It's a sorry day here at Rush Radio. We are dropping back to 'Valve of the Month' because it was becoming to erratic trying to maintain 'Valve of the Week'!
Anyway, here to welcome in the new regime, please give it up for the remarkably advanced for it's time, the Mazda QP230!
Introduced to the world in 1936, designed for battery operation, the QP230 is a directly heated double pentode for audio output use. It was designed to operate from a 2 volt accumulator filament supply and a 120 Volt HT battery. The two pentodes being designed to operate as a quiescent push pull output stage in class B1 . It's a veritable thermionic integrated circuit!
Let's look at the spec.
Standard British 7 pin base. Filament requires 0.3 amps at 2.0 volts.
Output power for cathode biased with 120V supply is a useful 0.85 watts for 5% THD, but can operate down to 100 volts of HT and still give 0.57 Watts of useful audio with a drive of 19 Volts pk-pk across the grids.
Optimum load impedance between 16 and 18kohms.
Anyway, here to welcome in the new regime, please give it up for the remarkably advanced for it's time, the Mazda QP230!
Introduced to the world in 1936, designed for battery operation, the QP230 is a directly heated double pentode for audio output use. It was designed to operate from a 2 volt accumulator filament supply and a 120 Volt HT battery. The two pentodes being designed to operate as a quiescent push pull output stage in class B1 . It's a veritable thermionic integrated circuit!
Let's look at the spec.
Standard British 7 pin base. Filament requires 0.3 amps at 2.0 volts.
Output power for cathode biased with 120V supply is a useful 0.85 watts for 5% THD, but can operate down to 100 volts of HT and still give 0.57 Watts of useful audio with a drive of 19 Volts pk-pk across the grids.
Optimum load impedance between 16 and 18kohms.
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