BBC Type B equipment

eve-bbc-type-b-amplifierBBC Type B modular equipment was introduced in the mid 1950s, to replace the larger and more expensive post war Type A installations.

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.

eve-bbc-type-b-installationAmplifiers were attached to specially designed frames, held in standard BBC issue 19″ racks.

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.


One thought on “BBC Type B equipment

  1. The C/9 was a distribution amplifier at the end of the transmission chain and had an input impedance of 50Kohm, its gain was 14.4db with an output impedance of 126 ohms. It could be used with an output pad to give 600ohms 0db level for distribution or through a transformer to give 0db at 5 ohms for ring main distribution. In Broadcasting house in the 70s I remember they modified them to give 75 ohm for longer cable runs without HF attenuation. 600 ohm runs lose HF after about 200 metres.

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