JCM 900- Which ones are the "good" ones

Led Sabblin

Member
Messages
1,219
Seems like there quite a few versions of the 900 maybe more than the 800 and not just one like the 2000 talking models and not head.combo, speaker config etc. Although the 2000 does have the EL84's in its combos and the TSL but I haven't really been able to tell how different the TSL is from the DSL in its overall sound
 

NoBrakes

Member
Messages
2,732
I had a JCM900 MkIII and a 4100 dual Reverb... The MkIII was great the Dual Reverb not so much... the MkIII was a single channel amp with dual master volumes... Of the Marshalls I had it's the one I should not have traded away... It was much thicker sounding than the 4100.. I think the MKIII evolved into the SLX.. It didn't have the gain that the SLX had.
 

ungarn

Member
Messages
3,252
The 900's that can be had cheap on craigslist are best!
Oh...right...avoid the Dual Reverb versions...
 

skunx

Member
Messages
1,864
I wouldn't kick any of them out of bed for eating crackers but for medium gain I love the mkiii. Pretty under the radar and a somewhat limited production Marshall (less than two years of production). Ended up selling mine, with the baby on the way and mostly home playing, but what a sick Marshall tone.
 

rawkguitarist

Member
Messages
10,703
For whatever it's worth, here's a little story I like regarding the single channel master volume JCM900s:

Many years ago, I opened for Eric Johnson with a 50 watt Marshall MkIII. His tour manager came up to me as I was setting up jokingly saying "now we can't have you sounding like Eric..." I usually had a warmer, more midrangy sound. I tweaked my amp a little to make it a bit brighter and less midrange to accommodate. ;)

To me, it wasn't that much different sounding than my real 50 watt plexi cranked. A little smoother, a little more compressed but very similar.
 

Trotter

Supporting Member
Messages
6,639
Dual Reverb versions sound good if you stick with Channel A.
This.

I always liked the cleans on channel A... and if you cranked the gain you could get some nice crunch.

I believe I read once that ZZ Top ran their Dual Reverbs this was as well.

Was never a fan of channel B

These amps need to be run loud and don't sound to great at bedroom volumes IMO.
 

skunx

Member
Messages
1,864
For whatever it's worth, here's a little story I like regarding the single channel master volume JCM900s:

Many years ago, I opened for Eric Johnson with a 50 watt Marshall MkIII. His tour manager came up to me as I was setting up jokingly saying "now we can't have you sounding like Eric..." I usually had a warmer, more midrangy sound. I tweaked my amp a little to make it a bit brighter and less midrange to accommodate. ;)

To me, it wasn't that much different sounding than my real 50 watt plexi cranked. A little smoother, a little more compressed but very similar.
Cool story!
 

jtm622

Member
Messages
9,316
I've got a 900 MKIII (model 2500), and it is pretty much just a continuation of the late 1980's version of the horizontal input Model 800 2204's - but having one extra gain knob... I also have a Model 800 2203, and yes - it is VERY similar sounding to that 800 when the gain is set at approximately the same... IMO, the MKIII's got that much desired "Model 800" sound in spades...

:)
 

yfeefy

Member
Messages
1,253
I liked the sound of my dual reverb - both channels - it did have to be pretty loud to sound its best.

bass and mids up, treble and presence way down helped.


recently I ended up replacing the preamp board with a homebuilt job, not primarily because the tone was bad - but it started having these occasional dropouts, and the volume wasn't what it should be.

It's basically a marshall 1987 preamp:








It's now a 4-input marshall, and sounds great too:



 
Last edited:

VA_siCkBoy

Member
Messages
1,462
I've got a 900 MKIII (model 2500), and it is pretty much just a continuation of the late 1980's version of the horizontal input Model 800 2204's - but having one extra gain knob... I also have a Model 800 2203, and yes - it is VERY similar sounding to that 800 when the gain is set at approximately the same... IMO, the MKIII's got that much desired "Model 800" sound in spades...

:)
That's the same model I have and I freakin' love it!
I scored it off ebay about ten years ago from a guy who kept it in his studio.
Looks brand new and sounds amazing. I hope I will never have to sell that one.


Here's a little info on it...
http://www.erikhansen.net/marshallmkIII.php
 

LPMojoGL

Music Room Superstar
Supporting Member
Messages
8,885
There's one of these Mkiii 1x12 combos for sale locally.
Now y'all have me interested...
 

VA_siCkBoy

Member
Messages
1,462
People pay top dollar for an original JCM800 and you can still get the model 2100 (100w) and 2500 (50w) for around $600-800.....it's a no-brainer for me.

I think it is basically a JCM800 with a little bit more gain on top....IMHO
 

jboyjams

Member
Messages
2,302
This.

I always liked the cleans on channel A... and if you cranked the gain you could get some nice crunch.

I believe I read once that ZZ Top ran their Dual Reverbs this was as well.

Was never a fan of channel B

These amps need to be run loud and don't sound to great at bedroom volumes IMO.
I agree.

When using Channel A and cranking it up, my 4502 (JCM 900 Dual Reverb 2x12 combo =C= EL34's) sounds a lot like my JMP 2204 and my 1987x the way I run them all.
 

pgissi

Member
Messages
2,481
MkIII is the only good one...
this topic gets resurrected now and then

I have the exact opposite opinion and for me the only one is the early MKIV, the EL-34 SL-X (2100 = 100 watts 2500=50 watts) that at some point were offered with 5881's, around '95.

