Wah Pedals - Misconceptions, Myths and Hype
Last updated 10/4/06
Before you send me emails trying to disprove or contend with whatever I have written in the following article, realize that my comments are borne out of personal experience with many different CryBaby wahs, mods to CryBabys, DIY CryBaby type circuits and other types of wah circuits such as the Maesto Boomerang, DIY and otherwise. Wah pedals have become something of fascination for me over the last year or so. It's amazing how many different wah circuits are out there, the similarities and differences between them and how they work. They are one of the coolest guitar effects ever invented.
Wah pedals and how they sound is an extremely subjective matter, so you are entitled to your own opinion about each facet of the circuit. I am simply sharing my views on certain topics that I see popping up pretty consistently. This is intended to be a supplemental document to my wah pedal mod pages.
"How can I increase the range of my wah pedal?"
There are some things that you could do to the circuit itself to increase the range, but for the amount of change that you gain by doing so, most of them are not worth the time and trouble. In a CryBaby type wah, the issue with the available range is mostly a mechanical one Ė the pot simply doesnít go thru its full rotation when the treadle is operated. The simplest way to extend the range of your wah pedal is to remove the rubber bumper at the heel and shave some material off of the bumpers on toe end of the treadle - then adjust the pot rotation and footswitch accordingly. This will give you approx. 5/16" more travel and can that make a significant difference in the sound. One thing to note is that the wah pot itself will not make the range wider or smaller - all it really does is select points between the upper and lower limits set by the gain of the first transistor.
Another thing that could be done is to increase the gain of the first transistor. This probably will increase the range of the wah to some extent, but the frequency response may be shifted and the noise floor may also be increased depending on exactly what you do to increase the gain of the first transistor. Exercise caution when taking this approach.
"I want to change the inductor in my wah. Will that make it sound better?"
That is a loaded question. The answer is sometimes yes, and sometimes no. The inductor is just a relatively small part of the overall picture. Its function is literally to make the wah circuit a resonant circuit. Whether itís a Fasel, halo, or any other type of inductor is mostly secondary compared to its primary function. It will affect the tone marginally, but I feel that there are more significant changes to be had by tweaking other parts of the circuit than by changing out the inductor. Some people claim that changing the inductor totally changed their wah, but that has not been my experience. This is a highly subjective topic, though, so everyone is going to have a different opinion on this as well as subject to the fact that everyone has varying degrees of sensitivity to hearing subtle changes in the way something sounds.
"I want to change the caps in my wah pedal. Will it improve how the wah sounds?"
Once again, this is a highly subjective topic. In my experience, any quality cap sounds as good as another. Some people feel that the caps are very important, but I canít hear much of a difference between different types, if any. I certainly would recommend staying away from ceramic capacitors, at least the low voltages ones (less than 1kV). Changing the caps out simply does not turn your wah pedal into another pedal. I feel that this is another area of mostly hype based on my personal experience and is also apparently the result of some of articles that been published on the internet. In all honesty, I changed out the caps in one of my wah pedals with tropical fish caps just because I think they look cool. Vanity of vanities! Just for the record, I couldn't hear any signicant differences afterwards.
"I want to change the transistors in my wah. Will it make it sound better?"
This is one thing that can make a definite noticeable change in how your wah pedal sounds, for better or for worse. As RG Keen has stated, "The sweep range of an inductor wah depends on how much gain the first transistor has. The emitter cap of the second transistor is multiplied by the gain of the first transistor. More gain, more capacitive multiplication, and more range. The wah pot can't possibly make the range wider - all it does is select points inside the maximums set by the gain. Using less of the pot sweep restricts you further, of course, but the more first stage gain, the wider the range." Keep in mind that changing the first transistor could also result in a noisier wah pedal. The second transistor is simply an emitter follower, so there isnít any great benefit to changing it other than to try to make the wah quieter by using a low noise type of transistor in its place.
"I have to have an ICAR repro pot or my wah will be lame sounding and wonít sweep right."
