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Prism II

Stereo Filter-Pad
The A+ Prism II is a new version of the Prism-9 complex effect pedal. Combining multiple techniques in a single unit, the device employs an outside-the-box approach to sound processing. The Prism II is comprised of subtractive and additive synthesis elements along with reverberation and various types of modulation (frequency, temporal and spatial). Rather than being lined up in a typical linear fashion, all parts of the system form a single "organism", allowing multiple parameters to be tweaked simultaneously. You could try and replicate it by using a chain of multiple time-synced effects — but that would be no easy feat, as the Prism II has 3 pitch shifting sections, 4 multimode filters, 2 modulation blocks, and a single reverb section. All the elements are organized in two identical chains (as the device works in stereo) with a separate mix section at each stage. The pedal's four LFOs provide extensive control over the stereo field and filter automation. The Prism II can be controlled via the TAP footswitch or synced to an external clock. Additionally, the device offers an expression pedal simulation mode along with a DETUNE function.

The Prism II is a compact inspiration generator which can single-handedly replace a sizable Eurorack system. In the guitar world, fully replicating the effect would be difficult even with a huge pedalboard.

The effect was inspired by various principles of sound synthesis, which have been present since the 70s but still aren't widely spread beyond fully-equipped professional studios. The Prism II is a one-of-a-kind pedal which can work with any instrument such as guitar, bass, mono- or polysynth, vocals or drums.
This color scheme is no longer available. Check out the Black Edition instead.

