My installation of this, as per diagram, reduced the 'pop' but didn't eliminate it. A fresh look at the diagram, with eyes accustomed to audio amps with differential inputs just like this, led me to the conclusion, borne out in practice, that Pin 3 is the best mute point. I don't know what currents flow, but with both pins 2 and 3 'earthed' what can go wrong? Pin 7 to earth gave just as much 'pop', if not more! Earlier trial by shorting the volume control wiper to 'earthy' side produced all sorts of squeals - track and lead capacitances playing tricks? Anyhow, my version, on veroboard floating loose on a couple of inches of ribbon cable wire, is quite stable.
The Vero module is dual-purpose: along with the anti-pop there is a 'super-cap', 100uF with an emitter follower to feed Q16 by 'tombstoning' R113. Complete elimination of tuning-click hash. All this on 0.6" x 0.6". All components sourced from a scrapped PC PSU (which also provided a toroid for a balun :) ). Photo(s) to follow if anyone's interested ...
Earlier reference to audio helped with this construction too. Years back (70's?) I created a stereo amp with Sanken 20W module power amps and preamp built around 4 discrete-component op-amps (essentially 741's), and I squeezed each of these into not much more 'real estate' than this latest effort. Memory dims, but if they were more than 1" square it wasn't by much. Circumstance forced disposal: some lucky audiophile got the ultimate quality there! :)
