Klavis Logica XT user manual V1.0 Page 1 of 11
Logica XT
Voltage-cont rolled multiple -input lo gic and gate processor
Introduction
Built upon the foundations of its acclaimed predecessor, this new version drastically expands the
feature set within the same footprint. All the original goodies are still there, now enriched by a
full list of state-based logic functions including a delay line. Faster processing allows perfect
handling of audio signals. User editable settings are stored in non-volatile memory.
With its versatility and features never seen before, the Klavis Logica XT will arouse your creativity
and bring inventiveness to your soundscapes.
Logica
Klavis
Div/2
Mode
& CV
Out
Inv.
XT
Manual
On
Or
And
Xor
1 Low
Even
Xtra
1
2
3
Clk
In
Clr
Clk
Set
Rst
Gater
1,2,3
Coin
D.S&H
1 High
Off
Gt~Tr
S/R. C
Features at a glance
14 modes of operation:
o 6 basic logic functions
o 2 forced states
o 6 advanced logic functions:
The Gater adds-up multiple gate signals while
maintaining each triggering with adjustable retrigger
gap time
Gate to trigger with adjustable pulse length
Chronological sequence validation (safe locker)
Toss a coin with different chance weighs from the 3
inputs
Flip-flop with separate Set and Reset
Digital Sample & hold, with adjustable delay/memory
line (from milliseconds to several seconds)
3 normalized input jacks + user defined manual button for quad
signal handling
Settings stored in non-volatile memory
Simultaneously normal and inverted outputs (e.g. And & Nand)
Dedicated divider by two output
Continuous manual + Bipolar CV control of the mode
LED column telling the current operation mode
LEDs on all outputs indicating the state
LED on manual button indicating its default status
Low consumption, skiff-friendly & compact module
Klavis Logica XT user manual V1.0 Page 2 of 11
Installation and security
Purpose
This module is meant for installation in a Eurorack-compliant chassis.
It adheres to Doepfer Eurorack mechanical and electrical specifications.
Do not attempt using this module in other mechanical or electrical contexts.
Installation
Before the installation, disconnect the mains power supply from your modular system. Some
power supplies are not safely isolated; there is a risk of injury!
See in the specifications if this module requires 5V from the supply rails. If 5V is needed and your
rack is not providing 5V, do not attempt connection!
Check that the current consumption requirements of this module, when added to your installed
set of modules do not exceed the available current from your supply. This is done by adding up
the current draw of all modules (mA) separately for each of 5V, 12V and -12V rails. If any of these 3
sums exceeds the available current of your supply for that voltage, do not connect the module to
your system; you need a stronger power supply.
The provided supply flat cable can only be inserted in the appropriate orientation at the back of
the module, so there is no risk of error on that end. However, you should pay attention to the
orientation of the cable in the socket of the supply PCB inside your chassis. Cheap sockets
without shrouding may allow you to plug in the connector the wrong way!
The red stripe on the cable should match a stripe printed on the supply board. The stripe also
indicates the -12V side. In case there is no stripe, a -12V marking is a safe indication of the
orientation.
Double check that the connectors are fully inserted and correctly oriented before switching on
the power supply. In case of an anomaly, switch off the power supply immediately and check
everything again.
Klavis Logica XT user manual V1.0 Page 3 of 11
Quick overview
The Logica XT combines up to 3 inputs and a push button to realize logic operations.
The functions are split into two main categories:
Simple logic operations (left column of the panel) are indicated by one LED
Advanced logic operations (right column on the panel) are indicated by a LED pair
Switching between the columns is done by a short press of the Xtra button.
The potentiomer selects a function in the column.
For some functions, a long press on the Xtra button allows editing related settings.
Changes are saved automatically without user intervention.
The module is delivered ready to use with sensible predefined settings.
LEDs
All outputs have LEDs that indicate a logic level 1 when on.
The manual button LED tells the setting of the button; the LED is ON when level is one.
Inputs & outputs
Input jacks 1, 2 and 3
With simple logic functions, these all work in the same way. Any signal can be brought to any
jack.
Normalization
With simple logic, unused jacks automatically get the necessary default value so that it is not
needed to replicate a signal if less than 3 inputs are required. This is called “normalization”.
Normalization allows having a logic condition being realized with fewer signals than inputs. For
example, a 2-input AND function would not work if the unused jack(s) were not normalized: the
condition where all inputs go on would not be possible without patching (duplicating) one of the
signals to the remaining input(s). Normalization is solving that for you.
Contrarily to the usual scheme where normalized inputs are chained, in the Logica XT, it is not
required using the jacks in a preferred order for the normalization to work. This is why the usual
arrows printed between jacks to indicate the normalization order are missing.
