electrolytic caps and Big Muff Pi

[bruin2k3]

Hi,
I'm looking at a schematic of the Big Muff Pi and I noticed that at the input, there's a electrolytic cap but it has negative toward the input. Wouldn't this effectively block the signal? Am I missing something? How does the signal get through the capacitor that's polarized the other way?

http://www.tonepad.com/getFile.asp?id=95

Thanks!
-2k3

[bato001]

Capacitors only block DC current. Your signal is AC.

[TV-Set]

Hi,
I'm looking at a schematic of the Big Muff Pi and I noticed that at the input, there's a electrolytic cap but it has negative toward the input. Wouldn't this effectively block the signal? Am I missing something? How does the signal get through the capacitor that's polarized the other way?

http://www.tonepad.com/getFile.asp?id=95

Thanks!
-2k3

Was just about to create a new topic, this thing was driving me nuts. I checked both GGG and TP schematics and they all seem to make a mess (in my head) of how they place some of the caps in the signal path. I always placed the negative lead facing where the signal goes, and on many forums and building instructions it says to be careful not to solder those the other way around. These BMP schematics ... dunno what to say, dunno who to trust seriously though them caps polarity must be important? plz help

[Dirk_Hendrik]

I always placed the negative lead facing where the signal goes, and on many forums and building instructions it says to be careful not to solder those the other way around.

When placing polarized caps in the signal chain one should analyze the DC voltage potential difference between the 2 nodes where the cap is connected to. Not the signal. The plus goes to the node with the highest DC voltage.
In this case the - of the cap is connected to ground through a 1meg resistor. Since there will be no DC current flow through that resistor the potential at the node of 1 Meg and input cap will be 0. The other, +, side is connected to the transistor which is not at 0.

If you would care to take a look at a Tubescreamer circuit you'll see that there's 2 occasions where both nodes are approx at 4.5 volts. For that reason a Non-polarized electrolit is chosen.

[bato001]

Dirk's explanation is dead on, but I always find that a picture helps, see below. The voltage readings may not be exactly what everyone gets on their BigMuff builds, but are an approximation of the average Muff.

Notice that the plus side of the electrolytic is towards the higher + voltage reading, and as Dirk said-the cap orientation has nothing to do with the signal chain.

[TV-Set]

Wow, thank you guys! That was really helpful, I learned something new and important today. Luky me, didn't put together the muff yet