Wah sounds octave like and dull

[mattpas]

Hey all,
I just made a clone of the Clyde McCoy and incorporated the Foxrox buffer.
Everything works but for some reason, when I have the wah heel back (bass side) the notes sound like there is a slight octave and the higher strings are octave-like and flat sounding.
I bypassed the buffer and it still does it so it has to be something in the wah side of the circuit. I am using a Red Fasel inductor and had BC109Bs in there at 330 HFEs but switched them out to 5089s at 470 hfes to see if that made a difference and it didn't. Everything else is a standard Clyde McCoy and I have checked and rechecked everything.

I would appreciate any suggestions.

[brett]

Hi
check the value of the parallel resistor.  Is it the correct value?  It needs to be just right for the inductance and capacitance (it's an RLC filter).  There's also a good chance that the capacitor isn't quite the rated value. 
Varying the resistance can turn a wah from a squeeky chirping bird to woomping whalesong.  It controls the Q of the filter (and maybe other characteristics?).  From memory, smaller resistance is chirpier.  Some people have 2 resistors switched for different tones.
good luck
 

[John Lyons]

Brett
By "capacitor" do you mean the 4.7uf? If not which do you mean.

[Joe Hart]

I've had this happen and it sounded like something's "resonating" in the circuit or kind of feeding back on itself at a strange frequency. Is this what yours is doing?
-Joe Hart

[mattpas]

I've had this happen and it sounded like something's "resonating" in the circuit or kind of feeding back on itself at a strange frequency. Is this what yours is doing?
-Joe Hart

It sounds like there may be a tiny bit of oscillation trying to sneak through. When you play with the bass side all the way back you can hear it through especially on the higher notes and it makes them sound flat like the strings are fretting out.

[brett]

Hi
the resistor is the 33k and the cap I was thinking about is the series 0.01uF in this schematic:
http://www.tonepad.com/getFile.asp?id=114

John - thanks for the heads up concerning the 4.7uF cap.  It does play an important role in the filtering, because it creates the AC gound.  If it were the wrong way around it might cause a partial failure (ie weird effects) because electro caps still have some capacitance when used backwards.  I figure that it might encourage oscillation because of insufficient damping and filtering.
cheers

[John Lyons]

I am trying to help Matt out on this one...
The 4u7 cap is oriented correctly and as far as I can tell,everything is "right".
The wah works well except at the heel down the high notes are somewhat dead sounding.
Sort of an octave ghost note riding on to of the high E string. I think it may be oscillation
but nothing seems to quell it. We've tried some capacitance from input to ground
and also at the output (which has worked for me in the past on a build).
Capacitance from base to collector might work. Matt have you tried this yet?
I know that Teese has used 10pf from B to C there.
The "sweep cap" is .015. everything else is stock Clyde McCoy.

[Paul Marossy]

How is it being powered? Have you tried it with a different guitar? Does it do it no matter where the wah pedal is physically located?

[John Lyons]

It does the same thins with different guitars, battery power, different locations.

[Paul Marossy]

It does the same thins with different guitars, battery power, different locations.

Well, that rules out those possibilities. Hmm... this is a weird one. OK, has anyone considered changing the inductor to see if maybe that is the cause of the problem?

[John Lyons]

I was thinking of that but I wasn't sure. Seem odd that the wah would work well but at one point sound "wrong".
I know the heel down position will oscillate/growl and can be a problem area for the nasties but the wah sounds
great otherwise so if the inductor is working seems odd that it would be bed just in the heel position.
Still, it would be one thing to try out and eliminate.

[ViolenceOnTheRadio]

If it's not due to a resistor value, which is probably what everyone is also assuming is the cause, then maybe you used a zombie cap?

Looks alive, almost functions like it's alive but, it is indeed dead!

[Paul Marossy]

I was thinking of that but I wasn't sure. Seem odd that the wah would work well but at one point sound "wrong".
I know the heel down position will oscillate/growl and can be a problem area for the nasties but the wah sounds
great otherwise so if the inductor is working seems odd that it would be bed just in the heel position.
Still, it would be one thing to try out and eliminate.

Could theoritically be a microphonic inductor that is oscillating at the lower frequencies.

[John Lyons]

Ok, thanks fellas. I'll change the the caps and inductor.
Not many parts so I'll divide and conquer

[Paul Marossy]

Yeah, the process of elimination goes pretty fast on a simple circuit like that.