Could the Logica XT clever jack behavior be called “cleverized” ?
Main output (Out)
This output provides the logic result of the operation currently selected.
Klavis Logica XT user manual V1.0 Page 4 of 11
Inverted output (Inv)
This output provides the opposite state of the main out (Out) jack. It therefore represents the
negative logic of the currently selected option. (see further)
Division by two output (Div/2)
This output toggles its state every time the main output transitions from off to on (also with
short pulses). It provides a division by two of the main output and can be used for clocking
purposes or sub-octave creation when handling audio signals.
CV control input
This input works jointly with the Mode potentiometer. Their settings are summed to select one of
the simple logic functions. With advanced logic functions, the CV input is not used.
Controls
Mode potentiometer
It selects one of the logic functions/modes in the currently active column.
Manual input button
This button acts as a fourth input.
The default status of the button depends on the logic function selected. Where it makes sense,
this default status can be changed by the user.
Xtra button – simple vs. advanced functions - editing
This button has two roles:
A short press toggles between the simple and advanced logic columns.
Holding the button enables the editing of the function currently selected (if available).
During editing, the CV is disabled.
o With simple logic functions, pressing the Manual button toggles its default state –
the result is reflected on the Manual LED.
o With some advanced logic functions, the potentiometer is adjusting a time
setting. This is detailed in the related functions.
When done with editing, release the Xtra button and the changes are automatically stored.
Logic terminology
There is a correspondence between various terms used when dealing with logic.
Logic
1 0 State and LED
On
Off
Voltage presence
Yes
No
Level
High
Low
Klavis Logica XT user manual V1.0 Page 5 of 11
Logic voltages
Logic signals are represented by a voltage or lack of it. In the modular world, any gate, trigger,
clock and even square output from an LFO or VCO can be considered a logic signal.
Logic functions are the interaction of logic signals. Logic functions do not respond to amplitude
nuances in the way analog signals do. Nevertheless they obey to electrical ranges and levels.
Logic signals are normally positive only; negative voltages are ignored and interpreted as zero.
Typically, a voltage close to zero volts will be considered logic 0 (off) and a voltage of at least a
few volts will be seen as logic 1 (on). Incoming voltages can go beyond or below what are valid
one and zero without any problem. In other words, you can’t go beyond On when it’s already On!
Therefore, it is perfectly valid to drive this module with almost anything, including analog signals
from any source. Moreover, you are not limited to “squary” type signals; any wave shape can be
used as a logic source signal. For example, passing the saw wave output of an oscillator through
an OR function will create pulses since only the positive half of the wave will be accepted, and
within that half, only levels high enough will produce a logic one on the output. So, changing the
amplitude or the voltage offset of the saw will change the width of the resulting pulse: saw to
PWM !
Simple logic functions
These are also known as combinatorial logic, or Boolean logic.
They are listed on the panel’s left column and indicated by a single white LED being lit.
Forced On & OFF states
When the potentiometer (or CV in) pushes the setting at the top and bottom of the logic options
offered in the column, the output is forced to a static level: To one when pushed full up, to zero
when pushed full down.
The On state has a dedicated LED at the top of the column; the Off state is indicated by all LEDs
of the column being off. With forced states, the input jacks are disabled; only the manual button
can be used to invert the output.
And & Nand
The main output goes on when all inputs plus the button are on. The manual button defaults to
ON. AND is somehow the logic equivalent of a VCA where one input has to be ON for the other to
pass through. The difference being that, contrarily to a VCA, all inputs are simultaneously
controlling and controlled.
Or & Nor
The main output goes On when at least one input or the button is on. OR is the logic equivalent
of a mixer: if there is something being on at any input there’s something coming out.
The manual push button defaults to Off.
Klavis Logica XT user manual V1.0 Page 6 of 11
Xor & Xnor
This logic option works like the OR, except that the main output goes off when all active jacks are
on. In the Logica XT an unusual 3-input Xor is implemented whose results are different from
chaining multiple 2-input Xor gates.
Also, conversely to other simple logic modes, the button is not equal to an input jack. Instead, it
feeds a cascaded Xor function. See the logical chain hereafter.
Out
in 1
in 2
in 3
Manual
stored value
(default = 0)
Xor can be used as a “digital ring modulator” such as implemented in the ARP Odyssey and KORG
MS-20 synthesizers. Feed two inputs with two oscillators to get the effect.
With 3 oscillators feeding this 3-in Xor, you can create sounds much different from cascading
multiple 2-input Xor; the div/2 out can even provide melodies out of subtly detuned static pitches!
