SCHLAPPI ENGINEERING NIBBLER User manual

NIBBLER MANUAL
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Technical Information 3
Voltage Levels 3
Current Draw 3
Module Description and Features 4
Introduction 4
Controls 5
Inputs 5
Outputs 6
Indicators 6
Block Diagram 7
How It Works 7
Binary and Accumulators 7
Synchronous/Asynchronous Operation 8
Phase Oset Switches 9
Waveforms 10
Patches to start exploring with: 11
Clock Divider 11
Clock Divider Drum Sequencer 11
Frequency Divider (or Subharmonic Generator) 12
Triangle Wave 12
Shift Register Noise 13
Rungler Variant 13
Simple Benjolin Variant 14
Sequencer (or Arpeggiator) 15
Phase Oset Sequences 15
Cross Patched Nibblers 16
Chaining Nibblers 16
Contact Info: 17

Technical Information
Voltage Levels
The Nibbler is designed for compatibility with Eurorac voltage standards. Inputs and
outputs are voltage and current protected and should not but damaged by any level
within the Eurorac ecosystem (-12V to +12v, or 24v pea to pea ).
Current Draw
+12V: 37mA
-12V: 17mA
SIGNAL TYPE LEVEL Notes
Gate outputs 0 or 10V
Stepped outputs 0 to 10V
Gate inputs 2.8V
threshold
Comparator input stage triggers around
2,8V

Module Description and Features
Introduction
The Nibbler is a four bit digital accumulator based on CMOS logic. What this means is that
it counts in binary from zero to fteen, with inputs and outputs for individual bits as well as
stepped voltage outputs (digital to analog converters). It does this with individual logic
chips instead of a CPU.
The concept here is that counting in binary (and its expression in bits) is inherently musical,
and we can use it to create both rhythms and modulation voltages (or melodies).
The interface is designed to to be playable, with switches for the binary counting as well as
two mode switches and two phase oset switches (so the second stepped analog output
can be oset in phase from the rst). There is also a large Cherry MX Brown eyboard
switch for resetting the register to zero.

Controls
Switches
Button
All the other inputs are aected by the ASYNC/SYNC control to either only have an
aect on the rising edge of the clock or immediately.
These inputs control the rate of counting.
These are the shift register inputs. The ASYNC/SYNC control similarly aects whether it will
shift only on a cloc or any time a pulse is received.
Inputs
All inputs are logic inputs with a threshold of around 2.8V that trigger on the rising
edge.
CONTROL DESCRIPTION
ADD 8 Adds 8 to the register
ADD 4 Adds 4 to the register
ADD 2 Adds 2 to the register
ADD 1 Adds 1 to the register
SUBTRACT/
ADD
Determines if the number formed by the ADD SWITCHES is added or
subtracted from the number already in the register
ASYNC/
SYNC
Determines if the output is updated only on a rising clock pulse (SYNC)
or every time an input is received (ASYNC)
OFFSET These two switches together set a phase oset for the second stepped
voltage. It can be 0º (both down), 45º (only bottom switch up), 90º (only
top switch up), or 180º (both switches up)
OFFSET
INPUT Description
CLOCK Clock input, also used for audio rate frequency division purposes.
Necessary for most operations.
RESET Clears the register, setting all outputs to 0, AC coupled so it can be
used as a hard sync input at audio rate
SUB This input interacts with the SUBTRACT ADD switch to change the
state to the opposite of the current setting.
INPUT Description
CARRY IN Intended for chaining multiple Nibblers, to make a larger register by
patching a CARRY OUT to a carry in. Eectively the same as GATE
1.
GATE 1 Adds with the ADD 1 switch to set the rate of counting.
GATE 2 Adds with the ADD 2 switch to set the rate of counting.
GATE 4 Adds with the ADD 4 switch to set the rate of counting.
GATE 8 Adds with the ADD 5 switch to set the rate of counting.
INPUT Description
SHIFT While SHIFT is high in SYNC mode any clock pulse will shift the
contents of the register up one, or if in ASYNC mode it will shift on
any pulse on this input.
SHIFT DATA Replaces the input of the shift register. With no input the top bit
(OUT *)cycles around and enters from bottom.
DATA XOR Performs an XOR function with whatever data is at the input to the
shift register
CONTROL DESCRIPTION
RESET Clears the register, setting all outputs to 0

