gecophone bc2580 bc2582 vintage radio wireless matching amplifier grid leak detector variometer museum vintage gec reactance reaction

This is the GECoPHONE two valve  LF amplifier model BC2580, built by GEC (UK) in 1922. It bears the BBC/PMG stamp and GPO Registration No. 3360.

This amplifier was designed to accompany the GECoPHONE BC2001 2 valve receiver, which would normally have been stood on top of the amplifier and linked to it by means of a kit of cables BC2582 that was available separately (see leaflet below). These cables linked the HT supply from the receiver to the amplifier and also routed the LT supply via the amplifier up to the receiver.

Housed in a polished mahogany cabinet with lift up lid, the amplifier has an ebonite front panel with the following controls (left to right): Valve No. 1 filament rheostat; Multi-position selector switch; Valve No. 2 filament rheostat. The selector switch is an impressive 8PCO device that allows the user to select between 'OFF', '0', '1' ,'2'. The numbered positions refer to the number of valves that could be brought into operation. In the '0' position the input from the BC2001 receiver was routed straight through to the output terminals. In the 'OFF' position the LT supply to the amplifier and receiver and the HT supply from the BC2001 receiver are turned off.

An interior view of the amplifier is shown below. The two valves shown date from c. 1928.

 

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The design is a simple 2 stage transformer coupled triode amplifier with provision for grid bias. The two filament rheostats and the 8PCO switch are clearly visible on the front panel. Just below the 8PCO switch is a 2mF HT decoupling capacitor. The device protruding through the left side-panel just behind valve no. 1 is a switch that allows the output to be routed to headphones alone or to both headphones and loudspeaker. The condition of the interior tends to indicate that, apart from the two 'modern' valves, the amplifier has not been touched since it was made in c. 1922.

I have not yet traced the circuit but eventually I will reproduce it on this page. In the meantime, here is a contemporary sales leaflet for this amplifier.    

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On the front page of the leaflet is shown a GECoPHONE horn loudspeaker. I have one of these loudspeakers in the museum and you can see a picture of it by clicking on the following link: GECoPHONE horn loudspeaker .

 

Copyright 2001, 2002 Lorne Clark