Here is the detail of the Xor/Xnor function:
Input jacks
Out jack = Xor
Inv jack = Xnor
All low
low
high
One or more high, but not all
high
low
All high
low
high
When only two jacks are connected you get a standard two-input Xor function
When a single jack is connected, the first Xor is bypassed
The manual button inverts the final result
Even & Odd
The main output goes on when an even number of inputs – including the button – are on. The
inverted output works the same for an odd number of inputs. The button defaults to off.
A sum of zero is considered even.
This function, made of chained Xor can also do a digital ring modulator, albeit less creative
musically than the dedicated 3-input Xor function above when used with 3 signals.
in 1
in 2
in 3
Manual
stored value
(default = 0)
Out
Klavis Logica XT user manual V1.0 Page 7 of 11
1 High
The main output goes on when only one input – including the button – is on.
The button defaults to off.
This function can complement a rhythm pattern generator by providing a gate for a fourth sound
when only one of the 3 other sound gates is active at a given step.
1 Low
The main output goes on when only 1 input – including the button – is off.
The button defaults to on.
Advanced logic functions
With these functions, the output depends on a sequence of actions or involves a time-related
effect. They are also known as sequential logic or state-based logic.
Differences with simple logic functions:
There is no input normalization (because it is not needed)
While editing settings, the manual LED is flashing
The default value of the manual pushbutton cannot be edited
The CV input has no effect
Gater
The Gater combines all inputs as an Or function does, but also retriggers the output every time a
new gate starts while one or more are already active.
All inputs work the same; the button brings a 4th gate signal.
The output signal reflects the duration of the incoming gate signals.
Editing
By maintaining the Xtra button, you can set the duration of the gap created for retriggering.
Turning the pot, the LED column indicates the duration as follows, LED off = 1ms, then one LED at
a time corresponding to values 2, 3, 4, 5, 6, 7, and 8ms; turning further brings a bar-graph that
reflects values continuously adjustable from 10ms to 1 second.
The default value is 3ms. It is recommended to set the shortest possible value that your target
modules accept such as to maintain a tight timing. Longer gap durations are here for more
creative purposes.
Gt ~ Tr - Gate to Trigger & Trigger to Gate
Gate or trigger signals on any input are converted to trigger/gate pulses of adjustable length.
All inputs work the same; the button brings a 4th trigger signal. All signals are combined (ored) to
the output.
Klavis Logica XT user manual V1.0 Page 8 of 11
Editing
Turning the pot, the LED column indicates the duration as follows, LED off = 1ms, then one LED at
a time corresponding to values 2, 3, 4, 5, 6, 7, and 8ms; turning further brings a bar-graph that
reflects values continuously adjustable from 10ms to 10 second.
The default value is 4ms which should suffice for typical Gate to Trigger conversion. Longer
triggers could be used for punchy envelopes (use an ADSR set to AR and acting as A, hold, D).
Trigger to gate is realized with longer durations whatever the length of the incoming signals.
1, 2, 3 – Sequence validation
In this function the numbering of the inputs is important. The output will go on only after the
inputs have seen triggers or gates in the proper chronology from input 1 to input 3.
Any time the sequence is broken (e.g. input 3 was activated immediately after input 1) the
validation is reset and should start again from the beginning.
After the output successfully goes on, any further signal to any input will shut it off (possibly
restarting a new sequence if that signal came on input 1).
Signals may overlap; only their rising edge is considered for proper validation.
The manual button inverts the current state of the output.
Coin
This function offers 3 heads or tails random generators with variable odds depending on the
input used. When won, the out goes on for the duration of the input signal.
When more than one input is used, winning signals are combined (ored) on the output.
A signal on input 1 has a fifty-fifty chance of passing through.
A signal on input 2 has one in four chance of passing through.
A signal on input 3 has one in eight chance of passing through.
The manual button creates a On that is mixed (ored) with the rest.
Set/Reset + Clock – S/R+C
The labeling of the inputs is in the black boxes above the jacks (Clock, Set, and Reset).
The function implements a typical flip-flop circuit. In its simplest use, feed any cyclic signal to the
Clock input and you get a division by two on the main output.
The set and reset inputs can respectively force and clear the output. A pulse at the clock inverts
the current result. The manual button is an additional clock option.
Without clocking, only using Set and Reset gives you an S/R latch whose result remains stable
until the other input goes high.
Only the rising edges of the incoming signals are taken into account.
Klavis Logica XT user manual V1.0 Page 9 of 11
Audio use
Since there is already a divider hardwired to the Div/2 out jack, you end up with a divide by four
circuit. Feeding this function with an oscillator simultaneously gives sub-octave and two-octave
lower audio signals.
Digital Sample & Hold – D.S&H
For this function, the labeling of the inputs is on the right side of the jacks (Clock, In, and Clear).
