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Size of "audio grade" electrolytic caps a problem?

Started by Justus, July 08, 2014, 06:50:04 PM

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Justus

I am about to make a decent sized mouser order for my first few pedals, and was going over and double-checking some specs.  I've found a couple posts here regarding electrolytics, one recommending audio grade caps, and another warning of cap size, recommending to keep them to 5mm diameter or 6.3mm for larger values.  The problem I'm running into is that the audio grade electrolytic caps on mouser are usually 10mm in diameter. 

Which advice is more important?  Anyone have a "favorite" electrolytic cap they use all the time?  (47uf, 100uf, 1uf, 220uf, 10uf)

EDIT:  And should I be looking for 5mm lead spacing on electrolytic caps?  That's kind of confusing as well, the build docs I'm looking at certainly don't appear to show lead spacing as wide on the electrolytic caps as they are on the box film caps.

Thanks for helping out a noob.   ;)

Bret608

I think lead spacing on electros is more like 2mm or 2.5mm. The 5mm or 6.3mm refers to the width of the capacitor case. Also important is the height--for most of the builds we do, you wouldn't want radial electros to be more than 11mm tall.

I don't think audio grade caps really make a difference, but then again I haven't been too scientific about it. The main thing for me was, as you said, most of them were too large. Just try a few where the size is acceptable but otherwise just get some regular Nichicons and be on your merry way!  :)

RobA

The Nichicon FG (Fine Gold) series in the 25V variety for the normal values are the standard sizes the effects PCB's seem to use (excepting 1590A builds). If you go to higher voltages, the seem to get bigger fast.

Audio electros aren't always the best choice in effect circuits. It depends on where they go. In the power supply sections and for things like charge pump caps, the power supply specific caps from Panasonic and Nichicon had measurably better results for me than the audio grade caps did. I only use the audio grade when the cap is going to be in the actual audio path.
Affiliations: Music Unfolding (musicunfolding.com), software based effects and Rockā€¢it Frog (rock.it-frog.com), DIY effects (coming soon).

Justus

Ok thanks, that makes more sense.  I was looking at electros with 5mm lead spacing and that's likely why they were all 10mm in diameter, lol!  So does it make a difference between 2mm or 2.5mm lead spacing, or is one close enough to the other that both will work in these projects?

pickdropper

Yep, Rob's got it right.

If you are building in 1590A, keep them to 5-7mm max height.

For most other boxes, 11mm is not a problem at all.

Lead spacing depends on the board layout.  2mm and 2.5mm are the most common.
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Justus

So how can you tell if it's 2mm or 2.5mm based on the layout?  Any examples?

stecykmi

0.5mm is tiny, you'll be able to make it fit for either type of cap

Justus

Awesome, good!  That way I don't have to worry about getting 2 of one and 8 of another or anything.