I figured there are a lot of very knowledgeable designers hanging around here so let me ask here. I have 200 wpc channel class A amps (Jungson) and the on/off switch cannot handle the spike in current when switched on, so the contacts melt together and it fails. My technician put in a relay to turn it on/off, which held out OK for a year or so, but now this blew up as well. We are looking for a higher amperage relay, but they tend to be noisy (hum), which is unacceptable. Is anyone aware of high current relay for audiophile application (i.e. very low noise) that I can use to build into my amps?
Relay for high current amp
- Thread starter edorr
- Start date
I had good experience with Magnecraft power relays - completely silent. As far as I remember VTL uses them in their big amplifiers slow start system.
http://www.serelays.com/library/magnecraft-catalogs/8501CT1003.pdf
Finding a relay is not the issue. Finding a high current one for audiophile (low noise) application is.
Edorr. It's not just the current it s the type of load it's pure inductive. And it sparks when it opens and this is what is burning it up. The relay you need must be for a Ac or dc motor. And the dc rating is more important then the Ac . As dc arches more so the relay will have to act fast and move a bigger distance . And silent relay I think would not be suitable . They must click to move fast and open fast. But no humming.
Al
Al
I'm pretty clueless about this stuff. If you have a specific recommendation for a particular relay I'll pass it on ti my technician...
We will need some extra information - what is the voltage you apply to the coil to control the relay?
A SS relay will not hum, and very few power relays I have seen/used hum unless they are defective. That said, you can always manage to get a bad one...
Some SS relays include a soft-start circuit to limit in-rush current. My old ARC amplifier also had a resistor that reduced in-rush current when you turned on the switch, then the relay inside would short it out after a brief delay. That sort of circuit should prevent relay destruction. You might suggest your tech add a soft-start circuit (usually just a series resistor) that the relay shorts. That would save wear and tear on the amp and the relay.
Most electronics supply houses carry a variety of relays but I don't have any specific recommendations. I am sure none of them say "audiophile rated", however, as that is not by and large their target market. Ask your tech to check out Allied, Digikey, Mouser, Newark, etc. I understand your, and his, dilemma -- there are hundreds of relays in the 20 to 40 A range. Except for the specific suggestions above, perhaps your tech could call or email one of the distributors and ask what they suggest? I would probably drop an email to all and see what they recommend.
Some SS relays include a soft-start circuit to limit in-rush current. My old ARC amplifier also had a resistor that reduced in-rush current when you turned on the switch, then the relay inside would short it out after a brief delay. That sort of circuit should prevent relay destruction. You might suggest your tech add a soft-start circuit (usually just a series resistor) that the relay shorts. That would save wear and tear on the amp and the relay.
Most electronics supply houses carry a variety of relays but I don't have any specific recommendations. I am sure none of them say "audiophile rated", however, as that is not by and large their target market. Ask your tech to check out Allied, Digikey, Mouser, Newark, etc. I understand your, and his, dilemma -- there are hundreds of relays in the 20 to 40 A range. Except for the specific suggestions above, perhaps your tech could call or email one of the distributors and ask what they suggest? I would probably drop an email to all and see what they recommend.
You could use a Zero crossing SSR and by pass with a mechanical Relay, there is few SSR out that have low noise emissions.
i.e.
http://www.root2.ltd.uk/index.html
And if they do switch on at Zero the inrush will not exceed there I2T rating, you could also make your own.
http://www.google.com/patents/EP1130777B1?cl=en
i.e.
http://www.root2.ltd.uk/index.html
And if they do switch on at Zero the inrush will not exceed there I2T rating, you could also make your own.
http://www.google.com/patents/EP1130777B1?cl=en
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For that type of duty it is not unusual to use a two pole switch and put the two poles in series (yes series), then when the switch opens you're asking the arc to jump two air gaps. As the switch opens it looks like the switch is opening at 2x the rate.
Cyclotronguy
Cyclotronguy
Thanks for bringing this back alive. I still have not solved my problem, and my relays are currently melted together and I switch my amps on and off by unplugging the powercords. I'll send this to my technician and see if he can engineer a solution.
I suggest using a snubber circuit across the switch contacts.
Something like a 100nF X2 type capacitor with a 100 Ohm resistor in series.
See https://www.buerklin.com/datenblaetter/D105640_TD.pdf?ch=30728 for a device integrating both components.
Your tech will know, when you show him...
It'll cost about 2 bucks plus the new switch.
The switch should survive you now...
Happy listening, Marin
Something like a 100nF X2 type capacitor with a 100 Ohm resistor in series.
See https://www.buerklin.com/datenblaetter/D105640_TD.pdf?ch=30728 for a device integrating both components.
Your tech will know, when you show him...
It'll cost about 2 bucks plus the new switch.
The switch should survive you now...
Happy listening, Marin
Thanks Marin,
My technician actually found very quiet 40A relays and will be putting these in. Since my existing relays are both toasted, your solution would be far more cost effective if my existing relays still worked, but since he has to reinstall new relays anyway getting the heavier duty ones will cost the same (most of the cost is labor). Thanks for looking into this though!
You may want to add the snubbers across the relay contacts then, will prolong their lives too!
The additional cost is next to nothing.
Enjoy...
The additional cost is next to nothing.
Enjoy...
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