Capacitor Question

Rory · 26th July 2001, 01:08 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, 03:03 PM

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, 07:33 PM

Rory,

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.

Jam

26th July 2001, 03:03 PM	#2
Jason Hubbard diyAudio Member Join Date: Apr 2001 Location: S.E. England	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.

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26th July 2001, 01:08 AM	#1
Rory diyAudio Member Join Date: Jun 2001	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?

26th July 2001, 07:33 PM	#3
jam diyAudio Member Join Date: May 2001 Location: Charlotte,NC,USA	Rory, 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. Jam

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