DC Offset readings?

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robgilmo

Member
2011-08-03 12:56 pm
Is this a normal reading? I set my multimeter to DCV 200m and let the amp sit for a few minutes with no speakers attached.
I got these readings
Left = - 09.2
Right = - 11.5

That seem a bit high to me, the amp is a Marantz PM6010 KIs.

The reason I ask is I can hear a hum when using headphones, on every source and not effected by volume. I can also hear a slight hum from the transformer when I get close to it with my ear.
 
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tomchr

Member
Paid Member
2009-02-11 12:58 am
Calgary
www.neurochrome.com
A few mV of offset on the output of a power amp is pretty normal.

Hum is AC and not affected by the few mV of DC on the output. Headphones tend to be rather sensitive so if there's any ripple on the power supply in the amp, or any coupling between the supply and the input stages of the amp you'll probably have a little bit of hum in the headphones.

~Tom
 
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