Intellijel Bifold User manual

Bifold Manual
Bifold
Dual Channel Wavefolder
Manual Revision: 2020.08.30

Bifold Manual 
Table of Contents 
Compliance 2
Installation 3
Installing Your Module 4
Overview 6
Bifold Front Panel 7
Controls 7
Inputs and Outputs 13
Usage Scenarios 16
Crossfading Folded and Unfolded Waveforms 16
Stereo Folding 17
Ring Modulation 18
Amplitude Modulation 18
Random Noise Generation 19
Technical Specifications 19
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Bifold Manual 
Compliance 
This device complies with Part 15 of the FCC Rules. Operation is subject to the
following two conditions: (1) this device may not cause harmful interference, and
(2) this device must accept any interference received, including interference that may
cause undesired operation.
Changes or modifications not expressly approved by Intellijel Designs, Inc. could void
the user’s authority to operate the equipment.
Any digital equipment has been tested and found to comply with the limits for a Class
A digital device, pursuant to part 15 of the FCC Rules. These limits are designed to
provide reasonable protection against harmful interference when the equipment is
operated in a commercial environment. This equipment generates, uses, and can
radiate radio frequency energy and, if not installed and used in accordance with the
instruction manual, may cause harmful interference to radio communications.
This device meets the requirements of the following standards and directives:
EMC: 2014/30/EU
EN55032:2015 ; EN55103-2:2009 (EN55024) ; EN61000-3-2 ; EN61000-3-3
Low Voltage: 2014/35/EU
EN 60065:2002+A1:2006+A11:2008+A2:2010+A12:2011
RoHS2: 2011/65/EU
WEEE: 2012/19/EU
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Bifold Manual 
Installation
Intellijel Eurorack modules are designed to be used with a Eurorack-compatible case and power
supply. We recommend you use Intellijel cases and power supplies.
Before installing a new module in your case, you must ensure your power supply has a free power
header and sufficient available capacity to power the module:
● Sum up the specified +12V current draw for all modules, including the new one. Do the same
for the -12 V and +5V current draw. The current draw will be specified in the manufacturer's
technical specifications for each module.
● Compare each of the sums to specifications for your case’s power supply.
● Only proceed with installation if none of the values exceeds the power supply’s specifications.
Otherwise you must remove modules to free up capacity or upgrade your power supply.
You will also need to ensure your case has enough free space (hp) to fit the new module. To prevent
screws or other debris from falling into the case and shorting any electrical contacts, do not leave
gaps between adjacent modules, and cover all unused areas with blank panels. Similarly, do not use
open frames or any other enclosure that exposes the backside of any module or the power distribution
board.
You can use a tool like ModularGrid to assist in your planning. Failure to adequately power your
modules may result in damage to your modules or power supply. If you are unsure, please contact us
before proceeding.
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Bifold Manual 
Installing Your Module
When installing or removing a module from your
case always turn off the power to the case and
disconnect the power cable. Failure to do so may
result in serious injury or equipment damage.
Ensure the 10-pin connector on the power cable is
connected correctly to the module before
proceeding. The red stripe on the cable must line
up with the -12V pins on the module’s power
connector. Different modules use different ways to
indicate the -12V pins. Some may be labelled with
“-12V;” a white stripe next to the -12V pins; the
words “red stripe;” or some combination of these.
Additionally, some modules may have shrouded
headers, thus preventing backward connections.
Most modules will come with the cable already connected but it is good to double check the
orientation. Be aware that some modules may have headers that serve other purposes so ensure the
power cable is connected to the right one.
The other end of the cable, with a 16-pin connector,
connects to the power bus board of your Eurorack
case. Ensure the red stripe on the cable lines up
with the -12V pins on the bus board. On Intellijel
power supplies the pins are labelled with the label
“-12V” and a thick white stripe. Sometimes the
connectors are shrouded, ensuring the cable can
only be oriented in one direction.
If you are using another manufacturer’s power
supply, check their documentation for instructions.
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Bifold Manual 
Once connected, the cabling between the module and power supply should resemble the picture
below:
Before reconnecting power and turning
on your modular system, double check
that the ribbon cable is fully seated on
both ends and that all the pins are
correctly aligned. If the pins are
misaligned in any direction or the ribbon
is backwards you can cause damage to
your module, power supply, or other
modules.
After you have confirmed all the
connections, you can reconnect the
power cable and turn on your modular
system. You should immediately check
that all your modules have powered on and are functioning correctly. If you notice any anomalies, turn
your system off right away and check your cabling again for mistakes.
