HELP with WAH-WAH pedals and really big CHOKES...?
Mark Garvin
>I'm building a wah pedal from a schematic I found on the net,
>and I can build it all except for the inductor. It's labelled 660mH, but
>I've can't find one larger than 150mH. Does this mean 660uH, like how
It means millihenries. Actually not that large as chokes go.
>Could I just buy four 150mH and put them in series, or would that do
>something bad. (Remember it's in an audio circuit, so signal distortion
>cannot be tolerated.)
Yes, try four 150's in series. But..no signal distortion? In a guitar
circuit? I would be very surprised if the circuit knows anything about
linearity. Most wahs don't. In any event, don't worry about it.
>Maybe some background would help me, also. All I know about inductors is that
>they block AC, I know nothing else.
They are sort of an opposite of a capacitor.
Where did you get the pedal itself? That must be a lot harder to find
than the inductor.
Mark Garvin
Michael P. Green
and I can build it all except for the inductor. It's labelled 660mH, but
I've can't find one larger than 150mH. Does this mean 660uH, like how
Or do I really need a big inductor?
I looked at the actual pedal, and the choke is about 3/4" to 1" in diameter
and about that same height. There's also a small thing in series with it
that I assume is another choke (it looks like a 1/4 watt carbon resistor,
but all it has is one black band).
Could I just buy four 150mH and put them in series, or would that do
something bad. (Remember it's in an audio circuit, so signal distortion
cannot be tolerated.)
Vox Wah, and sorta the same as the Maestro Boomerang Wah)
Maybe some background would help me, also. All I know about inductors is that
they block AC, I know nothing else.
Dan Green
ke...@austin.ibm.com
In article <5q4cdM...@delphi.com>, Michael P. Green <mp...@delphi.com> writes:
> I'm building a wah pedal from a schematic I found on the net,
> and I can build it all except for the inductor. It's labelled 660mH, but
> I've can't find one larger than 150mH. Does this mean 660uH, like how
> sometimes capacitors are rated as, say 47MF, when it means 47uF?
>
> Or do I really need a big inductor?
on Jamie's web page. The inductor really is 0.66 Henrys. The low signal levels
let you do this in about a 1" cube.
>
> I looked at the actual pedal, and the choke is about 3/4" to 1" in diameter
> and about that same height. There's also a small thing in series with it
> that I assume is another choke (it looks like a 1/4 watt carbon resistor,
> but all it has is one black band).
sided boards practical. It's a jumper wire.
>
> Could I just buy four 150mH and put them in series, or would that do
> something bad. (Remember it's in an audio circuit, so signal distortion
> cannot be tolerated.)
Four 150mH in series would work very well. Distortion is actually not a
problem in this circuit, as the vintage Vox wahs havew distortion in the
inductor, and this is responsible for their sought after tone.
>
> (BTW, the pedal is the Dunlop Cry-Baby Wah, which is very similar to the
> Vox Wah, and sorta the same as the Maestro Boomerang Wah)
Yep.
>
> Maybe some background would help me, also. All I know about inductors is that
> they block AC, I know nothing else.
>
You should read my effects faq, on the same web page, near the bottom. A couple
of practical matters overwhelm the ability to make circuits. Especially in
the case of wah pedals, the inductors are hard to find. The best source for
an inductor like this is -- yep, another wah pedal. They are not standard items.
Also, as I note in the faq, making a pedal assembly that is sturdy and
reliable is HARD to do mechanically.
It is far more practical to buy a used wah pedal.
R.G.
John Lundgren
Donald Kay
:I'm building a wah pedal from a schematic I found on the net,
:and I can build it all except for the inductor. It's labelled 660mH, but
:I've can't find one larger than 150mH. Does this mean 660uH, like how
:sometimes capacitors are rated as, say 47MF, when it means 47uF?
:
:Or do I really need a big inductor?
From the Wah Wah pedals I have looked at they require the 660mH
:I looked at the actual pedal, and the choke is about 3/4" to 1" in diameter
:and about that same height. There's also a small thing in series with it
:that I assume is another choke (it looks like a 1/4 watt carbon resistor,
:but all it has is one black band).
The 1/4 watt resistor like part is most likely a solid piece of wire
(Black band = 0 ohms) they are used in volume manufacturing as links
because they go through automated loading machines like every other
resistor
:
:Could I just buy four 150mH and put them in series, or would that do
:something bad. (Remember it's in an audio circuit, so signal distortion
:cannot be tolerated.)
You will alway get some distortion from cored inductors. But after
you've fuzzed it, Wah-Wahed it, and overdriven it into your Marshall, I
don't think you will notice.
:Maybe some background would help me, also. All I know about inductors is that
:they block AC, I know nothing else.
The inductance is only half the story for such an inductor. For the
size you describe and the way they are used the Q may have a significant
effect. Simply ensuring the DC resistance is the same will allow you to
get the Q right. If you put four of your 150mH inductor in series and the
resistance is less than that of the actual part you can connect a
resistor in series with your four to make the DC resistance equal.
Michael P. Green
>It's better if you can change thecircuit to use just capoacitors and
>resistors. This can be done with Twin-T notch filters or Bridged-T
>circuits. Often, oscillators are made with a Wien Bridge circuit.
I think I know that I notch filter filters out a certain frequency band.
I also don't know what a Wien Bridge is.
Thanks,
Dan green
Robert Luly
>Michael P. Green (mp...@delphi.com) wrote:
>:I'm building a wah pedal from a schematic I found on the net,
Hi
I used to do a lot of musical instrument work. The thing remember
about wah-wah circuits is the sound was created by sweeping a band
pass filter across a frequency range. The type of filter ( inductor,
RC etc.) was not as important as the characteristics of the filter
such as the bandwith, amplitude, and start and stop frequencies. All
in all an rc filter is easier to design and adjust because there are
no hard to get parts required. A parametric equalizer designed to
sweep from 200 to 2000 Hz should be a good place to start. This kind
of circuit will allow you to adjust each characteristic independently.
Most op-amp cookbooks have such circuits.
The most trouble I had with most wah-wah circuits was the pot in the
foot pedal. most of the circuits had DC on the pot and that caused
them to seem to wear out and become "noisy" because the DC caused a
kind of electroplating between the wiper and the resistive element.
Solution: don't put DC on pots.
Regards
R. Luly
Emmanuel FLETY
>
> Michael P. Green (mp...@delphi.com) wrote:
> :I'm building a wah pedal from a schematic I found on the net,
Hello every body !
I play the guitar too and i copied the classic crybaby WAHWAH. I had the
same trouble with the inductor. I couldn't believe myself when i made
the measure (just use a frequency generator and a resistor, capacitor
and inductor bridge : when measuring a voltage peak, it's the center
frequency of the brige. Then calculate L with this frequency, the
resistor and capacitor values).
You won't find any inductor of 660mH in electronic shops (i think).
You will have to make it yourself. Just buy a ferrit pot (i don't know
if these words are correct in english) and very thin Cu wire. The ferrit
pot must be sold with a paper that indicate how many turns for xx mH.
Be patient and turn, turn, turn...
Make sure there's no one around to disturb you while turning: ferrit
pot are very accurate and if you loose some turns, inductance value
won't be right. Good luck (i'm still turning 1500,1501,1502...)
Regards.
MANU (email at fl...@ircam.fr)