Electrolytic cap polarity direction?

[anonymous]

I am trying my hand at my first madbean build and I have some electrolytic caps of certain values to use where film may have been more convenient. How can I tell which direction to place the +/- leads when it is not specified on the build docs?

Thanks from a 1st time builder...

[rullywowr]

Welcome to the forum.  For electros, longer lead= positive(+).   Also there is a stripe on the can which is on the negative side.

And while you can usually replace an electro with a film, you usually cannot replace a film with an electro. 

Current flows both ways with films and electrons only like to be flowed one way.   Additionally, the consensus is that films sound better than electros so films are often found in the audio path.

On madbean projects, just look at the part on the PCB layout. If it is a circle, then use electro. 

[croquet hoop]

An interesting read: http://www.madbeanpedals.com/forum/index.php?topic=6723.msg57589#msg57589

There are more discussions that would be very instructive for a first time builder, so I heartily recommend that you search the forum a bit. There are lots of treasures of information to be found by every newcomer. There is nothing wrong with asking questions of course, but doing a bit of homework will help you tremendously.

As for your specific questions, I'll disagree in part with rullywowr:

And while you can usually replace an electro with a film, you usually cannot replace a film with an electro. 

True, you can usually replace an electro (polarized) with a film cap (non-polarized), but you can also usually replace a film cap with an electro cap provided you take care of the polarity (watch the schematic to see where the higher voltage is; that's where the + of the cap will go).

the consensus is that films sound better than electros so films are often found in the audio path.

True. But the consensus is also that it does not matter, and that you do not even have to use "audio grade" electro caps in the signal path; it will sound just fine (and you won't have to deal with a brick-sized cap).

[anonymous]

Thank you both - I seem to be having a bit of trouble finding the right threads to answer my questions, but I suspect I am not making the proper query!

[rullywowr]

Croquet is spot on.  I threw the loaded term "usually" in there just to highlight some basic rules of thumb in broad strokes for someone just starting out; regarding what components to use and the safest/easiest way of substituting caps.  It is by no means set in stone.

Once you can decipher a schematic and understand which side of the circuit has the larger voltage you certainly can replace films with electros if you are so inclined.

Also, the search function works best if used from the main forum page.  If you are in a subforum, it will only search that particular area.

[anonymous]

OK so I finally got all my parts in the mail... I am trying my hand at a Runt and accidentally got electrolytic 1uF caps (C9 on the Runt). My heart is telling me the positive should come from R9 and the rest of the circuit. The negative goes straight to Volume, so the other side coming in would have more voltage. Does that logic make sense? It happens to be in an "ending point" so I am not running in to other voltage sources, is that right? Is it a rule that there's always more voltage on the side closest to power?

Either way I am having a lot of fun populating the board! I will definitely order some film caps, as right now I just have electro and ceramic (should sound fun...)

Thanks!