Blues jr to a plexi preamp and 18 watt power section

[Shack]

I seen a you tube video where someone built such an amp, just not with a blues jr.  Is this something do-able? I have the blues jr and it seems like it would be cheaper than the princeton reverb I just built, since there is alot of the expensive stuff already here.

Might need to change a transformer or both, and would probably need a celestion for authentic Marshall tones. would use a SS rectifier of course and the EL-84s, I guess I would need to figure out the turret boards to use but seems like a cool project.

I dont know how to make a schematic except for drawing it out on paper, same for a layout......but it seems like it would make a nice project for me.

Any advice out there while im just dreaming about it?

[sluckey]

It's already been done. If you want a cathode biased PA, google "18 watt tmb lite". If you want a fixed bias PA, look at this...

     http://sluckeyamps.com/november/november.htm

[HotBluePlates]

My routine advice may apply:
If you're looking to modify an existing amp, life is easier if you keep the entire power supply & output section, including phase inverter and feedback loop (if any). You can then graft on whatever preamp you want ahead of the phase inverter.

[Shack]

nice....im gonna ponder this, because I need to have a Marshall here....all I got is sweet Fenders

[Shack]

And I agree with you HBP..but here I have all I need to use the chassis and faceplate and hopefully make a Marshall out of an amp I dont use


cant make it a 50 watt but could be cool

[sluckey]

The 18 watt TMB is much more popular than the November amp that I built. Both sound like Marshalls and will get as loud as your BJ.

[Shack]

yea, but id like to have the plexi pre amp if I did it, with the cathode follower tone stack....ill look at all of them

[Shack]

so the november amp may be what im thinking of

[Shack]

with a SS rectifier

[MFowler]

How about this layout

[HotBluePlates]

How about this layout

Head's up if you use this: you only need a single 1N4007 per leg of the PT high-voltage winding, not two.

Won't save you much money, but perhaps some space if you're building...

[Shack]

thank you...lots to plan out. if I get this right, ill have 2 amps in the 20 watt range, one Fender and one Marshall....then if I can get band micing amps, they will be what I need

[Shack]

Oh....maybe not that layout, but thx...I was thinking of marrying the output section and power supply of the blues jr to the plexi 6v6 front end....I would have to draw out a layout since I dont have good software, and figure out the best turret board to use, I dont make them.

[MFowler]

6V6 version

[Shack]

cool, thx

[Shack]

so what id like to do is take Dougs BJ power section and marry it to Sluckys plexi preamp.....think it would be a cool amp. My question is how do I get the layout and board when I dont know how to do it and dont wanna ask others to do it....ill draw it on paper which is ok....as long as I dont need debugging help, since I had issues with my PR and had a layout and schematic for others to help.


I think I can do this, but dont wanna rip the amp apart til I feel I have a good plan....if that makes sense

[sluckey]

so what id like to do is take Dougs BJ power section and marry it to Sluckys plexi preamp

I like this idea! My plexi preamp is almost identical to Doug's plexi 6V6 preamp. I suggest you talk to Doug about marrying his 6V6 plexi preamp and BJ poweramp onto a single board suitable for a BJ conversion. He has all the drawings involved and it would be fairly easy to blend the two together. He may do it for you if you commit to buying the board from him. There are probably others out there that would like to use your idea. Might even steer some more business toward Doug.

Doug and I use different layout ideas and also different Visio techniques. To combine our drawings is a lot more work than the above suggestion.

This project is very doable but it's fairly complicated. It will require a good electronics background. Ain't gonna be no color by numbers guide. And since this will be the first of a kind you may encounter challenges that will take you to the deep end of the pool. We'll be here to throw you a life preserver, but you'll have to swim to it.

 

[shooter]

marry it to Sluckys plexi preamp

I did something similar, only I married it to a matchless clubman PA.  Just take your time.  I did *re-do* the turret board, but 80% stayed the same

[Shack]

Thx Sluckey....ill ask him 

[Shack]

Well, I may have to design the layout myself, probably real good idea for me to do. My only problem is lack of software, so it may be tough for me to submit my ideas to you guys.


I have printed out layouts and schematics for the BJ conversion, 2 6v6 plexis and the november project, plus have what MFowler has provided me here.

Only thing missing from this chassis to a plexi is the second volume pot.......any ideas for that?

[sluckey]

Only thing missing from this chassis to a plexi is the second volume pot.......any ideas for that?

Dual concentric pots.

[Shack]

ok, I was worried that the dual pot in parts store may have turned together :)

[sluckey]

ok, I was worried that the dual pot in parts store may have turned together :)

Most of them do. That's why I specifically said dual concentric. That gives you a shaft within a shaft. You will need dual concentric knobs to go with it.

[dude]

That Super lite ll layout's tone section is weak, the cathode follower is much better but you'll need another 12ax7.


I've done that Super lite with 6v6s and el84's, the el84s sound much more Marsh-ally than the 6V6, (cathode biased). It's pretty loud too and that gain preamp volume is nice, blending the two gives clean to crunch.


But you'll be having another gain stage melting the two. 


al

[Shack]

Most of them do. That's why I specifically said dual concentric. That gives you a shaft within a shaft. You will need dual concentric knobs to go with it.

Hmmm awesome idea, only not easy to find it seems

[sluckey]

They're hiding in plain view. Try google for "concentric potentiometer". May as well search for "concentric potentiometer knobs" too. Plenty available. Easy to find on eBay also.

[Shack]

Will do.....and im going to try to figure out how to fit the Plexi preamp on the Blues junior turret board......think I can do it.

Do you and Doug put the fifth filter cap on the plexi because its a higher gain preamp?

[Shack]

If I am unable to locate that pot in those values ( dont seem to be anywhere) would it be better to eliminate one of the channels , or the presence/meat.....or the master volume ....since there is no place to put a 2nd volume pot on that chassis that I can think of.?

[sluckey]

Do you and Doug put the fifth filter cap on the plexi because its a higher gain preamp?

I put it in because I was copying Mark Huss and he was copying the original 1987 Plexi. They all have 5 filter cap nodes.

If I am unable to locate that pot in those values ( dont seem to be anywhere) would it be better to eliminate one of the channels , or the presence/meat.....or the master volume

If I had to eliminate one of those choices, I'd reluctantly drop the master volume. But I would not give up any of those features. I'd just use a dual concentric 500K ( I know I saw plenty of those) for the volume pots. It should sound the same.

[Shack]

Oh ok, thx.....I thought I needed 1M or nothing

[Shack]

What are the tonal differences between the plexi preamp and the jcm-800 preamp? I think that the jcm-800 was what I heard in the video, but that would have issues mounting in a BJ too....same amount of volume pots and extra inputs.

I play out this weekend so should be able to get my boards and I found a 500k/500k pot, so will go forward with the plexi plan, was just wondering:)