Skippy Tremolo

The SKIPPY tremolo is based on the vintage Vox Repeat Percussion. The original VRP is well known for it’s very hard, percussive tremolo sound, or chop. Certain combinations of speed settings and playing style can almost trick your ears into thinking that you are playing through a delay instead of a tremolo. For these reasons, the sound of this tremolo effect is often described as synth-like.


Originally, the VRP had only one control, Rate, to adjust the speed of the effect. In addition, the version that was built into the Vox Beatle Super Reverb amplifier also had an input jack for a foot pedal that enabled you to control the speed of the effect with your foot.

With additional controls and features, SKIPPY covers a much wider sonic range while still retaining all the character and bravado of the original VRP. Check out the video…


Depth – Adjust effect depth from subtle throb to hard chop.
Rate – Adjust effect speed.
Level – Adjust output volume to compensate for perceived volume loss with certain extreme settings.
Tone – Switch original Vox low-cut filter on or off. When on, output has a lot of treble and very little bass.
Mode – Switch between hi and low speed ranges. Low speed is normal tremolo range. Hi speed is pseudo ring-modulator range.


Plug CV pedal into control jack to vary speed with foot while playing.
Capable of ultra-wide range of speeds, up to pseudo ring-modulator speeds.
Accepts standard 9VDC, Boss-style, 2.1mm tip negative power plug.
Modern true-bypass footswitch and LED status indicator.
Hand made in USA using highest quality components available.


Another feature implemented in the PCB layout is a universal PCB footprint for the transistor in the oscillator section. By changing the value of one resistor and adding one additional resistor, the modern 2N6027 programmable unijunction transistor (PUT) can be easily programmed to function exactly like the old 2N2646 unijunction transistor (UJT). So the originally specified 2N2646 can easily be replaced with the modern 2N6027 without having to awkwardly bend the transistor leads around to achieve the proper pinout.

2N2646 (original UJT)

  • Install 2N2646 as shown (pink)
  • Do not install R12
  • R9 = 1k

2N6027 (modern PUT)

  • Install 2N6027 as shown (pink)
  • Install R12 as shown (pink)
  • R9 = 2k

If you’re interested, you can find more info about UJT versus PUT at this site…
All About Circuits

Here is an interior view of two SKIPPY pedals. The one on the left has a 2N6027 installed (as well as R12). The one on the right has a 2N2646 installed.


It is worth mentioning that the two pedals pictured above sound completely identical. There is no additional mojo to be had by using the outdated, sometimes expensive and hard-to-find 2N2646 UJT. The modern, affordable and readily available 2N6027 PUT works great and sounds perfect.

Additional Construction Documentation (link)