I set up a simple experiment to see how changing the supply filter capacitor values influenced the maximum amplifier output voltage before clipping. I had to use the parts I had on hand and this was a 9-0-9v 2a transformer and a TDA2040 audio power amp IC. The supply was setup to be a full wave split design with the cap values shown filtering each rail. The amplifier's output was connected to a non inductive 4 Ohm load. I measured the maximum output RMS voltage just before clipping at 40 and 120Hz (actually slightly off 120Hz so the signal would not be in sync with the 120Hz supply ripple).
Here are the results of the test
[IMGDEAD]http://www.jracrylic.com/pix/captest.jpg[/IMGDEAD]
The non clipped output voltage did not change much until I went smaller than 2,200uf filter caps. After this, the supply ripple was large enough to start affecting the output swing considerably.
Of course, this is only a 8 watt amplifier. Two channels and higher power demand much more current from the supply.
Here are the results of the test
[IMGDEAD]http://www.jracrylic.com/pix/captest.jpg[/IMGDEAD]
The non clipped output voltage did not change much until I went smaller than 2,200uf filter caps. After this, the supply ripple was large enough to start affecting the output swing considerably.
Of course, this is only a 8 watt amplifier. Two channels and higher power demand much more current from the supply.
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