Well got time for another study break, so it’s that time for another layout. Just like the last layout I posted, here’s another uber rare fuzz, a gift from the fuzz gods that no worshiper of fuzz should be without IMHO.
One of the more famous Tone Bender MKI influenced fuzz boxes and now
almost as legendary as its golden cousin was the John Hornby Skewes Zonk
Machine. A little more wacky in the graphics
department, but not as heavy duty or robust as the MKI, the Zonk Machine
was almost identical in its circuitry. Made between 1965 and 1966 in
Leeds, England, the Zonk Machine like the MKI was only
made in small numbers before the pedal was updated with a more modern
and easier to produce unit.
Layout 1: Original PNP
Layout 2: Original NPN
Some suggested gains and tips I found over at DIYSB:
Q1=53hfe
Q2=126hfe
Q3=98hfe
Q1=70hfe,
Q2=116hfe
Q3=97hfe
One suggestion with the leakage:
Q1=180hfe/.142ma
Q2=176hfe/.177ma
Q3=195hfe/.124ma
Values taken from an Original Unit
Q1=TI AO2 650 Hfe= 180, leakage= 0.12mA.
Q2=Mullard OC75 Hfe= 78, leakage= 0.29mA
Q3=OC44 Hfe= 58, leakage= 0
Tips for other builders interested in the Zonk Machine:
1. Socket all transistors because you’re likely to go through a bunch of them before you find some that work well.
2.
The Zonk is very bright. Play around with the input cap and try values
between .001uF and .01uF. Maybe even set up a three way switch to toggle
between different values.
3. Definitely use a log/audio taper “Fuzz”
pot. I used linear at first but it greatly limits the useful range of
the pot. The name “Fuzz” is a bit of a misnomer as it doesn’t really
fulfill most people’s definition of a fuzz control. It essentially
adjusts the bias of Q2. The Sola Sound Tonebender Mk1, which is a
topographically identical circuit (sans the 33K resistor), called this
pot “Attack” which is a bit more appropriate IMO.
4. Set up an SPST switch to bypass the 2.2M resistor for nasty, all-out craziness!
5. Some came with 25k Log Fuzz pot, and 220k resistor instead of 470k.