If you have a JCM800 2203/4 then the mod is affectibly already in the stock circuit, for the low input you go straight into V1b and on the high input you go into V1a then cascaded into V1b.

I always thought that the JMP 2203/4 and the JCM800 2203/4 were the exact same circuit

Custom62 wrote:

liam5150 wrote:If you have a JMP 2203/4 the you can do the "one-wire mod" to cascade V1a and V1b, thus adding an extra gain stage to the amp. If you have a JCM800 2203/4 then the mod is affectibly already in the stock circuit, for the low input you go straight into V1b and on the high input you go into V1a then cascaded into V1b.

I always thought that the JMP 2203/4 and the JCM800 2203/4 were the exact same circuit

Not according to the "History of Marshall" book with the schematic. I thought the same till i looked into the schematics of each.

I would imagine like most of Marhalls amps there was a cross-over period BUT the schematic are slighly different for a JCM800 2203/4 and JMP 2203/4.

On a JMP the signal chain would be Gain+Gain+Tone+Phase Inverter then on to power section (This is the same for high AND low inputs, you get different gain levels as the cathod resitors and bypassing are different for V1a/b)

On the JCM varient you have the same as above for the Low input, for the High input you have Gain+Gain+Gain+Tone+Phase Inverter then on to power section. Signal goes out of V1a anode to V1b, whereas the low input goes in the V1b skipping the first gain stage.

Shouldn't be too hard to tell by looking inside, or if yours is an early JMP it most likely wont be cascaded.

liam5150 wrote:

Custom62 wrote:

liam5150 wrote:If you have a JMP 2203/4 the you can do the "one-wire mod" to cascade V1a and V1b, thus adding an extra gain stage to the amp. If you have a JCM800 2203/4 then the mod is affectibly already in the stock circuit, for the low input you go straight into V1b and on the high input you go into V1a then cascaded into V1b.

I always thought that the JMP 2203/4 and the JCM800 2203/4 were the exact same circuit

Not according to the "History of Marshall" book with the schematic. I thought the same till i looked into the schematics of each.

I would imagine like most of Marhalls amps there was a cross-over period BUT the schematic are slighly different for a JCM800 2203/4 and JMP 2203/4.

On a JMP the signal chain would be Gain+Gain+Tone+Phase Inverter then on to power section (This is the same for high AND low inputs, you get different gain levels as the cathod resitors and bypassing are different for V1a/b)

On the JCM varient you have the same as above for the Low input, for the High input you have Gain+Gain+Gain+Tone+Phase Inverter then on to power section. Signal goes out of V1a anode to V1b, whereas the low input goes in the V1b skipping the first gain stage.

Shouldn't be too hard to tell by looking inside, or if yours is an early JMP it most likely wont be cascaded.

Hi , I do have the the book you refer to and I do know it is notorious for being riddled with inacuracies so It makes me wonder if the circuit info is not right as I do have a 1982 JCM800 2203 and a 1978 JMP 2203 and I can tell you after comparing them that the circuit is identical and they also sound same.
the only difference beteween a JCM 800 2203 and JMP 2203 as far as I can see is purely cosmetic
I also have a 1978 2204 which is only slightly different because its 50 watts not 100

Early JMPs were not cascaded. Later models were cascaded, and had the same circuit as the early 800 2203s.

The JMP just stands for Jim Marshall Products. The real designation for the circuit is if it's a 1959 (Plexi) or the 2203/4 (800) which, I've read that even the "JCM800" designation was actually the license plate number on Jim's car. Both circuits have had the JMP on them at one point or another, some of the earliest 2203/2204 models even had 4 inputs like the Plexis. And yes, the one-wire mod is for the 1959 or 1987 models.

Jay wrote:The JMP just stands for Jim Marshall Products. The real designation for the circuit is if it's a 1959 (Plexi) or the 2203/4 (800) which, I've read that even the "JCM800" designation was actually the license plate number on Jim's car. Both circuits have had the JMP on them at one point or another, some of the earliest 2203/2204 models even had 4 inputs like the Plexis. And yes, the one-wire mod is for the 1959 or 1987 models.

The 4 holer 800s were designated 1959/1987 circuits, not 2203/2204. The designated 2203/2204 circuits have always had two inputs, high and low.

also the 2203/2204 were not just 800s. The JMPs had 1959/1987 circuits as well as 2203 and 2204 circuits.

and here it is, from Marshall themselves (from an 80s Marshall catalogue)

During part of 1975 they had a transitional (temporary) model of the master lead that didn't use cascaded gain stages. That transitional schematic shows up in HoM.

Otherwise, JMP 2203/4 = JCM800 2203/2204.

tried it a couple of times.

No Sir....didnt like it.

If you've got a Superlead and want more gain and an EQ that actually works just build it into a 2203. If you really want an amp that's awesome add a PPIMV and a depth mod. Those relatively simple mods do wonders to the 2203 as far as allowing you to get really heavy modern tones or sweet classic tones depending on what you're after.

Holy shit! It's the one-wire mod in Japanese!

Hey Eugene - why were you named in the slut/spam thread?

Friend of yours?

mamberg wrote:Hey Eugene - why were you named in the slut/spam thread?

Friend of yours?

No clue who that is. I was just posting funny crap about it.