Kit builds one bias probe to be used with a multimeter

Mojo direct reading panel mount lighted current meter. These meters will add output section biasing, balancing and class to any tube amp project or build. Place them in series with your output tube cathode to ground on both sides of a push pull amp and get direct confirmation of current. Measures 0-100mA so measuring a single output tube per meter makes the most sense, switching can be added to toggle the meter between tubes. Direct measuring simplifies connection but since shorted tubes can damage the meter fusing is recommended within the cathode circuit. If 2 meters are used a balance circuit like the drawing below is suggested.

DCMA Meter Model
Bias Balance Model


Internal bulb is 12V 50ma.

TAD Bias Master EL84 Adapter / 2

Measures the current of 4x any standard base octal power tubes (6L6, EL34, 6550, etc). Measures EL84 current with optional noval proble set. See item #4152010 Bias Master EL84 Adapter. View our Tube Biasing Tutorial online.