Re: nf replacement up or down?

Posted by induction on May 31, 2015; 10:28am
URL: http://guitar-fx-layouts.238.s1.nabble.com/nf-replacement-up-or-down-tp20950p20958.html

lucas abela wrote

hi im building the echobender

http://tagboardeffects.blogspot.com/2013/03/casper-electronics-echobender.html?showComment=1433033240264#c7865860209438813306

i dont have a 27nf cap and as ive read you can use close values as replacements am wondering if its better to go up a value or down a value and what effect (if any) these decisions will have on the effect.

i have 22nf and a 47nf in stock

im guessing from what i read on another post that going higher usually adds more bass which is desirable for me as its for use with a drum machine but 22nf is closer to the original mark

what do you guys suggest?

The effect of changing a capacitor value depends on the function of the capacitor in the circuit, so you can't generalize 'going higher adds more bass'. In this case the 27n is part of a low-pass filter on the delayed signal. The point is that the PT2399 adds some high-frequency digital noise and hiss to the signal, so the low-pass filter sends that noise to ground, which removes it from the signal before it reaches the output. Increasing the cap size decreases the corner frequency, which essentially cuts more treble. It shouldn't have any effect on the original signal, just the delayed signal.

The rule of thumb in pedal circuits is '10% or less doesn't matter'. It's not universal but it's a good starting point. 10% of 27n is 2n7. So if you follow the rule, you can use anything from 24n3 to 29n7. Your 22n is off by 18%, which is much closer than your 47n, off by 74%. You probably won't hear much difference between 27n and 22n, but your repeats will probably be noticeably dark if you use 47n. If you have a 5n in stock, you can put it in parallel with your 22n to get 27n, but it's probably just fine with 22n.