Unwind axial caps for custom, precise values?

[ereder4]

I need some goofball values for an EQ i'm designing, and like to keep all my component values under 2% tolerance. Been thinking about getting something like Dynamicaps and unwinding them till they're exactly the capacitance I need.

Anyone ever try this? Might the way the're constructed give me some issues? I guess I wont know for sure till I just buy some and give it a shot.

http://www.partsconnexion.com/capacitor_film_dynamicap.html

 

[PRR]

Normally for 11.1nFd you buy a great 10nFd, a good 1nFd, a cheap 100pFd, and parallel them.

I don't do my own surgery, and I don't think I would be good unrolling caps. They supposed to be sealed, and tightly-wound.

 

[bruce0]

If it matters (audio precision probably doesn't require it) you can adjust various components.

Thin film resistors, possible but a nightmare.

Composite resistors easy to do.

Inductors, easy to do.

Capacitors, never tried, but my choice would not be to unwind a cylinder, instead I would attempt a stacked cap that used Schoopage (end contacts sprayed on invented by swiss engineer Max Schoop) where you could clip the caps (like old gold coins), to adjust the capacitance value.

WIMA caps are like this. Take a look at the wima tech documents on their site, to see how these are put together.  The goal would be to trim without shorting.

I thought the idea with passive eq's was to adjust resistance and inductance depending upon the section.

 

[gswan]

As PRR said, parallel up some good caps and you will have the value you want with the tolerance of the original caps used, and probably better unless they are all lop-sided in the same direction.
For example, parallel 11 x 1000pF and a 100pF and you will have an 11100pF cap. If you used 2% styro caps then your composite cap will be better than 2%.