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DIY For Audio
DIY amplifier making popping sound on speakers when switching OFF
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<blockquote data-quote="Steerpike" data-source="post: 877579" data-attributes="member: 807"><p>The root of the "problem" is that the main power supply reservoir capacitors retain charge for several seconds after AC mains is interrupted, and this prevents the muting/protection relay from dropping out the instant (a few milliseconds) after the mains is switched off.</p><p></p><p>You either need to power the relay drive circuit from its own power source - with minimal or no capacitors, so the voltage goes to zero very very fast, OR you need a sense line that monitors the AC of the transformer (not the DC) and opens the relay the moment the AC voltage drops.</p><p></p><p>A transformer - technically - does continue to deliver power after the primary current is interrupted: energy is stored in the magnetic field, which takes time to decay (this is the operating principle of car ignition systems, and CRT TV deflection coils). But this magnetic field decay is very, very quick in comparison to the charge stored in the main reservoir capacitors. If the capacitors are large, they can run the amp at low power for minutes after switch off.</p></blockquote><p></p>
[QUOTE="Steerpike, post: 877579, member: 807"] The root of the "problem" is that the main power supply reservoir capacitors retain charge for several seconds after AC mains is interrupted, and this prevents the muting/protection relay from dropping out the instant (a few milliseconds) after the mains is switched off. You either need to power the relay drive circuit from its own power source - with minimal or no capacitors, so the voltage goes to zero very very fast, OR you need a sense line that monitors the AC of the transformer (not the DC) and opens the relay the moment the AC voltage drops. A transformer - technically - does continue to deliver power after the primary current is interrupted: energy is stored in the magnetic field, which takes time to decay (this is the operating principle of car ignition systems, and CRT TV deflection coils). But this magnetic field decay is very, very quick in comparison to the charge stored in the main reservoir capacitors. If the capacitors are large, they can run the amp at low power for minutes after switch off. [/QUOTE]
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DIY & Tutorials
DIY For Audio
DIY amplifier making popping sound on speakers when switching OFF
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