Jcm 800 preamp tubes/valves

billando

I have started experimenting with preamp tubes for my jcm 800 2204. I was looking for some advice on how to get a more classic rock jcm 800 as opposed to a high gain jcm 800 if you understand me. Valves I have to play with are:
Nos mullard 
Sovtek 12ax7
Original Marshall ecc83 
3 x electro harmonix 
2 x nos Jan phillips 5751 

I know everybody is different and the 5751s have a lower gain output but how would you set it up? Just now I have the mullard in v1 and the Jan phillips in v2 and v3. Btw when I have the Jan phillips in v1 and v2 and the mullard in v3 it's really low on volume! 

Modulus_Amps

A 2204 isn't really a high gain amp, the problem with it is that with the gain turned down from 10 it just gets silly bright, unless you have cut the bright cap?

V1 and V2 are the gain stages before the master volume, so if you are playing with the master volume turned down try swapping the valves around in those two positions first, for less drive you probably want the 5751 in V1, assuming it is working properly

ICBM

Don't run a 5751 in V2, you'll probably kill it - the cathode voltage is too high for the valve rating. This is a problem with most valve types other than 12AX7s and 12AU7s, and even some modern (mostly Russian) 12AX7s don't like it - so don't put the Sovtek or the EHs there either.

Personally, I don't like 5751s, and I wouldn't put one in a Marshall at all.

For a proper classic JCM800 tone I would get three RFT 12AX7s. They are no longer as cheap as they used to be but they're the best-sounding in these amps - full and clear but also with plenty of gain and a good 'harmonic' richness.

But before you go any further... Marshall used RFTs (with Marshall labels) as stock in the later 70s and very early 80s - if you mean your Marshall valve is original to the amp it could well be one of these. If so, put it in V2, it will sound the best there and be the most reliable. I would put your Mullard in V1 and probably the Sovtek in V3.

billando

Thanks guys. How you describe with mullard v1 Marshall v2 and sovtek v3 is how it was before I got the 5751s to experiment. Not much love for the 5751s? Also the electro harmonix are new and currently in my jcm 900. Seem to be a good match for that amp. How about using them in v2 and v3? I know my 2204 isn't a high gain amp I always have it about 2 on master and preamp at 10 with my band. 

ICBM

Don't put an EH in V2. They will be OK in V1 or V3. Of the valves you've got, only put the Mullard or the Marshall valve in V2 (whatever age it is - they've only used types that will stand the higher voltage.) All NOS types are OK.

No, I don't like 5751s - to me, they have a 'smooth', slightly metallic tone I dislike. (I hate smooth sounds...) They aren't bad in some Fender-type amps but I wouldn't put one in a Marshall.

Preamp gain on 10 is *always* the right setting for a 2204 . Master on 2 is probably about right if you're trying not to be too loud...

billando

I like the old mullard in v1 so I'll try back to Marshall v2 and sovtek v3 and see how it sounds. I'm always throwing money I don't have at amps and guitars so money no object what would u put in v2 and v3? 

Btw 2 on the master kinda drowns out my drummer haha. It's the loudest jcm 800 iv heard! I would say it's similar to my 100w jcm 900 on 5!  

ICBM

billando said:

I like the old mullard in v1 so I'll try back to Marshall v2 and sovtek v3 and see how it sounds. I'm always throwing money I don't have at amps and guitars so money no object what would u put in v2 and v3?

RFT, definitely.

billando said:

Btw 2 on the master kinda drowns out my drummer haha. It's the loudest jcm 800 iv heard! I would say it's similar to my 100w jcm 900 on 5!  

They are. They're some of the loudest 50W amps ever made - much louder relative to their rated power than 900s.

If you even get the chance, try it with the preamp on 10 and the master on 6 . That's about where the power stage goes into overdrive, and it's simply the best rock tone ever. Apart from a 2203 at the same settings .

billando

Iv had it there with good quality attenuators. It does open up but attenuating that much sucks tone too much. The preamp on these amps are so good I prefer the master lower than attenuating. Just my opinion of course! Only amp I like the attenuator with is my bluesbreaker reissue 

ICBM

What attenuator are you using? Some are a lot better than others with some amps, including these... in particular, don't use a Hotplate. The Marshall Powerbrake is surprisingly good though.

billando

Iv used most of them. Hotplate, powerbrake....got a power station just now. It's the best one iv tried but I just think they all suck too much tone. In my bluesbreaker I only have to attenuate a little so it's bearable. When I say "sucks too much tone" it's most noticeable in a band situation I think. Iv tried low powered amps too. Have a nice 1974x but altho it's about the perfect volume it just doesn't sound as ballsy as the old el34 Marshall...again in my opinion! 

ICBM

billando said:

Iv used most of them. Hotplate, powerbrake....got a power station just now. It's the best one iv tried but I just think they all suck too much tone. In my bluesbreaker I only have to attenuate a little so it's bearable. When I say "sucks too much tone" it's most noticeable in a band situation I think. Iv tried low powered amps too. Have a nice 1974x but altho it's about the perfect volume it just doesn't sound as ballsy as the old el34 Marshall...again in my opinion! 

Completely agree. They don't really sound like a 'small Plexi', to me.

I actually like the 2203/4 best - I also think the MV set below halfway is fine, if you can't get away with more volume. I once did some work on a very early '76 (small logo/toggle switch) 2203 which I think is the best Marshall I've ever heard - just the absolute definition of rock guitar sound.

billando

Sounds good man. How would you say the jmp master volumes compare to the jcm? Jcm more aggressive? With power tubes then...I have winged Cs at the minute but after 2 years maybe time for a change. Any thoughts? Maybe if I'm only getting it to 2 on master the power amp tubes don't matter so much?   

ICBM

billando said:

Sounds good man. How would you say the jmp master volumes compare to the jcm? Jcm more aggressive? With power tubes then...I have winged Cs at the minute but after 2 years maybe time for a change. Any thoughts? Maybe if I'm only getting it to 2 on master the power amp tubes don't matter so much?   

In theory the early JCM800s (vertical input) are identical circuits to the late JMPs, but they don't quite sound like it to me - they sound brighter and a bit more edgy. Might just be valves or something though. The later 800s are quite a lot brasher.

Power valves still make a difference even when the power section is clean, just not as much. I actually like EH EL34s, but they don't last very long... they sound similar to the old RFT 'Siemens' EL34s which Marshall also used as stock at the time.

Teacherphil

There is a jcm800 mod that makes it less bright and basically turns it into a JMP. It's just a few resistors. As for the preamp valves I tried mullard, brimar,  JJ and the Chinese Marshall branded ones and there was certainly something more Marshally about the cheaper preamp valves.