Help choosing relay

[Buffalo Tom]

Im building a remote vibrato/reverb on/off switch for vintage Fender Super Reverb amp. Its a box with RCA contacts connected to the amplifiers switching jacks and then a TRS jack for the remote switching. I will use two relays, one for each function.

I will replicate this but with two relays.


Can I use a small signal relay like Fujitsu SY-9-K


https://www.mouser.se/datasheet/2/164/sy-472370.pdf

Or do I need something beefier? What kind of current/voltage am I switching? In vintage amps like this the effect switching circuit is a part of the audio path that's why I'm concerned.

[FiveseveN]

What kind of current/voltage am I switching?

Hardly any. Even the tiniest relays can handle it.

[PRR]

> What kind of current/voltage am I switching?

Reverb return is often 10 milliVolts at 1Meg or 0.01 microAmps.

Trem osc in a tube amp may have 50V at a Meg or so, 50 microAmps.

But why use a relay? Fender ran 15 or 20 foot cords on those pedals. The reverb side does need to be shielded, true. But prime signal does not flow in the switch wires, only boing and subsonic.

The real problem at these VERY low levels is tarnish. 120V even 5V will burn through switch tarnish. 10mV won't. You know sometimes you have to twist/wiggle your guitar plug for a good signal? Same tarnish. Those particular switches (Carling) that Fender used are really for large lamps and vacuum cleaners, but experience has shown that they smack their contacts enough to scrub tarnish. There are "dry contact" or "telephony" relays intended for very small audio, formerly with Gold contacts or sealed capsules (they seem to have newer alloys today).

[Buffalo Tom]

Hi Paul. Thanks for explaining the volt/current. Im building this for a studio and they need to control the effect switching from the control room.. Its 30 meter cable going into the wall patch-box and the switching is done with the amp switch function from a larger RJM switching rack. The best solution was to have short RCA cables from my switching box then a long TRS remote switch cable that I don't have to worry about.