Yes that was another repeat of Rock and Roll Britannia which has quite a few vintage bits in it [suitable for vintage viewers
]. He was demonstrating the kind of Bass guitar available before the embargo on American Instruments was lifted [described as a "plank"
]. The Murphy was the model with VHF so early sixties. It caught my eye as amps were expensive and only available on HP at that time so it was fairly common for us to resort to an old valve radio-sometimes through an extension spkr as the mags had warnings about radio spkrs/output stages not taking the strain. Of course distortion became the name of the game anyway. It took him ages to get any sound out [after 40 years he said]. Seemed to be the usual dodgy jack plug/socket problem. I presume he was just going in through the pick up socket. I suppose the baffle sets are pretty close to an amp cabinet anyway.
Dave W