earthing painted metal chassis (buzz + safety) - Page 2

scott17 · 11th February 2012, 04:43 PM

Sounds like something is amiss with the circuit ground. It seems like you might be getting the signal ground by way of the input cable ground from the source device. When you disconnect the inputs it loses the ground connection. By the way, does it buzz with only one input disconnected or do you have to disconnect both channels.

lost eden · 13th February 2012, 01:26 PM

The amp is built as 2 entirely separate monoblocks. Thus if I disconnect the RCA from the right channel, then the right channel will buzz, if I disconnect the RCA from the left channel then the left channel will buzz (I tested this last night just to make sure!).

simon7000 · 13th February 2012, 03:17 PM

Try removing the AC mains connection from one amplifier and see if the active channel still buzzes. If it does, on that channel reverse the transformer primary winding connections. See if the buzz gets louder. Reconnect the primary leads for the lowest buzz. (Duh, of course you knew that.) Now reconnect the other side and check for which way the primary windings give the lowest noise.

If all else fails place a 100K resistor at the input jack from hot to ground.

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11th February 2012, 04:43 PM	#11
scott17 diyAudio Member Join Date: Aug 2009 Location: JFK	Sounds like something is amiss with the circuit ground. It seems like you might be getting the signal ground by way of the input cable ground from the source device. When you disconnect the inputs it loses the ground connection. By the way, does it buzz with only one input disconnected or do you have to disconnect both channels.

13th February 2012, 01:26 PM	#12
lost eden diyAudio Member Join Date: Sep 2009	The amp is built as 2 entirely separate monoblocks. Thus if I disconnect the RCA from the right channel, then the right channel will buzz, if I disconnect the RCA from the left channel then the left channel will buzz (I tested this last night just to make sure!).

13th February 2012, 03:17 PM	#13
simon7000 diyAudio Member Join Date: Nov 2008 Location: Oakmont PA	Try removing the AC mains connection from one amplifier and see if the active channel still buzzes. If it does, on that channel reverse the transformer primary winding connections. See if the buzz gets louder. Reconnect the primary leads for the lowest buzz. (Duh, of course you knew that.) Now reconnect the other side and check for which way the primary windings give the lowest noise. If all else fails place a 100K resistor at the input jack from hot to ground.