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Bellari RP503 opamp positions & mods

Posted: Thu Jun 06, 2013 9:09 pm
by psycom
I'm having a heck of a time figuring out which opamp is for the compressor. Logically it would seem U2 would be the one as it corresponds with the front panel layout. However U5 appears to be connected to the compressors control if you follow circuit board traces.

I've read BOTH and have never found a schematic. Even Back Lion Audio doesn't have a clue as of today nor the group running this forum. I thank them both for really speedy replies.

This was originally a BLA mod but done by someone no longer associated with them. There are 5 opamps and U1 is the preamp, I found numerous replacement opamps but finally found one that really makes the most out of the unit. There's a toatal of 3 different opamps and one is for the preamp, one for the compressor and the others are either all for the eq section or dived between the eq and output.

I'm "thinking" that U2 is the compressor, U5 the output, U1 the preamp and U3&4 for the eq. However I have not found one sole on earth that can verify this. I'e aske guru Jim Williams and even he didn't know having not seen one of these little blue babies.

I can probably find a winning lottery ticket before I could find a schematic for this thing. It's really baffling me so I thought just maybe one of you folks have had 1st hand experience and give me the correct answer before I go completely bananas.

Anyone have any insight? All the links on the matter are dead so I'm going by info I found after a year of searching. There's also been several opamps used and I do know the final BLA one but just not sure the exact order of the chips.

I'll gladly share the opamps of choice if anyone can help me here. I don't have em in front of me or I'd post it now so I'll post later.

Thank you in advance for your help. A schematic would be a godsend if anyone is sitting on one.

Richard T Puncsak
Risson Amplifiers R&D
PMR Speakers R&D

Re: Bellari RP503 opamp positions & mods

Posted: Thu Jun 06, 2013 9:13 pm
by psycom
psycom wrote:

I've read BOTH and have never found a schematic.
What I meant by BOTH is I've seen articles that claim the one or the other is but I've not confirmed which is correct.

Sorry if was confusing. I went to public schools. Need I say more? :P

Posted: Wed Jun 19, 2013 9:24 am
by Voodoo Guru
Howdy Psycom,

Welcome to the Forum!!!

Unfortunately we don't have any information or schematics on the RP503.
Without actually having one to "backwards engineer" and see where the circuits are running to and fro, it's near impossible to say.

BLA was the only one that we know of that was modding them, but that was YEARS ago. They have since scrubbed their website of all that info.

We do know that when used in an RF Environment, that many many people have had RFI issues with them.

That's about all we know about it.

Take Care,