Wah pedals are pretty sensitive and interactions with besides noise are quite common.
But what can you do, if your wah starts to hum, hiss, murmur and chirp? What might be the cause?
Certainly, the wah with its inductor and its transistors is pretty microphonic and the reasons for besides noise are diverse, thus the measures to eliminate them are multifarious too.
Neon lamps for example, as well as the monitor of a computer, electricity lines and power supplies easily cause besides noise with wah pedals.
Microphonic Wahs benefit from a new inductor. Especially if your wah is an old one, the windings of the inductor sometimes got loose and now interact with any vibrations. Of course, you could waxpot the inductor carefully. But in this case, you need the same prudence and experience as for waxpotting pickups.
The transistors could also be microphonic. In this case, the replacement by selected new transistors.
Regarding wah pedals, the brand of the transistor doesn’t really matter at all, but the hfe which indicates the gain of a transistor is decisive.
Actually, it is possible to install a mounted transistor as far as it is pin compatible. Thus, you can vary the transistors for testing.
Planning your pedalboard, you should keep the following aspects in mind: never place your wah on the power supply, but rather as far away from it as possible. Thus, you can reduce the risk of interferences.
Above all, selecting the appropriate power supply is very important. Running a wah on battery would be the best way. But actually, this is cumbersome and not even environmentally friendly. But if you have decided to run your wah on battery, you could also connect it via a suitable adapter to the power supply jack. Thus, you can change the battery easily and you won’t have to worry about besides noise.
Choosing the right power supply is not even easy. I would counsel against digital switching power supplies. They will cause besides noise anyway. An old, unregulated power supply might be the better choice. It is worth it, to try it out.
The Voodoo Lab Pedal Power 2 provides two outputs which can be regulated and therefore, are especially suitable for wah pedals.
Vendors like The GigRig offer (pretty expensive) adapters/filters that are supposed to act like batteries. Maybe this might be the proper solution for you.
If the wah also produces besides noise while it runs on battery, the ground might be the problem. In this case, all grounding connections should be checked.
Danelectro as well as Vertex offer boxes that can be interposed between power supply and wah and power the respective pedal with power from a battery. The advantage of these boxes is, that they are activated via the power supply and when you switch the power supply off, your battery will also be disconnected. Consequently, you won’t have to remove the plug from the pedal to avoid the discharging of the battery.
The pot can also cause besides noise. Especially with old wahs I am annoyed about reading in forums that somebody restored his vintage McCoy Wah and replaced the old pot by a new one.
Every pot has a certain characteristic taper and a new pot will definitively alter the legendary sound of an old wah. Cleaning the pot would be the better option. Replacing it should be the ultimate step.
Another reason why the wah is prone to besides noise is the fact that it amplifies certain frequencies. This frequency amplification will always amplify besides noise as well. Thus, it is important to fine-tune the wah quite well. By replacing some resistors, maybe even by trim pots, this peak can be tuned.
If you definitively want to run your wah on a power supply, you could furthermore increase the filter of the power supply. A capacitor might smoothen the incoming power and the wah will get less noisy.
To sum up: yes, the wah is a diva. But with these suggestions, you ought to be able to reduce the besides noise of your wah somehow.