Rocket

Which amps are considered Plexi amps?

thanks

Marshall Amps

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wareagle

a plexi was the first type of marshall, the bodies were made of plexiglas im pretty sure? made from '62-73? i think, or was it '69?

stax

The face plate and back plate were plexi, the chassis were aluminum. In 69 the face and back plate changed to brushed aluminum, I believe.

Rocket

Oh its that simple. I keep hearing people refer to them and in the context of certain specs characteristics they have.

I was wondering if the two I have;

1. JCM 800 Lead Series, 100W, or

2. JCM 2000 Dual Super Lead, 50W

had the same design characteristics as the Plexi.

they both have stickers on the back that start with M-2005 and M-2006. Are the numbers after the M the year?

Thanks

mystic fred

"Plexi" or "Plexiglas" as Stax stated was the Perspex-like material used on the early amps up to 1969, all the subsequent models had brushed alumimium gold fascias and a steel chassis, as far as i know only the 90's JTM series were made to emulate the JTM45 sound and had plexi style fascias but i'm not sure if they are true plexiglas.

janarn

Marshall started with aluminium fronts in '62, and for a period they also had
plastic fronts.
The plexi fronts came in '65 and was replaced with brushed aluminium mid '69.

Aluminium chassis changed to steel chassis 66/67. Tubes changed from KT66
to EL34 about the same time.

So the Plexi area was from '65 to July '69.

Models in that period were:

JTM-45 (65-66), JTM-45/100 (late 65-66),
JTM "Black flag" or "reverse logo" (late 66-mid 67),
JMP (mid 67-mid 69)

JTM50 was the 50w 1963 Super PA (JTM MKIII)
JTM100 was the 100w 1968 Super PA (JTMV)
(The JTM MKIV was the tremoloversion of the JTM-45)

The 200w "The Pig" was made only in '67, and replaced with the Major in '68.

For the first year or so the amps had plexi front panels, and cream white
back panels. Then the back panels also changed to plexi.

The Lead (50w, model 1987) and Super Lead (100w, model 1959),
changed a lot after the Plexi area, and the metal face amps from
the early 70's sounds very different.

So if an amp is made '65 - mid '69 and has a plexifront it's a Plexi.
No other models are Plexies.

A Plexi RI should have the curciut from '65 - mid '69, and of course,
the plexi panels.

Ken

Wow, you have the two of the three best Marshall amps IMHO (the JVMs are great too!)

Both are quite different. The DSL has lots of modern type circuits like the LED that acts as a compressor on the Ultra channel. The 800 series actually has many variations; single channel, duel channel, no master volume, and I imagine are also different from a plexi but not nearly as much as the DSL.

Ken

Rocket

Thanks guys. This is an informative forum. Another one gave me some of the same info but not as detailed.

I've got some more questions but I'll start new thread..

Vintager12

Forgot the VM ?

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The Emperor of the Vintage Modern.

Ken

Same family, right?

ken

janarn

Hm? This is a thread about Plexi Marshalls.
And the best Marshalls are JCM800, JCM2000, JVM and VM?
How do you know?

I have had a JMP 2204 (same as the JCM800),
a JVM410H, and I tested out a VM before I bought the JVM.
I have also tried the DSL, both 50w and 100w.

And I agree that they all are good amps.

But I have four original Plexies, and I just have to say that
none of the other amps comes close to the sound of a Plexi.

Ken

And a Plexi won't come close to the sound of a DSL! LOL

Ken

janarn

And I would't talk about Plexies in a thread about DSL!

Ken

LOL Okay, you got me there! Some day I'll buy a plexi and see what all the hollering is about.

Ken

janarn

Do that, I'll buy your DSL cheap.

Ken

Oh, I'm keeping the DSL. My next amp will be some kind of JCM 800. And if I ever find a 1982 speaker cabinet bottom with the G12H30 speakers I'm all over it!

Ken

janarn

He, he, my next amp will be a JCM800 2205.

jcmjmp

Ummm.... no LEDs in the signal path of the DSL. Check your facts before you post.

Regardless, neither the JCM 800 or DSL are "plexi" circuits.

javier pintos

i have a DSL100, can someone explain me the difference (tonally) of a plexi and my DSL considering both channels and their respective modes?

I´m trying to learn not be a smart ass

cheers

janarn

This how a Plexi works, if you want a good vintage sound:

1. A direct signal through the whole amp. No loop, no channel switch.
Just the things that makes the guitar signal sound good.

2. Distortion from preamp tubes, power tubes, and speakers.
It is that distortion chain that makes the Plexi sound.
The good sound will come when the volume is at min. 6.
That's why you will need an attenuator.

On a DSL it's a little bit different:

1. Not so direct signal. The amp is made for more flexibility,
and that isn't always the best way to get the the best sound.

2. The distortion comes from the preamp tubes, and that is the
way the amp is made. The idea is that you can get a good sound
even at low volume. And you can.

javier pintos

Thanks Janarn

But given that you can still get power tube distortion and the speker distortion can still be there (is just a matter of power) you could sitll have all 3 types of distortion, then it would be a matter of how the signal path is onstructed, more elements in the DSL means that the tone is less pure but still somehow resemblant of a plexi?

In there a way to get somehow close on a DSL by adjusting settings to get close to a plexy sound?

Ken

It's a photo resistor. Check again on the Ultra channel.

Ken

janarn

The closest you can get is buying a 4x12" G12M or G12H cab,
and set the mastervolume on full.
Then try both channels, and see if you can balance the power tube
distortion and the speaker distortion, with the preamp tube distortion.

Kenny Allyn

Just courious where this one falls into place

It is a Super Bass I just picked up and an A series



No "Plexi" front but it also has no JMP on it either?

stax

That is a "metal face", it is most likely early enough that it has the plexi circuit (I believe the first year or so the circuit remained unchanged in the metal face). The Super Bass is basically a Super Lead, I believe you just need to change a couple of resistor values.

janarn

The Super Bass model code changed from SB/ to SB/A in July '69,
that was also the month they changed from Plexi to metal panels.
But some amps has the Plexi panels and the SB/A code.
The letter in the end of your serial number is the code for the year.
A=69/70, C=71, D=72, E=73.
Your polarity switch is placed where the JMP letters is on the front panel,
that's why you can't se them. The polarity switch was on US export models.

If this is a PTP Super Bass with original curcuit, don't change anything.
The Super Lead went through some changes after the Plexi area, but the
Super Bass didn't. Many of us think the Super Bass sound better than the
Super Lead.

Kenny Allyn

Thanks good info ... it appears to be a 72 then with PTP wiring

It sounds great, all Telefunken tubes in the preamp section and I run it into a 1960 model cab with the "Checkerboard" grill loaded with 25 watt greenbacks. I like to run it clean and it has a sound like a BIG Fender 59 Bassman, if I want breakup I use either a Roger Mayer Voodoo clean boost or a Voodoo Axe to push the front end.

I like the amp a lot

janarn

You got the right cab for the amp!
If you really want to find out how your amp can sound like do this:
Buy an attenuator, a Ultimate Attenuator, or a Hot Plate.

Set volume on high treble channel on 8 (use upper input)
(Don't do this without an attenuator, your speakers may blow)
Precense 0, Bass 0-3, Middle 8, Treble 5.

Turn down guitar volume for clean sound,
and use your cleanboost for lead sound.

Wooow!!

Ken

Nice amp!

My name is Kenneth as well, and my middle name is Allyn, spelled like yours! Small world?

Ken

solarburnDSL50

Lucky! Enjoy the tones man.

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