# PPI PowerClass Internal Crossover



## akdingo (May 19, 2011)

Been lurking here a while, search yielded no results so here goes-

I am planning going active 3-way using a PPI PC275 bridged to my sub. I would hate to waste the internal 24dB/oct Linkwitz-Riley crossover, but it has a fixed point of 90Hz. I would like to be able to lower the x-over point to 72 Hz, and feed the resulting HP output into an AudioControl 24XS (24dB/oct Linkwitz-Riley 2-way) for mids and highs. I already own one and reusing it would simplify things considerably.

First off - is this possible? If so, would it be similar to the AudioControl modules, replacing resistors? Does anyone have any information/ideas/schematics/etc.?


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## sonikaccord (Jun 15, 2008)

It's possible. You'll have find the op-amp(s) responsible for the xover though and find out what's connected to it and all of that jazz. Once you get the part numbers off the chip though you can usually look up the datasheets and the manufacturer of the chip will tell you how the circuit is implemented and how to modify certain characteristics and such.


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## Therum (Apr 18, 2009)

The datasheet is not gonna tell you how to modify the crossover circuit. The opamp should be a LM837. Changing the crossover freq "should" be as "easy" as replacing the 4+ resistors and 4+ capacitors that feed the inputs of the opamp. Oh yea. Thats per channel. I dont like to discurage anyone. But to me.... its a waste of time. You are not really gaining anything with the time invested. Buy a PRS-880.


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## akdingo (May 19, 2011)

Sounds like I'll be keeping my soldering iron cold for a while. This is sounding like a little more than I am willing to undertake on a 17 year old amp. Damn nostalgia...



> Buy a PRS-880.


I wish I could justify it - it makes perfect sense to me, not so much with the wife.


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