Ok, I've finally got round to etching the PCB, populating its and then testing the high pass filter.
The 50mm square enclosure was challenging - even fitting the two jack sockets was tricky, spacers on the outside. The tall caps and voltage doubler IC (for +/- 9v) fit at bottom right. All caps are either 10u or 100n for simplicity!
The PCB had to be carefully hacksawed(!) right to the edges of the tracks, I used soft faced vice jaws as a guide for the saw. Note one corner was too tight so I had to 'divert' the track:
Power LED just hard wired to the power connector and switched -ve via the ring of the input jack, so not on PCB. Need to put on a proper decoration - and the right way up!
First stick in a bottom B from my home-made frequency generator:
4V P-P, (actually no visible difference between in and out signals up to 6KHz - I didn't bother going higher):
As hoped, gain rapidly drops off below 31Hz.
This is 0.4V at 22Hz:
4.0 top 0.4 is gain of 0.1 that's exactly 20dB cut at 22Hz, which is pretty much excatly what the modelling software predicted. Kudos to Analog Devices!
The nay-sayers will say I should have made the cutoff higher, but it's (supposedly) 'infrasonic' signals below about 16Hz that are the main problem.