RMC - Poly-Drive X

[ggedamed]

A few days ago in my service popped in LGXT Godin guitar for repair.
The guys from the company RMC did not want to give me schematic for Poly Drive X preamp,
so I had to draw it. This is my drawing of the preamp for all those who need it as a reference or personal use.
More photos and information from my workshops on my Facebook page. https://www.facebook.com/pages/Apollo-M ... 5494552791

[apollomusicservice]

more guts

[patafix]

They made a revision in 2011. I ordered one. I can offer shots since I haven't installed it in my guitar yet.

There are a couple of mods from what I see, the most noticeable is the presence of two additional transistors and the swap of a tone cap from 33n to 47n...

[n9voc]

Thank you so much for posting this. I needed to replace the battery connection - and your pictures helped assure me that it was going properly polarized!

[Dirk_Hendrik]

Thanks fot the big job done! I'm still puzzled by IC1B though.

[lolbou]

And where does U+ come from?

[Dirk_Hendrik]

One would expect U+ to be some kind of biasing voltage for the 6 FET's. For that reason it's rather odd to see that the opamp that seems to source this U+ is derived through an integrating opamp from the summing bus of those FET's.

I am sure more the brilliant minds see the logic of the setup straight away.

[coldcraft]

guys, its called a servo.

[Dirk_Hendrik]

Yes, a-DC servo. Continue on the why?

[coldcraft]

I doubt there's a strong reason why. probably just because they could.

[papasteack]

The individual input circuit/eq for each piezo is really interesting. If someone can simulate it, i would be very curious to see curves of the different individual input stages...
Graphtech piezo doesn't do this kind of induvidual tweak with their simple summing board.