Prism II

The incoming signal goes into the three-channel pitch shifting section (octave down, fifth up, octave up). Each of the three channels has its own low-pass filter (LPF) and can be mixed in with the dry signal; the dry signal can also be excluded from the mix in Kill Dry mode. Marked with a dotted blue line in the schematic, the pitch shifting section is additive: it adds new "colors" to the incoming signal. The output of this section goes into the first filter.

All the four filters are identical, each one consisting of a splitter, three filter channels and a mixer. The processed signal can be mixed with the dry one via the cross-mixing section (filter output can also be subtracted from the dry signal at a desired ratio).
Each of the three filter channels has a 12dB/Oct slope and controllable resonance:

• The low-pass filter (LPF) cuts off the high frequencies.
  
• The band-pass filter (BPF) cuts off the low and high frequencies.
  
• The high-pass filter (HPF) cuts off the low frequencies.
  
  

Each of the filters can be offset from the frequency set by the BASE knob. Additionally, each filter has a ratio by which it is affected by the DEPTH knob. This allows the filters to move in and out of sync, and also in opposite directions. Combined with the cross-mix, these filter interactions can result in numerous sonic flavors ranging from classic "wah" sounds to complex notch filtering and even phasing. Since each of the two channels has its own set of four filters, the Prism II has a very broad sonic palette.

After the two filter blocks, the signal goes into the modulation section.

The mod section has its own LFO which runs independently from the main rate settings. This way, the signal "has a mind of its own" and doesn't just follow the main LFO. Depending on the cross-mix section settings, the modulation blocks can allow you to achieve simple 2-voice chorus effects, vibrato, mild flanging, or anything in between. There are two modulation blocks, and each one can have different settings.

Following the pitch shifting section, the two filters and the first mod block, the signal goes into the reverb section. That's where the real fun starts! Interface-wise, the whole section is represented by a single knob which controls reverb decay. Each patch has its own dry/reverb mix, but reverb decay can be controlled over a very wide range of values. When the knob is fully CCW, the reverb section is effectively disengaged; turning the knob fully CW results in multiple overtones and slowly decaying reflections. The reverb section can be viewed as an envelope generator in a virtual synth: it allows the attack, hold and release stages to be controlled simultaneously. The resulting sound greatly depends on which filter blocks (pre/post-reverb) are engaged. Yes, there are two more filters after the reverb block!

The second filter group and mod section are functionally identical to the first ones, but their impact on the sound is dramatically different. By using both filter groups at once or only one of them, you can achieve substantial variations in sound; even more so if you throw modulation into the mix.

The shelving HPF is the final touch to the signal chain. It prevents the Prism II from destroying your lows by reducing the impact of resonant peaks in the lower frequency range.

Following all the processing, the resulting signal goes into the output mix section, where it is mixed with the dry signal via the MIX knob. In Kill Dry mode, the MIX knob acts as the output volume control.

A complex set of LFO waves with extra waveshaping and cross-modulation controls filter cutoffs and movement in the stereo field.

• LFO MAIN: triangle wave; rate is set via the RATE knob or TAP footswitch. This LFO controls the overall movement but can be altered by LFO2 and LFO3, as well as by the LFO COMMON settings. This LFO's phase is reset when you turn on the effect and press the TAP footswitch.
  
• LFO2: sine wave; rate and amplitude are set via the config file (this LFO has no physical controls). This wave is summed with LFO MAIN, adding some controlled chaos to its movement. Some patches don't use this LFO.
  
• LFO3: saw/random wave; rate is linked to LFO MAIN rate at a certain ratio (such as 1/2x, 3x or 4x). This LFO affects the other LFOs' amplitudes by the following formula: LFO3*(LFO2+LFO MAIN). The result goes to LFO COMMON, where it gets clipped by the limiter.
  
• LFO COMMON distorts the incoming wave, turning it into a trapezoid wave (at values 1.1–3) or an "almost square" wave (at values 4–1000). This parameter is smoothed by a filter, which can let you achieve glide effects.

