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Old 5th August 2003, 07:55 PM   #1
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Default Preventing Thumping sound

Hi, anyone out there knows why I still get Thumping sound on my Loudspeakers, when I shut my amp, I've installed a speaker protection, but the thumping sound is still, there only when I turn off the amp. By the way I tapped on the amp's power supply for the speaker protection circuit, is that the reason.

Alvin
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Old 6th August 2003, 06:54 AM   #2
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Sounds like your output relay is not shutting down fast enough. You need it ot release as soon as the power switch is turned off. To do this, usually a transistor is coupled to the AC coming out of the transforner (before the bridge) through a diode and a small cap.

See the attached drawing. Your circuit is probably very different, but the idea of the fast shutoff on power down is the same and can be adapted very easily.
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Old 6th August 2003, 07:10 PM   #3
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Hi, do you mind if i post the speaker protection circuit, for you to have a look, you could then tell me how to do the mod, thanks for enlighting me on the topic, I'll have the schematics posted as soon as you agree. and thanks again.
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Old 6th August 2003, 08:04 PM   #4
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Post away!!
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Old 7th August 2003, 12:17 AM   #5
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Well, I don't know where you got this diagram from. It seems to me that this entire circuit introduces a hell of a lot of overspeech between Rch and Lch...
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Old 7th August 2003, 01:07 AM   #6
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With 22K resistors and a 100f cap going to gnd? Not a chance. The input is from the output of the amp.......

IIRC, this circuit is lifted from an old Pioneer or Kenwood (or was it a Marantz..??) Been too long. However, it doesn't do jack to the circuit except to protect from DC at the speaks.
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