In this article we’ll be looking at a step by step guide to adding a true bypass switch to our wah-wah pedal. In this example we’ll be using a Vox V847.a wah but this can equally be applied to the Jim Dunlop Cry Baby wah and pretty much any other wah-wah pedal that uses a ‘standard’ switch and not a true bypass.
First off, let’s look at why we’d want to true bypass a wah in the first place. There’s a huge amount of info out on the interweb about this so I’m not going to get in to a near copy-and-paste scenario. In a nutshell, the standard switch on a Vox/Cry baby wah will simply turn the wah circuit on or off but the guitar’s signal will still run through this circuit regardless. Many people consider the circuit, when not activated, to be rather tone-sucking and I must be honest, that’s a camp I fall in to. Because it’s the way they built them in the good old days brands like Vox etc want to stick with the original spec. I can see their point to the greater extent but times change and some things can be improved upon. Just because that’s how they did it back then doesn’t mean that’s how we have to do it now.
This mod is one of the most popular ones that I’m asked to perform and I’ll also be documenting other mods (such as a Boss DS-1 upgrade and converting an Ibanez TS9 to TS808 spec) in coming months. If you are thinking of mod’ing then please give me a shout, I’d love to help out. Ok, let’s crack on.
Here we have a standard, unmodified Vox V847.a wah wah. The ‘.a’ simply means that it has a 9v power input.
Now, we’re going to flip the wah over and remove the feet/base-plate screws. You can undo these most of the time with your fingers but I prefer to use a screwdriver so as not to wear out the rubber feet.
Now, these feet (and screws and other important parts) have a nasty tendency to roll around and off the workbench, on to the floor and into the most inaccessible of places. Use an old jar lid or similar receptacle to keep them close to hand.
Now it’s time to remove the baseplate itself and look at what we’re up against.
Ok, so here we can see the innards of the wah itself. There are a myriad of mods that we could make to this pedal and if it were an older version then I might be tempted. As this is one of the later models and one that I personally think sounds pretty good when it’s engaged, I’m going to just concentrate on the true bypass switch installation. We do have options for installing an LED activation light if we so desire and for changing the tonal qualities of the pedal itself but for now, I’m just sticking with the bypass. At this point, if you have a battery installed, remove it. Also, make sure there isn’t a power supply plugged into the 9v input jack socket.
Here is the switch that we’re going to be replacing. Note that we’ll need to unsolder the brown, blue and white wires. Your wires may be a different colour so you’ll need to use a multimeter to determine which wire is from the input socket tip, which one goes to the pcb and which one goes to the output socket tip. In this case the brown is the input, the white is the output and the blue is from the board.
Next, look at the input jack socket. Here we can see there is the brown wire that runs to the switch and a green wire that goes off to the board. It’s this that creates that resultant tone-sucking when the pedal is disengaged.
Unsolder the blue, brown and white wires from the switch……
Next up, unsolder the brown and green wires from the input tip connection on the jack socket.
Now cut 2 x 8″ of wire, I’ve used green and white. You’ll also need a short length of heat-shrink or insulation tape.
The next two photos show the switch removed from the unit.
Here is the switch that we’re going to be installing. It’s a 3PDT (Triple Pole Double Throw) switch. These are only a couple of quid, are very robust and should last many years.
I’ve measured up and found that the replacement switch is a touch shorter that the old one. This is going to cause issues when trying to press down and engage the wah. A simple and very effective solution is to use a ‘bump-it’. The photo below isn’t great but you can make out what a ‘bump-it’ is.
And here is a ‘bump-it’ attached to the top of the switch extending it and making it more comfortable to operate.
Next up, remove all the nuts and washers from the switch then discard one of the nuts (if it’s supplied with two).
Next up, place the locking washer on to the switch, install the switch in the body of the wah, install the plastic washer and then one of the nuts. Tighten but be careful not to over tighten as you could damage the switch.
In the next photo we can see the new switch in the body of the wah. Note how the connections run horizontally. There are nine connections, three rows of three. The middle row is common and the top and bottom rows are switched to and from. Things will become clearer in a bit. Also note that I’ve removed the brown wire as it’s surplus to requirements.
You should now tin six of the nine connections. Tinning makes soldering a lot easier. I’ve gone for the outer two columns.
Bit of a dodgy photo this one so apologies but we can see that I’ve soldered the white wire that leads to the output tip to the middle lug and the blue wire that comes from the board to the bottom lug.
Now I solder my green wire to the existing green wire….
….and cover the joint with some heat shrink.
Now run the green wire to the bottom lug on the opposite side to the blue wire.
Now solder the white wire you cut earlier to the input socket’s tip connection. Use a multimeter (set it to continuity) and identify which is tip if you’re unsure which connection is which.
And then run the white wire round to the middle lug opposite the output’s white wire.
So at this point, when the pedal is engaged the wah’s circuit will work and we’ll get that classic sound that we all love. But when it’s disengaged the pedal will be silent and no sound will come out of our amp, so we need to address that by putting a short jumper wire as shown in the next photo.
So as you can see in the photo above, I’ve wired the top outer terminals together. This makes the pedal true bypass and we won’t get our tone affected in any way. Now is the time to replace the battery, put the base plate back on and screw the feet back in to place. Test and enjoy!
If you’d like to know more about this mod and/or are interested in having other mods done on your pedals, guitars, amps etc then please get in contact here. Thanks for reading,