This versatile function is made of a Sample & Hold followed by an optional gate-shaper. There are
two working modes depending on the pot position: the first half is for pattern delay, the second
half is for general purpose sample and hold with delay.
1. Pattern delay
This is useful to create delayed rhythmic patterns.
A regular trigger/gate at typical pattern rate is brought to the clock input.
A gate pattern is brought to the data input
The output will provide a delayed copy of the pattern but shaped with the phase and
duration of the trigger/gate signal.
By maintaining the Xtra button pressed, you can set by how many steps the pattern will be
delayed. Turning the pot within its first half, the LED column indicates the delay as follows:
LED off = 1; input is copied to out on the next clock
then up, one LED at a time corresponding to 2, 3, 4, 6, 8, 12 and 16 steps,
then by LED pairs, for 24, 32, 48, 64, 96, and 128 steps.
Note: as long as data input is at least partly On while the clock signal goes On, the output will
provide a delayed gate with the same length as the incoming clock.
2. Digital delay line
This is used to arbitrarily delay a digital signal for up 5000 steps with a clock of any rate.
Contrarily to the previous mode, the output signal is not reshaped according to the clock shape.
When no jack is present at the clock input, the module generates its own 1 KHz clock internally.
This gives you a delay adjustable up to 5 seconds with a 1ms precision.
By maintaining the Xtra button pressed, the right half of the pot allows adjusting the delay from
1ms to beyond 5000ms. The LEDs are lit in bargraph way.
Practical aspects of the delay line
With clocks slower than 1ms, much longer delays are achievable (e.g. 20 seconds with 4ms
precision).
Notes for audio purposes
If the clock is modulated, and using an audio mixer, one can create typical double-
tracking, unison and flanging effects.
Klavis Logica XT user manual V1.0 Page 10 of 11
Summary – Simple logic
In this table, “inputs” include the manual button (except with Xor/Xnor)
White LED
Function
Out jack
Inv jack logic
Details
Top
On
On
Off
Input jacks are
disabled
Button inverts
2
Or
On if at least 1 input is on
Nor
Button defaults to
Off
3
Xor
On if 1 or more inputs are on
Off if all inputs are on
Button inverts the final result
Xnor
Button defaults to
Off
4
Even
On if the number of inputs high
is even
Odd
Button defaults to
Off
5
1 High
On if only 1 input is high
Off with 1 high
Button defaults to
Off
6
1 Low
On if only 1 input is low
Off with 1 low
Button defaults to
ON
Bottom
And
On when all inputs are on
Nand
Button defaults to
ON
None –
Below
lowest
Off
Off
On
Input jacks are
disabled
Button inverts
Summary – Advanced logic
White LED
Function
Out jack
Details
Top
On
On
Input jacks are disabled
Button inverts
1 + 2
Gater
On if at least 1 input is on; retriggers
with every new off-to-on input
transition while out is already on
Button is a 4th gate signal
Gap can be adjusted
2 +3
Gt → Tr
Any gate becomes a trigger or reverse
Duration can be adjusted
3 +4
1, 2, 3
On after sequence is valid
Zero in all other cases
Button toggles the
validation and output
4 +5
Coin
Copy of input if chance is OK
Button makes a gate
5 +6
S/R+C
Can be Set, Reset, or toggled
Button is a clock signal
6 +7
D.S&H
Follows the input after 1 to max Clock
pulses; zero when Clear
Button is Clear
Steps/delay can be adjusted
None –
Below lowest
Off
Off
Input jacks are disabled
Button inverts
The Inv out is the opposite of Out
The Div/2 out toggles when Out changes from low to high.
Klavis Logica XT user manual V1.0 Page 11 of 11
Specifications
Mechanical
Dimensions
mm
inches
Eurorack compliance
Height
128.40
5.06
3HE
Width
25.00
0.98
5HP
Depth behind panel (with supply cable inserted)
25.00
0.98
Supply
The supply socket is protected against reverse insertion.
Supply rail
Current draw
+12V
0 mA
-12V
1 mA
+5V
17 mA
Input/output
All inputs and outputs can withstand signals between -12V and +12V without harm.
Jack
Effective voltage range received or generated
CV control input
-5V to +5V
All outputs
0 or 5V (logic levels)
Input low to high change
3.5V or higher
Input high to low change
2.8V or lower (incl. negative)
Signals
Parameter
Values
Frequency range
DC to beyond audio
Packing list
The box contains:
Logica XT module
2x M3 black mounting screws + washers
Eurorack-compliant 16-pin supply cable
Quick setup notice
Klavis products, including PCB and metalwork, are designed and manufactured in Europe.
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