what do the diode and electro do in classic wah circuit?

[tehfunk]

I was wondering what the diode and extra electrolytic cap do in classic wah circuits like the crybaby. All I've figured out is that they are connected to the ac adapter and are only present in wah circuits that have an ac adapter... If I was going to mod a V847 which does not have an ac adapter standard, would I have to add the diode and electrolytic cap in order for it to function properly? Thanks!

[axg20202]

Power filtering (the cap) and reverse polarity power protection (the diode). Adding both would do no harm at all but neither are essential.

[Paul Perry (Frostwave)]

just had a thought.. wonder what a resistor in series with the power would do?
It's definitely going to have an effect (like, putting a resistande in series with a fuzz power supply).
not sure whether it is going ot be + or - feedback, though.. anyone feel experimental?

[ayayay!]

just had a thought.. wonder what a resistor in series with the power would do?
It's definitely going to have an effect (like, putting a resistande in series with a fuzz power supply).
not sure whether it is going ot be + or - feedback, though.. anyone feel experimental?

Not I.  Not today at least.  I've been horsing around with GCB-95's too much lately, and adding one more cotton picking thing to that circuit will probably make my head explode!  Ha! 

What do you say tehfunk?  You're the guy in love with wahs.  You feel up to it?  I'd love to hear these results too. 

[tehfunk]

ehh maybe I'll do it when I mod my v847, breadboard it or something. Though, I still don't understand what Paul is trying to say about what the outcome of the resistor in series with power supply would be. I don't get what he means by + - feedback, do you mean positive or negative effect? or what?

[andrew_k]

not sure whether it is going ot be + or - feedback, though.. anyone feel experimental?

I have a maestro boomerang on the breadboard at the moment, maybe I'll have a mess with the idea tonight or tomorrow (depending on available time)

[tehfunk]

sounds cool man. btw, I meant to ask, what exactly does power filtering do?

[R.G.]

sounds cool man. btw, I meant to ask, what exactly does power filtering do?

Your guitar makes a tiny AC (Alternating Current) signal. Actually, it's an alternating voltage because we try to make sure that almost no current really flows, but it's common to use the same words for both.

That means that the signal has a dead-zero average voltage, and there are alternating bits of the signal that swing positive and negative. Exactly what shape the alternations are and how often they occur is what you hear as pitch and timbre in your music. That is - all of that powerful, mystically beautiful music you can possibly make on your guitar is expressed as a fraction of a volt of electricity that waggles positive and negative between 82 times per second and a few thousand.

The rest of the world is saturated in power line frequency. This is the dreaded hum monster. It's everywhere in the civilized world, and great efforts must be made to keep it and its brother Radio Frequency (RF) out of other desired signals.

Filtering, whether in electronics, cooking or chemistry, is the process of separating one thing from another thing. My rainwater collection system filters out bugs, sticks, leaves, and microbial contaminants from the pure water.

Your pedal is designed to run on the pure DC that a battery puts out. DC is Direct Current, meaning, it does not alternate, but is solely positive or negative, and the implication is that it does not waver around on the side of the line it rests. Any time you power a pedal from something that's not a battery, there is the possibility of AC contamination getting in on the "DC" provided by the power supply.

Stay with me, we're almost there.

A power filter ahead of your pedal's actual power use is designed to reduce the polluting AC contaminants on the incoming DC and let your pedal be powered from pure(r) DC than it would otherwise have. It keeps the hum and RF monsters from creeping in on the "DC" power wires. The filter may have some resistance. As a result of Ohm's law your pedal causes its own pollution on the power supply by drawing current through the filtering resistance, and that can cause feedback which may help or hurt the pedal. A well designed filter also cleans this up by providing a low impedance at higher frequencies where the feedback can hurt more.

You have a lot of reading to do. If you're going to continue building pedals, you're going to need to get started on it. We've all been where you are. If you've ever watched the now-archiaic episode of Kung Fu where Grasshopper is faced with the pot of glowing coals and the burning hot dragon brands on the sides, and the masters line up to show him their dragon scars, you get the idea.