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Rory 26th July 2001 12:08 AM

In using a 12v power supply to power an amplifier, is it important to have a capacitor across the + and - terminals of the power input to keep power spikes from occurring? Does this serve any other purpose?

Jason Hubbard 26th July 2001 02:03 PM

Amplifier power supply
The capacitor between + & - is usually used to fill in the gaps in the "DC" waveform that appear on the output of a rectifier in a power supply that runs from the mains. The gaps will still be there, but very much smaller (called ripple)

If you are deriving your power from the mains then the power supply you are using should have a capacitor - Add one if it's not already there, without it you will get a prominent 100hz buzz in the speakers. Ensure the capacitor has a working voltage higher than 12 volts (shouldn't be a problem) - the bigger the capacitor the less ripple.

jam 26th July 2001 06:33 PM


Additional capacitance is usually required at the amplifier end of the circuit to prevent 'motor-boating', which is a low frequency oscillation that can occur if the power supply is located some distance from the amplifier.


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