[sdiy] filter for noisy DC power supply

[gordonjcp at gjcp.net]

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