JTM45 with tube reverb? Is it possible?

[SmokinJoeFan86]

Hey everyone, I've got a chance to spend some quality time with my dad's Metro JTM45 build. It's a killer amp for sure, but we've been bouncing around some ideas for a future build. In my mind my dream amp would be a perfect marriage between my two favorite amps, the Marshall JTM and the Fender Super Reverb. I know this isn't the best place for Fender talk but here it goes (I would love some input from guys who have done a blackface Fender build) :

-2 output tubes, preferably 40-50 watts via 6l6s or KT66s
-4 inputs
-basic treble, middle, bass, presense volume 1 and 2 (JTM style)
-tube driven reverb ala Fender
-more headroom than a JTM45 but a little less than the Super Reverb
-a bigger and tighter low end like a Fender, not a huge fan of the JTM45 mushier lows
-tube rectifier

***bonus: I'd like to add a gain boost similar to slamming the front end with a very mild overdrive. This is of course optional as I could always just use a pedal***

So what do you guys think? Is there enough room in say a 50 or 100w chassis to pull this off? Do you think I'd have a winner? Or a loser? Anyone try putting a tube driven reverb circuit in their Metro builds? Any help would be much appreciated!

[Flames1950]

Sure it sounds like a good idea. I drew up faceplate plans for myself a while back to do this very thing -- but the money to get started doesn't come as easy as it used to so it's still in the planning phase.

[Roe]

try a tremolo chassis

[MacGaden]

I´ve played through a modded Blackface Bassman a few times. The Bass input side, with the two tubes, was turned into a JTM45-style channel, the Normal was more or less still a AB763-style Fender. It sounded great, the two channels responded very differently to picking and pedals, a each had it´s own flavour. The JTM45-channel sounded like a brighter Marshall, but not shrill.. Very nice amp, and it got me thinking about what I´d like in an amp. I usually play through a Super Reverb and a Marshall of some sort, just in parallel, to get the clarity of the Fender, an the grunt of the Marshall.

What I´d like to do at some point:

1 full AB763-channel with reverb,-vibrato (Reverb on both channels),
1 full JTM/JMP channel, maybe even the Two-in-one SDM has on his site, with a master volume
LarryLoop,
Lar/Mar overall master,
6L6 tubes and Tube rectifier.

But that would take 7 preamptubes, two powertubes, and a rectifier... And a big chassis.
Take out the reverb, and it would still be 5 tubes in the preamp

Still thinking..

[Roe]

wouldn't that be 8 preamp tubes?

I'm starting on my second 7 preamp tube build now

[mathd]

I had started a schematic using orcad capture Pspice.
It was using a Fender delux reverb into a jtm45. Wasnt complete just needed some final work.

If i can get rid of the error i get when i try to open pspice then i try and post it here.

[MacGaden]

wouldn't that be 8 preamp tubes?

I'm starting on my second 7 preamp tube build now

Maybe..

V-1: AB763 channel
V-2-3: AB763 Reverb
V-4-5: JTM/JMP preamp
V-6: LarryLoop
V-7: Phaseinverter...

?

[mathd]

Ok here is it.(didnt really knowhow to take ss of a schematic).
It is uncomplete and obviously untested and It could easily be bypassed with a switch.
I used a transformer(couldnt find one without a ct) without a reverb tank for the simulation(dont know how to make a reverb tank )

[axeman]

That would be very awesome, if someone could put it together.

[Roe]

wouldn't that be 8 preamp tubes?

I'm starting on my second 7 preamp tube build now

Maybe..

V-1: AB763 channel
V-2-3: AB763 Reverb
V-4-5: JTM/JMP preamp
V-6: LarryLoop
V-7: Phaseinverter...

?

the reverb requirs another triode: 3 gainstages before reverb driver (2 stages) then 1 recovery stage

[MacGaden]

wouldn't that be 8 preamp tubes?

I'm starting on my second 7 preamp tube build now

Maybe..

V-1: AB763 channel
V-2-3: AB763 Reverb
V-4-5: JTM/JMP preamp
V-6: LarryLoop
V-7: Phaseinverter...

?

the reverb requirs another triode: 3 gainstages before reverb driver (2 stages) then 1 recovery stage

Please explain... there are 4 stages in two preamp tubes..?

[Mars Hall]

Please explain... there are 4 stages in two preamp tubes..?

Yes, the 12ax7 is actually 2 tubes in one.

[Mars Hall]

-2 output tubes, preferably 40-50 watts via 6l6s or KT66s
-4 inputs
-basic treble, middle, bass, presense volume 1 and 2 (JTM style)
-tube driven reverb ala Fender
-more headroom than a JTM45 but a little less than the Super Reverb
-a bigger and tighter low end like a Fender, not a huge fan of the JTM45 mushier lows
-tube rectifier

Sounds like at interesting build, although personally, I 've never missed having reverb on any Marshall's I've played through. As for the low end you can up the filtering and use a bigger choke, that should tighten up the bass for ya.

I did marry a Super Reverb tremelo to the jtm45 circuit in my BBri build. The voltages were similar enough to work well together. Turned out very nice.

[bulatovic]

Hey, Joe,


Sounds like a great plan!
You said you wanted it tighter than the original JTM45 and a bit more clean?
My suggestion would be:
Go with higher B+ voltage to make the amp a bit more clean, open and ballsy sounding, but also go with higher filtering. If you use Sovtek GZ34, you'll most probably be able to use, say 50uf on mains (Greg Germino uses 64uf! on his Club40) and maybe even on screens, though that might be a bit too much, so 50mains/32screens/32PI/dual 16uf preamp filtering. I'd do preamp filtering the way Larry did it on his JTM45 build (from HistoricLesPauls forum):

http://www.larry-amplification.de/JTM45 ... _1987+.jpg" onclick="window.open(this.href);return false;



quoting Larry:
"The differences on the board - on the "Larry style JTM45 board" - compared to the original board are easily explained:

In (on?) the orig. JTM45 both V1 & V2 are fed from the same HV node, sharing one 16µF filter cap. That's easy and cheap, but it's also one of the reasons, why this amp often is so loose, so flubby in the lows. I've separated the HV supply for both now, though not in series, but in parallel, as it's done i.e. in the SLO100, in my British Purist, also."

Other than that i wouldn't change anything else...
It'll be cool to hear it with some fendery reverb!
Wish you good luck with the project and have to say that i just can't wait to see/hear how it came up!

Good luck!!!

Luka