Here the bias is adjusted with one hand, and little chance of being shocked or burned. It gives a quick indication of circuit health, and an indication of how much stored charge is left after the amp is turned off. It is always a good idea to have a meter on the B+ supply when powering up a new circuit. The large meters indicate the bias current for each channel and the small meter indicates the B+ supply voltage. Below you will see three meters connected into a Tubelab SE amplifier. This procedure makes electric shock very unlikely. The other hand (and the rest of your body) does not touch ANYTHING. When you have to make adjustments, then one hand, on an insulated screwdriver goes near the amplifier. No fingers (or any other body part) should be near the electricity. Hook them all up to the amplifier BEFORE turning on the power, and then simply stand a safe distance away, and flip the switch. Since these multimeters cost less than some of the parts used in this amplifier, it makes sense to use more than one.

Check bias guitar amp tubes