Got my hands on a JCM900 MKIII

[Disturber]

 

I've been looking for a 4x12 1960BX, or AX. Or a 1960TV. This rigg popped us in the for sale ads. I asked the seller if he would sell me the cab only. He said no, but offered me to buy the rigg for 900 bucks. I told him I did not need the amp. He said: "buy the rigg, sell the amp". So I did. 

The rigg had been standing in a pro studio for like 9 years or so. The amp is from 1990 and the cab from 2010.

I took two UK G12M-25s out of the cab and put in two reconed mid 70's G12H-30s I had laying around, in an X-pattern. This really woke up this cab. I found it a bit thin sounding at first and a bit stale. With the mix speaker set up it sounds killer.

I've read that the 2500 MKIII was made by Marshall only from 1990 to 1991. And that it is the best sounding model in the JCM900 line. It's pretty much a hot rodded 2204, with an extra diode clipping gain stage that is out of the circuit if the gain knob is on zero. So I took it for a test spin before I sold it off again. 

The JCM900 sounded pretty good. Without the diodeclipping Gain knob engaged it was very similar to my old 2104 combo in tone and feel. But the mids was perhaps a bit grittier. When I added just a push (on 2) from the Gain knob it fattened up the tone, made it a bit more plexi sounding. Great for singlecoils. It could push a tele into that Strat + Silverjubilee tone that I love, think John Frisciante. A bit of a fuzzy Marshall tone that sounds pretty damn sweet. With humbuckers it got a bit dirtier. And with the Gain even hotter I got into Slayer Anthrax distortion territory. Not my thing, but cool.

I used it at rehersals yesterday and the mids in this amp really cuts through. I was not 100% percent happy with the tone and feel from the amp when playing it alone. But with the band It stood out better. Just the right frequencies in the mids to not compete with the bass guitar, or the other guitarist. I enjoyed playing it.

What I did not like was that it was kinda stiff. I find 1980s JCM800s like this too. Guess I am to used to 1970s Marshall JMPs. I spent an hour this Sunday playing the JCM900, then before I was going home I plugged my JTM50 into the 1960AX cab - and Boom! There was the tone I like. More organic, fatter, more bass and more distinct, more jucie but less distortion. And the feel of the amp was much nicer too, it responded better with the guitar when I used the volume control or on how hard I hit the strings.

Still, the MKII JCM900 is a good amp. I could have used it as a backup as it had good tones, just not JMP good. I put an ad out yesterday at lunch, had the amp sold by nine o clock. It was a good test run! The cab is a keeper. 

 

Edit. The weird thing I read about these JCM900s is that Marshall but in a bias resistor that had a value that was to high. And indeed. I checked the bias on the original RFT EL34s. They were biased at around 19mA. Way thin sounding. So I twisted the bias control all the way and got the tubes up to around 25mA. I could not get them hotter. The amp sounded way better like this. Then I tried a Chinese pair of EL34 and they measured 29mA in the amp. And again the amp sounded better. So If I had kept the amp I would have needed to swap that bias resistor out, so that the tubes could be set to a proper bias setting. Weird thing by Marshall, to do it like this....?? Probably one reason why the 900s has a bad rep.

[Never2Late]

I've heard MANY stories about the JCM900 - some good, mostly bad, from owners who bought the wrong version/model and had issues with the circuit boards.  There was one model that was the 'holy grail' of 1990s Grunge tone, don't recall what it was, but supposedly offered diode clipping in the pre-amp stage for terrific distortion tones?  Anyone have a clue what I'm babbling about?

[RobB]

1 hour ago, Never2Late said:

There was one model that was the 'holy grail' of 1990s Grunge tone, don't recall what it was, but supposedly offered diode clipping in the pre-amp stage for terrific distortion tones?  Anyone have a clue what I'm babbling about?

This one: JCM 900 SLX

[black magic]

I`ve been looking for both of those amps for a while now. The SL-X came in 6L6 and EL34 versions. Most are 6L6. I`m looking for the EL34 version.

[RobB]

Get the 50w. Plenty loud. 

I had a full stack SLX during the, “grunge era”, in Chicago. Just used a wah, DD-3 and the channel switcher. Great rig. Surprisingly, I never ran into the issues people complain about. Guess I lucked-out on the QC on my amp. 

[LucSulla]

33 minutes ago, RobB said:

Get the 50w. Plenty loud. 