Outputs
Gate outputs are either 0 or approximately 10V
Analog stepped voltages output 0 to 10V
Indicators
All inputs and outputs have blue LEDs indicating their current state, at audio rate they
may show a solid blue. The reset button also has an LED underneath it.
LABEL NAME DESCRIPTION
STEPPED
OUT 1
A weighted sum of the register bits as a stepped analog
voltage
STEPPED
OUT 2
The register bits summed with the two oset switches to
create a static phase oset
NAME DESCRIPTION
CARRY The CARRY out goes high for one clock pulse when the register
overows. You can use this to chain additional Nibblers for a bigger
register, or as another gate output. This is probably the output to
use if you are using Nibbler as a clock divider.
OUT 8 Gate output for the top bit of the register, which represents 8
OUT 4 Gate out put for the register bit that represents 4
OUT 2 Gate output for the register bit that represents 2
OUT 1 Gate output for the bottom bit of the register, which represents 1

Block Diagram
How It Works
The combination of switches and gate are the input for a 4 bit binary word. This will
be a number between 0 and 15. This is added to the number already present in the
register (a 4 bit memory unit) and then stored back in the register. This conguration
of an adder and a register is known as an accumulator.
Accumulators are a fundamental digital building block and have many interesting
properties, one of which is that it is the digital equivalent of an integrator (the
mathematical operation) and is a big part of most lter or oscillator designs.
This particular register also has a bit shifting operation built in, which rotates the bits
from lowest to highest at each clock pulse while shift is high (in synchronous mode).
Binary and Accumulators
Binary is a number representation which only uses ones and zeros, and each
position corresponds to a power of two. With a four bit word we have 1, 2, 4, and 8,
which together can add up to 15.
0
0
0
1
0
0
0
1
0
0
0
1
0
0
1
0
0
1
0
0
1
0
0
0
1
0
0
0
0
0
0
0
1
1
3
0
0
1
0
2
0
1
0
1
5
0
1
0
0
4
0
1
1
1
7
0
1
1
0
6
1
0
0
1
9
1
0
0
0
8
1
0
1
1
11
1
0
1
0
10
1
1
0
1
13
1
1
0
0
12
1
1
1
1
15
1
1
1
0
14

If the number in the register goes above 15 it overows and wraps around. For
example if there is 14 in the register and you add 4 then the new value will be 2. You
can think of this as a modulo 16 operation.
This has two cool properties: One is that if you are counting by one, then each higher
bit will be half the frequency as the previous one, allowing for use as a clock divider
or octave down eect. The other is that if you increment the counter (accumulator) by
an odd number, then you will get a waveform (or sequence) that will keep wrapping
around with an oset and take some time to repeat. See the waveforms page.
Synchronous/Asynchronous Operation
The “SYNC / ASYNC” switch determines if the output is taken from the register, which
will update only on a rising clock pulse, or from the adder which will change
immediately. This can be useful for wonky patterns or changing the audio rate eect.
For clean sounding rhythms and modulation it probably makes sense to keep this
switch set to SYNC, however at audio rate you can think about modulating the gate
inputs as frequency modulation. Frequency modulation inherently lters modulation
close to or above the carrier (in this case the clock signal).
In the ASYNC mode (taking the output from the asynchronous adder) then you will be
getting a combined phase and frequency modulation eect at lower modulation
frequencies and at higher frequencies the phase modulation will dominate. At audio
rate which one you want will probably be determined by whether you want that lter
eect or not, try both!
See the Three Body manual for more about phase and frequency modulation. The
same principles all apply here, except the clock input of the Three Body’s oscillators
is a xed 12.5MHz and the accumulator is 36 bits deep. This allows for many orders
of magnitude higher precision and delity, however the point here is to interact with
the bits directly.
The ASYNC mode also has a somewhat unusual normalization, the SHIFT and
CLOCK inputs are XOR’ed together and sent to the clock of the shift register.
This means that in ASYNC mode you do not need to use the CLOCK input to use the
SHIFT input, making the shift register functionality independent of the accumulator
functionality. This can then be used for a Rungler patch as detailed in the patch
section of the manual.
14 + 4 = 18 - 16 = 2

Phase Oset Switches
The two oset switches can be used to create a second stepped voltage oset in
phase. The four osets are shown below. At audio rate this won’t make much of a
dierence (unless you are doing oscillographics) but at LFO rate for modulation this
can be used so one sequence is at it’s highest value when the other is at its lowest
(180 degrees) or oset just slightly (45 degrees) or 90 degrees o.
The intention here was to have two modulation voltages for use with the Three Body
and other stereo processes. It would also make a lot of sense to feed into a
multichannel quantizer and get and eect of multiple melody lines following each
Lower oset
switch
Upper oset
switch
Degree
oset
Numerical
oset
down down 0 0
up down 45 2
down up 90 4
up up 180 8
Longer sequences can be created by modulating the gate inputs.
The SUBTRACT switch (and related gate input) alters the direction of counting. If you
look at the waveforms page you will see that that can also be achieved by changing
the frequency word (setting of the switches). In this case they are primarily intended
as performance controls to allow for more dynamic sequences.