Prism II: Key Features

  • A complex and unique filter-pad pedal.
  • Fully featured stereo signal path allowing for mono signal expansion.
  • Three global modes: tap tempo, LFO reset, expression pedal simulation.
  • Scalable tap tempo, which allows to speed up or slow down the modulation in the 2x – 32x range.
  • The pitch shifting section allows adding octaves (upper/lower) and a fifth to the incoming signal.
  • Four LFO-controlled multimode filters with tweakable ranges.
  • The reverb section between filter groups allows for soft pads, lush spatial processing, and harmonic tremolo in reverb tails.
  • Signal modulation allows for chorus, vibrato and soft flanger effects. In conjunction with filter modulation, a phaser effect can be also achieved.
  • 12 unique algorithms which can be fine-tuned via the config file.
  • Firmware updates and fine-tuning via microUSB.
  • Detune Mode: gradual pitch shifting of the transposed signal.
  • "Favorite": the option to save and recall a preset from the device's memory.
  • External tap tempo/Favorite control input, which accepts passive controllers, MIDI Clock/Start and analog triggers (S-trig/V-trig).
  • Fully analog dry signal chain.
  • Switchable tails in bypass.
  • Kill Dry: the option to exclude the dry signal from the output in order to use the pedal in Wet-Dry-Wet configurations or external mixing setups.
  • Lightweight and compact aluminium enclosure featuring top-mounted jacks for improved connectivity and easier pedalboard management.
  • Universal power intake in the 9-12V range; low current draw by digital device standards (100-150mA).
You can find a detailed description of the Prism II's signal path and each of its elements on this page.
Is a monophonic signal input. In a mono signal chain, use this input exclusively.
Is an input for the second signal source. A stereo setup can be achieved by simultaneously connecting two mono signal sources to the LEFT IN and RIGHT IN inputs. The Prism II does not support TRS connections.
Is the left channel output. Connect it to the signal receiver. In a mono signal chain, use this output exclusively.
Is the right channel output. Connect it to the signal receiver. A stereo setup can be achieved by simultaneously connecting the LEFT OUT and RIGHT OUT outputs to two mono inputs. The Prism II does not support TRS connections.
The mono and stereo modes are described in detail further on.
Is an input for external tap tempo control (via a normally open momentary button, MIDI Clock/Start or S-trig/V-trig). The Favorite preset can also be controlled through this input.
The EXT. TAP functions are described in detail further on.
Is a power supply input (9-12VDC).
is a port for connecting the pedal to a computer for servicing, configuration and mode switching.
The Prism II has dual-function controls: each knob and switch can have several purposes. The primary functions are printed in white on the pedal (and in black in this text). Secondary functions which can be accessed by holding down the TAP (ALT) footswitch are marked blue. The ones which can be accessed by holding down the BYPASS (DETUNE) footswitch are marked red. In this text, each function is printed in black, blue or red following the same principle.
The BASE knob
Sets the base filter frequency value. In most cases, the LFO oscillates between the minimum and maximum values. The BASE knob sets the minimum value (frequency) for the device's filters.
The DEPTH knob
Sets the maximum filter frequency value (the filter's frequency mod depth). The higher this value, the more impact the LFO has on the BASE knob (movement of the base filter value across the frequency range). Set the DEPTH knob fully CCW for static filters or fully CW to make them move from the min value to the max.
The RATE knob
Determines the speed at which the filters move along the LFO shape. The range is 60 to 0,125 seconds (0,01666(6)Hz – 8Hz). The BEAT switch provides additional control over this range.
The REVERB knob
Controls reverb decay time. Turn this knob fully CCW to disengage the reverb block. The reverb to dry signal ratio is fixed for each algorithm, but turning the REVERB knob allows you to go all the way from slight signal coloration to huge pad-like tails.
The MIX knob
Controls wet signal volume. The Prism II was designed as a send effect where the processed signal is mixed in with the dry one; however, you can use the Kill Dry mode to exclude the dry signal from the output. In Kill Dry mode, the MIX knob controls output volume.
The MODE switch
Selects the algorithm (patch). For a detailed description of patches, please refer to the "Banks & Patches" section.
The BEAT switch
Selects a subdivision for the time set by the TIME knob or the TAP footswitch:
  • UP: 3/4 (dotted eighth note).
  • CENTER: 1/1 (quarter note).
  • DOWN: 2/3 (quarter note triplet).
The subdivisions can be altered via the config file.
The BYPASS (DETUNE) footswitch
Has multiple functions:
  • Press once to turn the effect on or off.
  • Press and hold to go into Detune Mode (gradual detuning of the signal at a set rate).
  • Press twice to recall the Favorite preset or switch back to live control.
  • Press and hold while changing the MODE switch setting to select the bank (this behavior can be changed via the config file).
  • Press and hold while changing the BEAT switch setting to select bypass mode and control the Kill Dry function.
The TAP(ALT) footswitch
Has multiple functions:
  • Press twice to set LFO rate.
  • Press and hold the TAP and BYPASS footswitches simultaneously for 3 seconds to record the current settings as a Favorite preset.
  • Press to access the secondary functions printed in blue.
  • Press and hold while in EX mode to trigger the expression pedal simulation envelope.
  • Press and hold while changing the MODE switch position to access the Cyan bank.
Press and hold the BYPASS/DETUNE footswitch:
The BANK switch
While changing the BANK switch position to select a patch bank (each bank holds 3 patches):
  • UP: the Blue bank.
  • MIDDLE: the Red bank.
  • DOWN: the Magenta bank.
For a detailed description of the banks, see the "Banks & Patches" section.
The BEAT switch
While changing the BEAT switch position to select the bypass mode:
  • UP: "No tails" mode.
  • MIDDLE: "Tails" mode.
  • DOWN: "Kill Dry with tails" mode.
For a detailed description of the modes, see the "Bypass & Indication" section.
Press and hold the TAP/ALT footswitch:
The TYPE switch
While changing the TYPE switch position to select one of the three global modes:
  • TP: tap tempo mode. LFO rate is controlled by the RATE knob or the TAP footswitch.
  • RS: the RATE knob controls LFO rate; LFO phase is reset to zero with every press of the TAP footswitch.
  • EX: expression pedal simulation mode. LFO MAIN is turned off and the movement across the frequency range is controlled by ATTACK and RELEASE times. In this mode, the BASE knob sets the minimum value of the virtual expression pedal, while the maximum value is controlled by the DEPTH knob. The envelope is triggered upon pressing the TAP footswitch. Press and hold the TAP footswitch to enter the envelope's HOLD stage.
The TAP SCALE knob
While turning the TAP SCALE knob to scale the tempo set by the TAP footswitch, which operates in the 0.2 – 2s range. In tap tempo mode, scaling the tempo this way lets you access tempos that are inconvenient to tap in. The available division/multiplication range is 2x to 32x. Turn the knob CCW to slow the LFO rate down (divide) or CW to speed it up (multiply).
The STEREO knob
While turning the STEREO knob to control stereo width. The knob's main function is to offset LFO phase in one of the channels. Offset depth varies from patch to patch, depending on the initial settings. The higher the setting, the wider the stereo field.
The DETUNE knob
While turning the DETUNE knob to control the depth of gradual wet signal detuning in Detune Mode (accessed by pressing and holding the DETUNE (BYPASS) knob).
The ATTACK knob
While turning the ATTACK knob to set attack time in EX mode.
The RELEASE knob
While turning the RELEASE knob to set release time in EX mode.
The BANK switch
While changing the BANK switch position to access the patches in the Cyan bank. For a detailed description of the banks, see the "Banks & Patches" section.
In TP (tap tempo) mode, the LED over the TAP/ALT footswitch glows magenta when you press and hold the footswitch. It indicates that secondary functions of the controls are being accessed.

