Help Me! Identity Crisis.JCM800 vs. Plexi Marshall Content

[MetalManiac]

So..this is all borne out of my money situation where Ive got so many irons in the fire tonally w/ amplification that Ive got to try and maximize each dollar spent, and with my less than optimal situation, that means getting rid of stuff to fund other stuff.

Well, tonight I cranked wide- open up my JMP 1978 Marshall, and no doubt its a killer amp! Its totally badass , more gain..tighter..etc., etc., but its just that compared to the 'Plexi' I cranked ( actually a very early '72 pt. 2 pt. w/laydown x-formers) there was this massive girth , or something, not even gain, but this palpability -slash dimensionality, plus a wicked crunch and bright edge to the overdriven tone that left me really less than inspired with the JMP.

Now, I know I'll regret selling the JMP , thats a given, so I'm really up in the air about all this. Volume may be an issue with the Superlead "plexi', but really, even the JMP sounds best balls to the wall.

Not sure what I'm driving at. I guess thats why I'm asking. I'm thinking the 'Superlead '72' with a pedal would see me allright. IDK..its a Marshall Thing, maybe you wouldn't understand. hah.

EDIT-My brain is constipated

 

[hydro]

Re: Help Me! Identity Crisis.JCM800 vs. Plexi Marshall Content

I dunno man... I have been contemplating selling my dual recto both to free up some $ and because I am not sure I will be using it much since I got a Mesa 5:50+ that I find more versatile and easy to deal with. But then I have a lot of love for my recto and I think, if I'm lucky I'll only get just shy of a grand for it and end up wanting it again later on after all...

I guess my point is that if you have doubts about selling it at all, and you don't absolutely have to, you should hold off.

Second quick story, fwiw: I had a little Marshall 3203 Artist that I used for a while, but it just couldn't keep up volume-wise with the band so I upgraded. Amp had some problems anyway and it sat unused for several years; but just recently I started playing in another (quieter) band and this amp turns out to be just the ticket for the other guitar player. So with some (hopefully) minor repairs it will be back in action soon and will be a great amp that we couldn't go out and buy for what it is going to cost to get fixed. So even though it wasn't *the* amp it still ended up being useful and I'm glad I never ended up selling it.

 

[Lake Placid Blues]

Re: Help Me! Identity Crisis.JCM800 vs. Plexi Marshall Content

This has always been the conudrum with master volume amps; they don't really give up the goods until they are just as loud or just about as loud as its non master volume brother. Nonetheless, the extra compression in the pre-amp makes them less dynamic.

Do you have a good attenuator?

 

[crusty philtrum]

Re: Help Me! Identity Crisis.JCM800 vs. Plexi Marshall Content

I'd like to say something favourable about the JCM800.

Unfortunately I'm not a liar, so I can't.

 

[STRATDELUXER97]

Re: Help Me! Identity Crisis.JCM800 vs. Plexi Marshall Content

I had a JCM 800 for awhile.Got rid of it for the NMV 50 watter that I've now owned for years(in my photo)..You have to get that 800 up pretty loud or its all compressed preamp crap.

 

[Gone_Shootin]

Re: Help Me! Identity Crisis.JCM800 vs. Plexi Marshall Content

I guess I'd keep the Plexi and do the One Wire mod and look into a negative feedback control for the PI tube or look into getting it lowered. I've done both of these mods to my JVM and they both are capable of adding gobs of gain. The One Wire adds more preamp distortion, which you may or may not want, but you can have it set up with a potentiometer so you can control how much extra gain, if any, it adds. The same goes for the PI Negative Feedback control, except that it controls how soon the poweramp starts distorting. In other words, you can make the poweramp distort at a lower volume. One word of caution, though, if done improperly, it can cause instability issues.

Here's some resistor values that'll give you an idea of what I'm talking about:

R58 = 47k -- late '60s Plexi
R58 = 74k -- early '70s MkII Plexi
R58 = 82k -- stock JVM
R58 = 137k -- EVH's Plexi
R58 = 176k -- JCM800 2203
R58 = 177k+ -- a Marshall with almost a Vox's lack of headroom in the power amp

R58 refers to the resistor in a JVM, but the concept will carry over to your Plexi. The components will have a different designation, though. And if you need help figuring out how to do these mods to your Plexi there are several very knowledgeable guys over at JMVforum.com. Casey_Butt & Santail (Mr Santiago himself) in particular come to mind.

Here's the thread I got the info from (the Negative Feedback mod thread): http://jvmforum.com/phpBB3/viewtopic.php?f=31&t=4467

And the Plexi One Wire/aka: 3rd Gain Stage Bias mod: http://jvmforum.com/phpBB3/viewtopic.php?f=31&t=5271&sid=a403f9f3af877f825dbd324160e40bcd