DC Balance Adjustment

Use an O'scope to Bal DC Use your Ears to Bal DC

 


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Last Edited:
12-Sep-2004

 
The purpose of the DC Balance adjustment is to minimize the 120 Hz power supply ripple (noise) at the final output of the amplifier. The channel's phase-splitter tube is always removed during this test. This eliminates the negative feedback loop, permitting a more precise DC Balance adjustment. If you reach the end of your DC Balance adjustment before nulling out the 120 Hz hum, your output tubes are more than likely mis-matched.

For many years the H.H. Scott "factory-recommended" DC Balance procedure required using an oscilloscope connected across a load resistor on the speaker terminals. Others have reported good results using accurate AC multimeters.

Also included is the later factory procedure from a 222D Service Bulletin which recommends using your ears and speakers.

 

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