Calling all wah-wah users! A cheap, easy & very effective mod

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.

The unmodded Vox V847 wah-wah
The unmodded Vox V847 wah-wah

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.

The unmodded Vox V847 wah-wah
The unmodded Vox V847 wah-wah

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.

Use an old jar lid or tin cup to stop things rolling around
Use an old jar lid or tin cup to stop things rolling around

Now it’s time to remove the baseplate itself and look at what we’re up against.

The inner workings of a Vox V847 wah
The inner workings of a Vox V847 wah

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.

The switch that we'll be replacing
The switch that we’ll be replacing

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.

The input jack socket - identifying the wire(s) from the tip
The input jack socket – identifying the wire(s) from the tip – Why do they still make them like this?

Unsolder the blue, brown and white wires from the switch……

Unsolder the wires from the switch
Unsolder the wires from the switch – On closer inspection it looks like the white wire is still connected but it’s just the angle I took the photo at.

Next up, unsolder the brown and green wires from the input tip connection on the jack socket.

Unsolder the green and brown wire from the input socket tip connection
Unsolder the green and brown wire from the input socket tip connection

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.

Cut two lengths of wire and a small length of heat-shrink
Cut two lengths of wire and a small length of heat-shrink

The next two photos show the switch removed from the unit.

 

The body of the wah with the switch removed
The body of the wah with the switch removed
The switch itself
The switch itself

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.

The replacement switch
The replacement switch

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.

Bump-its - stick on plastic bobbles
Bump-its – stick on plastic bobbles

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).

Remove the nuts and washers from the switch
Remove the nuts and washers from the switch

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.

The new switch has now been installed
The new switch has now been installed

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.

The underside of the new switch
The underside of the new switch

You should now tin six of the nine connections. Tinning makes soldering a lot easier. I’ve gone for the outer two columns.

Tinning the connections on the switch
Tinning the connections on the switch

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.

Starting to wire up the switch
Starting to wire up the switch

Now I solder my green wire to the existing green wire….

Extending the green input wire
Extending the green input wire

….and cover the joint with some heat shrink.

Use heat shrink or insulation tape to cover the joint
Use heat shrink or insulation tape to cover the joint

Now run the green wire to the bottom lug on the opposite side to the blue wire.

Connecting up the green input wire
Connecting up the green input 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.

Solder the white wire to the input tip connection
Solder the white wire to the input tip connection

And then run the white wire round to the middle lug opposite the output’s white wire.

Connect the white wire up to the lug opposite the other white wire
Connect the white wire up to the lug opposite the other 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.

The completed re-wire
The completed re-wire

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,

 

Rich