# 96 Fender Prosonic Combo Lar/Mar PPIMV question



## Ruddiger (Jan 11, 2008)

Hi everyone, 

I've installed a Lar/Mar style PPIMV in my 88' Marshall 2203 with my basic abilities and knowledge. I found it so useful that I'm looking to install one in my Prosonic combo. I'm not able to figure out if I have to approach things differently due to the circuit's triple rectification configuration. Everything looks straight forward but I'm looking to avoid any 'stupid mistakes' so if you're able to offer any guidance, I'd be very grateful.

In case you're so inclined; the schematic can be viewed here;

http://support.fender.com/schematics/guitar_amplifiers/Prosonic_schematic.pdf

Thanks in advance


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## WCGill (Mar 27, 2009)

The rectification won't really affect the LarMar master. Looking at the schematic I see the amp already has a master volume. Will there be two or will you be rewiring?


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## gtrguy (Jul 6, 2006)

GONE


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## Ruddiger (Jan 11, 2008)

Hi and thanks for the responses,

gtrguy; I discretely added it to the rear panel; essentially the plexi circuit is similar to that of a 2203 so you get the same benefits. My 2203 really comes alive and opens up when the master is above 7, and now, at lower volumes, it retains that 'big' sound. I would recommend one for sure.

WCGill; this is why I'd like to add one to my Prosonic. The amp sounds fat and opens up after about 5 on it's existing master volume which again, is not very practical. So basically, I will be adding a second volume control allowing me to retain that 'pushed' sound at lower volumes. 

The circuit at the phase inverter seems similar to the 2203 but has a wire leading to the rectification switch I'm not sure of. 

Thanks in advance


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## gtrguy (Jul 6, 2006)

Ruddiger said:


> gtrguy; I discretely added it to the rear panel and what it does, essentially the plexi circuit is similar to that of a 2203 so you get the same benefits. My 2203 really comes alive and opens up when the master is above 7, and now, at lower volumes, it retains that 'big' sound. I would recommend one for sure.


Interesting! With the different preamp architachturee of the 2203 I wasn't sure it would benefit from the LarMar... cool to know it does. Thanks for the info!


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## Ruddiger (Jan 11, 2008)

I thought this image might help;

My confusion is with that brown wire coming off the bias resistors and going to the rectifier switch. With the last PPIMV I installed, I had to remove the bias resistors and route a wire from their central point (essentially where that brown wire is) straight to the new master volume pot - then, of course, off to the power tubes. I'm just not sure how to handle this configuration.

Thanks


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## WCGill (Mar 27, 2009)

It should be the same. The two 220k resistors are replaced by the dual 250kB pot and the 2.2m safety resistors. I'm assuming the brown wire is your bias feed and so should go to the dual pot according to the hook-up diagram for the LarMar. With the change in the B+ with the 3 different (2?) rectifier configurations, the bias must also change to maintain proper dissipation.


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## Ruddiger (Jan 11, 2008)

WCGill;

That's pretty much what I needed clarification on. I'll wire things up that way and see if I have any fireworks.

Thanks so much!


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## Ruddiger (Jan 11, 2008)

Hi again, 

I just wanted to follow up with this; I installed the PPIMV and it works really well. Thanks very much WCGill; you're responses were helpful and much appreciated!

Here's another gut shot in case anyone's looking to do the same as I couldn't find any when I was searching before I decided to post.


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