Diamond Spitfire II Standard Retube Kit

These are adjustable bias amps. All you need to check and adjust the bias is a bias probe and a Multimeter, or our all-in-one Eurotubes "Pro One" bias probe that reads both the plate current and the plate voltage simultaneously. The E34L's, EL34 II's, EL34's, KT77's and 6CA7's all bias the same.

You can use the Generic bias video we did on a Marshall 800 and the procedure is the same.

The video below explains the difference between bias probe types.