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Class D Switching Power Amplifiers and Power D/A conversion

removing hum (noob question)
removing hum (noob question)
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Old 15th May 2016, 10:43 PM   #1
lactose is offline lactose
diyAudio Member
Join Date: Sep 2015
Default removing hum (noob question)

I bought one of these:

2X50W Digital Amp Amplifier Board with Radiator TDA7492 D Class High Power Hot | eBay

It has no volume control; no big deal, I figured I'd control it on the source. I soldered a 3.5 jack to a board and the audio cable to it. It works, but when volume on the computer is turned to zero, you can hear a soft hum.

Would this be fixed with like a pot being used as a preamp? I have some 50k pots laying around, not sure if they'd work.
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Old 19th May 2016, 08:40 AM   #2
gwingn is offline gwingn  United Kingdom
diyAudio Member
Join Date: Mar 2016
It may do, but it very much depends on where the hum is coming from.
a) First make sure your wiring to the board is as short as possible and tightly twisted to minimise noise pickup.
b) DIsconnect the input and listen. if the hum is still there it is coming from the amp and nothing will help (short of modifying/redesigning the board).
c) If the hum is only there when your input is connected and the hum is at a constant level irrespective of computer volume setting then adding a pot will reduce the amplifier gain and hence the hum.
d) If it is like (c) but the hum increases with computer volume setting the pot won't help at all. You basically have a bad sound source and need a better one.
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