Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: RoadShow on February 12, 2021, 04:53:41 pm

Title: JTM45/2204 combo with reverb and FX loop
Post by: RoadShow on February 12, 2021, 04:53:41 pm

Hello,

For a while now I've contemplated hardwiring an amp that combines selection of the sounds of the mixed JTM45 or cascaded 2203/4 to get the best of both worlds in one amp (already built a HW JTM45 and 18W Marshall).  So, I scrutinized schematics, realized it is possible, and as I searched I found sluckey had already created the combination with a simplified single jack front end as well:
Marshall_Dual_50 Marshall JMP Series 1987 and JCM-800 2204
https://el34world.com/charts/Schematics/files/Sluckey/Marshall_Dual_50.pdf (https://el34world.com/charts/Schematics/files/Sluckey/Marshall_Dual_50.pdf)

Of course my imagination has been running wilder and my thoughts included adding reverb and an FX loop.  In the search, I also read this:
https://el34world.com/Forum/index.php?topic=7957.0 (https://el34world.com/Forum/index.php?topic=7957.0)
where in replies 15 & 16 sluckey gives guidance to add the reverb between the Treble wiper and the Master Volume control.

So, would it be possible to add an FX loop there in series with a built in reverb based off of the Fender Deluxe Reverb with the reverb section circled in the attachment inserted at that point in the Marshall_Dual_50?

I suspect using a JTM45 transformer with enough heater supply for the extra tubes would be necessary.

What other things do I need to consider and what might I run into?

Thx,

Bill

Title: Re: JTM45/2204 combo with reverb and FX loop
Post by: tubenit on February 13, 2021, 05:50:16 am

IF I were attempting what you're considering ……………………………

I'd use the Zero Loss FX loop here:  https://store.metropoulos.net/products/zero-loss-fx-loop-kit

And place it right after the tone stack and then use a one tube reverb something like the schematic attached. 

I would have the reverb AFTER the FX loop using delay or some other time based effect.

With respect, Tubenit

Title: Re: JTM45/2204 combo with reverb and FX loop
Post by: wdelaney72 on February 15, 2021, 09:00:53 am

Quote from: tubenit on February 13, 2021, 05:50:16 am

IF I were attempting what you're considering ……………………………

I'd use the Zero Loss FX loop here:  https://store.metropoulos.net/products/zero-loss-fx-loop-kit (https://store.metropoulos.net/products/zero-loss-fx-loop-kit)

And place it right after the tone stack and then use a one tube reverb something like the schematic attached. 

I would have the reverb AFTER the FX loop using delay or some other time based effect.

With respect, Tubenit

Yes...the Zero Loss is super easy to install and totally transparent. You can add / mod all you want around that.

Title: Re: JTM45/2204 combo with reverb and FX loop
Post by: RoadShow on February 15, 2021, 11:33:23 am

Thx guys,

I ordered the zero effects loop yesterday.  Definitely looks like the way to go.

I've also been reviewing the many one tube reverbs and plan to implement the one of sluckey's with dwell that Tubenit attached.

Today I'm working on the turret board layout with the additions and slight subtractions and how to fit the knobs, extra tubes, etc. on the blank Mojotone chassis.  One thought is to use a concentric 1M pot for the JTM45 portion.  Do you know of another blank chassis that is wider?  I can make it all fit, but wouldn't mind having say a 20" chassis width instead of 17".

Bill