Help with active feedback looper - please. Cool looking sorta.

[blackieNYC]

Very challenging. Must get someone to read this.   I need a little help here.  I have this REALLY cool Splitter/Mixer/FX Looper pedal working, perf boarded, and all wired into a box with a zillion knobs and switches. Scroll Down and check the two part schematic. Input driver, split point, three of Mr Keens polarity reversers serve as reversers and send output buffers. Two of the three(schematic link below) go to Send jacks, the third goes straight tothe 3-channel mixer, with a summing amp with gain followed by a booster with eq. Everything works great. Except one feature.  I want to include feedback, from output to either send. I have I my seen this on passive FB loopers before.
This gets a little complicated.  First, the three polarity reversers, and the dry channel, are going to be configured to reverse phase, to make up for the summing amp which inverts phase. This introduces a problem.  At first I added a 500k pot (no ground) from the output to each send. This is how the passive I mean loopers work.  A switch is there to stop leakage.  I tested with a delay set to single repeat, and with the passive circuit feedback control I was able to get some multiples, but, as I turned up the feedback control things got quieter. Because the feedback loop has only one phase reverser, and cancellation occurs. ( the summer amp. The reverser on each send split is outside the feedback loop.  Odd number of reversals, final output phase is inverted)
I want to be able to put this thing into oscillation with the delay, and have plenty of FB when i put other pedals in the loops. So, with thing built already and past the point of complete redesign, I decided to add a polarity reverser  and a gain stage to the feedback loop itself. This part of the circuit is on the breadboard, wired int o the pedal.  And it is not working.  The circuit ( shown in the circle) is working- I don't know how to insert it between an output point and a send point.  It reverses phase, and so does the summer amp, so the feedback loop should be in phase with itself and build up into multiple repeats. It doesn't. I have tried inserting the circled reverser/ gain stage into the path in several places.  When I do, I get some varied results but basically the output of the inserted circuit drops 10-15 dB, FWIW, but primarily - I haven't achieved feedback. The multiples never show up in the echo. I've even brought the feedback circuit output into the 2nd return, hoping to find the echoes there.  Can anyone see a way to insert this inverting gain circuit into this pedal? Thanks for reading
Two photos- the input splitter half, and the mixer output half with output circuit, including a drawing of the feedback circuit to be interested, if possible. Some details are left out- ther are rc filters on the sends, fully bypassed with switches.
Please take a look.  Soon I'll show you how cool this thing actually looks. Thanks so much.  Ok, got the schematic photo going:


     

[blackieNYC]

It has many many holes.

[kaycee]

I can't help, but I am impressed with the build, looks like a synth module!

[duck_arse]

I don't think I can help either, but.

in your circle, you have a 3u3 input cap followed by 91k to ground, but with another resistor to Vb connected at the same point. I think the 91k should be on the dod250 side of the cap, yes?

[blackieNYC]

in your circle, you have a 3u3 input cap followed by 91k to ground, but with another resistor to Vb connected at the same point. I think the 91k should be on the dod250 side of the cap, yes?

Hmm.  Must be a leftover from when the DOD circuit was freestanding and in need of a pull down?  Thanks- ill try that. But my Vbias isn't dropping due to the resistor.  Maybe the AC is. 

I confess- I have access to a drill press at work. And the board is perf wired point to point. Expect no photos of the solder side.