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Old 6th Dec 2022, 10:26 pm   #30
Jolly 7
Octode
 
Join Date: Feb 2018
Location: Southampton, Hampshire, UK.
Posts: 1,063
Default Re: Noise issue with DIY variable PSU and audio amplifier

[QUOTE=joebog1;1519095]Thanks Lucien, I said this in post 3 or 4.

Quote:
Originally Posted by joebog1 View Post
Sounds to me like its coupling back through your earth and negative of the power supply. I am assuming of course that they are common to the single transfomer and rectifier, audio amp, and power supply.

You could fix that by using a transfomer on the input of the audio amp. It will need to be primary and secondary NOT an auto transfomer.


Cheers

Joe
Hi Joe..I tried an old audio input transformer, similar to an LT700, with isolated primary and secondary windings, but that did not get rid of the issue. I fed the audio signal to the primary and connected the secondary to the amplifier's signal input and ground.
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