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Bifold Manual 
Overview 
Bifold is a dual channel wavefolder, where one channel (the P channel) has a sonic characteristic
inspired by the Buchla-style P arallel “deadband” folding circuit, while the other channel (the
S channel) is more characteristic of a Serge-type S erial folding circuit.
Besides offering two unique flavours of wavefolding, Bifold features numerous feedback and routing
options along with CV control, enabling you to mix, blend and crossfade those flavors into a rich stew
of unique waveforms and harmonic movement.
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Bifold Manual 
Bifold Front Panel 
Controls 
1. FOLD knob - This knob sets the initial amount of wave
folding applied to both the IN P [D] (parallel) and IN S [E]
(serial) folders and sent to the OUT P [A] , OUT S [B] ,
and MIX [C] outputs.
Any modulation applied to the FOLD P [G] or
FOLD S [H] CV inputs varies the amount of folding
around the value set by the FOLD knob, with positive CV
increasing the amount of folding applied by the
respective ( P or S ) circuit, and negative values
decreasing it.
NOTE: When set fully counterclockwise, no signal
appears at any of the outputs unless CV is applied to the
FOLD P [G] or FOLD S [H] CV input and/or their
respective attenuators [13, 14] are turned up (i.e. NOT
fully counterclockwise) .
2. XFADE knob - Controls the relative mix of the two folders present at the MIX [C] output. When
fully counterclockwise, only the P arallel circuitry is heard at the MIX out. Turning the XFADE
knob clockwise crossfades from the Parallel folder to the Serial folder, with both circuits
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Bifold Manual 
feeding equal signals into the MIX output at the noon position. When fully clockwise, only the
S erial circuity is heard at the MIX out.
You can choose whether to feed the crossfader with either
channel’s unfolded (dry) signal ( IN P [D] or IN S [E] ) or with
its folded signal. This is accomplished with the XFADE P [7]
and XFADE S [8] input select switches, and enables you to
blend a folded signal with a dry signal for more sonic
diversity.
3. SYM-X-AUX switch for Parallel Folder - The position of this
switch affects the signal being fed into the P arallel folder.
Specifically:
SYM - When set to SYM (up position) a DC offset of
up to ±5V is added to the IN P [D] value, which
affects the symmetry of the wavefolding. The
amount of offset (and asymmetry) is controlled by
the corresponding attenuverter knob [5] .
AUX - When set to AUX (down position), the AUX [F] input is added to the IN P [D]
signal (after being attenuverted by the corresponding knob [5] ). Note that if nothing is
connected to the AUX [F] jack, then the signal appearing at the MIX [C] output is used
as the AUX input.
X - When set to X (middle position, no external voltages are added to the IN P [D]
value, so the input to the P arallel folder is symmetrical and unmodulated by any
external input.
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Bifold Manual 
4. SYM-X-AUX switch for Serial Folder - The position of this switch affects the signal being fed
into the S erial folder. Specifically:
SYM - When set to SYM (up position) a DC offset of
up to ±5V is added to the IN S [E] value, which
affects the symmetry of the wavefolding (shown in
the illustration on the previous page). The amount of
offset (and asymmetry) is controlled by the
corresponding attenuverter knob [6] .
AUX - When set to AUX (down position), the
AUX [F] input is added to the IN S [E] signal (after
being attenuverted by the corresponding knob [6] ).
Note that if nothing is connected to the AUX [F]
jack, then the signal appearing at the MIX [C] output
is used as the AUX input.
X - When set to X (middle position), no external
voltages are added to the IN S [E] value, so the
input to the S erial folder is symmetrical and
unmodulated by any external input.
5. SYM-AUX attenuverter for Parallel Folder - Depending on
the setting of the P arallel folder’s SYM-X-AUX switch [3] ,
the knob either attenuverts a 5V DC offset voltage (when
set to the “SYM” position) or it attenuverts the AUX [F] input
voltage (when set to the “AUX” position). It has no effect
when the corresponding SYM-X-AUX switch is set to the
“X” position.
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Bifold Manual 
6. SYM-AUX attenuverter for Serial Folder - Depending on
the setting of the S erial folder’s SYM-X-AUX switch [4] ,
the knob either attenuverts a 5V DC offset voltage (when
set to the “SYM” position) or it attenuverts the AUX [F]
input voltage (when set to the “AUX” position). It has no
effect when the corresponding SYM-X-AUX switch is set
to the “X” position.
7. XFADE P input selector switch - The position of this
switch selects the signal source that feeds into the
crossfader’s P -side input (counterclockwise rotation of
the XFADE [2] knob), which is then mixed with the
selected S -side input and sent through to the MIX [C]
output.
