Applying C Battery

Radio Record, Volume III, Issue 14, 18 October 1929, Page 31

Applying C Battery

Method of Improving Tone [z is surprising the very large number of sets at present in use without a "C" battery. This small battery, the price: and upkeep of. which is almost negligible, is very frequently omitted by set designers and constructors. Its purpose is twofold :- 1. To improve the tone by impressing the voltage swing on the centre point of the valve’s curve. : 2. Bo reduce the drain of "B" battery current. A "OC" or grid bias battery is very connected up. Examine the last stage and it will be noticed that on one side of the transformer a wire goes to the valve socket (G) and another to the "A" negative. This is the offending wire. Break the connection and take it instead to the negative terminal of a suitable. battery. The positive of this battery is connected to "A-." The value of such a battery will depend upon the valve used in the last stage. A table showing the number of grid volts for various valves would involve a large amount of space, but the manufacturers mark. clearly on each carton the amount of bias to be applied, and this should be the value of the battery. If a complete battery with this voltage is not obtainable, either connect two in series or arrange the tappings so that the difference between the two is the voltage required. The last valve of a multi-valve set is not the only one that should be biased. It is preferable to put a small bias of 44 volts om the second audio valve. This is done in the same method as previously described. If your set is not biased, muke this small outlay in expense and you will be surprised with the remarkable improvement.