Bias-Adjustment

Bias probe for indirect measurement of quiescent bias current of a tube. The adapter is inserted between the tube and the socket and gets connected to a standard voltmeter (not included). Pay attention to the quality of the measuring device and sufficiently charged batteries!

The quiescent current is measured indirectly via a precision resistor integrated in the adapter. The advantages of this measuring method are harmless voltages at the measuring plugs, which are in the mV range, as well as short ways for the current, since it does not need to be fed through the measuring device (common practice with many measuring adapters of Far Eastern production). As a result, there is no risk of oscillations of the amplifier which can lead to possible damage of the tubes or the amplifier itself.