NOOB relay based switching questions.

[The Rotagilla]

I've been messing with relay based switching and have the code where I want it but have run into two issues that I could use input on.

1) On a couple of my builds (overdrive/distortion pedals) I'm getting what can best be described as a squeak or metallic ping that comes through my amp whenever the relay switches to the ON state. I'm pretty sure it's not the coding so could I have a microphonic part somewhere? The relay? The switch? Anyone else run across this and is there something I can do to quiet it?

2) I'm using the short shaft SPST momentary switches from Mammoth Electronics and sometimes the pedal doesn't switch smoothly/cleanly. For example...

- The circuit will be on but the LED is off and I have to hit the switch again.
- I'll go to turn the pedal on or off and will have to double tap it to work

This doesn't happen with every switch and it also doesn't happen every time so I'm thinking it's not a coding issue (but wanted to be sure). Does anyone else have experience with these switches and did you run into the same issue?

Thanks in advance.

[WormBoy]

Switching can cause noise in various ways, and relays will add another one: see http://www.geofex.com/article_folders/rmtswtch/rmtsw.htm (where also a nice solution is provided). In any case, it will be good to make sure that input and output of the board will be grounded when not in use, or at least that they have a path to ground (for the output that can be the volume pot, which is often threre already). Some designers have added a tempory muting function to their relay switch boards, which IMO is not the right way to go. Not sure if this is helpful in any way for your particular case, but I wanted to share these thoughts anyway  .

[Tuxedo3]

If I'm not mistaken this is from the relay.
The best current way to do this (that I know of) is to add a temporary mute through the use of a photoFET and some creative code on the microcontroller. Check out Coda-Effects explanation of photoFETs if you haven't already, it's the way to go.