swap non polarized for polarized in MXR Noise Gate???

trad3mark · Post by **trad3mark** » 02 Feb 2010, 18:13

Hey all,
I'm planning on building this: http://www.tonepad.com/getFileInfo.asp?id=77

I have everything EXCEPT the 1uf NP. In this schematic, is it possible to either a) use a polarized one? or b) replace it with a lower value (0.47uF is the closest i have.)

cheers,
tm

NickS · Post by **NickS** » 03 Feb 2010, 13:05

I think it's best to stay with NP. I would use 2 x 0.47 in parallel.

trad3mark · Post by **trad3mark** » 03 Feb 2010, 13:12

or two 2.2uF electrolytes back to back in series? But do i go - + , + - or + -, - +?

NickS · Post by **NickS** » 03 Feb 2010, 14:27

There's no reason why it should matter. My only concern is that unlike in speaker crossover circuits, another common application of "bi-polar" electrolytics, where you can be sure that there is no net voltage across the capacitor when there is no signal, the quiescent state of this circuit will be 0.6V-0.7V positive at the transistor end. When signal is applied, the transistor base-emitter junction should act as a rectifier, causing the transistor end to go negative temporarily. If you want to try a single electrolytic, I would put the positive at the transistor end and the negative at the 22K resistor end.

trad3mark · Post by **trad3mark** » 03 Feb 2010, 16:34

cool. i'll try them both. cheers.

mwynwood · Post by **mwynwood** » 21 May 2012, 12:42

I'm building theTonepad Gate at the moment and was wondering the same thing.
I don't have a 1uf NP - what did you guys find worked?
Thanks!

Fender3D · Post by **Fender3D** » 21 May 2012, 15:40

MXR had a 10nF capacitor there

Seiche · Post by **Seiche** » 21 May 2012, 18:15

NP is misleading imho, because everyone thinks they have to find a NP electrolytic. Any cap will do that's not a polarized one. Just use a wima cap or the likes.