Breaking the 10:1 bypass capacitor rule of thumb?

Posted by jyourison (A) on March 11, 2011 at 09:16:35

I hear people in the asylum advocating for mixing capacitor dielectrics thoughout an amplifier. Right now I'm listening to coupling capacitors in a breadboarded amp. I'm swapping film and foil, paper-in-oil, teflon, and waxed/oiled paper and foil.

My questions: I have a selection of caps in values of 0.1 muF, .047 muF, .068 muF, etc. I would like to try mixing dielectrics in a lower ratio than 10:1, which I understand to be a typical rule of thumb. For example, I'd like to parallel .068 and .047, 0.1 and 0.068, or even 0.047 and 0.047, each a different cap type within the paralleled set. What might be the upside and downside effects or risk in doing this? Would any characteristics of dielectrics be synergistic or would they tend toward neutralizing each other? Is the 10:1 ratio mostly a nod to keeping costs down, or are there other reasons for it?

My goal is three-fold: (1) transparency/accuracy, (2) full extension of bass and treble, and (3) still keeping some liveliness in the music. Perhaps unrealistic, but this is what I'm listening for. I like accurate sound without its becoming dull.

I am currently listening to and swapping FT-3, K40Y-9, K42Y-2, Panasonic film and foil ECQ-P(U), and vintage paper Good Alls (surprisingly extended and neutral!). The coupling cap value range I'm shooting for is 0.1 - 0.2 muF. I'm thinking about ordering some micas and kbgs to try as well.

Any thoughts on mixing dielectrics in the coupling capacitor location while also breaking the 10:1 ratio guideline?

Thanks,
Jeff

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Breaking the 10:1 bypass capacitor rule of thumb?

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