AWA PA1005 PA AMPLIFIER
Standard mic, PU (record player) and tone controls. Bass cut control on the rear, which is part of the negative feedback network. Designed as a 100v line system, perhaps intended as a portable system.
Slightly unusual in that this has a quad of 6AQ5 on the output stage. They’re described as a miniature 6V6 – they have the same specs at 250v, which is listed as the max voltage that these can handle. 12AX7s used for the preamp & phase inverter. The valves all tested OK.
The quad of 6AQ5s is cathode biased, the preamp valve heater was used as part of the resistance to ground for the 6AQ5s – some amps do this to provide a DC heater voltage, with the hope of reducing hum.
B+ is pretty low at around 250v
Output transformer
Turns ratio of 25.5 to 1 on the output marked as 15 ohm (between the 40 – 60 secondaries). Despite saying it’s suited to 15ohms, the calculations seem to work out better at 8ohms.
A pair of 6AQ5s at 250v wants to see 10kp-p, therefore a quad wants about 5k. 25.5 squared, times 8 = 5,202
Secondaries: Common, 40, 60, 120, 200, 315 & 630 ohms
It has quite a chunky mic input transformer: AWA 7XD51768, intended to match low impedance microphones to high-impedance triode grids.
Components are the same as what’s used in many other AWA amps – always good to see mustard caps.
