How similar does a JCM900 Mk III 2500 sound to a JCM800 2204?

[Deftone]

This is what a slx sounds like




I’ve read the mkiii sounds similar but I haven’t heard it

I love my SL-X. The JMP and the SL-X are my two favorite Marshalls.

But my SL-X has 5881's. It's a bit darker and more sinister than my MKIII or my 2204's.

 

[knulp]

I love my SL-X. The JMP and the SL-X are my two favorite Marshalls.

But my SL-X has 5881's. It's a bit darker and more sinister than my MKIII or my 2204's.

Mine had 5881 and now el34 but unless really cranked I liked the 5881 too
Sinister it’s a perfect fitting word
For me it’s perfect except for modern compressed hi gain at low volume where you prefer the dsl
But high volume heavy crunch it’s an explosive amp,there’s something to the dynamics when you plug straight and don’t have to fight to reach the desired gain level with volume or pedals.
And if you keep the gain low you get one of the most desirable blues tone and you’ll stop dreaming of a plexi

Yes I like it

 

[Deftone]

FWIW:

"There are three different variants of the JCM900. The most common models are the 4100 (100 watt) and 4500 (50 watt) "Dual Reverb" models, which are a descendant of the JCM800 2210/2205 design." "These models feature two channels, a largely solid-state preamplifier, and diode distortion."

"The 2100/2500 Mark IIIs are essentially JCM800 2203/2204s with added diode clipping controllable via a knob on the front panel and an effects loop." "These are fairly uncommon and were not in production for long before being replaced by the 2100/2500 SL-X, which replaced the diode clipping from the Mk III with another 12AX7/ECC83 preamplifier valve."

https://en.wikipedia.org/wiki/Marshall_Amplification#JCM900

Read the comments section on this YT vid from the original MKIII designer..... ( @okkhmjoe )

"My original prototype was built my modifying a 50 watt MV Combo and then my 100 watt 1959 super lead. Basically, working at Marshall, I saw a lot of really messed up modded amps. 99% of the time, people wanted them returned to stock. So, in essence, I learned alot of what NOT to do... Occasionally, someone would do something cool, and I guess I would store that in my memory bank...



Leon Todd released an updated vid on the MKIII a couple weeks ago....

 

[Derrick111]

A lot of Marshalls can cover each other's territory. That's something a lot of people don't consider. How well and how close they do it depends on the model and the user's ability to dial it in. The 800 can sound like a 900 and the 900 can sound like an 800, but only to a degree. The two are really different amps. The magic of the 800 is not really something that you can achieve with the 900. The hi gain crunch is beyond what the 800 can do (at least without a pedal or un-modded). The beauty of the 800 is that it can do that with pedals or tweaks, and it is a very dynamic amplifier. The 800 is not a one trick pony at all if you know how to go about things. I went from early Marshalls, to later 70s Marshalls, to JCM800s and I have no problems getting the early sounds, the 80s sounds, the 90s hi gain sounds, and clean sounds all from a single completely stock JCM800 2203 or 2204. I had a 900 and have been supplied them on tour, but they always sounded like a 900 to me... maybe other people can do better at getting other sounds from 900s, but I feel like the 800 is a much more dynamic amp that's strength can't be duplicated by the 900, while the 900 can be reasonably duplicated by an 800. Bottom in is if you want the sound of an 900, that is what you should get. If you want the sound of a 800, then getting a 900 to try and save money might well disappoint.

 

[Tatzmann]

I have a '90 JCM800 2204 and a '91 JCM900...

Many of the late 1980's JCM800's ('89 and '90) have 2k2 screengridresistors fitted, just like the 900's have. Plus the one channel mastermodels do have a 100pf cap from the plate to cathode at V1a. It's there to carry some highend away.

These changes may contribute to the '90 2204 sounding closer to your mkiii.

 

[Deftone]

Many of the late 1980's JCM800's ('89 and '90) have 2k2 screengridresistors fitted, just like the 900's have. Plus the one channel mastermodels do have a 100pf cap from the plate to cathode at V1a. It's there to carry some highend away.

These changes may contribute to the '90 2204 sounding closer to your mkiii.

For sure.

And the late JMP's 2203/4's are very similar to the early 2203/4 JCM 800's, correct?

IMHO People need to be more specific when they say "800" and "900." So many variations, not just different models but changes over the years as well.

 

[knulp]

For sure.

And the late JMP's 2203/4's are very similar to the early 2203/4 JCM 800's, correct?

IMHO People need to be more specific when they say "800" and "900." So many variations, not just different models but changes over the years as well.

Those are very minor tweaks,if they are the only differences the amps are literally the same with sens off on the mkiii

Time to search for the schematic,I’ll get back

The slx is surely different,but not really worlds apart

I don’t know why but I never heard of someone modding a slx,.
It’s a crazy good platform:4 gain stages,2 gain controls,2 master and a good loop! Low noise..
And the usual compliants are very easy to overcome ,too much highs ,no bass ,somewhat fizzy
While I don’t have any of these problems,they are not deal breaker for anyone into modding and tweaking

The difference between those 900 and a plexi or a 2203 for me are more about the differences between a 2 stage and a 3 or 4 stage preamp

 

[Tatzmann]

So many variations, not just different models but changes over the years as well.

