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Heathkit AA-121 * PT hum * Coupling cap question

Posted by lektrik (A) on January 13, 2015 at 21:22:26

Got my re-capped Heathkit AA-121 up and running and it does sound clean and clear. I did notice at idle that there is an audible power transformer hum within four feet of the amp. Is this normal for this model? I know how to damp the transformer mechanically. Is there a way to electrically reduce this hum/vibration without dulling the amps performance?

I also thought the sound that the re-capped amp puts out is kinda thin, lacking bass and mid-bass. Could that be the small yellow Mallory or Illinois brand film caps the previous owner installed or could it be the .047uf value of the coupling caps?

I would like to get this amp sounding a bit better. Any help would be appreciated.

Larry D.

Edits: 01/13/15

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