The BiasTester™ (mV) Version is an easy-to-use inline adapter that is plugged in between the amplifier and output power tube so the current flowing through the tube can be monitored. And available with plate voltage switch option - BiasTester-MPD.

There is an optimum current range for a correctly biased amplifier. Most amplifiers have a bias control adjustment to compensate for variation found among power tube manufacturers and their specifications. The benefits of a properly biased amplifier are maximum tube life and great tube tone.

This probe has a 1 Ohm shunt resistor which works as a simple current-to-voltage converter. This means that a 35 mV multimeter reading coresponds to 35 mA tube current. This Tester can be used with any standard multimeter that has a 200 mV DC voltage scale. Built very durable with careful detail given to construction with only the best quality parts.

FEATURES Quality US made phenolic socket and 8-pin base. Excellent cable strain relief to prevent pullout and twist at probe. 1-Ohm 1% tolerance power shunt resistor. Cathode Current Output: 1mV/mA DC. 24 inch length double insulated cable. Standard banana plug connector. Typical multimeter Input Range - 200 mV DC. With Plate Voltage Switch Option Shown Left Photo Plate Voltage Output: 1mV/V DC. Plate Voltage Measurement Error Typically< 1% Sealed miniature qualtity toggle switch. Switch mounted on sturdy high impact A/B instrument case.

The Bias Tester™ works with any musical instrument or hi-fidelity audio amplifier that uses the following tubes: 6L6, 6V6, 5881, EL34, EL37, 6550, 7027, 5932, 6CA7, KT-66, KT-77, KT-88, 7184, 7D11, 12E13, 1622, 5871, 7581, 7408, and more!! This probe measures the cathode current on pin 8 of the tube.