FOLD OUT P (up position) - the output of the
P arallel folder ( OUT P [A] ) feeds the P -side
(counterclockwise) input of the XFADE circuit.
IN P (down position) - the input of the P arallel
folder ( IN P [D] ) feeds the P -side
(counterclockwise) input of the XFADE circuit.
This is particularly useful if you want to mix a
folded signal with a dry signal, making the
XFADE [2] knob function as a sort of wet/dry
control.
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Bifold Manual 
8. XFADE S input selector switch - The position of this
switch selects the signal source that feeds into the
crossfader’s S -side input (clockwise rotation of the
XFADE [2] knob), which is then mixed with the selected
P -side input and sent through to the MIX [C] output.
FOLD OUT S (up position) - the output of the
S erial folder ( OUT S [B] ) feeds the S -side
(clockwise) input of the XFADE circuit.
IN S (down position) - the input of the S erial
folder ( IN S [E] ) feeds the S -side (clockwise)
input of the XFADE circuit. This is particularly
useful if you want to mix a folded signal with a dry
signal, making the XFADE [2] knob function as a
sort of wet/dry control.
9. MIX LED - Indicates presence of signal at MIX [C]
output. The brightness of the LED indicates the amount
of signal present (the brighter the LED, the louder the
output). The color of the LED indicates the polarity, with
red=negative and green=positive. At audio rates, the
colors oscillate so fast that the LEDs will basically appear
orange.
10. PHASE switch - Inverts the phase of the S erial folder
that feeds the XFADE circuit, which can change the
sonic attributes at the MIX [C] output, as well as allow for
ring modulation (discussed in the Ring Modulator
section, later in the manual).
11. OUT P LED - Indicates presence of signal at OUT P [A] .
The brightness of the LED indicates the amount of signal
present (the brighter the LED, the louder the output). The color of the LED indicates the
polarity, with red=negative and green=positive. At audio rates, the colors oscillate so fast that
the LEDs will basically appear orange.
12. OUT S LED - Indicates presence of signal at OUT S [B] . The brightness of the LED indicates
the amount of signal present (the brighter the LED, the louder the output). The color of the
LED indicates the polarity, with red=negative and green=positive. At audio rates, the colors
oscillate so fast that the LEDs will basically appear orange.
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Bifold Manual 
13. FOLD P attenuator - This knob attenuates the voltage
patched into the FOLD P [G] CV input jack.
When set fully clockwise, all the voltage appearing at
FOLD P is used to control the amount of folding sent to
the Parallel folder.
When set fully counterclockwise, the input CV is fully
attenuated, and none of the FOLD P voltage is used to
control folding.
NOTE: If nothing is plugged into the FOLD P [G] jack,
then Bifold internally normals +5V to that jack, meaning
this knob acts as a 0V (counterclockwise) to +5V
(clockwise) attenuator.
IMPORTANT: If the FOLD [1] knob is set fully
counterclockwise and nothing is connected to the
FOLD P [G] CV input, then you must set the attenuator
knob to some value above 0 (fully counterclockwise) in
order to hear any output.
14. FOLD S attenuator - This knob attenuates the voltage
patched into the FOLD P [H] CV input jack. It works
exactly like the FOLD P [13] attenuator knob (described
above), but governs the S erial folder circuit instead.
15. XFADE attenuverter - This knob attenuverts the voltage
patched into the XFADE [I] CV input jack.
When set fully clockwise, all the voltage appearing at the
XFADE [I] jack is used to control the amount of
crossfading. When set fully counterclockwise, the full
inverse value of the control voltage is used. When set at
the noon position, the XFADE input CV is fully attenuated, and does not affect the XFADE
amount.
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Bifold Manual 
Inputs and Outputs 
A. OUT P - Output of the P arallel wavefolder circuit.
B. OUT S - Output of the S erial wavefolder circuit.
C. MIX OUT - Output of the mixed (crossfaded) P arallel and
S erial folder circuits.
D. IN P - Input to the P (parallel) wavefolder circuit. This
circuit is a Buchla-inspired parallel “deadband” folder.
The signal sent here is folded by an amount set by the
FOLD [1] knob and the FOLD P [G] CV input and its
corresponding attenuator [13] . Folding is further modified
by the position of the Parallel folder’s SYM-X-AUX [3]
switch and its corresponding attenuverter [5] .
The folded output appears at the OUT P [A] jack, and
can also be mixed and crossfaded with the Serial folder,
with the combined output sent to the MIX [C] output jack.
E. IN S - Input to the S (serial) wavefolder circuit. This
circuit is a Serge-inspired serial folder. If no jack is
inserted into IN S , then the signal at IN P [D] also feeds
the Serial circuit.