Tweaking the secondary control functions (printed in blue) has no effect on the primary control function values (printed in white), and vice versa.
The primary and secondary functions are independent from each other, but only the latest one you've tweaked will have a physical representation (because they are controlled by the same knob or switch).

Prism II: Signal Path

The signal path for each of the two channels looks like this:
The Prism II has 12 algorithms (patches). Each patch may or may not use all of the device's signal chain elements. The Prism II patch library will be expanded over time; additionally, you can try programming your own algorithms through the config file.
We are going to publish new patches on the Prism II support page and on social media, so stay tuned.


The Prism II has four LFOs. Three of those control filter frequency and stereo width, while the fourth one controls modulation. The rates for two of the LFOs are set by the RATE knob or TAP footswitch. The diagram and description below will let you visualize the interactions better.

Modulation Rate Setup

Use the RATE knob or TAP footswitch to set the mod rate in quarter notes, then use the BEAT switch if you wish to turn those into triplets or dotted 8ths. You can also set your own tap division values through the config file. The TAP LED displays the set LFO rate. The range of the RATE knob is 60 to 0.125s (0,01666(6) – 8Hz); the set rate can be sped up via the BEAT switch.

The TAP footswitch and the RATE knob have the same effect on modulation rate, which is determined by the control that has been used last.

The TAP footswitch operates in the 0.2 – 2s range. Additionally, the TAP SCALE knob can be used in TP mode to divide or multiply the rate by fixed values between 2x and 32x. Turn the knob CCW to slow the LFO rate down (divide) or CW to speed it up (multiply).

In EX mode (expression pedal simulation), filter cutoff movement is controlled by the ATTACK and RELEASE knobs; LFO MAIN is disengaged in that mode. An AHR (attack/hold/release) filter envelope is triggered upon pressing the TAP footswitch. As long as you hold the TAP footswitch down, filter cutoff will stay at the value determined by the DEPTH knob.




The STEREO knob affects LFO phase in the right channel. As a secondary function, it is accessed by holding down the ALT/TAP footswitch.

Set the knob fully CCW to have the phases perfectly in sync. In the fully CW position, the phase is offset by 180 degrees. Keep in mind that phase offset values can be different from 0 in various elements of the signal chain; this means that the STEREO knob will either "expand" the stereo stage or move the elements to different positions in the stereo field, depending on the patch.

