question about relay ratings for audio connections

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John G123

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Hello,

This will be crazy simple for most of you guys.

I'm trying to build a device that has 8 balanced audio inputs and outputs. When a 12v power supply is disconnected I want all of the audio lines to disconnect..

So I"m thinking I need 8 single pole or 4 dual pole relays that use 12v signal as a trigger. When 12v goes away the relays will open thus interrupting the hot signals of the balanced audio lines.

My question..

While shopping for these relays, I'm not seeing much that has a low enough rating for line level audio. Such as this signal relay from digi key https://www.digikey.com/en/products/detail/panasonic-electric-works/TXD2SA-12V-1-X/5871910 or this automotive relay https://www.digikey.com/en/products...8hEpHJgABAEF9INhwCqAnysAPKoALK46NgArjy4YqKiQA

Audio line level is usually around 1v and 10ma. If I use a relay that has a contact voltage of 12v and say 5amps would that be fine?

Cheers
 
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Don't worry about voltage rating. You just need to stay under that rating. A 120V relay will switch low level audio just fine. Or a 12V relay. or a 400V relay. Normally the low voltage relays will be smaller.
 
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The signal relay for digikey would be a good choice. It is sealed and has precious metal contacts, which will help with very small signals, as it reduces the likelihood of getting a bad contact due to contact oxidation.

Relays used with large voltages and currents are less likely to be affected by contact oxidation, as the larger voltage will break though slight surface oxidation. Therefore heavy-duty relays are will often have contacts more suited to large currents and resistance to arcing, and less suited to very low level signals.
 
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Yes, it would be best to use a relay with precious metal contacts rated for low level voltages and currents, as the higher rated relays may give problems with contact oxidation blocking the signal or causing signal noise due to high contact resistance.
 
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John - you mentioned opening one lead of a balanced [i assume professional] audio line, specifically the hot lead. this will leave the cold half connected to your input, presumably some sort of term resistor and diff op amp. My gut feel is to always treat both lines of a diff signal the same. i'm concerned about potential ground loops your product could be blamed for. idk your cost sensitivity, but a 2 pole relay opening both lines would ensure total isolation, and no hum or digital noise to irritate the audio engineers who'd spec your product. google ground lift xlr hum to see the magnitude of pro audio problems and the hoops people jump through.
 
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