122: Difference between revisions

For low noise performance and freedom from oscillations, the power supplies in the 122 are carefully bypassed.  The B+ supply of +135VDC comes in to the 122 through an octal connector.  The raw voltage coming in is used for the plate supply of the output (fourth) stage.  That voltage is low-pass filtered to produce voltage "C" which is used as the plate supply for the third stage.  Voltage "C" is low-pass filtered to produce voltage "B", the plate supply for the second stage.  Finally, voltage "B" is low-pass filtered to produce voltage "A", the plate supply for the first stage.  The result is that the sensitive first and second stages have well filtered plate supplies.  This technique is also seen in other gear from the era, such as the McIntosh MC-30 audio power amplifier.

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