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Moving position of a relay in an amplifier circuit

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texaslonghorn

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I have an audio amp that has a circuit protection relay in the audio signal. The relay is closed for normal operation (so current to the coil only comes on in the event protection is needed). My question is this - I really want to move this circuit protection function out of the audio signal path and into the main power circuit. But it seems that if I simply move it, then the amp will shut down when the relay opens - but when power turns off, current to the coil will stop immediately and the amp will turn back on immediately. If the protection circuit is still triggered, then this on-off will simply continue to cycle. Obviously not what I want. Any suggestions? Is there a different type of relay - maybe a timer relay - that would solve this cycling problem? I am in the US, so mains are 120V 60Hz, relay coil voltage is 12vdc, amp PSU is running 63vdc, and .the existing relay is rated at 15A for 250VAC and 24vdc. Thanks for your help.
 

texaslonghorn

New Member
I will try to post the schematic. I want to move it because I don't think a relay in the audio signal path is optimum for the sound quality.
 

texaslonghorn

New Member
Here is the schematic. I am trying to move RY001 (shown near the outputs) to interrupt the DC power supply, but I want the relay coil trigger to remain as it is here.
 

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Nigel Goodwin

Super Moderator
Most Helpful Member
I will try to post the schematic. I want to move it because I don't think a relay in the audio signal path is optimum for the sound quality.

It makes absolutely no audible (or measureable) difference at all - leave it where it is, it's a vital protection for your speakers.

It's also normally OPEN, and only closes after a time delay, and if it's safe to do so - which is why you can't use it to switch the supply rails (which wouldn't do the job anyway).

If you're really obsessive about it, then simple short the relay contacts out, and let your speakers take their chances.
 

mneary

New Member
The relay keeps the speakers disconnected until the amplifier stabilizes. This delay is R010, C024, Q005, and Q006.

If you move the relay to the power supply, then the speakers won't be protected while the amplifier's bias levels are settling. Since the output stage is DC coupled, this could be anything, including one of the supply rails, far too much for the speakers.

If you do move the relay in the power supply, in a fault condition the speaker protection will be delayed by several seconds while the filter capacitors dump their charges into the poor speaker.
 
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