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How does a Wah, "wah"???

10/30/1997 9:54 PM
Ben Shelton	How does a Wah, "wah"??? SO, Can anyone out there give a decent explanation of how wahs work?? I'd lke to do some experimenting on mine but have no idea where to start. If I knew which component did what I'd have a much better place to start from. One other thing on the wah subject. What the he@! are "tropical fish" caps and what were they made of???? I'd like to find a current production cap to do the same job. Thanks, Ben

10/30/1997 9:54 PM

Ben Shelton

How does a Wah, "wah"???

SO, Can anyone out there give a decent explanation of how wahs work?? I'd lke to do some experimenting on mine but have no idea where to start. If I knew which component did what I'd have a much better place to start from.

One other thing on the wah subject. What the he@! are "tropical fish" caps and what were they made of???? I'd like to find a current production cap to do the same job.

Thanks, Ben

10/31/1997 7:57 AM
rg	The classical two transistor wah is one of those circuits where everything matters. The master of this particular circuit it Geoffrey Teese, who makes and sells the Real McCoy Wah pedal, which can be adjusted to do substantially ANY wah sound. Here are a few things I have done: -change the value of the 0.01 leading from the emitter of the second transistor, changes the base frequency range. - change the 33K ohm resistor connected across the inductor to change the "sharpness" of the bandpass. - change the emitter resistor of the first transistor to change the overall gain and the sharpness simultaneously - change the value and balance of the 0.22uF caps to change the sharpness, distortion at resonance and control range simultaneously "tropical fish" caps are named for their multicolored outer surface. Don't know the material. The other parts make so much difference that I would recommend using current production Mylar or polypro and twiddling all the rest of the stuff before counting on the cap material to be a big deal. The one thing you will not be able to do is fix the inductor much. I spent a couple of hours in a measurement lab with a vintage Fasel inductor, a modern Vox reissue inductor, a signal generator and a spectrum analyzer. The Fasel inductor, when fed a sine wave, distorts and produces a second harmonic in addition to odd harmonics. The second harmonic is bigger than the third. The Vox reissue produces only odd order harmonics under the same conditions, as the theory says it should. For some reason (I have some theories, natch) the Fasel actually produces a distortion spectrum similar to a triode under overdrive conditions. I believe that this is why the Fasel is legendary. I still have the test data.

10/31/1997 7:57 AM

The classical two transistor wah is one of those circuits where everything matters. The master of this particular circuit it Geoffrey Teese, who makes and sells the Real McCoy Wah pedal, which can be adjusted to do substantially ANY wah sound.

Here are a few things I have done:
-change the value of the 0.01 leading from the emitter of the second transistor, changes the base frequency range.
- change the 33K ohm resistor connected across the inductor to change the "sharpness" of the bandpass.
- change the emitter resistor of the first transistor to change the overall gain and the sharpness simultaneously
- change the value and balance of the 0.22uF caps to change the sharpness, distortion at resonance and control range simultaneously

"tropical fish" caps are named for their multicolored outer surface. Don't know the material. The other parts make so much difference that I would recommend using current production Mylar or polypro and twiddling all the rest of the stuff before counting on the cap material to be a big deal.

The one thing you will not be able to do is fix the inductor much. I spent a couple of hours in a measurement lab with a vintage Fasel inductor, a modern Vox reissue inductor, a signal generator and a spectrum analyzer. The Fasel inductor, when fed a sine wave, distorts and produces a second harmonic in addition to odd harmonics. The second harmonic is bigger than the third. The Vox reissue produces only odd order harmonics under the same conditions, as the theory says it should.

For some reason (I have some theories, natch) the Fasel actually produces a distortion spectrum similar to a triode under overdrive conditions. I believe that this is why the Fasel is legendary.

I still have the test data.

10/31/1997 9:12 PM
Ben Shelton	Thank You Thank You Thank You Thank You!!!!!!!!!!!!!!!!!!!!!!!!!!!!! This is exactly what I've been wanting to know. I am pretty happy with my crybaby as far as the tone goes but the position and curve of the "wah" is not to my liking. ( I am so glad someone out there knows these things and is patient enough to pass it on BTW) So... I'm sure RG will keep me busy for the next couple of weeks with these mod experiments. I'm also gonna try the wah/volume mod found at RG's web page WWW.Eden.com OK for a bit of trivia. I have a dunlop crybaby without the external power jack, but the inductor doesn't match any of the descriptions I've seen. It's about the same size as the rest but it is a light brown, mounted on four metal posts, has apparantly two layers of some type of ceramic mterail held together by a small brass bolt and screw. Can anybody identify this particular inductor???? As I said, it beat the new crybaby for warm type tone (which is easy) and a new vox (which isn't as easy) so I'm pretty happy with it. Thanks again RG

