My JTM50/JMP50/1987 build...so it begins....

[dizzyhippoman]

Hi everyone...

Parts are arriving. Chassis is from Triode USA. Small parts are from Valvestorm. 20" wide headshell is being made at Sour Mash cabinets in Marianna Fl just down the road. Transformers have been ordered from Triode, Classictones.

Very excited for my first amp build...Completed my first all custom guitar build (Warmoth) a few months ago (pictures below).

Heard Angus and Malcolm on a boom box in 1980 on the school bus and my life was never the same.

wish me luck!
eric

[Roe]

nice amps. these can vary from a jtm45 to a jmp50

[dizzyhippoman]

I may have my nomenclature wrong, Roe....this will have SS rectifier and 50uf filter caps...more a Jmp-50 maybe?

eric

[harleytech]

I built one and put it in a Bluesbreaker cabinet with two Greenbacks and with a Master Volume... I love it !! Sounds great !
Got chassis and small parts from Valvestorm... It also has a Heyboer OT , Classictone PT and a Mercury Choke... Some of my other builds in the background of first pic
Also built 50 & 100 watt Superleads not shown.. Amp building is addictive... You'll love it !

[dizzyhippoman]

Those look great Harleytech! I hope for similar results!

any recommendations on grounding ? Standard vs "Larry"?


eric

[dizzyhippoman]

I guess i am gonna wire this similar to a 1987 model. Split cathode, .0022 bypass on the bright channel. Not sure if i am going 330uf or 230uf on normal channel cathode.

There are so many variations of the vintage Marshalls. Part of the charm.

eric

[harleytech]

Those look great Harleytech! I hope for similar results!

any recommendations on grounding ? Standard vs "Larry"?


eric

Thanks dizzy... I just used standard grounding as with all my amps - All are quiet and I don't see the need to alter from that...
JMHO...

[harleytech]

I guess i am gonna wire this similar to a 1987 model. Split cathode, .0022 bypass on the bright channel. Not sure if i am going 330uf or 230uf on normal channel cathode.

There are so many variations of the vintage Marshalls. Part of the charm.

eric

Yep !
I already have a 1987 50 watt SL that I built so I wired up my JTM50 like a JTM45 with a few cap and resistor changes for the EL34's and it just ROCKS !
I went with a 220uf... No .0022 bypass... Shared Cathode on this one...

[Colossal]

That's a very sweet build. You should be proud.

[Roe]

I may have my nomenclature wrong, Roe....this will have SS rectifier and 50uf filter caps...more a Jmp-50 maybe?

eric

that's fairly accurate for a late jtm50 or early jmp50.

I'm running 64uf, 32uf, 32uf, 22uf, 22uf as well as 27k@16ohms, larry grounding, 3n3 coupling cap at v1b (for tighter bass), switchable 100/5000pf bright caps, 270k mixer resistors, 56k/270pf tonestack, 27nf coupling caps in the phase inverter (for tighter bass)

[harleytech]

That's a very sweet build. You should be proud.

Thank You...

[dizzyhippoman]

a little more done after a round of golf today....Triode USA informed me friday my transformers won't be shipped till first of June because of the extended shutdown in Chicago where they are made. Darn....

[dizzyhippoman]

I notice on the heater wiring others have done, most all do the 1 wire on one side of socket and the other going around to other side of socket. A large loop around the socket. Is there any reason people don't go right down the center of the socket with both wires? This would seem to lessen the crossing of audio signals connecting to the socket.

Almost all the plexi's i see are done this way. Does it really not matter or does the "old" traditional way work better?

thanks,
eric

[pompeiisneaks]

I like the explanation given by the valve wizard:

http://valvewizard.co.uk/heater.html

He even shows pictures of good vs bad methods near the bottom.

On the other hand, I've literally just used non wound wires and sent them in directly from an area away from the tubes directly to the pins like his 'good' example linked above with no negative hum impacts.

I've also worked on an am, I can't recall which one it was now? (reeves space cowboy maybe?) Where the heaters were literally straight wires put between the pins, and the sockets were setup (all of them, power tubes and preamps) so that they were in a straight line. Then the pins were bent pretty low near the chassis away from the rest of the tube and rotated at 90deg so that the straight wires could just be run through them all. He put some shrink tube between each segment as well, but it looked like it was one solid wire the whole way. Pretty neat, and a dead silent amp.

~Phil

[dizzyhippoman]

Thanks for the reply Phil...

I think Soldano does the straight wiring thing. I have read that as long as the wires run parallel they dont have to be twisted. The twisting keeps them parallel. Either will cause the fields to cancel each other.

I just wonder if everyone does it that way because "Marshall" did it that way.

the Valvewizard way seems much better, but what do i know!

eric