[sdiy] Module power - regulated or filtered (passively)?

[Neil Johnson]

Brian wrote:
> Personally, I would not assume that a series resistor was intended as “protection.”

Indeed not, unless you're using fusible resistors.

> Since all integrated circuits should have a bypass capacitor, then a series resistor in front of that is going to create an RC filter. I would assume that the RC filter was intended, and the “protection” was merely a partial side-effect.

Bypass/decoupling capacitors have a very different role to play than a
series low-pass filter.  For one thing the values of decoupling caps
tend to be much smaller: a 22R series resistor and a 100nF decoupling
capacitor have a -3dB point around 72kHz - way above audio and no help
to combat falling PSRR.

Pete wrote:
> > The problem I have with the 10R solution is that if it's a VCO and it draws any significant current *and* uses the rails for reference (which a lot of those using this method seem to do), it can lead to an unstable VCO.  It doesn't take much to be audible, and I have encountered this with "real" designs in the DIY space.

When the cost of a ref diode is cents, why not do the right thing?  *shrug*

Neil