why does 12u7 need certain amount of gain to stop hum 120??? - diyAudio
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Old 15th October 2008, 10:54 PM   #1
prorms is offline prorms  United States
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Default why does 12u7 need certain amount of gain to stop hum 120???

why does 12ua7 need certain amount of gain to stop hum 120 hz ??
about 5% and up thd i do not hear the hum cycle .
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Old 16th October 2008, 04:33 AM   #2
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Location: Mar del Plata, a BIG seasonal getaway city, can see the Ocean from our residence.
Do you mean a 12AU7 right??
What circuit does it reside in?...I would guess the front end of an Amp or Pre-amp.
A 120 Hz audible hum is usually a power supply problem....Do you have a schematic we can all peruse??
______________________________________________Rick ..........
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