[sdiy] filter for noisy DC power supply

Richie Burnett rburnett at richieburnett.co.uk
Wed Oct 22 23:52:03 CEST 2014


Yeah, output ripple for a 6-pulse rectifier is 14%, and 12-pulse rectifier is only about 3%. The lack of DC link capacitance doesn't do much for the hold-up time of the power supply though if a few cycles of the mains supply suddenly go AWOL!!! 

-Richie,


---- gordonjcp at gjcp.net wrote ----

>On Wed, Oct 22, 2014 at 12:42:33PM -0700, David Griffith wrote:
>> The gizmo is a Behringer Microphono PP400 turntable preamp.  It has
>> unbalanced inputs and outputs. I haven't yet bought it.  On Amazon,
>> one of the reviewers says that it has a hum that he cured with a
>> simple circuit inline with the power supply.  I'm trying to figure
>> out what that circuit might be.
>
>Proper voltage regulator.  Smoothing only takes you so far.
>
>Incidentally, old (like, 1970s old) computer power supplies for minicomputers often drew three-phase power and had *no* smoothing capacitors at all.  The output of the rectifier was sufficiently smooth to feed directly into linear series regulators.
>
>-- 
>Gordonjcp MM0YEQ
>
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