10/31/1997 9:12 PM

Ben Shelton

Thank You Thank You Thank You Thank You!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

This is exactly what I've been wanting to know. I am pretty happy with my crybaby as far as the tone goes but the position and curve of the "wah" is not to my liking. ( I am so glad someone out there knows these things and is patient enough to pass it on BTW)

So... I'm sure RG will keep me busy for the next couple of weeks with these mod experiments. I'm also gonna try the wah/volume mod found at RG's web page WWW.Eden.com

OK for a bit of trivia. I have a dunlop crybaby without the external power jack, but the inductor doesn't match any of the descriptions I've seen. It's about the same size as the rest but it is a light brown, mounted on four metal posts, has apparantly two layers of some type of ceramic mterail held together by a small brass bolt and screw. Can anybody identify this particular inductor???? As I said, it beat the new crybaby for warm type tone (which is easy) and a new vox (which isn't as easy) so I'm pretty happy with it.

Thanks again RG

11/2/1997 10:09 PM
Ben	All right everyone, I have tried out the first of RG's suggested wah mods i.e. changing the valeu of the 33K resistor across the inductor. I don't have any special test equipment besides the Bentronics 1000 audio analyzer so you'll have to just take my word for it. I removed the resistor from the circuit and replaced it with a 100k b pot. This didin't seem to have much effect from 33k-100k on my dmm but from 0-12k there seemed to be a noticable change. I unclipped the 1ook and put in a 10k pot in sieries with a 5k resistor. This seemed to give me some control around the apparrent sweet spot at 6k. I would like tot try this out with a 15k linear and log and a 25k linear and log but I'll have to go and buy them first. The results IMHO.... The effect was like that of a "wetness" control on an effects loop. The less resistance, the less wet. Like I said anything over 33k seemed to be redundant and innefectual. Try this out and please get back to me. I also wanted to ask in reference to the change of the .01 cap at the second tranny's emitter, Would this also be similar to adding a cap in parralell to the 33K resistor which is across the inductor. A friend and I both paid for this mod from an unamed source though it is a little different from what RG has proposed. RG, How would this be different? Doesn't it make the overall capacitance lower since they are in sieries??? My basic electronics is terrible so how does the parrallel resistor effect this part of the circuit ( the modded circuit that is?) Just a word, I am pleased with the mod I bought but I was not pleased about the price. The effect was to lower the frequency range a bit. This can be a very effective way to combat the shrillness of modern wahs. Laters, and keep on experimenting, Ben

11/2/1997 10:09 PM

Ben

All right everyone,
I have tried out the first of RG's suggested wah mods i.e. changing the valeu of the 33K resistor across the inductor. I don't have any special test equipment besides the Bentronics 1000 audio analyzer so you'll have to just take my word for it. I removed the resistor from the circuit and replaced it with a 100k b pot. This didin't seem to have much effect from 33k-100k on my dmm but from 0-12k there seemed to be a noticable change. I unclipped the 1ook and put in a 10k pot in sieries with a 5k resistor. This seemed to give me some control around the apparrent sweet spot at 6k. I would like tot try this out with a 15k linear and log and a 25k linear and log but I'll have to go and buy them first.

The results IMHO....

The effect was like that of a "wetness" control on an effects loop. The less resistance, the less wet. Like I said anything over 33k seemed to be redundant and innefectual.

Try this out and please get back to me.

I also wanted to ask in reference to the change of the .01 cap at the second tranny's emitter, Would this also be similar to adding a cap in parralell to the 33K resistor which is across the inductor. A friend and I both paid for this mod from an unamed source though it is a little different from what RG has proposed.

RG, How would this be different? Doesn't it make the overall capacitance lower since they are in sieries??? My basic electronics is terrible so how does the parrallel resistor effect this part of the circuit ( the modded circuit that is?)

Just a word, I am pleased with the mod I bought but I was not pleased about the price. The effect was to lower the frequency range a bit. This can be a very effective way to combat the shrillness of modern wahs.

Laters, and keep on experimenting, Ben

11/3/1997 7:16 AM
r.g.	The 0.01 cap and the inductor form the primary resonance of the bandpass filter that is the wah. The parallel resistor is the component most associated with the damping of the resoanance. Ah, yes, the "unnamed source" mod. I've seen it. It's far better to use a rotary switch to select one of a number of replacements for the 0.01; this is what the EH wah and the Foxx Fuzz Wah did, and is more straightforward than the parallel cap. The parallel cap acts like a capacitive divider driving the inductor. This works like a resistive divider; the drive level is lowered by the divider ratio, and the capacitors appear to be in parallel, given that the emitter of the second transistor looks like a low impedance source. It is not as effective a way to do the mod, but it does allow you to change the range without unsoldering anything, which is apparently why "unnamed" did it that way.

