Understanding Pythagoras op amp set up

[eatswires]

I'm playing around with the Pythagorus schematic and trying out a few ideas for modifications, namely some additional layers of splitting and blending with other signals. https://docs.pedalpcb.com/project/Pythagoras.pdf

Is this description generally an accurate understanding of everything going on with the two TL072s?

IC 1.1 - High impedance input buffer, ready to be split into a dry and a wet signal to be blended back later

IC 5.2 - Another non-inverting buffer to bring the gain back up on the wet signal after going through the fv-1

IC 1.2 - Summing op amp stage for blending wet and try signals, also volume control via the feedback

IC 5.1 - Uses the last op amp slot from the second TL072 to to flip the phase back form the previous inverting amplifier and do a bit more conditioning before output.

Am I missing anything? Way off anywhere?

I'm wondering if it's viable to mess around with those last two stages to turn one into another split stage and the second into a blend and volume stage, or whether it's time for TL072 number three haha.

Thanks!

 

[YourGuitarist]

That sounds about right.

IC 5.2 is a buffer but it isn't providing any gain. The passive components before it form a bandpass. Possibly to remove some digital noise/distortion. That buffer is most likely there to separate the filtering preceding it and the output impedance of the FV-1 from interacting with the input impedance for the inverting summer that is IC1.2.

Increasing C12 will form a low pass that changes frequency with volume. Increasing C13 will form a static low pass.

You could look at adding some hard clipping diodes preceding IC1.1 to then add clean gain after with IC1.1 to help with noise but you'd have to be careful about harmonics generated that can be folded back down into LF aliasing. I would increase C4 to lower its corner frequency if so.

 

[eatswires]

That buffer is most likely there to separate the filtering preceding it and the output impedance of the FV-1 from interacting with the input impedance for the inverting summer that is IC1.2.

I see! I'm currently learning a lot about various ways to use op amps, really appreciate the clarification!

 

[YourGuitarist]

There's a great set of tutorials on op-amps by electronics tutorials on the web. For op-amp EQs, check out Elliot sound products.

 

[eatswires]

Great resources!