I had a full stack SLX during the, “grunge era”, in Chicago. Just used a wah, DD-3 and the channel switcher. Great rig. Surprisingly, I never ran into the issues people complain about. Guess I lucked-out on the QC on my amp. 

I played an early run JCM 2000 TSL 60 watt for 12 years and never had an issue, and those things were supposed to self destruct if you just looked at them funny. 

[RobB]

25 minutes ago, LucSulla said:

I played an early run JCM 2000 TSL 60 watt for 12 years and never had an issue, and those things were supposed to self destruct if you just looked at them funny. 

You obviously never played the TSL 212 combo, haha! Oy, vhat a schtinkah!

[LucSulla]

56 minutes ago, RobB said:

You obviously never played the TSL 212 combo, haha! Oy, vhat a schtinkah!

Hey, for what I needed at the time, that amp did some work!

 

[RobB]

Well, good on ya, son. Ya lucked out. My long-time band partner had nothing but problems, starting with the pedal-switch crapping out. He got a lemon.

 

[Disturber]

11 hours ago, Never2Late said:

I've heard MANY stories about the JCM900 - some good, mostly bad, from owners who bought the wrong version/model and had issues with the circuit boards.  There was one model that was the 'holy grail' of 1990s Grunge tone, don't recall what it was, but supposedly offered diode clipping in the pre-amp stage for terrific distortion tones?  Anyone have a clue what I'm babbling about?

The MKIII has diode clipping. When the Gain knob is on 0 the diodes are out of the circuit, and It sounds very much like a 2204 JCM800. I think it has good tones, but I had to be careful when I dialed it in.

The SL-X has an additional 12AX7 instead. This gives the SL-X more gain. The preamp is different between the two, so It's not that related to the JCM800s as the MKIII. 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. There is no Marshall mojo in 5881's, stay away.

Then there is the JMC900 Dual Reverb. It seems to be the most hated of the three JCM900 models. Funny enough this is the model that Marshall has chosen to reissue. You can buy it new today. I would not touch it.

I don't have problems with diode clipping cirquits in Marshalls. These are the models that have it, that I can think of:

JCM800 2205 & 2210 - Great amps. Used by many well known players such as Michael Schenker, Zakk Wylde & John Norum etc. They had killer tones with these amp. I hade a JCM800 2205 for over 15 years and it was a killer amp. I really miss it.

The Silver Jubilee series - These are iconic. Slash, Bonamassa and John Frucsiante comes to mind as users of this model. They use diode clipping. I have hardly ever heard anyone slag them of for that reason. They are very fine amps that sounds great, period.

The JCM900 MKIII - I found this amp to be pretty good. Not just the sound I am going for as I love non master volume Marshalls. But the one I played this weekend can compete with a 2204 JCM800. I even got some silver jubilee tones from it when I used a single coil guitar. The diode clipping gain is great for single coils, it fattens them up. For humbuckers, just leave the diode clipping Gain off, and it sounds like 2204.
 

 

[Biz Prof]

7 hours ago, Disturber said:

 

Then there is the JMC900 Dual Reverb. It seems to be the most hated of the three JCM900 models. Funny enough this is the model that Marshall has chosen to reissue. You can buy it new today. I would not touch

Agreed. Has a bandmate who bought one new in '90. He let me borrow it a few years later when I was gigging with my college era band and had my four-holer in the shop. I couldn't get rid of that thing quickly enough; it was a total dog. The experience soured me on 900s and 5881s as power tubes. 

[Hamer95USA]

On 3/26/2019 at 5:14 PM, black magic said:

I`ve been looking for both of those amps for a while now. The SL-X came in 6L6 and EL34 versions. Most are 6L6. I`m looking for the EL34 version.

If you can't find one used with the EL-34 power tubes, buy the SL-X with the 6L6 power tubes, take it to your amp tech, and have it rebiased for EL-34 power tubes. I did that to a JCM 900 4501 1x12 combo amp with a pair of 6L6 power tubes. It made the amp much better, but the amp didn't sound as good as my '92 6101 combo amp, so I traded it for a Soldano Astroverb 16 combo amp.

 

                                                                                                                                                                                                                                                                                  Guitar George

[black magic]

Good info fellas!!  I just bought a really nice Carvin X100B head. The latest version and last version with EL34`s. It sounds fantastic. It sounds really good thru my Marshall 4x12 with G12T-75`s. I bet it is really ear bleeding thru one with Vintage 30`s. Bad part is, it didn`t come with the footswitch. They are very hard to find as well.