Sola Sound / Vox - Tone Bender 3 Knob (MKIII) / Fulltone - Soul Bender

[NOTE - This post also contains details of the Fulltone Soul Bender]

Vox Tone Bender Mark III

Introduced in 1968 the Sola Sound Tone Bender MKIII is the last in the line up of the classic Tone Bender circuits. It produces a more mellow, less aggressive fuzz than the MKI & MKII Tone Bender circuits. Once again it uses a 3 transistor design but the structure is significantly different to previous incarnations of the Tone Bender. As you can see below the Tone Bender MKIII came in various guises:

Sola Sound Tone Bender MKIII

Colorsound Tone Bender MKIII

Another Sola Sound unit

Sola Sound Tone Bender MKIII Gutshot

Now although the fuzz produced by the MKIII isn't as agressive as previous Tone Benders it can still produce an unholy amount of Fuzz. Here's a demo video of the MKIII Tone Bender circuit in action (Note - it's a Pigdog MKIII):

Here's the schematic for the most widely distributed version of the Sola Sound Tone Bender MKIII:

In the original the transistors were unmarked PNP Germanium and the diode was a 1N270. I'd recommend using a pair of lower gain (40-60 hfe) for Q1 and Q2 and a higher gain 90-120hfe for Q3. If you want to see the variations on the Tone Bender MKIII design then check out: http://fuzzcentral.ssguitar.com/3knob.php, there are details on the Park Fuzz Sound and Prescription Electronics Yard Box there.

Here's a vero layout created by Electric Warrior (Note - he used a 250K Volume pot):

And here's some images of his completed build:

And here's some info regarding the Fulltone Soul Bender:

And a description:

"Our Soul-Bender is based on the legendary Colorsound and Vox Series III ToneBenders made by Sola-Sound/England in the late '60's that was used by Beck and Page on much of their circa 1968-70 recordings.

Equipped with 3 gain-matched germanium transistor for a FAT, searing lead tone, I also made the Tone control response and range more usable and much less shrill sounding... Full clockwise is SMOOTH sounding.

The Soul-Bender cleans up when you back-off on the guitar's volume control. This pedal has tons of tonal character and even harmonics and of course, true bypass w/ LED is included with every one."
And a vero layout for the "Boutique Bender":

For more info on the Sola Sound Tone Bender MKIII check out Effects Database here: http://www.effectsdatabase.com/model/solasound/tonebender/mk3

And here's the Freestompboxes.org forum topic: http://www.freestompboxes.org/viewtopic.php?f=19&t=7728