What hot rodded mod options to do I have with an extra preamp tube installed?

[RWMusic]

My '76 JMP 50 has a extra preamp tube because it has a tube buffered effects loop. Also has a pre phase master volume. I feel like I can take advantage of this and get the amp remodded into some kind of hot rodded marshall like a Jose, etc.

I was hoping to get some potential options on what is available to me with these extra things in the amp. I am into the 80's tones, specifically George Lynch and Warren Dimartini.

Possibly some type of Jose mod or a Frank Levi/Caswell mod? Didn't he use an extra tube from a Tremolo model to add extra gain?

 

[Leonard Neemoil]

Lynch Mod or Mr. Scary instead?

 

[RWMusic]

Lynch Mod or Mr. Scary instead?

I thought those work better on 2203/2204's?

 

[Leonard Neemoil]

I thought those work better on 2203/2204's?

Yeah, I really don't know, that's why I put the question mark at the end. Just thinking of things to use to keep the amp original. People smarter than me should be able to elaborate. Hopefully they'll chime in soon.

 

[RWMusic]

Yeah, I really don't know, that's why I put the question mark at the end. Just thinking of things to use to keep the amp original. People smarter than me should be able to elaborate. Hopefully they'll chime in soon.

The amp is already modded with an extra tube, just not in the way I would like, so keeping it original isn't a concern.

 

[Ronquest]

So, you are willing to give up your FX loop?
There are so many distortion pedals out there to get you those tones. Not sure how you feel about the amps tone now (other than wanting more 80s gain), do you like/love it or just want something different all together. In all seriousness I've seen too many mods turn a great amp to crap, when the owner really should have gotten a different amp. And this is coming from someone who builds and mods.

Without much work at all you could just make the loop 2 more cascaded gain stages, by converting the first cathode follower/buffer. At this point these stages are clipping and shaping your tone. You'd actually be dumping most all of the extra gain anyway. Now this would effect both channels. If you're looking to hotrod just one channel and leave one stock that's a few more wires and depending on the tube location and layout may be an issue. Lot's of options!!!

Any pictures of what you have now?

 

[RWMusic]

So, you are willing to give up your FX loop?
There are so many distortion pedals out there to get you those tones. Not sure how you feel about the amps tone now (other than wanting more 80s gain), do you like/love it or just want something different all together. In all seriousness I've seen too many mods turn a great amp to crap, when the owner really should have gotten a different amp. And this is coming from someone who builds and mods.

Without much work at all you could just make the loop 2 more cascaded gain stages, by converting the first cathode follower/buffer. At this point these stages are clipping and shaping your tone. You'd actually be dumping most all of the extra gain anyway. Now this would effect both channels. If you're looking to hotrod just one channel and leave one stock that's a few more wires and depending on the tube location and layout may be an issue. Lot's of options!!!

Any pictures of what you have now?

I'm trying to figure out what to do with the amp overall. I originally bought it thinking it was hot rodded but realized after I received it that it's a stock JMP 50 with an added tube effects loop and master volume. The master is a pre phase so it lowers the gain when turning it down which is also what I didn't want. It also had the bright cap removed so it is a lot tamer than my 72 JMP 50.

I figured I could take advantage of what it has and hot rod it, since that was my original use for it. Or I can just yank out the effects loop and return everything to stock since I have a Power Station. Maybe leave the master volume and make it a PPIMV.

or just leave it alone and use a pedal.

Here are some pics:

jmp50-1 hosted at ImgBB

Image jmp50-1 hosted in ImgBB

imgbb.com

jmp50-2 hosted at ImgBB

Image jmp50-2 hosted in ImgBB

imgbb.com

jmp50-3 hosted at ImgBB

Image jmp50-3 hosted in ImgBB

ibb.co

 

[Ronquest]

Mmmm,...Power Station!

Interesting tube addition there. How does the amp sound?

Guess you could mess with it a bit. Easy enough to just rewire for a gain stage or 2 prior to one of the channels and leave the the other stock. Noise will most likely be an issue with it's location. Is that the socket location for most "add a tube" mods?

 

[RWMusic]

Mmmm,...Power Station!

Interesting tube addition there. How does the amp sound?

Guess you could mess with it a bit. Easy enough to just rewire for a gain stage or 2 prior to one of the channels and leave the the other stock. Noise will most likely be an issue with it's location. Is that the socket location for most "add a tube" mods?

It sounds decent. My 72 is a lot more aggressive with more gain, but that is because it has a 5000 bright cap.

This one is a lot more mellow. I don't like it anywhere below 7. I think because it has no bright cap, anywhere from 1-5 sounds like crap to me.

I only play Marshall's cranked up with an attenuator, not clean or edge of breakup.

My hope when I got the amp was for it to be hot rodded. I got excited watching the videos on the Steve Vai Jose mod Marshalls that Pete Thorn did on Youtube, and I wanted something like that.

The ad for the amp made it sound like it was what I was looking for. The ad even mentioned it had a "High Gain Mod", which turned out to be BS.

 

[playloud]

With the extra tube you have plenty of options. You could repurpose as extra gain stages, as @Ronquest suggests, or keep the FX loop and make the amp more like a 2203 (cascade channel I into II and tweak values of surrounding components). I believe Jose often added a gain stage to each channel with the extra tube.

The master could easily be converted to a "Jose master" between CF and tone stack (using clipping diodes), although location is not ideal.

This one is a lot more mellow. I don't like it anywhere below 7. I think because it has no bright cap, anywhere from 1-5 sounds like crap to me.

Usually it's the other way round (bright cap -> crap sound at low volumes). I suspect it just isn't giving you enough breakup at those settings.