Connection Options

LEFT IN is the main input. If you are using the pedal with a mono signal source, use that input exclusively. Connect the signal source to the LEFT IN input, then connect the LEFT OUT output to the signal receiver.

Using RIGHT IN in mono setups is not recommended.

In order to convert a mono signal to stereo, connect the signal source to LEFT IN (the main input jack), then connect LEFT OUT and RIGHT OUT to the signal receiver. The dry signal will be placed in the center, while the wet signal will be spread across the stereo image depending on the STEREO knob's position.

When both LEFT IN and RIGHT IN are engaged, the pedal goes into dual mono mode and the channels are processed independently.

The dry signal in the left channel goes to LEFT OUT while the dry signal in the right channel goes to RIGHT OUT. In this mode, you can plug either a stereo source or two mono sources into the pedal. The two mono sources will be processed in parallel.

The Prism II has no audible delay effects; however, it has four resonant filters.
WARNING! Using the double processing mode IS NOT RECOMMENDED.

This type of connection will create a feedback loop, causing the pedal to immediately go into self-oscillation which may damage your hearing and/or speakers. Be careful to never use this connection type unless you're 100% sure it is the desired effect.

Banks & Patches

The patches are organized into 4 banks, each holding 3 patches.

To select a bank, press and hold the BYPASS footswitch and move the MODE/BANK switch to the desired position:
  • UP: Blue Bank (the BYPASS LED glows blue).
  • MIDDLE: Red Bank (the BYPASS LED glows red).
  • DOWN: Magenta Bank (the BYPASS LED glows magenta).
After that, you can release the BYPASS footswitch and use the MODE switch to navigate within the bank.

To select patches from the fourth bank (Cyan Bank), press and hold the TAP footswitch and move the MODE/BANK switch to any position. After that, you can release the TAP footswitch and use the MODE switch to navigate within the bank.

The config file provides access to another way of selecting patches.

All patches have been significantly reworked compared to those found in the Prism-9. Some of the algorithms have a similar character to the original ones, but their functionality has been greatly improved.

Bypass and Indication

The dry signal path is fully analog throughout the whole pedal. No distortion is applied to the dry signal. Due to the Prism II's active bypass, there is no audible clicking, and three independent global modes are available (selectable by the BEAT switch while holding down the BYPASS footswitch):
  • UP: "No tails" mode. The effect is only heard when the pedal is engaged in the signal chain and turns off immediately when the BYPASS footswitch is pressed.
  • CENTER: "Tails" mode. After you have switched the pedal off via the BYPASS footswitch, it keeps playing reverb reflections but the incoming signal is no longer processed.
  • DOWN: "Kill Dry with tails" mode. The dry signal is completely removed from the output. Just like the previous mode, this one only engages the input when you press the BYPASS footswitch. The reverb tails are played till the end, so that the sound doesn't get cut off abruptly. This mode is highly recommended when using the Prism II as an insert effect (where only the wet signal is needed) or in external wet/dry mixing setups.
The bypass mode is displayed upon selection and upon power-up. The LED above the BYPASS footswitch flashes five times in one of the following colors:
  • Red: "No tails" mode.
  • Blue: "Tails" mode.
  • White: "Kill Dry with tails" mode.
The BYPASS/DETUNE LED has five functions:
  1. On/off indication. If the pedal is bypassed (disengaged from the signal chain), the LED doesn't light up.
  2. Active bank indication. Upon power-up, the LED displays the selected bank: Blue, Red, Magenta or Cyan.
  3. Detune Mode status indication. When the BYPASS footswitch is held down, the LED flashes in various colors.
  4. "Favorite" status indication. When the Favorite preset is recalled, the BYPASS/DETUNE LED glows green. If the pedal is bypassed, the LED flashes briefly to indicate that the Favorite preset will be active when the pedal is turned on. If the Favorite preset has been changed but not saved, the LED flashes briefly.
  5. Bypass mode indication upon selection or power-up.
The TAP/ALT LED has four functions:
  1. Tempo indication. The TAP LED flashes in sync with the current tempo, taking the BEAT switch and TAP SCALE knob values into account.
  2. USB connection indication. The TAP/ALT LED flashes blue/"current mode" when the pedal is connected via USB.
  3. TP mode indication. The TAP/ALT LED lights up in magenta in this mode. It also indicates that secondary functions (printed in blue) are being accessed.
  4. Global mode indication:
  • White: TP (tap tempo mode).
  • Red: RS (LFO reset mode).
  • Yellow: EX (expression pedal simulation mode).

