I have assembled the tester and tested the amp. It passed. However when I actually use it I can hear a buzzing sound from the amp and the speakers after a few seconds. Once I turn it off I hear a click and the noise stops.
I have double checked the connections and wires but can't see anything wrong.
I also tried removing the connection to PE (via the case which is the center of my star Earth) from the Audio In ground thinking that it could be causing the noise but that didn't help either.
Do you have any suggestions on what could be causing the noise?
I have double checked the connections and wires but can't see anything wrong.
I also tried removing the connection to PE (via the case which is the center of my star Earth) from the Audio In ground thinking that it could be causing the noise but that didn't help either.
Do you have any suggestions on what could be causing the noise?
Are you saying that the buzz starts a few seconds after switching on? If so, does it come with the music or later?
Yes, after switching the amp on.
It's not from the music. It starts even if there isn't any music on.
It's not from the music. It starts even if there isn't any music on.
Is there a speaker protection relay that is delaying the output for that few seconds after switch on?
I'm not sure but it seems that the relay is connected to the speakers on one side and to the protection IC (UPC1237) on the other side.
Also my transformer supplies 20 VAC while the minimum is 22 VAC. When I ordered it I expected such a difference to be fine. Would this be the case or could it be causing the speaker protection to turn on?
Also my transformer supplies 20 VAC while the minimum is 22 VAC. When I ordered it I expected such a difference to be fine. Would this be the case or could it be causing the speaker protection to turn on?
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