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RE: I wasn't discussing what you hear

A larger shunt capacitor will always create greater peak current in the diodes and transformer secondary. However, the larger cap does not always create a smaller pulse width. In addition to capacitor value, pulse width and shape are affected by load resistance, series resistance and the slope of the wave over the period of conduction. The latter is particularly important, because the speed with which the "inrush" of current can take place when a diode first conducts is strictly limited by the slope of the wave. In the end, when all the factors are accounted for, there is no fixed relationship between capacitor size and pulse width or shape, even if the load remains unchanged.

This is evident when the circuit is analyzed using SPICE. In the circuit above, the 20,000 uF shunt capacitor creates current pulse widths in the diodes of approximately 4.3 mS. Contrary to the theory promoted in this discussion, reducing the capacitor to 20 uF creates a smaller pulse width of about 2.8 mS. However, when the capacitor is made even smaller, say 2 uF, pulse width increases again to about 5.3 mS. Lack of a definitive relationship between capacitor size and high frequency content is further emphasized when FFT plots are created using these values. The power supply with a 20,000 uF capacitor simply does not contain increased high frequency energy.

Finally, there's the fact that at 20 kHz, a 20 uF shunt cap exhibits 0.4 ohms to ground, whereas a 20,000 uF cap presents 0.0004 ohms. In this context, the idea that the larger cap would pass more high frequency energy into the amplifier looks really silly.


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