Why are electrolytes used...

[mnordbye]

I'm relatively new to effects building... What i'm curious about is why the electrolytic capacitors are used. Is the fact that they have polarity a reason?

Magnus N

[Seljer]

they offer much much larger capacitances is a much smaller space
the downside is that they're polarized and will burn up if you apply voltage in the wrong direction

[Timebutt]

So basically you can blow up capacitors by
1) putting too much voltage on them
2) applying voltage in the wrong direction (if it is an electrolytic cap)

It's just: I was modding my Russian Big Muff for true bypass yesterday, and when I applied power with a 9v adaptor immediately after inserting the input jack a 22nF electrolyt cap just blew up! Is this because the adaptor just put out too much voltage (it's a weird general adaptor, not meant for pedal use ) or is it because I switched the polarity up wrong?

[R.G.]

Could be either one.

The only remote-control way of us figuring it out is to ask - did your mod involve removing the cap in question?

[Timebutt]

No in the mod I didn't remove the cap in question: all I did is rewire the switch so that it is true bypass and I switched the LED.
One thing: the adaptor I used has a switch to change polarity: perhaps the switch was in the wrong position and this is what caused it?

[mnordbye]

Ok. it's like, if you find there's an polarized(electrolytic) cap in a schematic, would it make any difference/mistake if one would put a non polarized one there? That's what i meant in the first place (figured that out just about now  )

One more quite newbie question, but here i go. Does current only flow in one direction in typical guitar effects?
P.S. Feels weird asking that last question.. 

Magnus N

[JimRayden]

Propably the latter. 9V adapters shouldn't give out more than 12V without load. The caps are at least 16V for a 9V circuit, so no overvoltage I presume.

Ok. it's like, if you find there's an polarized(electrolytic) cap in a schematic, would it make any difference/mistake if one would put a non polarized one there? That's what i meant in the first place (figured that out just about now  )

You won't find the same size, or if you will, it'll be a huge one.

One more quite newbie question, but here i go. Does current only flow in one direction in typical guitar effects?

In relation to the ground, yes.

--------
Jimbo

[petemoore]

9V adapters shouldn't give out more than 12V without load.
  I certainly wouldn't count on that^..I'd always count it instead, with a Dmm which is not far off calibration on the low side...compare that the  DMM 'readings < ratings' on the components the measured voltage will be applied to.
  For polarized caps, be certain that the - marking is to the most negative of the two connection points in the circuit [easy to find if it's marked ground in neg gnd circuit].

[darron]

The positive terminal in a Fuzz Face circuit I built shorted to ground one night (with a battery in). I had a 1000uf capacitor across the power for supply filtering. In the morning the capacitor was busting/popping out of its outer wrap. The capacitor was still working. I suppose the Fuzz Face, even with the supply cap, doesn't need any protection for shorted power? But for reversed polarity it would? If that's true then I suppose the battery took a lot more of the fall than the capacitor and burnt up in heat there. I'm interested to learn a bit in this thread too (:

Thanks.

[soulsonic]

Polarized electrolytics are pretty much standard for power supply purposes, they are happiest smoothing and filtering the ripple and crud out of DC voltages. And they work good for emitter/source/cathode bypass caps..... but, I HATE seeing them used as signal coupling caps (like in most fuzz faces). Polarized caps just aren't intended for this, and the polarized cap introduces distortion to the constantly-changing polarity AC signal that's trying to pass through it. This is a case where non-polar or bi-polar electrolytics are a much more appropriate choice - and they're not necessarily bigger either! I've seen a 10uF nonpolar electrolytic cap that was exactly the same size as the equivalent polarized 10uF cap, and they were both tiny. Now, if you got a 10uF FILM cap, then yes, that would be much bigger, probably too big to use in alot of pedals. Though they tend to be rather big, I personally prefer film caps to ANY kind of electrolytic cap, they just sound better to me and you don't have to worry about them dying with age.

The only thing that's worse than using a polarized electrolytic for a coupling cap is using a tantalum cap. Tantalums should be considered strictly power supply ONLY. Their characteristics with audio signals are dismal and they have a horrible reputation for failing in strange unpredictable ways. An excellent example would be my Dunlop reissue Fuzz Face: It used a 2.2uF tantalum cap as it's input coupling cap. I noticed it was beginning to have problems with the sound sort of fading in an out, so I cracked it open to give it a look. I saw the tantalum cap and immediately replaced it with a high quality 1uF film cap (I didn't have any trouble making it fit either). Not only did this solve the problem, it also made the pedal sound 100% better than it ever did - almost on the level of a fancy boutique fuzz. I seriously hadn't realized how much a tantalum "chokes" the tone of a signal before doing that mod/fix - I now replace tantalums whenever I see them used as coupling caps. I have used tants in power supplies before and they're just fine for that (as long as you can deal with the failure modes), I just avoid using them as coupling caps.

[gez]

You can buy small, low-voltage ceramic caps of 'large' value (up to 100u IIR).  Only 'problem' is they're surface mount. 

My pedals are electrolytic cap free these days. 

[Ben N]

I have a stash of 25uf/25v non-polarized electrolytics that I mistakenly got for cathode bypass duty on 12ax7s in amps. Do I understand from the prior posts that I can use them for this purpose?

Ben

[soulsonic]

Dude, not only can you use them, but lots of people swear they'll sound better than the standard polarized ones. I used non-polars as cathode bypass all the time with no problems, only good sound.

[Ben N]

Thanks!