Marshall JTM45 or 1987 build

[AppleScruff]

Hey all! I need your opinions here.... I am about to start a new amp project and I am not sure wich one to build. Which one do you like best? I will be building a head so the tremolo does not come into play here. I do have a 6G6-A Blonde Bassman you know one of the ones without the rectifier tube. I hate these tough choices.

Has anyone here put KT-66's in a 1987 model instead of EL34's? How do they sound?
Thanks

[Wannatone]

AppleScroff,

not sure if I´ve understood the topic

You´re going to slaughter the Blonde BM to build a JTM-45 or 1987 on the chassis???

And, a 1987 IS a JTM-45 (Lead version).

JTM-45´s had always been equipped with KT66´s. There is no such as a JTM-45 that came with EL34´s. Guess you mean a JMP-50.

Adrian

[LPC]

Did JMP's come with 66's? Just curious...they came out in the 70's right? Is that what angus used/uses?

[AppleScruff]

No I have NO intentions of converting the Bassman..... I just was letting everyone know what other amp I had in case one of my choices sounded similar to it. There are many differences between the JTM-45 is and the 1987. The JTM-45 has a rectifier tube and different output tubes and slightly different power supply (the JTM-45 had 5881's or KT-66's and the 1987 had EL34's). The JTM-45 had a shared cathode sections on the first preamp stage and the 1987 had separete cathode resistors and capacitors. The 1987 had a capacitor across the cathode resistor in the second gain stage .68uf the JTM45 did not. The "Bright" cap across the volume pot is diffferant. The summing resistors are 270K in the JTM45 and 470K in the 1987 the Tone stack is differant in both. There are other changes as well but those cover most of them.
They are simular but each will sound very different but they can both be built using a simular board layout. My question was what one is considered the "one" to build? They are both "Plexi's"but differant animals.
Sorry for the confusion.
Thanks

[Wannatone]

JTM-45 1987 (Lead model) is the one to build, IMO.

Get some good ol´ KT66´s and Mullard ECC83´s as well as a Mullard GZ34, and you have the right glass for your build.
Well, how about trannies? There´s the choice between the older style RS trannies and the later Drake´s. MM recommended. I´d go with the RS Deluxe clone, just cuz I´m curious to hear the difference to my ´66 JTM w/ Drake iron. The RS Deluxe is likely the best guitar amp OT ever built, though...

Adrian

[Alex_Law]

I think perhaps I'm a little confused. The Doyle book seems to suggest that the 1987 isn't a JTM45; it's a 50W amp with a solid state rectifier, no GZ34.

My reissue 1987 doesn't have a tube rectifier, and Marshall do have a JTM45 reissue with a GZ34. The 1987 is supposed to be more-or-less a 50W version of the 1959.

Oh, and the 1987 has EL34s, too!

Alex (not an expert, just lookin' at the specs)

[Wannatone]

Hi Alex

1987 model = JTM 45 in 1965/66 w/ GZ34 and KT66´s
1987 model = JTM 50 in late 1966 w/ GZ34 and EL34´s
1987 model = JTM (50 Watt) in 1967/68 w/ SS rectifier and EL34´s
1987 model = JMP (50 Watt) in 1968 and later...

Adrian

[Alex_Law]

Thanks, Adrian!

[DaMule]

Scruff-

Which one to build, JTM45 or 1987, depends on what you want the amp to do. They are not that different that you can't try both ckts. or any variations in between. Prolly the only significant commitment you'd have to make up front would be the trannies, unless you're willing to buy two (or more?) sets. Do you wanna get the KT66 or EL34 sound? Once you narrow that down, the rest is mostly ckt. tweaks. As for rectum fires (sic), I like having the option of SS or tube. having the tube socket of a JTM45 chassis will give you both, since you can plug an SS into the socket.
To wit, I'll be building a 50W plexi into a JTM45 chassis. I've decided on EL34's. Get appropriate trannies for these and the rest is gravy.

Steve

[AppleScruff]

Well I made the raw turret board on friday not knowing wich one I was going to build......... I decided to build the 1987 lead model circuit (I put the componants on last night) but now I need to decide what iron to use the RS type or Drake type?? DaMule I think thats a good Idea to have the rectifier socket on the chassis or at least leave room for it to put on later. Has anyone had any experience with Mojotones transformers?
Thanks,
Steve