How much capacitance

[Paul Kraemer]

Those following recent discussion on the SB-200 and SB-220 (or any) 
amplifiers and considering replacement of the (6) electrolytic capacitors 
with newer, better, higher capacitance value units might do well to consider 
for a moment the slippery slope down which they may be headed.
Pick out any book on power supply design and observe what happens to inrush 
line current and diode (same as transformer secondary) current as the 
capacitance value of the filter capacitor is increased by orders of 
magnitude. THEY INCREASE!
If you are in the design phase of a new product, fine, put in as much 
capacitor as your pocketbook can afford, then pick out the remaining 
components to stand up to the stress.
If you are working with vintage products with un-obtainium components that 
you care to prolong the life of you might be well advised to follow the 
advice of one author "use the minimum capacitance which results in 
acceptable ripple"
An argument might be made that Heath would have used larger capacitors if 
they had been readily available 50 years ago. Or, was it a decision which 
involved all the factors in play? Switches, diodes, transformers, 
performance goals, and marketing.
We seem to have grown to a point in this society which presumes that more is 
better than a lot more is even better still.
Sometimes more is not better, it is just more.
To me, the promise of a few more watts resulting from a slightly increased 
high voltage and possible slightly improved IMD (I'm guessing on that one) 
just aren't worth the potential damage to other components I can't replace 
and paying twice as much for filter capacitors as I would need to.
Just some ramblings for your consideration.
Paul K0UYA

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