I have an exceptionally simple linear power supply used by a stereo LM3886 based amplifier I built a few months ago. Occasionally, I hear moderately load pops on the speakers and telltale sounds giving the impression a neighbour is using an electric drill. I know there is a specific filter for this, but I want to avoid using a 'death capacitor'. The usual filter consists of a voltage-dependent-resistor, VDR, with a voltage/current characteristic similar to a stretched 'N'. Two other capacitors are used but they are grounded at one end and the other two remaining ends connect to the mains' N and L terminals.
Can I effectively use a somewhat inefficient filter with resistors instead of two capacitors with one of them connected like the dreaded 'death capacitor'? I am attaching the circuit. My questions is about resistors R1, R2 and U1.
Can I effectively use a somewhat inefficient filter with resistors instead of two capacitors with one of them connected like the dreaded 'death capacitor'? I am attaching the circuit. My questions is about resistors R1, R2 and U1.
Using a ground may help you remove the unwanted interference.
If it is mains borne, a common mode choke and a metal box that is earthed should help.
If it is RF interference, the metal box should help if earthed correctly.
The best way is to remove the interference at source but that is probably not possible.
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If it is mains borne, a common mode choke and a metal box that is earthed should help.
If it is RF interference, the metal box should help if earthed correctly.
The best way is to remove the interference at source but that is probably not possible.
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The mains transformer has its iron core grounded. I will try to add an earth to the common terminal of the DC output and check whether it will make a difference. If not, I will try a common mode choke.JonSnell Electronic said:
Errata Corrige: The transformer's iron core is earthed. The DC part of the power supply is currently not earthed but floating.
I have to wonder whether the approach proposed isn't barking up the wrong tree. You can inadvertantly introduce mains noise if you're not super careful with ground routing, especially in the power supply section. So a thorough review of the entire ground layout is the first thing I'd suggest.
If possible, I would also suggest checking with inputs disconnected / shorted.
If possible, I would also suggest checking with inputs disconnected / shorted.