Electrolytic caps and reliability D :

[McSpunckle]

So, I wanna use 10uF electro caps in some stuff just to be DAMN SURE no low end will get lost, and they're smaller/cheaper than 1uF film.

So, how long do they last in a pedal's signal path?

Using this site: http://my.execpc.com/~endlr/reliability.html , I came up with 32 years assuming a 16 volt cap run at 3.5 volts (max output I've gotten from a pedal), at 25 degrees (I'm assuming the cap won't heat up much at all in a signal path). The cap is rated for 2000 hours at 16 volts and 85 degrees.

That seems... really long, but I know there are some pretty old pedals out there with electros that are still working, and electros have just gotten better. Maybe reliability isn't something to worry about too much in this case? All the information I can find kind of assumes you're really pushing the cap, and I haven't had any luck finding anything but vague info otherwise.

Keep in mind I only plan on using higher value caps as output caps where the volume control could interact and raise the cutoff frequency of the high pass filter.

[dune2k]

I'd say about 25 years (which corresponds with your findings). The thing is that they don't have to completely fail but their capacitance might change over time. You could also try tantalum caps, they are even smaller and don't degrade (as much) over time. Keep in mind though that tantalum caps have less good qualitys for audio purposes than elecrolytic caps (=they are supposed to sound worse). I used tant caps to build a SHO clone and I guess I couldn't tell any difference. So try it out, worst case would be you have some tantalum caps you don't need (and that you could still use to launch fireworks ).

[McSpunckle]

Thanks for the info! I was getting lots of results basically acting like you should just socket them and put some extra in the box...

Even if the capacitance shifts, it won't be too noticeable. But the caps do more than that as they age. They get leaky and such. But, that probably won't be a huge deal... if the caps are starting to fail when the pots are getting scratchy and the switches are giving out.. well, not much you can do but go to town restoring anyhow.

[azrael]

"lose low end"? That's not really how it works.

What circuit is this?

[dune2k]

"lose low end"? That's not really how it works.

Probably used as coupling/in-/output caps. When they're smaller they will start cutting bass/lower frequencies.

[McSpunckle]

"lose low end"? That's not really how it works.

What circuit is this?

Yeah, there's no way a high pass filter could ever cut low end. Ever. : p

If you use .1uF before a volume control, the cut-off frequency of the filter gets higher, within the range where it'll cut bass frequencies. raising it to 1uF is plenty, but those caps are larger and pretty expensive. 10uF basically means everything gets through no matter what.

If you wire the the first lug of the volume pot (instead of the wiper), the effect is minimised, but you can't wire up two circuits together that way (without buffers, obvs).

[azrael]

There's more to bass rolloff than just cap size. The many iterations of the Russian Big Muff Pi have 0.1 microfarad coupling caps, and does just fine on the sign of low end. That's why I asked what circuit it was.

[McSpunckle]

The low end doesn't disappear. Set a russian Big Muff to a darker setting and roll up the volume, and it'll be there. But if you want a bright fuzz with or booster that keeps low end on bass, .1uF won't work as well if the volume control is down pretty low. Get the resistance down to about 10K, and it really gets noticeable.