Noise and Hum in audio Circuits
i currently have a car stereo set that i use as an amplifier in my living room. but my main problem is that i a lot of noise hum.
post by FP
Ensure that the power supply has a full wave or bridge rectifier. If power supply transformer is say 12-0-12 two diodes must be there and a center tap ground OR If a square or round bridge is used with four leads or four diodes, then it is fine. Half wave rectification or a blown or leaky diode can cause this problem. Put all the filter caps you want and add a series choke as well the better the power supply the audio will be good.
The power supply transformer rating - voltage and current both may need to be boosted. Some very low budget transformers do not use CR-GO (or CR-NGO ?) plates for lamination (i think it is Cold Rolled Grain Oriented ). They use plain thick metal iron plates without coating and hence hysteresis and eddy current both cause problems.
Then you have ground loop hum and noise of semiconductors, the speaker ground and amplifier ground carry current and they should be directly connected to power supply ground, These you can understand by looking at these pages......
hut.fi/Misc/Electronics/docs/groundloop
sound.westhost.com/noise.htm
educypedia--audio.htm
channld.com/hum.html
i am only aware of Philips transistor based designs used 20 years back, but the above links have up to date info,
delabs