Certainly true. Some very late 80's JCM800 "NMV" models didn't even had a filterchoke. They came with a modern looking milled aluminum wirewound resistor, which looked oddly out of place, but was definately factory fitted.

 

[Derrick111]

For sure.

And the late JMP's 2203/4's are very similar to the early 2203/4 JCM 800's, correct?

IMHO People need to be more specific when they say "800" and "900." So many variations, not just different models but changes over the years as well.

The late JMP's 2203/4's are indeed very similar to the early 2203/4 JCM 800's. The difference is more cosmetic than circuit difference. On the other hand, the 800 and 900 are radically different circuits and it sounds like it. The screen grid resistors or a plate to cathode cap don't make them any more brothers and sisters than you and I wearing a red shirt makes us siblings. The preamps in these two amps are not even close.

 

[Tatzmann]

The screen grid resistors or a plate to cathode cap don't make them any more brothers and sisters than you and I wearing a red shirt makes us siblings. The preamps in these two amps are not even close.

Noone said that. I said "this may contribute to them sounding closer to each other".

 

[Derrick111]

Noone said that. I said "this may contribute to them sounding closer to each other".

Sorry, I wasn't implying that you were Taz, so perhaps I could have worded my statement clearer... It might bring false hope for the uninitiated reading that there's a few shared parts between the two models that could make the two amps sound closer. In my experimentation, it did not. A lot of people land here while doing research or after cruising eBay before hastily deciding to pull the trigger on a 900 for a brilliant way to get the 800 sound for cheaper so I was just trying to avoid misunderstanding or false hope.

 

[Deftone]

I stand by my statement. I own them both and I A/B them right next to each other. My JCM900 MKIII sounds identical to my '90 JCM800 2204. I can't tell them apart. That's with the gain sensitivity on the MKIII turned all the way down but everything else is set the same. In fact a member on another forum did run out an buy an MKIII and he loves it.

My '85 800 2204 w/6550's sounded different, much brighter. My '79 JMP w/ 6550's sounds different, my 2555 w/EL34's sounds different, my 900 SL-X w5881's sounds different, my 800 2205 w/EL34's sounds different but the MKIII and the '90 2204 sound identical.

 

[knulp]

I stand by my statement. I own them both and I A/B them right next to each other. My JCM900 MKIII sounds identical to my '90 JCM800 2204. I can't tell them apart. That's with the gain sensitivity on the MKIII turned all the way down but everything else is set the same. In fact a member on another forum did run out an buy an MKIII and he loves it.

My '85 800 2204 w/6550's sounded different, much brighter. My '79 JMP w/ 6550's sounds different, my 2555 w/EL34's sounds different, my 900 SL-X w5881's sounds different, my 800 2205 w/EL34's sounds different but the MKIII and the '90 2204 sound identical.

What kind of 800 is your 2204?

 

[961le]

I love my SL-X. The JMP and the SL-X are my two favorite Marshalls.

But my SL-X has 5881's. It's a bit darker and more sinister than my MKIII or my 2204's.

Ditto, play mine all the time (el34 ‘93). Gets very convincing mule/dose tones out of it. Once I sorted out my preamp tubes it really woke up. Was going to get a slo30, but now nope. Pocket the 3k , use and enjoy what I have.

 

[Deftone]

What kind of 800 is your 2204?

A Marshall? I don't understand the question.

 

[Deftone]

Ditto, play mine all the time (el34 ‘93). Gets very convincing mule/dose tones out of it. Once I sorted out my preamp tubes it really woke up. Was going to get a slo30, but now nope. Pocket the 3k , use and enjoy what I have.

I would love to try an EL34 SL-X. I'd love to try a 900DR with EL34's as well. That said, having a few other EL34 amps (2204, 2205, 2555 & MKIII) I think I prefer my SL-X because it has 5881's.

 

[knulp]

A Marshall? I don't understand the question.

Ops yeah I didn’t consider that the 2 channels is a 2205 and not a late 2204..mea culpa

Sometimes at work I type without thinking as I should

However,I only played the 800 2204 a lot of years ago but I can’t say even my slx to be a radically different amp

 

[Deftone]

Ops yeah I didn’t consider that the 2 channels is a 2205 and not a late 2204..mea culpa

Sometimes at work I type without thinking as I should

However,I only played the 800 2204 a lot of years ago but I can’t say even my slx to be a radically different amp

I feel like my SL-X is very similar to a 2204, just a bit darker sounding due to the 5881's.

 

[knulp]

My tech when changing my amp from 5881 didn’t need to change the bias circuit,but only the screen resistors .
That’s with jj el34 mkii
And this happens if you set the bias as recommended by Marshall,cold.
This way,original bias circuit and upped screen resistors,you can switch between 5881 and el34 and compare.
If you don’t crank it you may prefer 5881 but they are not going to make much difference anyway

 

[knulp]

In the end I don’t think you prefer the slx because of the 5881.