High Current relays for speaker switching?

[Zero Cool]

Anybody have any favorites for relays for speaker switching?

I would like to upgrade the speaker protector relays in my amp. they are pretty small even with parralleled contacts. This is a 200+ Wpc @ 8 ohm amp so that is 5 amps at 8 ohms and at worst case thats 20 amps. granted that is not really continuous current etc.

what do you reccomend for some nice, good quality, last a lifetime type relays?


Zc

[imix500]

Mercury displacement type maybe?

[XEAGLEKEEPER]

mercury-wetted relays are for low voltage signal switching,
A mercury wetted relay is a form of reed relay in which the contacts are wetted with mercury. Such relays are used to switch low-voltage signals (one volt or less) because of its low contact resistance, or for high-speed counting and timing applications where the mercury eliminated contact bounce. Mercury wetted relays are position-sensitive and must be mounted vertically to work properly. Because of the toxicity and expense of liquid mercury, these relays are rarely specified for new equipment.

Not- rohs compliant in case you are a green-peace geek.

[imix500]

I have some that are good for 480v 40A, not exactly low voltage signal levels. They use a metal slug pulled down towards the coil into a pool of mercury. The displacement forces the mecury up to the contacts. They were very popular for industrial appliciations. They have of course been replaced by more eco/health friendly devices.

[XEAGLEKEEPER]

I think we are talking about two different types of relays.Yep just looked it up .They might work I'll bet they are pricey though.The F-15 test stations I worked with had alot of the wetted reed relays.I've never seen a displacement relay Ive seen lots or mercury switches.

Actually I think Zerocool could do just fine with 10-15A Omron PCmount IMO.

[imix500]

Indeed. Mercury's do a great job but have thier limitations. Omron, AB and Telemacanique make some darn good relays.

[andy_c]

There's a quote about relays from Doug Self's book that caught my eye. Apparently, certain types of relays introduce more distortion than the amplifier itself, but his description left me wondering exactly how to tell if the relay in question might have such a problem.

I'm wondering if someone with more experience with different relay configurations and constructions might be able to shed more light on this? I'm looking for a very beefy relay for a high-power amplifier but would like to avoid this problem like the plague. Here's the quote.

"A much more insidious - unexpected - form of non-linearity can occur if the relay is constructed so that its frame makes up part of the switched electrical circuit as well as the magnetic circuit. (This is not the case with the audio application relay discussed above.) A relay frame is made of soft iron, to prevent it becoming permanently magnetised, and this appears to present a non-linear resistance to a loudspeaker level signal, presumably due to magnetisation and saturation of the material. (It should be said at once that this is described by the manufacturer as a 'power relay' and is apparently not intended for audio use.) A typical example of this construction has massive contacts of silver/cadmium oxide, rated at 30A AC, which in themselves are linear. However, used as an amplifier output relay, this component generates more - much more - distortion than the power amplifier it is associated with."

[Zero Cool]

Hmm wow I have never heard of anyone using mercury relays for speakers? I wonder what effect the mercury would have on the sound if any? if it would for some odd semiconducting junction or something. has anyone heard of any major MFG's using those?

I wonder what Pass or Krell uses?


Zc

[imix500]

Heh, I can run one through the Audio Precision at work tomorrow. Might be interesting.

[Richard Ellis]

Check these out....www.gigavac.com lotsa different versions.
___________________________________Rick........... .