Plexi 50 MV mod?

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Chubsman
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Plexi 50 MV mod?

Post by Chubsman »

Hello,

I am building a PLxi50 and see amps with an added MV mod.... Usualy takes the place of one of the inputs...

Can anyone guide me in the right direction to find how to intigrate this to my amp?
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tooloud
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Post by tooloud »

here is one found all over the internet
HERE
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spunky
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Post by spunky »

I am very confused by the mod directions.
It says to remove volume 2 pot and put the master volume in it's hole and to secure volume 2 pot by soldering it to volume 1 pot and it becomes a gain control.

How do you access the gain control if it is inside the chassis that is mounted in a cabinet?

I thought you removed one of the inputs and mount the MA in that hole......




:roll:
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playazinc
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Post by playazinc »

I usually put them in the back, but i once used a push-pull switched pot in place of volume 1 to selectably control either volume. I moved all of the controls except for presence down one hole and put the MV right in front of the PI.

Schem:
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loverocker
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Post by loverocker »

Yup - that's the same PPIMV I put in an Artiste-Plexi conversion (http://www.ampmaker.com/stuff/artiste/) The 'Rich mod' is slightly different.

Chubsman - if you're building an accurate-looking plexi clone, you have to decide where to put the MV pot. I think that putting it in one of the input socket holes is ugly and A Bad Idea (lead dress reasons).

OK - for a vintage Marshall, it's the least worst option, but for your own build, you might as well put the MV control where it should be - on the front panel close to the PI circuitry.
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tooloud
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Post by tooloud »

I put mine in one of the speaker output jack holes on the back.......
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rollingelbow
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Post by rollingelbow »

Chubsman you ever try this mod? How did it sound. I have a dual pot on the way but am also looking at building the attenuator clone we've got floating around right now. My plexi clone sounds great cranked.. wonder how much of that greatness will stay so i am interested in any soundclips you guys have.
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layboomo
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Post by layboomo »

rollingelbow wrote:Chubsman you ever try this mod? How did it sound. I have a dual pot on the way but am also looking at building the attenuator clone we've got floating around right now. My plexi clone sounds great cranked.. wonder how much of that greatness will stay so i am interested in any soundclips you guys have.
H, if you want a better version go to metroamps forum PPIV MV thread and look at what Rockstah did with 250K pots instead of the 500k. I did it both ways and his sounds the best IMHO. Makes sense really because if you notice the resistors are 220K in the schematic, the 250 K is a much better match. Also forget about that back to back pot nonsense....just move your presence control to the back in 1 of the speaker outs and put the mater right up front. Works great and looks original too!
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rollingelbow
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Post by rollingelbow »

Yeah the 250 k dual pot is what i am waiting on.. i used his post and findings as the base. I was going to use one of the speaker jacks in the back as apparently being closer to the output tubes cuts down on hum and possibly oscillation without using shielded wire. Then again the key is still to wind them tight. I also don't really want to have to undo any connections around the presence pot unless I would want to switch it back.(though i am aware this mod really nullifies the presence knob for the most part)
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