Axis Wah - redundant parts in the output buffer?

[Thomeeque]

 Hi!

About output buffer of Fuzz Central Axis Wah - ain't RC at input redundant? Is there C=0.05uF to decouple and R=1M to bias to 0VDC? If yes, then IMO it's not necessary, DC is already at 0V at output of basic wah circuit (pulled down by the wah pot)..



Or is it more complicated, am I missing something?

Thanks, T.

[jasperoosthoek]

That seems pretty redundant to me. Any other votes?

[Lurco]

highpassfilter?

[Thomeeque]

highpassfilter?

"..This problem can be solved by adding an output buffer to the Axis Wah, which won't alter the tone of the pedal."

So probably not. T.

[jasperoosthoek]

It is a low pass filter with a cutoff frequency of about 3 ohms (neglecting the gate capacitance). Not a high pass filer 

[Thomeeque]

It is a low pass filter with a cutoff frequency of about 3 ohms (neglecting the gate capacitance). Not a high pass filer  

It *is* high-pass filter topologically of course, but tuned to not alter audio range (meant just to decouple DC, not to apply audible high-pass filtering)

But here is some interesting reading.. just going thru it..

T.

[Lurco]

It is a low pass filter with a cutoff frequency of about 3 ohms (neglecting the gate capacitance). Not a high pass filer 

sorry, I can`t read, and misname frequency in Hertz http://en.wikipedia.org/wiki/High-pass_filter and have a rumblefilter in my recordplayer!

[amptramp]

The source cited by Thomeeque is correct in that some JFET's would require positive gate biasing, but this could be done by lifting the bottom of the wah pot above ground.  Since there is no DC being transferred by the pot, it would not care if you had a diode inserted between the low end of the pot and ground and a resistor going to the positive supply.  You could use anythig from silicon to LED to set the gate voltage where you want it.  The impedance of a forward-biased diode is low and so is the noise and it will regulate the voltage quite well.

[jasperoosthoek]

  Meant to say low cut filter...

[Thomeeque]

 I have build Axis Wah's output buffer (including RC at input) yesterday - DC at FETs source was 0.9V, it's a dangerously low I'd say.. Some lift-up at gate will be IMO necessary.. We'll see, I could not strum hard enough yesterday, it was already late night when it was finished T.

[zambo]

I built this wah without the buffer at the output and it seems to be pretty mild...is it supposed to be or does the buffer make it more wah wah ish??

[jasperoosthoek]

The buffer makes it interact better with fuzz circuits. Without the buffer the wah doesn't "wah" anymore when you connect a Fuzz Face after it in the chain. It will sound like it is fully pressed down. Just listen to psychedelic solos in Voodoo Child Slight Return to get an idea what that sounds like (not the intro though that was done with the FF turned off). Especially the solo after the first verse which was done with a wah directly into a FF. At the end of the solo Jimi actually switches the wah on and off very rapidly to get a wah sound.

The buffer will restore normal operation of the wah so you can use it normally with fuzz effects.

[zambo]

I understand that part of it, I use tube distortion pedals or the amps distortion anyway...What I mean is, It still sounds like a wah pedal its just a lot more subtle and "transparent" for lack of a better word. I could almost leave it on all the time toe down although it would be a little to bright. Does the buffer bring out the wah more or is it just a more subtle design? Thanks for the info on Voodoo Chile btw ....I didnt know that part of the story and its one of my favorite songs ever!

[jasperoosthoek]

I never used a buffered wah so I can't help you with experience. But I expect that the output buffer doesn't do much if you use tubes after the wah. The only thing I can suggest is to change the range: Open the wah, disconnect the pinion (I think that's what it's called) and rotate the gear one notch. Make sure it is not too far as rocking the pedal might damage it then.
If you are still not sure then just record some wah on chords and notes and post it here.

Btw, I have a stripped down version of the original voodoo child. No studio gimmics where it sweeps from the left to the right. Just the bare track. You can hear much better what he does with his effects. I think I even can hear the wah switch itself as he knocks it on and off.

[Gus]

I just saw this thread.  You can add another EF buffer using a >500 hfe transistor.  Direct couple(maybe a series 100 ohm to 1K for stability C to B) the EF base to the Q1 collector use a 10K emitter to ground

[ayayay!]

I just saw this thread.  You can add another EF buffer using a >500 hfe transistor.  Direct couple(maybe a series 100 ohm to 1K for stability C to B) the EF base to the Q1 collector use a 10K emitter to ground

EF?  (sorry...)

[John Lyons]

Emitter Follower / "Buffer", BJT, output taken from the emitter.

[zambo]

I have to try this project again, Mine never did end up working right.

[anti-idiot]

It's not my intention to hijack this thread, but i took a look at the pcb, and found an empty space for the additional cap found on JH-1 wah.

PCB: http://fuzzcentral.ssguitar.com/axiswah/axiswahlayout.gif

JH-1: http://fuzzcentral.ssguitar.com/schematics/jh1.gif

the cap is parallel with the inducto 10n. Does anybody know what it does? Also, there's an aditional 22n cap at the pot, what's that for?

Thank you