If you're a musician, you'll appreciate the sound of a properly biased tube amp.  Your wallet will appreciate the longer life you can get from your output tubes.  Our bias tools are easy to use, and provides a fast and accurate way to get the best sound from of your amp. Matched output tubes and proper bias are the ingredients to quality sound and longer tube life.   

A bias probe is inserted between an output tube and the amplifier. It monitors the total current flowing through the tube. Current is read on a digital voltmeter (DVM) and may then be easily adjusted to the required settings, which are provided in data tables in the Pilot's Manual.

Eurotubes™ Bias Probe™
For 8-pin power tubes such as 6L6 and EL34.   Requires separate digital volt-ohmmeter capable of reading current.  Complete with detailed instructions.



The Eurotubes™ Bias Probemay be used with any amplifier that provides for adjustable bias and uses 8-pin
power tubes with the cathode connection on pin 8, including:

EL-34 KT-66 KT-77 KT-88
6CA7 6L6 6V6 5881


Note:  Some amplifiers offer adjustable bias, and some do not.   The bias probe  will properly measure the cathode current on most all amplifiers, even if they do not offer a bias settings (certain Music Man amps are an exception).  You may wish to have certain fixed bias amps (such as Mesa Boogie®) modified by a technician to provide for bias adjustment.  Vintage blackface Fender® amps from the 1960's offer true bias adjustment.    Silverface Fender®s from the Fender® CBS era offer a bias balance  control, which balances the bias between the output tubes, but doesn't really offer  full bias adjustment.    Most Marshall® amps with 8-pin output tubes offered adjustable bias up through the 1990's.    For other brands of amplifiers, refer to the manufacturer's literature and specifications to see if the bias is adjustable.

 TUBE BIAS CALCULATOR (for push pull class AB1/AB2)

Tube Type

Plate Voltage

Power W

Plate Current mA
Cathode Current mA
+/- 10%
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