Relay pop?

[JimRayden]

Should I be afraid of pops when using a tiny relay for true bypass? Could the current thrust through the coil bleed into the signal path, just as with LED in some cases.

I'm planning to use another relay for the LED simply because I can't find one with 3 poles and to at least avoid the LED-current-pop.

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Jimbo

[R.G.]

Relays can pop for the same reason as LEDs, that being ground current. You solve this with careful wiring to keep the ground current - and power supply current for that matter - out of the supply/ground path of the active circuits.

Relays can also pop because there is a capacitance between the coil and the metal contacts that carry the audio signal. The capacitance is small, but there, and the voltages on the coil are big and fast, so you can couple some of the coil drive and release transient in. You stop this one by either shielding the contacts (but the manufacturer has to do this one) or by slowing down the edge of the coil voltage.

Slowing down the edge of the coil voltage usually also slows down the edge of the coil current, and may be a solution to the current pop as well.

It all depends on the details: how much current the coil pulls, where the current flows, how much capacitance from coil to audio path, how fast the current and voltage edges.

All of this is in the articles on relays at GEO.

[TELEFUNKON]

don`t forget the diode across the coil!

[JimRayden]

Thanks, RG. Useful as always. I did remember reading about the relay stuff somewhere, thanks for pointing out it was GEO.

don`t forget the diode across the coil!

Don't worry, I won't 

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Jimbo