Furman PQ-3 DIY

[caspercody]

Hello

I created a veroboard and made the Furman PQ3, and it worked on the first time powering up. Honestly I was shocked as this is a big board and lots of wiring.

I attached an image of the schematic I used. The input goes directly to pin 3 of the Gain pot, and exactly as shown on the attachment up to Op-amp J. I then have output from pin 7 to the 33uf (C12) and 11k to ground (R74) then output.

I did not add anything else on the schematic after this point.

I have a couple of questions:

What does Op-amp H and beyond do in the schematic (starting at R55 to the output jacks in the schematic)?

Does anyone have a better input and output to use besides the Op-amp H and Op-amp G (input jack and gain pot)?

 

[Blackboarcult]

IIRC that kind of contraption is from back when engineers wanted to make sure that an opamp would be able to drive low loads. This can also be found in the Intersound IVP preamp, or some early 80's Fender circuits. You could safely remove the transistor push-pull stage and use any decent opamp instead (not LM358). As for opamp G, you can make it noninverting, but then the circuit will be inverting at its output... But then you can make H noninverting too