Buffer question

[mozz]

Ok, bought a few pcb's for a buffer, 1 in 3 out, switchable phase. Transformers are mouser 10k/10k. Picture is of 1 channel so i don't post this guy's whole schematic (comes up on google search as almost first design so he really copied it anyway). I would usually use perf or scratch build but i have very limited space underneath a pedal board inside a box.

Guy was kind of reluctant to answer questions as i guess he didn't want to give out schematics or parts list until you bought it. Anyway my question, why is there a cap before the transformer? Now i am doing some searching and i see designs which don't have that. Also if it is needed, should the value be higher?

Kind of also thought it was weird he also used the second half of the TL072 (could have used a single per channel) when all you need to do is swap the primary for phase change?

And last question, this is probably going at the end of a pedal chain to drive a pair of amps. Since there is a third channel, and i am not concreted into layout or pedal order yet, and i do have a germanium fuzz and tonebender and such others, i have a old triad input transformer, 600 ohms to 50k, if i ran that, TL072 driving the transformer, and the 50k going to the fuzz input would that work and keep my cleanup on the fuzz? Fuzz outputs would be on a separate loop or something.
EDIT: Thinking about this running 50k into the fuzz would not let me get cleanup as the only thing that would change is input level, 50k would stay constant.

[PRR]

Very small stray DC can upset a transformer's core flux. (May not matter with these parts.)

A cap can limit lows which will distort a small transformer.

OTOH: normally we want 50-500 Ohms between an opamp and a complex load like a long line or a transformer. For similar reasons we may like 5k-30k in line with an opamp input. The phase-flip "could" be implemented with one opamp and a DPDT switch on a transformer winding. And this 100nFd cap may give a roll-off at 166Hz, discounting an octave of guitar. It's not a bad plan. Just not all-purpose.

[iainpunk]

Very small stray DC can upset a transformer's core flux.

which could cause magnetic clipping (core saturation), which can be a cool effect for drive pedals, not for buffers.

cheers