11/3/1997 7:16 AM

r.g.

The 0.01 cap and the inductor form the primary resonance of the bandpass filter that is the wah. The parallel resistor is the component most associated with the damping of the resoanance.

Ah, yes, the "unnamed source" mod. I've seen it. It's far better to use a rotary switch to select one of a number of replacements for the 0.01; this is what the EH wah and the Foxx Fuzz Wah did, and is more straightforward than the parallel cap. The
parallel cap acts like a capacitive divider driving the inductor. This works like a resistive divider; the drive level is lowered by the divider ratio, and the capacitors appear to be in parallel, given that the emitter of the second transistor looks like a low impedance source. It is not as effective a way to do the mod, but it does allow you to change the range without unsoldering anything, which is apparently why "unnamed" did it that way.

11/5/1997 2:04 AM
Ben	Yeah. Unnamed sold a former customer of mine new orange drops, a pre cbs kit (remember this one), a hop up the normal channel, a midrange kit, a master vol, and a master presence kit for his dead mint 1963 bandmaster. Now, this guy is so not with it that he thinks he is getting such a great deal with all these kits for an amp that I assume sounded great to begin with. The amp coulda been sold as was and a SF coulda been hacked up instead. The only saving grace I have to say is that after I redid all the crappy soldering the amp sounded great. Really great. Unnamed does have a tendedcy to just find a place to "alligator clip" his mods on top of existing circuits/components. If the would be modder can't handle the mod the right way they should ley someone else do it for them... Woww, sorry to ramble. It is so late/early I'll be back in touch when I have the time to try out some other mods. BTW RG, have you had a chance to test out any of the "next generation" Fasel style inductors??? At $30 I don't know if I'd plunk down on one that hadn't had some lab work done to it or at least some competent ears to scrutinize it. Bye for now and as always thanks to all, Ben

11/5/1997 2:04 AM

Ben

Yeah. Unnamed sold a former customer of mine new orange drops, a pre cbs kit (remember this one), a hop up the normal channel, a midrange kit, a master vol, and a master presence kit for his dead mint 1963 bandmaster.

Now, this guy is so not with it that he thinks he is getting such a great deal with all these kits for an amp that I assume sounded great to begin with. The amp coulda been sold as was and a SF coulda been hacked up instead. The only saving grace I have to say is that after I redid all the crappy soldering the amp sounded great. Really great.

Unnamed does have a tendedcy to just find a place to "alligator clip" his mods on top of existing circuits/components. If the would be modder can't handle the mod the right way they should ley someone else do it for them...

Woww, sorry to ramble. It is so late/early

I'll be back in touch when I have the time to try out some other mods.

BTW RG, have you had a chance to test out any of the "next generation" Fasel style inductors??? At $30 I don't know if I'd plunk down on one that hadn't had some lab work done to it or at least some competent ears to scrutinize it. Bye for now and as always thanks to all, Ben

11/5/1997 8:00 AM
R.G.	Re the new fasels - I have not heard them. I do know that the core material used in wah inductors is critical. The old "great sounding" fasels used a cheap material that actually became slightly magnetized, something that linear inductor cores are NOT supposed to do. This caused a magnetic offset that let the inductor itself to saturate asymetrically. By the way, if you want a great wah, contact Geoffrey Teese. He has pursued the insides of these things to a mania, and can turn out essentially any wah sound you like. The Real McCoy is expensive, but can be adjusted to have about any wah sound you like. He also sells drop in mods for Vox Reissues to turn the Vox into a killer wah. I don't have any financial interest in Teese's business, he just makes a great wah. There is a phone number on my web page for him.

11/5/1997 8:00 AM

R.G.

Re the new fasels - I have not heard them. I do know that the core material used in wah inductors is critical. The old "great sounding" fasels used a cheap material that actually became slightly magnetized, something that linear inductor cores are NOT supposed to do. This caused a magnetic offset that let the inductor itself to saturate asymetrically.

By the way, if you want a great wah, contact Geoffrey Teese. He has pursued the insides of these things to a mania, and can turn out essentially any wah sound you like. The Real McCoy is expensive, but can be adjusted to have about any wah sound you like. He also sells drop in mods for Vox Reissues to turn the Vox into a killer wah. I don't have any financial interest in Teese's business, he just makes a great wah. There is a phone number on my web page for him.

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