Favorite Preset

In order to store the current settings into a Favorite preset, press and hold the TAP footswitch and the BYPASS footswitch simultaneously for 3 seconds. The preset will be recorded into the pedal's internal memory, and the BYPASS LED will light up in green.
To recall or exit the Favorite preset, briefly press the BYPASS footswitch twice. If the BYPASS LED is glowing green, the Favorite preset is active. If the Favorite preset has been recalled but the pedal is bypassed, the BYPASS LED lights up briefly: this provides visual feedback regarding the settings which the pedal will employ when engaged.

When a Favorite preset is active, controls on the pedal have no effect until you turn/switch them. When a control setting has been changed, the BYPASS LED flashes briefly to indicate that the new settings haven't been saved yet. To save the changes, press and hold the TAP and BYPASS switches simultaneously for 3 seconds. If you exit the altered Favorite preset without saving, the changes you made won't be recalled the next time you activate the Favorite preset.

When the Favorite preset is active, there is no bank indication. All settings (including bypass settings, global mode and modulation rate) are saved in the Favorite preset.

The Favorite preset can be controlled externally via the EXT.TAP input. To do that, open the config file and set the #GLOBAL_JACK_EXT_TAP parameter's value to 30. Use a quick press on the button to recall or exit the Favorite preset. To record a Favorite preset, press and hold the button for at least 3 seconds (the settings will be recorded as soon as you release the button). This works with passive controllers (normally open button) and S-Trigger/Gate signals.

The Favorite function can be disabled via the config file: to do that, change the #GLOBAL_FAV_OFF parameter's value to 1. The function will be disabled globally, meaning that the Favorite preset won't be recalled either by the Prism II's own footswitch or by an external controller.

Detune Mode (Gradual Signal Detuning)

The Detune Mode only affects the pitch shifting section. If the pitch shifting section isn't engaged in the patch, the Detune Mode has no effect.

To enter Detune mode, press and hold the BYPASS/DETUNE footswitch for at least 0.3 seconds. The gradual signal detuning will manifest differently depending on the patch. The more transposed signal the patch employs, the more pronounced the detuning will be.

The DETUNE knob (ALT+RATE) controls the depth of the detuning effect.

NB! The description on this page refers to firmware v1.2. If you purchased your Prism II before August 30, 2021, you need to update the firmware. Please visit the support page for detailed instructions.


  • LEFT IN / RIGHT IN: 6.3mm, mono, unbalanced, 1MOhm input impedance. LEFT IN is the main mono input.
  • LEFT OUT / RIGHT OUT: 6.3mm, mono, unbalanced, 100Ohm output impedance. LEFT OUT is the main mono output.
  • EXT.TAP: 6.3mm, normally open momentary button, MIDI Clock/Start, or 5V analog trigger (S-trig/V-trig) with up to a 2-second interval between two consecutive signals.
  • Power: 2,1/5,5mm, negative tip. The pedal can't be battery-powered. Use a regulated PSU only.
    • 9V DC 150mA.
    • 12V DC 100mA.
  • Dimensions (LхWхH): 110х104х56mm (4.3x4.1x2.2").
  • Weight: 350g (0.77lbs).

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