SYNTH
Kastle is a mini modular synthesizer
with headphone output, 2 in/out
ports for interfacing other gear and
it runs on just 3 AA batteries. It is
DIY friendly and ideal for beginners
in modular synthesis, but it will add
quite some unique functionality to
any modular synthesizer systems.
It delivers the fun of modular
synthesis at cost and its into
your pocket so you can play it
everywhere!
It has unique digital lo-i sound and
it can be melodic as well as very
noisy and drony, soft or harsh. It is
designed to be fun on its own but
it is most powerful when combined
with other modular gear.
Kastle is an open source DIY project
which runs on two Attiny 85 chips
that which can be reprogrammed with an Arduino (google: “programming Attiny 85
with Arduino”). One chip is dedicated to sound generation while the other handles
modulation. Several irmwares for the Attiny chips are available.
The Synth version combines complex oscillator and LFO with stepped waveform
generator.
The oscillator section has 3 sound parameters pitch, timbre and waveshape - all
under voltage control and with 3 diferent synthesis modes. It has a main output
and a square wave output. Both can be used independently or combined. The 3
synthesis modes are phase distortion, phase modulation (also known as FM) and
track & hold modulation. Each mode utilizes two oscillators. The Pitch controls
the main oscillator, the Timbre sets the pitch of the modulating oscillator and the
waveshape depends on the synthesis mode. The waveshape also controls the pulse
width of the square wave output from the main oscillator.
The voltage controllable LFO has a triangle and square output and a reset input.
The stepped waveform generator is inspired by the Rungler circuit by Rob Hordjk.
It can produce 8 diferent voltages either in random order or in 8 or 16 step looping
patterns depending on how the BIT IN is patched.
ABOUT
© complex oscillator
© 3 synthesis modes: phase distortion, phase modulation and track & hold modulation
© pitch control with ofset and CV input with attenuator
© timbre control with ofset and CV input with attenuator
© waveshape control with ofset and CV input
© voltage controllable LFO with triangle and square outputs and reset input
© stepped voltage generator with random, 8 step and loop 16 step mode
© 2 I/O CV ports are available and can be routed to any patch point
© the main output can drive headphones
© 3x AA battery operation with power switch
© open source
© possibility of exchanging diferent LFO and OSC chips
what is in the box
© kastle synth
©10 patch cables
© sticker
© for environmental reasons we are excluding the batteries in the package
FEATURES
A
Percussive sounds
Connect the LFO PULSE to the LFO RST socket. This results in SAW waveform at the
LFO TRIANGLE output (because as soon as the TRIANGLE starts rising it receives
the PULSE and therefore goes to the highest point and starts falling and therefore
skips the rising stage). Use the SAW waveform to modulate any or multiple of the
oscillator parameters. On top of that connect the STEPPED output to LFO RATE
socket. Adjusting the LFO RATE and the RATE MOD knobs will result in different
lengths of SAW modulation signals and therefore different rhythms.
B
Different rise and fall times
Connect the LFO PULSE to the RATE MOD socket. Now the RATE MOD and LFO
RATE knobs set different proportions between the rise and fall time of the triangle.
This will also create a swing effect on the STEPPED waveform. You can also use the
STEPPED output to connect to the RATE MOD socket to change the slope time with
every new voltage generated at the STEPPED output.
TIPS & TRICKS
C
Thick sound
Connect the OSC PULSE to the OSC OUT socket to mix both oscillator waveforms
together. This can result into really thick sound which is great for further filtering.
D
Sync
The LFO and STEPPED generator on the Kastle can by synced with other gear.
You can use the LFO PULSE out when you want the Kastle to be the master clock
or connect clock from another device to the LFO RST when you want it to be the
slave. Simply connect the I/O jack to you device and patch the L socket to the LFO
RST or LFO PULSE.
E
Connect everything to everything!
There are several connections that might surprise you in exploring the sounds.
Here is few of the ones you should try out for sure:
Connect OSC PULSE to the BIT IN to create varying random patterns.
Connect OSC PULSE to any of the OSC inputs to see what happens.
Connect any LFO signal to the MODE pin to change the synthesis mode on the go.
Connect OSC PULSE to the LFO RST pin to create chaotic modulation waveforms.
Kastl takes some common synthesis methods and implements them with a very
lo-fi twist which gives it very distinct character full of aliasing artefacts.
I
Phase modulation
Very similar to FM (frequency modulation) is method pioneered by John
Chowning and later used by Yamaha for their famous DX synths. Kastle
implements only two operator sinewave PM with a modulation amount. Pitch sets
the main oscillator (carrier) , timbre the modulating oscillator (modulator) and
waveshape sets the amount of modulation.
II
Phase distortion
Was historically first used in 1984 in Casio synths of the CZ range. It is based on
two synced ramp oscillators. The synced (higher tuned) oscillator is scanning the
sine wave wavetable and is multiplied by the inverse of the lower tuned oscillator.
In practical terms this was supposed to emulate sweeps of resonant filter on
a sawtooth waveform. The implementation in KASTLE is adaptation of this method
SYNTHESIS TYPES
See
www.bastl-instruments.com
for more information.
with wider ranges on the oscillators and more formant vocally character. There is
also the third WAVESHAPE parameter which adds noisier high-pass character to
the sound.
III
Track & Hold modulation
This is not so common synthesis method. The main sinewave oscillator is going
thru a comparator which turns it into variable pulse width waveform which is
gating a track & hold circuit.The second oscillator is being fed thru the track &
hold which means when the pulse of the main oscillator is high the signal passes
and when it becomes low it holds static voltage. The threshold (waveshape) on the
comparator sets the pulse width therefore the amount of the modulation and pitch
and timbre set the frequencies of the oscillators.
