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Old 18th August 2005, 12:24 PM   #1
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Default Looking for the best relay

Relays seem like a necessary evil on power-amp outputs if you want to prevent on/off thumps and protect the speakers from destructive DC off-set. Right? Or not right?

The right type to use, in my mind, would seem to be normally-open-contacts type. Then they would start open and only close when the time-constant is through and no DC is sensed.

Then the quality of the contact's metal and plating seems to be essential. I have never seen any article reviewing relays brands or types, which I think would be more important than resistors, capacitors, diodes or even cables.

Does that metal & plating affect sound quality? Which is best?

Most do not specify what they use, and many of them look dangerously like nickel plated metal, probably copper.

Silver, gold-plate and silver cadmium-oxide are also popular on those that do specify the contacts. Which would be best or what sould we look for?



Carlos
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Old 18th August 2005, 02:51 PM   #2
Leolabs is offline Leolabs  Malaysia
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Most branded stuff will do the job
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Old 18th August 2005, 03:19 PM   #3
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Quote:
I have never seen any article reviewing relays brands or types
There was a refence to a German magazine article comparing low signal relays once. A search within the relay attenuators thread will probably locate it.

High current relays seem even more problematic. It will be very interesting to compile some info on commercial high end amps - what percentage do use relays and what brands.

As far as i am concerned any effort to avoid a relay along the speaker output is justified.
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Old 18th August 2005, 03:21 PM   #4
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Originally posted by Leolabs
Most branded stuff will do the job

Doing the job is not enough. It has to be done properly, and by that I mean with as much quality as possible.

People care for nickel-plating on an RCA connector, and don't think on the metal to metal contact of a relay.


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Old 18th August 2005, 03:22 PM   #5
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Avoid AgCdO because they are intended for hard loads and not small current.

Avoid also goldplated because the gold is thin and torn away rather fast.

Hardsilver is good, AgNi.
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Old 18th August 2005, 05:02 PM   #6
jcx is online now jcx  United States
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sequenced/rate controlled power supply turn on could eliminate the need for a relay in some amps

another option might be for most of the feedback to come from the speaker side of the relay - only enough to establish the dc operaing point would be connected when the relay is open - this gives high dc gain when the relay is open so the offset would need trimming or servoing
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Old 18th August 2005, 05:23 PM   #7
jdoorn is offline jdoorn  Netherlands
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I used this one in my amplifier, two in parallel per channel to be sure.
They are from Amplimo, so I guess they are not available everywhere:
Click the image to open in full size.

This high quality relay can be used in combination with all the Amplimo power amplifiers. (1 relay per module is needed)
The module and loudspeaker will only be protected against overheating, high-frequency oscillations and DC on the output when a loudspeaker relay is used.

This unique AMPLIMO relay has been designed for switching loudspeakers. It contains a tungsten leading contact which can switch 100A (at 50V) loudspeaker current.
After closing, this contact is bridged by a gold plated silver contact, giving negligible contact resistance even at small currents.

When switching off the loudspeaker the silver contact opens before the tungsten contact.

The silver contact is protected by the tungsten contact, it never switches high currents, so it will not burn in. The gold-plating prevents oxidizing of the silver contact, so even years later the contact resistance is very low.
Coil voltage 24VDC nominal, at 70°C 20.4V to 33.5V.
coil resistance 900 ohm
Ambient temperature 20 to 70°C
Convenient for power amplifiers of 5 to 200W
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Old 18th August 2005, 05:23 PM   #8
Bensen is offline Bensen  Belgium
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Hi there,

Have you seen this relais:
http://www.vego.nl/amplimo/07/07.htm

It's a relais with a 100A rating NO contact, and right after is closes there closes a second smaller contact made of silver. This relais only costs 8.15€ here in Belgium.

Greetz
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Old 18th August 2005, 05:24 PM   #9
Bensen is offline Bensen  Belgium
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jdoorn,

You've beaten me.
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Old 18th August 2005, 05:28 PM   #10
jdoorn is offline jdoorn  Netherlands
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Quote:
Originally posted by Bensen
jdoorn,

You've beaten me.

But I forgot to add the URL !

Regards, Jan
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