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A new output valve of high mutual conductance, no less than 10 mA/V., is announced by Marconi and Osram. This is the N41, and it is a pentode rated for 250 Volts anode and 200 Volts screen potentials, and when used with a bias resistance of 90 Ω it passes 32 mA anode current and 8 mA screen current, so that the grid bias is -3.6 Volts. The optimum load is 7,800Ω, and the heater consumes 2 Amperes at 4 Volts.
In view of the small input which it requires, the valve is particularly recommended for use with resistance coupling following a diode detector. The total grid to cathode resistance must not exceed 500,000 Ω, including the grid leak, any grid circuit decoupling resistance, and the grid stopper. This last component is advised by the makers in view of the high mutual conductance of the valve. The valve is fitted with at 7-pin base, and is priced at 18s. 6d.
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