This is another hotly debated topic. There is apparently some differences in the tapers of the various pots used over the years in vintage wah pedals. Some of the old 100K pots even measure nearly 200K! The pot is only part of the equation. You also have to look at what the rest of the circuit is doing, too. I personally like the Dunlop Hot Potz II pots the best of the ones I have tried. The sweep characteristics are pretty good and they are tough as nails as far as longevity is concerned. The actual taper of the vintage wah pots is debatable, and they seem to vary too much to nail it down anyway. The bottom line is whether or not you like it. Donít let someone elseís opinion make up your mind for you.
"I have an old wah with the infamous TDK 5103 inductor in it. I have to change it."
Baloney! One of the most expressive wah pedals that I own is an 80s TDK inductor equipped wah pedal. Once again, I feel that a lot of the attitude towards this particular inductor is hype that has been created by articles on the web, hearsay and manufacturer gimmicks. Everyone seems to be after (re)creating the Clyde McCoy sound, and thatís what the low opinion of the TDK 5103 inductor is based on. If you like the sound of it, then donít change it! Donít be swayed by what everyone else is saying.
"The Clyde McCoy was the best sounding wah ever."
Really? I ask you what you base that opinion on Ė what someone else has said, or from your own personal experience? In my opinion, there are other wah pedals that blow the Clyde McCoy away, but everyone has different personal preferences. Even in the original Clyde McCoys, it was a crapshoot Ė some sounded good and some didnít. The variability of the parts comes into play here. The halo inductor does seem to be a factor here, though, along with all the other circuit components viewed as a whole.
"I have to true bypass my wah."
Maybe, maybe not. In the case of the GCB95/GCB95 variant wah pedals, I say donít bother. The input buffer is just as good as true bypass due to its very high input impedance of the input buffer, and by the way, it also helps when using fuzz pedals and that sort of thing. When it comes to vintage wah pedals, they almost always show a major improvement when true bypassed since the "tone sucking" is pretty bad in a typical non-true bypass vintage wah pedal. It can be a little tricky to match bypassed and effected levels after true bypassing, but a little tweaking of the input resistor, and if required, the resistor on the emitter of the first transistor will usually resolve that problem without changing the tone too much. The tone will usually change somewhat after true bypassing.
"How can I change the sweep range to make it higher or lower?"
1. Adjust the rack and pinion gears to change how the pot rotates in relation to changes made by operating the treadle. The pot can be adjusted to accentuate the highs more or the lows more.
2. Physically change the sweep cap. This is a very simple mod. All that has to be done is to change the 0.01uF capacitor in parallel with the inductor. Making it smaller shifts the range up and making it larger will shift it down. I personally like a 0.015uF to 0.022uF cap Ė it makes it sound fatter. I donít like a thin, nasally sounding wah pedal. Give me something with meat!
"Jimi Hendrixís wah had a 470K pot. I need to get one for mine, too."
I would say donít bother with that unless you are just some kind of Hendrix freak and have to have it. There is no evidence that I can find that suggests that the early Vox wah pedals used a 470K pot, ever. The fact that Jimiís wah apparently had a 470K pot in it most likely has more to do with Roger Mayer tweaking it to Jimiís liking than some bright idea someone at Vox had one afternoon in 1968. And, incidentally, the patent documents also indicate a 100K pot.
"My wah pot is scratchy, but I donít want to replace it because itís original."
If you plan on actually using your vintage wah, just replace the pot! If you want to hold onto the original pot, put in a baggie and put in in a safe place where youíll remember where it is. Itís better to have a functional wah than one that sounds like fingernails scratching a chalkboard.
There is also a method that is suggested by Craig Anderton to use an LED/LDR combo to electrically isolate the pot. That would buy some more time, but eventually, the pot will wear out to the point where even that won't help anymore.
"Iíve heard that you can take apart an old wah pot to clean it and make it stop making scratching noises."
