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The problem with large capacitors

The problem with large capacitors is they compete with your output tubes for the power supply’s current. A small capacitor has much less surface area between its elements. Because of this, it also has a lower electro-motive tendency to draw current to recharge itself. The weaker electro-motive tendency of the smaller capacitor also gives up its energy more freely than the large capacitor.

If a transit comes along and demands current, the small capacitor will deliver that current much faster and more easily than a large capacitor. In addition, once the transit is gone, the small capacitor only recharges to the extent that does not interfere with the output tube. However, the large capacitor with its stronger electro-motive tendency will compete with the output tube and be a current hog until it recharges. Therefore, amplifier overload or clipping conditions take longer to recover with larger capacitors in the power supply.

When thinking about power supplies, you must differentiate ripple reduction from energy delivery. While a large capacitor may appear to have better regulation and superior ripple reduction, it is very poor at delivering energy quickly.

I personally find that anymore than 50uF in a single spot tends to slow the amplifier down, and transparency decreases. I just use another LC section if more ripple reduction is needed to get things quite.

Rgs, JLH

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