Quote:
Originally Posted by Takapuna
As I understand it:
Making the input capacitor smaller reduces the peak currents for the rectifier and transformer, thus giving them an easier ride and dropping fewer volts across their internal resistances. It obviously leaves more ripple for the following LC or RC combination(s) to deal with but if the following capacitor is made large this can be dealt with.
Unbalancing the values in the other direction, making the input capacitor large and the output capacitor smaller has the advantage of further reducing voltage ripple straight away…as it were. This leaves less work for the following LC/RC combination. I appreciate this leads to high peak currents and can stress transformers rectifiers and the input capacitor if they are not rated for the ripple current.
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You may want to check PSUD2 again about first capacitor ripple current versus capacitance value. Often in practise the first filter capacitor has to be a certain size to provide a sufficient ripple current rating, and a smaller capacitance value part can't be used.
If you can hear or have the ability to measure power system related noise, then distance and layout (mechanical and electrical) of the power supply are your best friends for reducing power supply related ripple/noise at the amplifier, so starting with an external power supply module is worthwhile if it is shielded and distant. Layout and distance is also important in such a power supply module (rather than cramping all parts together), from orientation of PT and chokes, to how the caps are connected to/from, and how you manage the 0V line and protective earthing of the equipment.