Marshall JCM 800 Cali Mod (Fortin)

[JacksonMarshall]

Hey guys...First post here, I'm a regular over at Marshall and the Mesa/Boogie forum...anyhow.

I recently acquired a JCM 800 2203 with the Fortin Cali Mod. Sick amp, I love it. Question tho, it's got EL34's and I know from most feedback I read they are the preferred tube but I just never seem to like EL34's in my amps, more of a 6550 or 6L6 kinda guy. As of recent I am leaning more and more toward the 6L6.

Anyone here with a Cali modded Marshall running 6L6's? I find the amp super bright and too mid rangy, don't get me wrong I'm not a scooped mids guy, I like mids, but the amp is a bit harsh sounding. Figured the 6L6's my smooth the tone out a bit.

Any feedback?

Thanks.

 

[Mr. Willy]

Modded high gain amps get their dirt from the preamp more than the power section. Changing output tubes won't have as much difference as you would expect. If you did hear a difference, it's more than likely in your head because you think you should be hearing a difference. You're going to get closer to the sound you want by making changes to the preamp.

 

[Mr. Willy]

Also, a lot of guys snip the bright cap in those Marshalls for the very reason you mentioned. As for the midrange, that is a tonal characteristic that makes those amps sound the way they do. You could try a different cabinet/speakers to get a more scooped sound.

 

[steve_k]

Welcome......email Mike with pics of the amp, or where you got it from. He keeps detailed records of all his mods and usually installs a bias mod with a trim pot capable of biasing up everything from 6L6's to 6550's. As an alternative, you can toss some KT77's in the amp and they should bias up as it is. They are more like a 6L6 on steroids to me. My Cali has 34's in it and is just right!

Steve

 

[Digital Jams]

What settings?

Where is the clipping toggle?

Cab and speakers?

What options does it have?

Sorry for all the questions but you need to be more specific, lots of variables involved. For example a speaker change is far more useful than changing power tubes.

 

[JacksonMarshall]

Good point. I haven't heard any tubes other than EL34's in my Cal amp. But El34's definitly sound thinner to me when compared to say 6550's and 6L6's, could be the way the amp (or say preamp) is voiced. I haven't heard any one amp with EL's and then after with 6550's or 6L6's, so I do see what your saying.

In that case, I remember Tung Sol's 12AX7's sounding a bit fatter/warmer. I have a mix of a JJ, two Groove Tube and one Chinese 12AX7 in there now...

Yeah I do have V30's in my 1960B cab also adding to the mid range...On my stock 800 I usually keep my mid at 7-8 even at 10 sometimes, I do love the mids, just a bit ice picky at times.

Even still, this amp is one of the best amps I've heard/played, just trying to fine tune...

 

[JacksonMarshall]

What settings?

Where is the clipping toggle?

Cab and speakers?

What options does it have?

Sorry for all the questions but you need to be more specific, lots of variables involved. For example a speaker change is far more useful than changing power tubes.

I keep all my toggles switched to the left.

Has 6 toggles, a Thump, Hair and then two others, one under each of the two Master Volumes and another two under each of the two Gain pots. The Gain1 also pulls for Tight or can be pushed in for Spongy, I keep it pulled.

Eq's are all in around 4-6, even leaving them all close to 5 the amp sings.

Marshall 1960B with V30's...Jackson King V with EMG's (18 volt mod).

 

[Mr. Willy]

Good point. I haven't heard any tubes other than EL34's in my Cal amp. But El34's definitly sound thinner to me when compared to say 6550's and 6L6's, could be the way the amp (or say preamp) is voiced. I haven't heard any one amp with EL's and then after with 6550's or 6L6's, so I do see what your saying.

In that case, I remember Tung Sol's 12AX7's sounding a bit fatter/warmer. I have a mix of a JJ, two Groove Tube and one Chinese 12AX7 in there now...

Yeah I do have V30's in my 1960B cab also adding to the mid range...On my stock 800 I usually keep my mid at 7-8 even at 10 sometimes, I do love the mids, just a bit ice picky at times.

Even still, this amp is one of the best amps I've heard/played, just trying to fine tune...

Not sure what 34's you have in her now, but JJ E34L's have a big bottom/scooped mids thing going on with them. You could try those. Also, imho JJ preamp tubes are really dark. You could try all JJ's in the preamp and see if that helps. This would be a fairly inexpensive experiment.

 

[JacksonMarshall]

Good point. I haven't heard any tubes other than EL34's in my Cal amp. But El34's definitly sound thinner to me when compared to say 6550's and 6L6's, could be the way the amp (or say preamp) is voiced. I haven't heard any one amp with EL's and then after with 6550's or 6L6's, so I do see what your saying.

In that case, I remember Tung Sol's 12AX7's sounding a bit fatter/warmer. I have a mix of a JJ, two Groove Tube and one Chinese 12AX7 in there now...

Yeah I do have V30's in my 1960B cab also adding to the mid range...On my stock 800 I usually keep my mid at 7-8 even at 10 sometimes, I do love the mids, just a bit ice picky at times.

Even still, this amp is one of the best amps I've heard/played, just trying to fine tune...

Not sure what 34's you have in her now, but JJ E34L's have a big bottom/scooped mids thing going on with them. You could try those. Also, imho JJ preamp tubes are really dark. You could try all JJ's in the preamp and see if that helps. This would be a fairly inexpensive experiment.

I have Winged C's which are great from my experience. Never tried JJ's...thanks for the advise tho.

Yeah off to start looking for some preamp tubes, seems to be the most logical step to take, quick, easy & cheap and likely the remedy needed.

 

[JTyson]

My JMP Cali will run any octal-based tube with a quick rebias (it has an external adjustment), there were things that I liked about 6L6's in it, the bottom is a little more pronounced and rounder, but its less edgy and dosent have the same mids as 34's, which is my fav in it
I did like 6550's in it, but still went back to 34's. I'm not a 6L6 guy.. I do like them in some other amps though
To each his own They are absolutely killer amps
Welcome aboard BTW

 

[Clpether]

Funny! I also use the toggles to the left and have winged C's in mine. I can see how you would find it thin at first which is easily rectified by eq adjustments and proper speaker/cab use. I gotta tell you in a band mix what sounds thin at home sounds awesome in with two guitarists. You will be surprised at how well you cut through the mix. My cali/sykes is what I have wanted out of an amp forever.

 

[rupe]

Try 6CA7s...they may be what you're looking for