as above.
The relay contacts has X amps @ X VAC + Y amps @ y VDC in its specs
My guess is I need to be looking at VAC? thank you.
The relay contacts has X amps @ X VAC + Y amps @ y VDC in its specs
My guess is I need to be looking at VAC? thank you.
Y amps @ y VDC is more critical, in case of DC at output due to catastrophic failure. We don't want relay contacts wielded together due to lower current capability
e.g. for a LM3886 chipamp working at +/- 30VDC , 10 amps @30 VDC relay would be a bare minimum , anything above would that would be more suitable
You are right in your assumptions about VAC ratings , as music is AC
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DC at speaker output?
That is usually mV.
Multiply V x A =W, double it, use that as the minimum contact rating.
AC, not DC.
That is usually mV.
Multiply V x A =W, double it, use that as the minimum contact rating.
AC, not DC.
" DC at output due to catastrophic failure." ,you might have missed it as I was editing
Ahh, I missed that, yes.
And add a series capacitor for protection, the poster appears to be a novice?
And add a series capacitor for protection, the poster appears to be a novice?
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No. 20A at 50VDC should be more than enough. Although hard to find and quite expensive.
A 240vac relay will weld its contacts interrupting quite low DC currents, just not designed to cope with large DC.
You will need the DC rating to handle the event of an output transistor going short circuit. The reason you will want to interrupt that current is because your speakers will melt and cost a great deal more that a couple of transistors to replace.
A 240vac relay will weld its contacts interrupting quite low DC currents, just not designed to cope with large DC.
You will need the DC rating to handle the event of an output transistor going short circuit. The reason you will want to interrupt that current is because your speakers will melt and cost a great deal more that a couple of transistors to replace.
Find the relay needed, usually a 3A DC is 10A AC
Use a rating equal or more than power supply, should be enough.
As for volts, more than 100 or so, those are easier found than 50V.
Use a rating equal or more than power supply, should be enough.
As for volts, more than 100 or so, those are easier found than 50V.
He is trying to build a direct coupled amp using +/- bipolar supply, so no output DC blocking capacitor
You can also use the schematics of commercial amps to learn the circuit design and relay selection.
Special audio purpose relay (Out of stock but just to get idea)
https://shop.dadaelectronics.eu/loudspeaker-relay-24v-lr-24-amplimo-108462111.html
SSR used by @Bonsai in this speaker protection kit
https://www.diyaudio.com/community/members/ed-linssen.22792/
https://www.diyaudio.com/community/threads/output-relay-for-power-amp.212150/
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I don't think EMR's are a good idea in an audio amplifier. Under fault conditions, you can have 10's of volts DC and 10's of amps to break and relays do not like that. They also get pitting on the contacts, so there is a wear out mechanism to consider - solid state relays have none of that. I have a commercial amplifier and one of the tests is driving a load with 50ms pulses at 60A. The protection disconnects the speaker at >60A using SSR's. This test can be repeated ad infinitum - no EMR could handle that. There are a lot of good SSR speaker protection designs on the forum to choose from.
If you just want speaker muting and are not concerned about protecting speakers under fault conditions, then use a relay, but don't expect anything more.
Here is Michael Bean's design that got me going down the SSR route 10 yrs ago
This subject has been discussed on the forum in quite a few places. See here for the long discussion on the subject: -
https://www.diyaudio.com/community/threads/output-relays.191449/
YMMV
🙂
If you just want speaker muting and are not concerned about protecting speakers under fault conditions, then use a relay, but don't expect anything more.
Here is Michael Bean's design that got me going down the SSR route 10 yrs ago
This subject has been discussed on the forum in quite a few places. See here for the long discussion on the subject: -
https://www.diyaudio.com/community/threads/output-relays.191449/
YMMV
🙂
Too many commercial designs have relay problems due to the use of an unsuitable relay that goes high resistance after a few years. Others probably won't break a fault current if needed.
Bean counters trim too much
If you look at the OPs posts, he appears to be new to the field and is trying to build a design which I feel is complex for a first build.
So my advice was to study, as it were, rather than copy some design.
He has started a few threads here, most of the questions are basic, things we take for granted.
Please take that in mind when going through his threads.
So my advice was to study, as it were, rather than copy some design.
He has started a few threads here, most of the questions are basic, things we take for granted.
Please take that in mind when going through his threads.
