BBC OBA Type 8 type amplifier

 

OBA 8 amplifier and psu

The OBA/8 system was introduced in 1938. IntendedĀ for portable use with war in Europe looming, it was more lightweight then predecessors and utilised a pentode valve for the first time in British amplifier design.

The whole system, designed for self operation, consisted of two OBA/8 amplifiers (one on standby), a passive MX/18 mixer, LSU/1 loudspeaker and comms.

bbc-oba_8

Many units, particularly the MX/18 mixer, continued to find a use long after peace had been declared, in provincial studios and of course the Radiophonic Workshop.

eve-bbc-mx_18

Here is a picture of Daphne Oram with three such passive mixers, which utilised wire wound constant impedance attenuators (and an OBA/8 in the foreground).

daphne-oram-with-bbc-passive-mixers

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BBC Portable Attenuator

eve-bbc-portable-attenuator-patOne of a number of different attenuators designed by the BBC, the portable PAT/3A was intended for the test engineer in the field.

Extremely useful for ‘padding down’ the input of other fixed gain BBC equipment such as Type A and Type B valve amplifiers.

Note the screw terminals which were common on outside broadcast and field test equipment.