Hello,
I am building Rod Elliots Speaker protection circuit to use in my leach amp and I am trying to choose a relay.
Below are two choices:
NTE R25-1D16-12
http://www.nteinc.com/relay_web/pdf/R25.pdf
or
Tyco's OZ series
http://relays.tycoelectronics.com/datasheets/OZ-OZF.pdf
Does anyone have any experience with this. Why is the NTE relay 8 dollars while the tyco is only 1? Are there different characteristics that I am not noticing (build quality?)
One final question for a different but related project, Mouser Electronics claims that this relay below is rated at 10A but the data sheet seems to say that its 5A at both 240V and 120V. Is it 10A or 5A at 120V? Can anybody tell?
http://relays.tycoelectronics.com/datasheets/OMI-2P.pdf
Any input on either topic would be greatly appreciated
Thanks in advance
Wes
I am building Rod Elliots Speaker protection circuit to use in my leach amp and I am trying to choose a relay.
Below are two choices:
NTE R25-1D16-12
http://www.nteinc.com/relay_web/pdf/R25.pdf
or
Tyco's OZ series
http://relays.tycoelectronics.com/datasheets/OZ-OZF.pdf
Does anyone have any experience with this. Why is the NTE relay 8 dollars while the tyco is only 1? Are there different characteristics that I am not noticing (build quality?)
One final question for a different but related project, Mouser Electronics claims that this relay below is rated at 10A but the data sheet seems to say that its 5A at both 240V and 120V. Is it 10A or 5A at 120V? Can anybody tell?
http://relays.tycoelectronics.com/datasheets/OMI-2P.pdf
Any input on either topic would be greatly appreciated
Thanks in advance
Wes
In my opinion the Tyco OZ series seems to be quite suitable.
I would go for the single make type OZ-SH-112LM1,294 (12V) or the 124LM1 (24V).
These have large QC tab connect terminals for attaching heavy gauge speaker wires and the contact area is large enough to handle the current while having low contact resistance. The only problem I have found using sealed relays for this application is that over time the contact resistance can become intermittently high. I have drilled a small hole through the case and sprayed in some good contact cleaner lubricant and this has fixed the problem. Preferably, a drop of Stabilant 22A on each contact is the way to go if you can get at the contact and can afford the stuff.
I would go for the single make type OZ-SH-112LM1,294 (12V) or the 124LM1 (24V).
These have large QC tab connect terminals for attaching heavy gauge speaker wires and the contact area is large enough to handle the current while having low contact resistance. The only problem I have found using sealed relays for this application is that over time the contact resistance can become intermittently high. I have drilled a small hole through the case and sprayed in some good contact cleaner lubricant and this has fixed the problem. Preferably, a drop of Stabilant 22A on each contact is the way to go if you can get at the contact and can afford the stuff.
Contact resistance
Only Tyco specs the contact resistance at 100 milliohms, too high for a speaker relay IMHO. Normally speaker relays would be mechanicaly large open frame units.
Also the NTE relay uses Cadmium over silver contacts, depending on how much you believe in exotic cables, this is probably not a good metal choice.
If the amplifier output is capacitor coupled the relay will not stop speaker thumps unless a resistor is wired to precharge the capacitor (to the other speaker leg) through the back contact of the relay.
A 100 watt amplifier can source 5 amps into 4 Ohms, probably double that during peaks. My home amplifier can source up to 40 amps so a bigger relay might be a wiser choice.
(rherber1) A relay that shows high contact resistance after a few uses (less than 1,000) is most likely underated, pits are being burned into the contacts. I think that after a while the cleaner trick will stop working. You may already be giving up some sound quality.
Only Tyco specs the contact resistance at 100 milliohms, too high for a speaker relay IMHO. Normally speaker relays would be mechanicaly large open frame units.
Also the NTE relay uses Cadmium over silver contacts, depending on how much you believe in exotic cables, this is probably not a good metal choice.
If the amplifier output is capacitor coupled the relay will not stop speaker thumps unless a resistor is wired to precharge the capacitor (to the other speaker leg) through the back contact of the relay.
A 100 watt amplifier can source 5 amps into 4 Ohms, probably double that during peaks. My home amplifier can source up to 40 amps so a bigger relay might be a wiser choice.
(rherber1) A relay that shows high contact resistance after a few uses (less than 1,000) is most likely underated, pits are being burned into the contacts. I think that after a while the cleaner trick will stop working. You may already be giving up some sound quality.
Re: Contact resistance
As I said above, lack of contact wetting current can lead to high contact resistance. The relays used where this symptom was evident were rated for 16 amps and had large area contacts made of low oxidation material. There was absolutely no sign of pitting. During operation as a speaker protection relay there is no dc current through the contacts and because they are only operated during switch-on and switch-off they don't actually get a lot of action to maintain a very low resistance.
