CAPACITORS: When/why did capacitor value standards change?

Colin Wonfor

Dear Colin, a question which has been nagging away for a few days now: why were capacitor value 'standards' changed around early 70s, and why such seemingly arbitrary numbers? In my Quad 33/303 there's several electrolytic caps featuring values such as 2uF, 12uF, 25uF, 50uF, 100uF..... When (and why) were values changed to 10uF, 22uF, 33uF, 47uF etc. ? Why for example, change the 50uF standard to 47uF, and yet 100uF remains a standard today, for example. Odd-squared! Cheers, John.

Blame the Yanks! All Cad packages I use are in Metric but all parts are in inches, Yanks again. Also the electrolytic capacitance tolerance is crap; some are +20% through to - 50% and so fixing a value is – as you say – arbitrary. Nowadays we can do much better, but the paperwork might take too long or something to fix.

Thank you for the question.

Colin

See what Colin is up to HERE and ... HERE

colinwonfor@gmail.com

 

Leave a Reply