Sometimes you can actually do this, but I donít generally recommend it for the typical vintage 100K wah pot. Itís a lot simpler to just get a new one that will last longer than the original one did. There are some exceptions, as in the case of the very hard to find heavy duty 25K pot used in the Maestro Boomerangs. Those are worth the time and effort to recondition. In the typical old 100K pots, unless the conductive surface is quite thick, anything gained by the cleaning will be temporary and the scratching sounds will soon return. For replacements, I personally recommend the Dunlop Hot Potz IIs Ė they have a good sweep and they last next to forever (translation = no scratching noises for many years to come).
"Iíve heard that you can use WD-40 to clean and lubricate pots."
I do not recommend this. I donít think it is good for the pot - there are solvents in it that could actually damage the pot over time. Contact cleaners can work, but if there is a lot of gunk inside the pot, it is a very temporary measure.
"The Vox Clyde McCoy was the first wah pedal on the market."
I am currently researching this, but Maestro claims that the Boomerang was the first wah pedal on the market. The first actual wah circuit to be patented appears to be the celebrated Clyde McCoy circuit. I am looking into this further. Details on the history of the Boomerang are a lot sketchier than the Clyde McCoy, however.
"Why do I get a nasty hum when I use my wah pedal?"
Inductor based wah pedals are very sensitive to EMI (Electro-Magnetic Interference) due to the fact the inductor itself is senstive to EMI. Fans, compressors, computer monitors and wall warts are all things that can make your wah pedal hum. It can become really apparent when you are using a high gain distortion pedal. Unfortunately, the only thing that really eliminates it completely is more distance between the wah pedal and the source of EMI. This is because it is actually magnetically coupled. The only real solution is to get it as far away as possible from the offending source of noise.
"An inductor with a low DC resistance sounds better."
An inductor with a lower DC does resistance result in a higher Q factor. In a wah pedal circuit, the DC resistance is of little consequence until it gets up to several hundred ohms. Then you might be able to hear some differences, but they would be subtle. In new manufacture wah pedals, the resistor that is in parallel with the inductor reduces the Q. The lower the value of the resistor, the lower the Q. This resistor isn't required for the circuit to function. As a matter of fact, the original Vox wah circuit didn't even have one. It was added at a later date, for whatever reason(s).
A point of interest in the original wah pedal document is the addition of the 1.5K resistor in the feedback path of the sweep cap to the base of the first transistor. This was added, according to the patent document, because "the innate Q of the circuit, in fact, is so high that it was found favorable to insert resistor 36 (1.5K) in order to admit some of the non-favored (off-peak) frequencies into the amplifier, so that they could pass to the output. Without the resistor 36 (1.5K), virtually the only frequency appearing at the base 24 (1st transistor) would be the selected frequency, because of the high Q of the circuit. The presence of resistor 36 (1.5K) allows all frequencies to be developed to a certain extent thereacross, and hence to be passed onto the amplifier. Based on this, I would ask why one would want to try increase the Q of the circuit? I think it would just make for a lackluster sounding wah pedal.
"Where can I find a copy of the Vox wah pedal patent document?"
You can view a copy of it here. This is a copy of the official, approved patent document in PDF format.
"The Maestro Boomerang is just another CryBaby copy."
No, it is not. There are some similarities between the two circuits, but the differences between the two circuits are significant enough to make them two different animals. Secondarily, they are each manufactured under two different patents, although the end result of each is similar. To my ears, the Boomerang sounds much fatter and pleasing to the ear - the CryBaby sounds much more harsh to me. Just my opinion, of course.
"The Vox wah pedals have a longer travel than the CryBabys do."
I do not know where this started, but I have both types of wah pedals, and the measurements I have taken do not indicate any significant differences - they are basically the same thing. I think this rumour may have been started due to differences in the sweep characteristics in the various wah pots used over the years and attributed to there being a physical differences in the two pedals. I have not seen any evidence to support this claim as being true.
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