Here’s the Vox Tone Bender, a great early fuzz pedal that’s sure to please.

The build I’ve done here is the NPN version of the pedal, so it’s slightly different from the original, which used PNP transistors. The big difference here is that this NPN layout allows for negative ground, putting inline with the what’s standard these days; this will work with the 9V power adaptors you’re used to.

The other addition to the original Tone Bender build is the inclusion of a trimmer potentiometer coming out of collector of the second transistor. This was an addition made by Tagboard Effects (where I got the layout). This allows you to adjust the bias of the transistors and therefore the overall gain and therefore fuzz level. Older circuit designs like this often used transistors that you just can’t get anymore, so adjusting the trimmer pot will help you tweak and dial in the exact sound you’re after.

If you like fuzz, Vox’s Tone Bender is a great choice. Like so many fuzz pedals, this one is a good choice for beginners, which is why it’s on my easy DIY guitar pedal builds list. Give this a shot as an early build.

Jump to stripboard layout.

Vox Tone Bender Wiring Schematic

Check out the wiring schematic for the Tone Bender.

Wiring diagram for the NPN version of a Vox Tonebender.

And here’s the bill of materials.

Notes
R11M
R247k
R310k
R4820R
R51K
C1100nF
C215uF22uF can be used here instead
C347uF
C44.7nF
Q1, Q2Germanium2N series silicon transistors won't work, other silicon transistors may.
P11K LinAttack potentiometer
P250K LogLevel potentiometer
P310K trim
Jacks, power supply, etc.Don't ForgetThe stuff you usually use.

If you’ve built or seen fuzz circuits before, this will look pretty similar! But hey, it works…

One important thing to note here is on the transistors. As mentioned, this is the NPN version of the original circuit. Changing it up to NPN makes it so that this pedal design conforms to modern power paradigms. So, if you wire your power supply the usual way, this circuit will work. Silicon transistors are easier to come across than germanium ones, so you’re welcome to try those. That being said, I’ve tried a variety of 2N series silicon transistors and I haven’t been satisfied with any of them (more on this later). You’re welcome to try silicon, but germanium is probably the way to go. I’ve read that the AC176 may be a good choice here, but these can be harder to come by. At the moment I’m waiting for some germanium transistors and will report back with suggestions when I have them.

Plus there’s the trim pot that let’s you adjust the gain a bit, so even if you can’t get the right transistor, you can adjust the pedal a little bit. But again, silicon transistors don’t sound great in this circuit.

Another pointer on this circuit is that the 15uF capacitor for C2 can be replaced with a 22uF. A lot of other circuits use 22uF capacitors, and I always have a few of them handy. 15uF capacitors aren’t used as often, and, for this build, I forgot to buy any! C2 is just an output capacitor, which stabilises the current and voltage, so it shouldn’t affect the tone due to the change.

Feel free to also play around with:

  • Add tone control. I found the Tone Bender a little bit heavy on the bass; it sounds great, but if you want a bit more treble, tone control may be the way to go.
  • Try different transistors. This will change up the sound of the pedal greatly. There are a lot of choices to play with!
  • While you have P1 and the trim pot to adjust the gain for Q2, Q1’s bias isn’t adjustable. Try something different for R3, or even chuck a resistor going to ground below Q1!

Vox Tone Bender Stripboard Layout

As mentioned, fuzz pedals generally don’t use a lot of components, and the Tone Bender is no different. This makes the stripboard layout for it pretty easy! You can see that come of the components are a little crowded in the first half of the board, but they’re actually not hard to solder; it’s a bit of a squeeze on the top of the board, but not on the bottom!

This is the layout from Tagboard Effects, but as usual, I’ve provided both a layout with component numbers and with values, just in case you want to change something up.

Here it is:

Stripboard layout for the NPN version of a Vox Tonebender guitar pedal.

My Experience Building The Vox Tone Bender

This was a super cruisy guitar pedal build. Fuzz circuits are usually fun and simple builds. The only challenge, of course, is sourcing the right transistors!

As the time of writing, I still haven’t settled on the level for the trim potentiometer because the transistors I have on hand don’t seem to be right on any gain setting. This thing sounds fantastic on certain levels of gain, but not great on others (more on that later). The trim pot takes away some of the gain, which can be a good thing. 

A future build of this may replace the trim pot with a normal one so I can make adjustments to both. Who knows. It will depend on what transistor I finally settle with.

How Does The Vox Tone Bender Sound?

This is a real classic fuzz. I recently made a Harmonic Jerculator which had some great tone to it, but, since the Tone Bender predates the Harmonic Percolator (which the Jerculator is based on) but about a decade, it just has that more raw sounds. And, of course, it’s very 1960’s. 

As mentioned, I’ve only tried this build with 2N series silicon transistors. I’ve found higher gain transistors like the 2n5088 with the trim pot turned up all the way has some potential at mid-range levels, but at lower levels there’s virtually nothing and at lower levels there’s a bit of a buzz behind the fuzz which isn’t great. There’s clearly a lot of potential in this pedal, but it needs the right parts.

In my research into the right transistors, I’ve read that circuits like this depend on germanium transistors being relatively imperfect and having a certain degree of leakage; this probably would help stop the buzz I’m hearing.

But, in the few spots this pedal actually sounds good with 2N transistors, it sounds fantastic! It’s a pretty bright tone, but also relatively responsive to changes in pickup selection. It’s an old fashioned kind of fuzz, but that’s what you want out of a classic circuit from the 60’s.

Like a lot of simple early pedals (and modern guitar pedals for that matter), there’s a lot that you can do with the Tone Bender that doesn’t involve adjusting the pedal itself. Lowering the guitar’s volume (and therefore the input signal into the pedal) takes away a lot of the distorted aspects of the sound without changing much of the organic feel to it. Pickup selection also does quite a lot to change the sounds coming from this thing. Because of this, I’m actually able to get past some of the problems I’m getting from the transistors by minimising the signal going into the pedal itself.

I’ll report back on this once I have some different parts to test it with. I’m excited because, as mentioned, there’s a lot of potential here!

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