Based on a smaller and more readily available valve, the ECC81 (or 6060 with lower microphony) the Type B became a familiar sight in many BBC studios across the land, including of course the Radiophonic Workshop. It is surprising that so few appear to have survived!
King of the roost was the AMC/5 microphone amplifier with fixed gain stages of 40 to 70dB. This had been developed from the earlier general purpose GPA/4 amplifier which was also used for microphone applications. Further down the gain chain was the C/9 line amplifier with 10dB in hand.
Consoles were passive, constant impedance, utilising Painton stud faders and in some instances with quadrant faders, such as at the Radiophonic Workshop as seen here in the capable hands of Delia Derbyshire.