Calibrations And Adjustments - Classe Audio DR 25 User Manual

Calibrations and Adjustments

Bias adjustment:
Note: Bias adjustment should be made without any load connected to the amplifier's output, and no signal
connected to the amplifier's input.
1. Connect a multimeter to one of the emitter resistor leads and set the multimeter to mV scale.
2. Turn trimpot R13 counterclockwise until it reaches 0 . A click should be heard.
3. Turn on amplifier, and let it warm up for 15 minutes on idle.
4. Adjust trimpot R13 to get a 14mV reading.
5. Let the amplifier warm up for a 24 hours period with signal and load.
6. Remove signal and load, and reconnect the multimeter, setted to mV scale, to one of the emitter
resistor leads.
7. Readjust R13 to 22mV
DC offset:
Note: DC offset adjustment should be made without any load connected to the amplifier's output, and no
signal connected to the amplifier's input.
1. Connect a multimeter to the output binding posts and set the multimeter to mV scale.
2. Adjust trimpot R4 in order to reach 0mV. It is easier to turn the trimpot ½ turn at a time, and let DC
offset stabilize in order to get an accurate reading.
3. A tolerance of ± 1mV is acceptable.
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