[sdiy] Power supply spike

[Mike]

> The power supply in my modular produces a large spike on the primary side
> when I switch it on so I need to have my monitor speakers switched off
> before I switch the modular on or off otherwise it results in a very loud
> plop.
>
> I've seen a lot of mains filters that filter incoming noise, but what do I
> do to keep these spikes from going out?

This is very dependent upon what is connected when you power up. Best
suggestion is an output muting circuit - a simple reed-relay and timer
circuit will do the job. There are a quite a few designs that can be adapted
from audio amps. I had them in one of my old mixers to avoid damage to the
PA in the event of a mains glitch. You could add 'power good' lights etc to
it as well - or even make it drop out on a supply fails, (like if you losy a
15 Volt rail).

On a similar topic, the recently posted idea of a seperate supply for logic
and indicator lamps/LEDs is a good one for keeping the background hash down.

Mike