The signal sent here is folded by an amount set by the
FOLD [1] knob and the FOLD S [H] CV input and its
corresponding attenuator [14] . Folding is further modified
by the position of the Serial folder’s SYM-X-AUX [4]
switch and its corresponding attenuverter [6] .
The folded output appears at the OUT S [B] jack, and
can also be mixed and crossfaded with the Parallel
folder, with the combined output sent to the MIX [C]
output jack.
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Bifold Manual 
F. AUX IN - If either of the SYM-X-AUX switches [3, 4] is
set to the AUX position, then the signal received by this
jack is added to the signal that’s sent to the
corresponding P arallel or S erial folding circuit. The
amount and polarity of added AUX signal is determined
by the position of its associated SYM-AUX
attenuverter [5, 6] .
If nothing is patched into the AUX input, then Bifold’s
MIX [C] output feeds the AUX input.
G. FOLD P CV IN - This input accepts a ±10V control
voltage for externally controlling the amount of folding
applied to the P arallel wavefolder.
The control voltage modulates the amount of initial
folding as set by the FOLD [1] knob, and is attenuated
by the corresponding FOLD P [13] attenuator knob.
Positive voltages increase the amount of folding above
the value set by the FOLD [1] knob; negative voltages
decrease it.
When the FOLD [1] knob is fully counterclockwise,
sending 0V - 5V to the FOLD P [G] jack governs the
folding (though a little ‘extra’ folding is available with up
to 10V of CV input). When the FOLD [1] knob is higher
than its minimum position, then negative voltages
applied to FOLD P decrease the folding, and positive
voltages increase it.
If nothing is plugged into this jack, then +5V is internally
applied, which can be attenuated using the
corresponding FOLD P [13] attenuator knob.
H. FOLD S CV IN - This input accepts a ±10V control voltage for externally controlling the
amount of folding applied to the S erial wavefolder. This circuit is a Serge-inspired serial folder.
If no jack is inserted into FOLD S , then the signal at FOLD P [G] also feeds the CV input for
the Serial folder.
The control voltage modulates the amount of initial folding as set by the FOLD [1] knob, and is
attenuated by the corresponding FOLD S [14] attenuator knob. Positive voltages increase the
amount of folding above the value set by the FOLD [1] knob; negative voltages decrease it.
When the FOLD [1] knob is fully counterclockwise, sending 0V - 5V to the FOLD S [H] jack
governs the folding (though a little ‘extra’ folding is available with up to 10V of CV input). When
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Bifold Manual 
the FOLD [1] knob is higher than its minimum position, then
negative voltages applied to FOLD S decrease the folding,
and positive voltages increase it.
If nothing is plugged into either this jack or the FOLD P [G]
jack, then +5V is internally applied, which can be attenuated
using the corresponding FOLD S [14] attenuator knob.
I. XFADE CV IN - This input accepts a ±5V control voltage for
externally controlling the amount of crossfading between the
P arallel and S erial folders, as heard from the MIX [C]
output. The input voltage can be attenuverted using the
corresponding XFADE attenuverter [16] .
The control voltage modulates the amount of initial
crossfading as set by the XFADE [2] knob, and is
attenuverted by the corresponding XFADE [15] attenuverter
knob. When the value of the XFADE [2] knob and the
attenuverted XFADE [I] inputs sums to zero (or a negative
voltage), then only the P arallel channel feels the crossfader.
When the value of the XFADE [2] knob and the
attenuverted XFADE [I] inputs sums to +5V, then only the
S erial channel feels the crossfader. Summed voltages
between 0V and 5V create a blend of the two channels.
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Bifold Manual 
Usage Scenarios 
Aside from such obvious applications as 1) two totally independent wavefolders, or 2) a single
two-folder circuit with variable series/parallel routings, there are several other sonically interesting
usage scenarios, as outlined in the following sections.
Crossfading Folded and Unfolded Waveforms 
You can use Bifold to mix together two different waveforms from a single (or multiple) oscillators —
one folded and one unfolded — then crossfade between them to create complex and evolving
waveforms. To do so:
1. Patch the MIX [C] output into your audio system.
2. Set the XFADE knob [2] fully counter-clockwise (toward “P”).
3. Send a sine wave (or any other waveform) into IN P [D] .
4. Set the XFADE P [7] input selector switch to the “FOLD OUT P” (up) position.
5. Set the XFADE S [8] input selector switch to the “IN S” (down) position.
6. Flip the PHASE [10] switch to the left, putting the two folders in-phase with one another.
7. Send one of the oscillator’s other waveforms (such as a triangle) into IN S [E] .
8. Rotate the FOLD [1] knob to dial in the desired amount of wavefolding.
Because the XFADE knob [2] is set fully counter-clockwise, only the P -side input (a folded
sine) is heard in the MIX [C] output.
