Introducing a post overdrive tone circuit

[craigslee]

Hi amp guru's!,

I need some straightforward advice regarding a circuit I've hopefully attached. http://users.tpg.com.au/9876/Bench%20Circuit.JPG

I'm introducing a post overdrive tone circuit to my amp's overdrive signal. I have cut the pre master amps' PCB circuit path and need to confirm exactly where I introduce the input signal from my amp to the new circuit, and additionally where I output it.

I'm a little stumped because the diagram indicates what appears to me to be two possible input paths from the 13k Zsrc (one input path pre all three 100k pots (bass treble & mid) and another past the mid pot direct to R5.

Then the signal appears to be output from a point between both R4 & R5?

Is this correct?

Thanks in advance.

[defaced]

Input at the top, ground at the bottom, output between R4 and R5.

[craigslee]

Thanks heaps defaced.!!