This
is a BENJOLIN version adapted for eurorack (16HP) which includes several mods
of the original design including output signals boosted to eurorack
standards and CV signal normalisations, controlled by the CV
attenuators, when no external input is
connected. The circuit and PCB layout
is based on forestcaver's open source files
and on this module only the panel design and the non-smt assembly is by
me. The panel is made from sturdy standart PCB material , with a black
solder mask
and a chaotic copper trace pattern underneath it. Most of the labels
consists of exposed ‘copper’, so they are shiny silver (see images).
Additionally the panel has white screen print designs.
And in here here i've added also a more detailed presentation/lecture by Rob Hordijk .
"The Benjolin is a multi-function synthesizer designed by Rob
Hordijk. The module consists of four separate function blocks: two VCOs,
a state variable filter and an additional circuit, invented by Hordijk
himself, called a rungler. This particular arrangement emerged from
Hordijk's efforts to design a synthesizer that was, as he puts it, "bent
by design". As such, the module functions according to principles of
chaos theory, where short to long sputtering patterns spontaneously
transform themselves, at times, gradually, at others, quite suddenly,
morphing into new pattern doublings and bifurcations.
The chaotic
character of the Benjolin is anchored in Hordijk's rungler circuit. In
essence, the rungler is an 8-step shift register that takes its data
input from one oscillator (OSC X) and its clock input from the other
(OSC Y). The output of the shift register is then fed into a primitive,
digital-to-analogue converter, creating a stepped voltage pattern of
variable length and depth, what Hordijk terms a “stepped havoc wave”.
This rungler wave is then wired back into the oscillators, via the
attenuator knobs (Run X and Run Y), creating the complex interference
system that lends the Benjolin its unique, aleatoric character.
The
inclusion of a voltage-controlled filter expands these possibilities
further into the audio realm. Its design includes Hordijk's signature,
Z-plane modulation circuitry, which produces all-harmonic distortion.
This gives the filter that kind of warm, organic character, reminiscent
of classic tube amplifiers. This is most palpable when the resonance of
the filter is turned to the maximum, with both oscillators running in
the audio range.
The filter's input comprises a mix of a PWM wave
(derived from the triangle waves of each oscillator) and the rungler
signal itself. As with each of the oscillators, a rungler attenuator
(RUN F) allows modulation of the filter as well. To round things out, CV
inputs for both the oscillators and filter are normalized, each via
their respective attenuators. This allows for cross-modulation between
the oscillators and a “sweeping” effect for the filter, hitched to
Triangle Y."