NOTE: if nothing is patched into the FOLD P [G] input, then you will not hear any output until
you start to fold the waveform using either the FOLD [1] knob or by turning the FOLD P [13]
attenuator to any position other than fully counterclockwise.
9. Rotate the XFADE [2] knob fully clockwise to hear only the S -side input (an unmodified
triangle wave, in this example).
10. Adjust the XFADE [2] knob to set the balance between folded and unfolded waves, and adjust
the FOLD [1] knob to dial in the desired amount of folding.
You can modulate both the XFADE and FOLD amounts using the FOLD P [G] and
XFADE [I] CV inputs, along with their respective attenuators.
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Bifold Manual 
Stereo Folding 
Some very interesting stereo effects can be achieved by sending OUT P [A] to one stereo channel,
and the OUT S [B] jack to the other. For example:
1. Patch a waveform into the IN P [D] jack and leave the IN S [E] jack unpatched.
By default, IN S is normalled to IN P if nothing is connected to it.
2. For now, set both folders’ SYM-X-AUX switches [3, 4] to the middle “X” position.
3. Patch OUT P [A] to the left channel of your stereo monitoring system and OUT S [B] to the
right channel.
4. Set the FOLD P [13] and FOLD S [14] attenuators to their minimum values (fully
counterclockwise).
Note that, if the FOLD [1] knob is also fully counterclockwise, no signal will appear at the
outputs.
5. Slowly rotate the FOLD [1] knob to increase (clockwise) or decrease (counterclockwise) the
amount of folding, creating an interesting stereo effect since the two fold circuits have different
sonic characteristics.
6. Set the FOLD P [13] and FOLD S [14] knobs to offset the amount of folding applied by each
channel.
7. Try different SYM-X-AUX [3, 4] switch positions and vary the corresponding parameters to add
further variation between channels.
8. Try sending a control voltage into FOLD P [G] , and varying the amount of attenuation using
both the FOLD P [13] and FOLD S [14] attenuator knobs.
Or, for real chaos, send different control voltages into FOLD P [G] and FOLD S [H] .
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Bifold Manual 
Ring Modulation 
You can use the Bifold as a ring modulator, as follows:
1. Set both the Parallel and Serial SYM-X-AUX switches [3, 4] to the middle “X” position.
2. Set both the XFADE P [7] and the XFADE S [8] input selector switches to their down
positions.
3. Flip the PHASE [10] switch to the right, putting the S -side out of phase with the P -side.
4. Patch an oscillator into IN P [D] , and monitor the MIX [C] output.
5. Rotate the XFADE knob [2] until you hear no sound from the MIX [C] output.
The knob will be approximately straight up.
6. Patch a second oscillator into the XFADE [I] CV input and set the XFADE [15] attenuverter
fully positive (clockwise).
The oscillator plugged into IN P [D] is ring modulated by the oscillator plugged into the
XFADE [I] input, and sent to the MIX [C] output.
Amplitude Modulation 
You can also use the Bifold to create Amplitude Modulation (AM). To do so:
1. Follow steps 1-6 in the Ring Modulation description, above.
2. Plug a dummy cable into IN S [E] .
3. The waveform patched to XFADE [I] input is now amplitude modulating the waveform patched
into IN P [D] .
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Bifold Manual 
Random Noise Generation 
Use the module’s built-in feedback path to create all manner of strange and chaotic blips, hisses and
noise bursts. To do so:
1. Unpatch everything except the MIX [C] output.
2. Set both the Parallel and Serial SYM-X-AUX switches [3, 4] to the AUX (bottom) position.
3. Set each channel’s SYM-AUX attenuverter [5, 6] to a value other than null (i.e., not straight
up).
4. Set the Fold P [13] and Fold S [14] attenuators to some value greater than minimum
(i.e., not fully counterclockwise).
5. Set both the XFADE P [7] and the XFADE S [8] input selector switches to their up
(FOLD OUT P, FOLD OUT S) positions.
6. Twiddle the FOLD [1] and XFADE [2] knobs, as well as the two SYM-AUX attenuverters while
listening to the feedback noise being sent from the MIX [C] output.
Enjoy the squeaks, clicks, squawks and hissing variants of noise that result.
Technical Specifications 
Bifold
Width
8 hp
Maximum Depth
38 mm
Current Draw
94 mA @ +12V
94 mA @ -12V
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