LFO2 and LFO3 affect LFO MAIN at a set ratio and have extra settings in the config file. In EX mode, LFO MAIN is disengaged and replaced by the ATTACK and DECAY parameters.

MOD LFO is configured via the config file and has no physical controls. Its main purpose is soft modulation, which is set differently for every patch.

The EXT.TAP jack is an input for external control over the Prism II's parameters. It has several operation modes:

• Passive controller (normally open momentary button). This mode precisely copies the functions of the TAP footswitch and is active by default.
  
• S-trigger — "short circuit trigger", analog trigger/gate with the same polarity as the pedal's. This is the recommended trigger type. Use the config file to select this operation mode. Two sub-modes are available:
  
  • The TAP footswitch retains its functions even when the clock signal is connected.
    
  • The TAP footswitch is only active in EX mode and can be used to access secondary control functions in any mode; all of its other functions are transferred to the external clock source.
    

• V-trigger — "voltage trigger"/"positive trigger", analog trigger/gate with polarity opposite to the pedal's. If no external signal is coming into the EXT.TAP input, the LED will light up, and some of the pedal's functions will be inactive. Those functions become active as soon as a clock signal is connected. Use the config file to select this operation mode. Two sub-modes are available:
  
  • The TAP footswitch retains its functions even when the clock signal is connected.
    
  • The TAP footswitch is only active in EX mode and can be used to access secondary control functions in any mode; all of its other functions are transferred to the external clock source.
    

Use this trigger type if you have no S-trigger source or if you prefer V-triggers for other reasons.

• MIDI Clock. The pedal accepts two parameters from the MIDI System Real Time protocol: Clock (sets LFO rate, takes over the RATE knob's functions) and Start (resets the LFO). Use the config file to select this operation mode.
  
• Favorite preset control. Use a passive controller (a quick tap on a normally open button) or an S-trigger signal to recall or exit the Favorite preset. To record a new Favorite preset, send an active Gate signal into the pedal or hold down the external controller for over 3 seconds.
  

The pedal is designed to be clocked in quarter notes with time between two control signals ranging from 0.005 seconds to 2 seconds. The lowest BPM is 30. The stable BPM range is 30 to 300. The accuracy depends on the stability of the incoming clock signals.

In order to sync LFO phase with the tempo of the song, make sure to press the BYPASS footswitch on time. When the pedal is engaged, LFO phase is reset to the initial values determined by the active patch.

The passive and active (S-trig/V-trig) external control options assume full control over the TAP footswitch's functions, as determined by the global mode:

• TP: they set LFO rate (replacing the RATE knob).
  
• RS: they "press" the TAP footswitch to reset LFO phase.
  
• EX: they "hold down" the TAP footswitch as long as the Gate signal is active.
  

The active modes can work both with triggers and gates. Gate signals are crucial for expression pedal simulation (the EX mode).

MIDI Clock takes over the RATE knob: LFO rate is set as soon as a MIDI signal source is connected to the EXT.TAP input. The MIDI Start command can be used to reset the LFO externally. To connect a MIDI signal source, use a 6.3 Type A stereo jack (TRS). You don't need to set the MIDI channel. More MIDI-related functions are in development; stay tuned for the news on our social media.

The BYPASS LED glows blue.
MODE switch position:

• UP: Synthation Flow. "The Prism at its finest". This patch pays homage to Michael Garrison — particularly to his "Images" album which still sounds amazing 35 years since its release. Finally, this kind of sound is available in a simple guitar pedal. All three octaves and a fifth are used in the pitch shifting section. Only the pre-reverb filter block is engaged, resulting in mild filtering with barely noticeable movement. The reverb sounds soft but completely replaces the dry signal. All those elements together create a lush pad for the incoming signal. This patch is probably the closest one could get to the original Prism-9.
  
• MIDDLE: Shu Melody. With its clear sound and mild post-reverb filtering, this patch works great for melodic lines where you might want a soft pad which doesn't get too crazy. The reverb smoothens the tone, while the rather simple LFO wave is handy if you want to boost mod rate into the audio range via the BEAT switch. This patch works best in Kill Dry mode.
  
