[sdiy] filter for noisy DC power supply

Michael E Caloroso mec.forumreader at gmail.com
Thu Oct 23 03:10:54 CEST 2014


I have encountered unregulated wallwarts.  These can cause 60hz hmmmm
in the audio.

MC

On 10/22/14, Richie Burnett <rburnett at richieburnett.co.uk> wrote:
> 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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