I have mil spec reed relay elements, which as you know are hermetically sealed units, and after sitting unused for many years they have developed high contact resistance (usually less than 5 ohms). It usually takes a number of operations to get the resistance back to normal. All relay contacts rely upon frequent operation to produce the necessary rubbing action at the contact points to maintain low resistance.
hermanv said:
As I said above, lack of contact wetting current can lead to high contact resistance. The relays used where this symptom was evident were rated for 16 amps and had large area contacts made of low oxidation material. There was absolutely no sign of pitting. During operation as a speaker protection relay there is no dc current through the contacts and because they are only operated during switch-on and switch-off they don't actually get a lot of action to maintain a very low resistance.
I have mil spec reed relay elements, which as you know are hermetically sealed units, and after sitting unused for many years they have developed high contact resistance (usually less than 5 ohms). It usually takes a number of operations to get the resistance back to normal. All relay contacts rely upon frequent operation to produce the necessary rubbing action at the contact points to maintain low resistance.
Do the relay switches carry much current at the time they're switched? If not, you should be looking at gold contacts.
http://www.leachintl2.com/english/english2/vol6/properties/how4.htm
Wow, thanks for all the replies. I actually have had a lot on my plate lately so I just went with this relay:
G8P-1A4P-DC24 ( price around $3)
http://www.mouser.com/index.cfm?han...e_pcodeid=65309
based on a recommendation on another thread. Let me know what your oppinions are on this relay, and hopefully sometime soon I'll be able to let you know how it works out.
I figure I can upgrade some other time since these were only 4 bucks.
Thanks again,
Wes
G8P-1A4P-DC24 ( price around $3)
http://www.mouser.com/index.cfm?han...e_pcodeid=65309
based on a recommendation on another thread. Let me know what your oppinions are on this relay, and hopefully sometime soon I'll be able to let you know how it works out.
I figure I can upgrade some other time since these were only 4 bucks.
Thanks again,
Wes
In the best Soviet amplifier, which really sounded great even on heavy speakers, there was a relay of a copy of the M300 Leach International
General purpose relays are not suitable for high quality audio. Their frequency range is not standardized at all. And contact materials, along with silver, often contain tin oxide for arc resistance.
For example, the relay РЭС52 (W260, M 210 Leach International) is a sealed relay and is intended for switching electrical circuits of direct and alternating current with a frequency of up to 10,000 Hz.
General purpose relays are not suitable for high quality audio. Their frequency range is not standardized at all. And contact materials, along with silver, often contain tin oxide for arc resistance.
For example, the relay РЭС52 (W260, M 210 Leach International) is a sealed relay and is intended for switching electrical circuits of direct and alternating current with a frequency of up to 10,000 Hz.
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The contact resistance of a broken relay is unstable. But I'm sure measuring this resistance can be very fun, but most likely counterproductive. Why is OMRON 50-60 Hz general purpose better than a military grade high speed relay with standardized operation and efficient arc extinguishing even at 10 kHz?
Loudspeaker Protection and Muting
Loudspeaker Protection and Muting
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At a guess, a "general purpose" Omron would never be better than a military grade relay - given the testing most military/aerospace parts have to endure.
But if all you want is a speaker relay, I would take something decent like Omron over anything cheaper. I am sure there are equal quality brands, but of all the relays I have handled the Omron's (for general purpose use) always seem well made.
But if all you want is a speaker relay, I would take something decent like Omron over anything cheaper. I am sure there are equal quality brands, but of all the relays I have handled the Omron's (for general purpose use) always seem well made.
Nikolay Sukhov. A unique person by the way.
I would very much like to meet him.
Unique text from this person about audio. большое интервью с Николаем Суховым @4K_part1_ - YouTube
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You want phosphor-bronze or beryllium copper spring contacts in a relay for speaker protection ideally, as there's no magnetic distortion. With high current signals the ferromagnetic nature of steel can generate measurable distortion if its used in the signal path. Higher quality relays with lower contact resistance specs tend to not use steel for the contact springs as steel has more resistance.
Wes, you haven't identified what the DCV rail is on your ss amp, or the DC resistance of your speakers. Those 2 parameters give an initial estimate of prospective fault current, and source voltage driving an arc.
Those relays don't simply provide data on the number of max opening actions at rated DCV and max current, so it would make sense that at least one more series contact is included to support at least exceed the DCV of your amp, over and above the 24VDC datasheet rating.
Does your amp use unregulated filtered DC rails, or regulated? Is there any additional protection buried within the output stage circuitry of the amp (eg. PTC's, fuses, emitter ballast resistors)?
Those relays don't simply provide data on the number of max opening actions at rated DCV and max current, so it would make sense that at least one more series contact is included to support at least exceed the DCV of your amp, over and above the 24VDC datasheet rating.
Does your amp use unregulated filtered DC rails, or regulated? Is there any additional protection buried within the output stage circuitry of the amp (eg. PTC's, fuses, emitter ballast resistors)?
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