Meter is a plus or minus 100 milliamp center null DC ammeter. This let's you center speaker balance in a stereo system. Change amplitude of AC source on left and note wave through ammeter.
Diodes are common 1N34, 1N34A, 1N46, 1N48, 1N51, 1N60, or equiv.
Adjust size of 270 ohm .5 Watt dropping resistors so you do not exceed range of ammeter or larger resistors if large power amplifier is used.
