Engl Powerball E645 & Powerball 2 E645-2 High Gain Opion

These are adjustable bias amps and 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. These are available under the "Related Products" tab.

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

The video below explains the difference between bias probe types.