All tube path except for the OP-Amp based FX Loop and A/B Master Volume Switching setup which are transparent tonally.

It is the most 800 sounding imo and its basically a hot rodded 800 with the addition of a "Sensitivity" control which is post V1 and Pre-Amp pot and is VR2 on the shematic. The Pre-Amp and Sensitivity are where you can find classic 800 to modded 800 tones.


http://www.drtube.com/marshall.htm#JCM900
The 2100 & 2500 amps were superceded by the SL-X amps in 1993


I couldn't disagree with this more and he omits the major difference, the non SL-X JCM900's are laden with Op-Amps and clipping diodes. You won't find that in any 800 or the SL-X. So this less than accurate and somewhat biased review is the reason the SL-X flys under the radar in addition to misunderstanding of how the Pre-Amp and Sensitivity control should be dialed in.

1) Pre-Amp must be dialed in at least 60 to 75% (at least) and for me I turn it up 75% since the Pre-Amp pot is just south of V1 and this is where the tone and gain are staged early on. Too little Pre-Amp can you leave you lacking drive, thinner sounding.

2) Sensitivity for me is 13 to 14 on the dial and above 15 it can be overdone but having the ability for more is better than wanting it and not having it, you just have to use restraint lest your tone get over compressed and fizzy. YMMV and remember when dialing this in you are essentially setting how hard you are hitting the gain stage following VR2 which has already seen some Overdrive from V1. Think of it as a pre-amp saturation control that occurs before the other saturation control, the master volume.

Where most mis-dials happen is when Pre-Amp is set lower and Sens is set higher and that will get you thin, shrill and fizzy. Turn the Pre-Amp up like you would any hi gain master amp, set the sens to start at 13 to 14 and the amp comes alive and you can roll back your guitar pot for fat cleans at stage volume or just under.

Marshall could have done a better job with some dialing tips then.

I will say my only critique is the Output Tranny, the bean counters had the last word but its splitting hairs.

To summarize, the SL-X is a 1 channel amp with a series fx loop and 2 Master Volumes for boosting solos and you won't find yourself saying, "I only use chan A or Chan _ is the only good chan".


Q: What about the JCM 900 SL-X? Isn’t it the same amp?
A: Yes and no. The reason I say this is because the circuitry in the SL-X is different from the MkIII to a point. The most obvious difference between the MkIII and the SL-X just from looking at them from the outside is the additional 12AX7. This gives the SL-X more gain but in my opinion, takes away some of the character. Looking at the schematics, the preamp is different between the two, more specifically, from the input to V1 to the start of the tone stack. From there onwards, the two share the same tone stack, effects loop and power amp. The SL-X was produced between 1993-1999. Many of the SL-X amps came with 5881 power tubes instead of EL34′s when Marshall switched over in late-1993 to early-1994. This change is another reason why to me, the SL-X lost some of that Marshall mojo. My advice for the SL-X is the same as for the 4100/4500 Dual Reverbs; if you want one, get one with EL34′s.
 

smj

Member
Messages
1,776
I had a 4100 head and 4x12 cab when I was 16. This was before anyone really had an internet connection. I thought it was the coolest thing ever.

I eventually moved on to other amps.... But we actually have a 4100 head at our church. I keep it on Channel A and use plexi voiced pedals for higher gain. It can be a little shrill, thin, and overly crispy on the B channel.

I remember Jeff Healey liked those MK's back in the day.

Sean Meredith-Jones
www.seanmeredithjones.com
 

HoboMan

Silver Supporting Member
Messages
17,026
There's one of these Mkiii 1x12 combos for sale locally.
Now y'all have me interested...
I have the 2501 1x12 MKIII 50 watt combo.
It's a KILLER, KILLER combo.
Very compact but it ROARS.
Keeps up with my JCM800 combo.

It used to be my "leave at rehearsal" amp. I tossed it in a corner and cranked it up. It had more than enough volume to keep up with the band (and we're pretty loud).

At gigs I plug it into a 2x12 cab. The tone is fat, overdriven Marshall all the way.
I actually use it more than my JCM800 for gigs. Seems to have more bottom & lower mids.

Here's a tip if you go try that one out. The tendency for many users is to crank the gain and then start turning up the "Sensitivity" knob (second gain knob). I did this in the beginning but I read somewhere that it will sound better with the gain around noon and the sensitivity around noon.
This really fattens up the tone.

Just a great all around combo.
 

Mark Robinson

Gold Supporting Member
Messages
8,291
I'm selling a 100 watt dual, single 12" in the emporium now, very cheap. If you run it into a good cabinet a Dual Reverb will sound pretty good. You need to get it biased etc. The reverb isn't great, use the loop with delay instead, or just delay up front. I always sound like me into that amp. Never knew it "sucked" until I read a lot of crap on the net. It does Marshall sounds, and does them at a variety of volumes, and that's good!

I've never loved the G12T75 Celestions that Marshall sold in that era, and those 4 x12" loaded that way are not great. Why do you think folks pay so much for greenbacks, blackbacks, Scumbacks etc? Because they are way the hell better, just listen.

The biggest problem to me with the dual is the shared EQ, a step back from the JCM 2210 and 2205. It can work well for buckers, but not a great thing for Strats and Teles. With a single coil, you get the low gain channel sounding great, then your lead channel is too bright.
 


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