Speaker protection relay

[PH104]

Does anyone have any recommendations for relays to be used between output of a powewr amp and speaker?

Thanks

Phil

[Lisandro_P]

I built a relay protection board for my amp based on one of Rod Elliot's projects. I used a pair of goodsky ( http://www.goodsky.com/ ) 12v relays; these are rugged devices, relatively easy to get and reasonably cheap. Plus, they can be pcb mounted easily.

The devices i used were one GU-SS-112d (rated 30 amps at 20vdc) and one GZ-SS-112d (20 amps at 24vdc). The reason i used two different ones is i had a spare GZ from another circuit (a remote on/off switch, for the same amp), and when i went to bought a new one i preferred another with a higher amperage rating.

[PH104]

Lisandro - Thanks for the info. I was looking at a very similar relay by Omron, which is easier for me to get.

I saw recently the PRD series by Potter & Brumfield. Don't have the URL but enter the two words PRD Tyco into a Google search and you'll find it.) They are the only power relays I've seen that have solid silver contacts instead of silver-cadmium oxide. They are open and so would be easy to clean. I also read that the contacts slide against one another when closing so that also helps in wiping the surfaces for better contact. Trouble is they're BIG and expensive. I'll probably go the route you suggested since I don't think I have room in my amp chassis for them.

Thanks again

Phil

[Lisandro_P]

I had a chance to open a relay identical to the ones i'm using, and the contact area is some speciall alloy (gold i presume, but i really can't tell). The rest of the contact is rugged, mechanically that is. AND, they're sealed from factory, so tarnishing is not an issue.

If you can get pcb mount relays, that'd be great. Keep in mind my amp gives relatively low power (20w peak), so neither high voltages or currents are present (even if the supply happens to short ), so i'm kinda comfortable with it. The whole thing fitted into an 8 x 10 cm veroboard (two relays, two detection/triggering circuits and two vu-meters i'm adding to). Good luck!

[Samuel Jayaraj]

Omron's G5Z relays have a solid gold bar that makes the contacts and it is claimed by the manufacturer that it is a relay that least degrades the audio passing through.

Unless your entire signal chain exhibits a high sonic resolution, generally good quality relays should pose no problems. Other good choices would be Shrack, Fujitsu, Panasonic (National). Manufacturer sealed units are preferred to avoid tarnishing effects and higher amperage rating than minimum requirements would allow better dynamics.