0001110011100011
0010110100101101
0110011001100110
0101010101010101
0
0
1
1
0
1
0
0
0011001100110011
0101010101010101
0000000000000000
0001000100010001
0011011011001001
0101101001011010
0011001100110011
0101010101010101
0
1
0
1
0010110100101101
0110011001100110
0101010101010101
0000000000000000
0
1
1
0
0000111100001111
0011001100110011
0101010101010101
0000000000000000
0
0
1
0
0010101011010101
0111100001111000
0110011001100110
0101010101010101
0
1
1
1
0101010101010101
0000000000000000
0000000000000000
0000000000000000
1
0
0
0
0101010110101010
0000111100001111
0011001100110011
0101010101010101
1
0
0
1
0000000011111111
0000111100001111
0011001100110011
0101010101010101
0
0
0
1
0111111110000000
0111100001111000
0110011001100110
0101010101010101
1
1
1
1
0100100110110110
0010110100101101
0110011001100110
0101010101010101
1
0
1
1
0101100101011001
0011001100110011
0101010001010100
0000000000000000
1
0
1
0
0000000000000000
0000000000000000
0000000000000000
0000000000000000
0
0
0
0
0111100001111000
0110011001100110
0101010101010101
0000000000000000
1
1
1
0
0110011001100110
0101010101010101
0000000000000000
0000000000000000
1
1
0
0
0110001110001100
0101101001001010
0011001100100011
0101010101010101
1
1
0
1
Waveforms
The four switches of the nibbler can be thought of as dening 16 states, waveforms, or
sequences (depending on how you are using it). They are shown below (counting up, from
left to right) along with the binary representation (which would also mirror the gate
outputs).
You can see that counting by zero yields nothing, while counting by one creates a rising
ramp, counting by fteen creates a falling ramp, and the waveforms in between are
mirrored around counting by 8, which creates a series of pulses at half of full-scale
amplitude and half the rate of the incoming cloc .

Patches to start exploring with:
Clock Divider
Set all switches down except for ADD 1
This means it will be in synchronous adder mode and
incrementing by 1 with each clock pulse
Patch a clock signal into the CLOCK input
Use the CARRY as your clock divider output
This should give a clock division of 16
If you use the ADD 2 switch instead of ADD 1 you will get
a clock division of 8
ADD 4 by itself will give you a division of 4
ADD 8 will give you a division of 2
If you combine switches into odd values you will get a
division of that number over sixteen. For example ADD 1
and ADD 2 together will give you a division of 3/16.
Clock Divider Drum Sequencer
Set the controls the same as the clock divider patch but
instead of just using the CARRY out use all of the gate
outputs.
Start by patching the OUT 8 to a kick drum sound
Use OUT 4 to trigger a snare or tom
Use OUT 1 to trigger a high hat
This will have the kick sound on every 16th clock, the snare
on every 8th, and the hi hat on every other clock.
After this, explore what rhythms dierent combinations of
the switches create.
Things will become much more interesting if another
Nibbler or clock divider is used to modulate the gate
inputs.
Also try using the stepped outs as a clocked modulation
signal within the patch.
1
1 1
1 1 1 1
11111111

Frequency Divider (or Subharmonic
Generator)
Patch an audio rate signal into the clock input
Listen to the rst STEPPED OUT
If only ADD 1 is up you will get a ramp wave at 1/16 of
the input frequency.
See the waveforms page for the waveforms that will be
created by other switch combinations (or see above in
creating a triangle wave)
Send signals into the gate inputs to create timbre and
pitch changes (since it will change both the frequency
and waveform). This is a good wave to create chiptune
arpeggios and basslines.
Using the gate outputs as well will give you
harmonically related pulse waves.
The CARRY out will give you a very thin pulse wave 1
clock pulse long.
Triangle Wave
Set the Nibbler to count by 1 by ipping the ADD 1
switch up and all other switches down
Patch a clock into CLOCK
Use STEPPED OUTPUT 1 as your output
Patch CARRY out to SUB in
When the CARRY output goes high it will trigger the
subtract input, changing the direction of counting
This will create a triangle shape at 1/32 the frequency
of the input clock

