Request for two small steel rod-esque lathed part!

[Ross77]

PICs are actaully pretty feeble things processing wise.

And I thougth they were the answer to all processing problems, is the clock speed to slow?

Do you know the spec of the inductors in the Wah Wah? In therory, I could probably wind such an inductor...but why? (are they hard to get or something unique about them?)

No not hard to get but at £20 from the gud ol US its a bit pricey. 520mh is the magic value apparently. Read an article on old vintage Wah's and it seems that the sound is due to the magnetic build up of the pot core and suggested that an additional second winding could provide this varible magnatism (if that sounds correct) to recreate the sound?

I know lots about guitars but electronics to that level is beond me...:heehee:

[HankMcSpank]

And I thougth they were the answer to all processing problems, is the clock speed to slow?

Yes...I think they go up to 20Mhz (though I just run mine at 4Mhz ....I'm placing modest processing requirements & higher clocks just results in more heat/consumption)

No not hard to get but at £20 from the gud ol US its a bit pricey. 520mh is the magic value apparently. Read an article on old vintage Wah's and it seems that the sound is due to the magnetic build up of the pot core and suggested that an additional second winding could provide this varible magnatism (if that sounds correct) to recreate the sound?

Well, i know a little about electronics...but inductance & the associated magnetism is something I've never had to apply a lot of thought too. (& is a specialist field in itself). i know the basics.

As it goes, the single string sustainer coils I've wound are about 1mH ...520mH seems like a whacking big inductance (you sure you don't mean 520uH?) , but then there's the question of what type of core, wire gauge used blah blah (things get really esoteric when it comes to old vintage components!). Have you a link to the coils in question?

[Ross77]

As it goes, the single string sustainer coils I've wound are about 1mH ...520mH seems like a whacking big inductance (you sure you don't mean 520uH?) , but then there's the question of what type of core, wire gauge used blah blah (things get really esoteric when it comes to old vintage components!). Have you a link to the coils in question?

Definatly 520mh

http://geofex.com/Article_Folders/wahpedl/wahped.htm

Its a few scrolls down. and easyier reading on the site....

The best explanation I could come up with is this. The inductor in the classic wah setups carries the DC bias current for the first transistor. While this is only microamps, long exposure to this unidirectional bias could result in a remanent magnetization of the inductor core if the core material was not very good in the classical, linear EE sense. It's possible that Vox merely specified the circuit, the maker (Jen, I think, in Italy) made the early wahs from as inexpensive a material as they could, and the slight deviation from linearity resulted in a sound that the folks at Vox liked. That is - it was a happy accident resulting from being cheap. I've never heard another explanation that accounts for the differences. There are differences, and measurable ones, and ones that square with reasonable explanations for how the thing works and sounds. This legend's true.
I have not seen or heard any of the supposed "next generation" Fasel style inductors, so I can't say whether they are true to the originals.
One thing that became obvious is that you could artificially get a more linear core material to have an offset, and in the easiest way. If we're always pumping current through the inductor, we can get any offset we like by just pumping more. If we were to put a second winding on a wah inductor, we could force DC through it from a current source circuit, which would force the "center" of the magnetic operation toward one or the other saturation points. Of course, this is not possible with a pre-wound and potted wah inductor, but is emminently feasible if you happen to wind your own. It's even more feasible if the inductor you use happens to have a second winding, like the Radio Shack transformer that is mentioned later. This secondary can just be hooked up and current fed through it. I intend to do this as as soon as I get some bench time. Note that I've been saying "current source". You can't just use a resistor, because transformer action would reflect this resistance into the inductance winding as a load and damp the resonant action of the inductor. The minimum you need is a transistor connected as a current source to keep from doing this.

Any help would be most appeciated.

[HankMcSpank]

I'm sure you've grasped it all, but from my (quick) understanding the much cherished old VOX wah were analysed under lab conditions & ultimately acted in a way that wasn't expected. It would appear the inductor core (which is made of ferrite not meant to have to hold any permanent magnetic qualities) had become in part magnetized (he'd guessing the DC current the wah circuit has permanently running through the industor may have led up to this). The end result is that when you feed an AC signal into the inductor, the inductor core will saturate faster in one half of the signal waveform than the other...apparently this sounds good in a wah circuit! (I can't say...this is all news to me!)

Therefore he goes on to hypothesize that this could be 'frigged' using a modern bespoke wound inductor, buy adding a second winding and then pumping some DC current through it. This would generate a magnetic field, utlimately turning the ferrite core into a pseudo magnet...you then have the aformentioned non linearity that is sought.

he doesn't give any figures for the amount of turn the second core should have...so you'd be very much into trial & error territory. And without having access to his data (scope traces at set frequencies for the original VOX inductor etc), it'd likely be a futile (& long drawn out) affair!

But by the looks of it, the inductor used in the Wah circuit has a ferrite core, an inductance of 500mH and about 50-70 ohms of DC resistance. I'm not sure how physically big those inductors are, but that surely amounts to a lot of windings (so I'm guessing they use very thin copper wire)

[Ross77]

Thanks Hank. yeah I got the basics, although I understood your explanation better. I was looking for a starting point for the magnatising coil, as you said there are no values given.

The main inductor bit is easy, its about 550 turns of 38AWG wire on a pot core. finished size is about the same as a stack of 3 £1 coins.....

As I said I planned to look into this later (too many projects) but Ive got side tracked when I saw this thread about coil winding..

May have to pick your brains when I get round to it.