Shift Register Noise
Patch an audio rate signal into the CLOCK input
Patch another audio rate signal into the SHIFT input
Set the ADD switches to some combination that include
both down positions and up positions
Listen to a stepped output
Try this in both SYNC and ASYNC mode
In SYNC mode you will get a sample rate reduction and
ltering eect with by slowing down the clock input.
In ASYNC mode you will get another avor of noise
with a bit more high end to it
By sending a third signal into the DATA XOR input you
will get another ring modulation type eect
You can also replace the data in the register bu
inserting a signal into the SHIFT input
The shift registers can be chained with multiple
Nibblers by patching the top bit (OUT 8) into the next
Nibbler’s SHIFT DATA input. This can be done in a
circular chain.
Rungler Variant
All switches down except ASYNC should be up
Patch OUT 8 into DATA XOR
Patch one oscillator into SHIFT
Patch another oscillator into SHIFT DATA
Use the stepped voltage outputs
Depending on the rate of the oscillators the output
can be either LFO or audio rate and it can be
patched into back into the oscillator frequency
modulation inputs for a Benjolin like patch.
The Nibbler is only 4 bits instead of 8 so the patterns
will be a bit dierent than Rob Hordijk’s Rungler but
it is an interesting way to generate some psuedo
random patterns.
The ADD switches will also change the pattern as
will all inputs.
See next page for more.

Simple Benjolin Variant
All switches down except ASYNC should be up
Patch OUT 8 into DATA XOR
Patch the right oscillator into SHIFT
Patch the left oscillator into SHIFT DATA
Patch a stepped voltage output into the FM input on both oscillators.
Patch a waveform outputs from the oscillators as well as (optionally) the stepped
voltage output from the nibbler into an audio mixer.
The true Benjolin would run these waveforms into a lter which would also be
modulated by the stepped voltage and an oscillator.
Experiment with the amount of FM and rate of the oscillators for dierent melodies
and rhythms.
The bit switches on the nibbler will all alter the pattern as will the oset switches if
that stepped output is being used.
To make things even wilder use the center output on the three body to modulate any
of the inputs on the Nibbler, I had particularly good luck with the CLOCK or GATE 1
inputs at LFO rates.

Sequencer (or Arpeggiator)
Patch a clock into the CLOCK input
Patch the STEPPED OUT 1 into a frequency input of an
oscillator (or through an attenuator into the RATIO input
on the Three Body)
Each combination of the ADD switches will create a
dierent sequence (see the waveforms page)
These sequences can become dynamic or ever-
changing by patching another sequencer, clock divider,
or other signal into the GATE or SHIFT inputs.
Two nibblers with the OUTS and GATE ins cross patched
(OUT 8 to GATE 2 and OUT 2 to GATE 8 for example)
creates some nice generative type sequences
Simultaneously using the gate outs (like the Clock
Divider Drum Sequencer patch) will turn the Nibbler into
a full sequencer.
If being used as an arpeggiator, try using the gate output
of a keyboard into the RESET input to restart the
arpeggio with each new note played
Phase Oset Sequences
This is the same set of patches as the above
Sequencer or Arpeggiator except now we use both
stepped outputs.
To get a feeling for what this can do run it at LFO rates
and patch one stepped output into one oscillator (or
Three Body ratio) and then send the other into the
frequency input of another oscillator.
With both switches down you will get the same
sequence on both, ipping up just the bottom switch will
get a slight oset (45 degrees), just the top will get you
90 degrees, and both at once will put them 180 degrees
apart (so that when one is at it’s lowest point the other
is at it’s highest.
Lower
oset
switch
Upper
oset
switch
Degree
oset
down down 0
up down 45
down up 90
up up 180

Cross Patched Nibblers
Send the same CLOCK signal to two
Nibblers
Set them both to SYNC mode
Try cross patching the gate outputs and
inputs
Try hitting the reset on only one of them
You will nd that this creates a dierent
sequence each time you do it
Use this patch along with any of the other
patches described in this manual, you will
nd it is particularly good for create more
complex rhythms or melodies that may not
repeat for quite some time or change
somewhat unexpectedly
If you only have one Nibbler try using any
logic you have to modulate the gate inputs
for a dynamic sequence
Chaining Nibblers
With two Nibblers patch the same clock
signal to each
Patch the CARRY out of the rst one to
the CARRY IN of the second.
Now you have an 8 bit deep register which
can divide up to 256
The rst Nibbler will control the lower 4
bits and the second Nibbler will control the
upper 4 bits.
If you wanted to divide by 256 you would
set the rst Nibbler to add by 1, and put all
switches on the second down (so it is
adding by 0).
Each stepped out will still only be 4 bits,
you could mix them together so that the
rst nibblers output is 1/32 of the second
nibblers to achieve 8 bits, but it might be a
ddly thing to try to accomplish.

Contact Info:
If you have any questions please contact Eric Schlappi at: eric@schlappiengineering.
com