• DOWN: CM116. Another classic sound: this time, you can use your guitar or bass to get tones reminiscent of Tangerine Dream. LFO wave multiplication is quite uncommon in the guitar world. The incoming signal is enriched and expanded by the pitch shifting section. Both the pre- and post-reverb filter blocks are used; those aren't fully mixed in with the dry signal, resulting in a well-balanced sound. LFO2 is 32 times faster than the main one, so you can get rhythmic patterns at low values of the RATE knob or constant filter movement at higher ones.

The BYPASS LED glows red.
MODE switch position:

• UP: BUTTER. The mild filtering in this patch works best with a slow LFO set at medium depth. The algorithm features a bit of upper and lower octave signals. One of the filters moves in the opposite direction to the others, adding some instability to the sound. The reverb is turned up high in the mix and has a long decay, resulting in a soft pad with prolonged attack and release times. Coupled with the reverb, the slow and shallow modulation creates noticeable pitch warbles.
• MIDDLE: MS20X3. To a certain extent, this patch pays homage to the MS20 filter. Three of the filters are set to highlight various harmonics (with resonant peaks at +12 and +19 semitones); the fourth filter provides smoothness to the overall sound. Stereo modulation creates a constant movement. The reverb is mixed in with the main signal without overpowering it. This patch works particularly well in Kill Dry mode with a harmonically rich incoming signal (such as distorted guitar). Depending on rate settings, you can get classic filter sweeps or alien signals from this algorithm.
• DOWN: CM122 + RND. Another variation on the CM116/Tangerine Dream sound — with some extra tricks up its sleeve. In this patch, 16 random steps are multiplied by the main rhythm, making it more expressive and unpredictable. Filter effects are more pronounced here; both the pre- and post-reverb filter blocks are still used. The reverb is turned down a bit to highlight the stepping sequence in the filter mod.

The BYPASS LED glows magenta.
MODE switch position:

• UP: MEOW. The name speaks for itself: this patch can meow like a clowder of cats. The frequencies highlighted by the filters have different LFO depths. This algorithm combines long reverb decay with soft spatial and temporal modulation. The patch can be used with little to no filter movement for endless ambient soundscapes.
  
• MIDDLE: Illusions Far. This inspiring algorithm is reminiscent of your favorite childhood toy. It sounds as if a swarm of tiny robots is transposing the sound in a way that the incoming signal is pretty much eliminated. The sound is then processed by HPFs set to medium resonance and low depth. The soft modulation and soothing reverb provide the finishing touches. The DETUNE mode is particularly pronounced in this patch.
• DOWN: Robot in my head. This algorithm employs pitch shifting and ring modulation in LFO2 and LFO3; the RATE knob controls the tone. The parallel reverb processing in the patch retains the incoming signal's attack. The signal itself is significantly colored and expanded by the pitch shifting. Due to the constant movement across the stereo field, the separation between the incoming signal and the generated pitches is even more noticeable. Try setting the BASE knob to low values with slow filter movement, then change the speed to several Hz via the RATE knob. Also, don't hesitate to try out the extreme knob positions.

Use TAP + MODE to switch to this bank.
The BYPASS LED glows cyan.
MODE switch position:

• UP: STATIC. This electrified patch features ring modulation in the reverb, the mod sections, and LFO2. The effect is particularly pronounced at higher REVERB knob values. The post-reverb filters have mild settings which allow reverb tails to stay audible after the filters are closed; this works great in all modes, including the EX mode (virtual expression pedal). The name "STATIC" is not only a nod to electricity but also a hint that the algorithm sounds really nice even with no filter mod (with the RATE knob fully CCW).
• MIDDLE: Dawn at the mirror lake. This sound is reminiscent of points of light dancing on the water on a warm summer day. The movement of resonant filters is intertwined with the warm reverb texture. Combined with a somewhat unpredictable LFO shape, the bright filters create complex patterns with airy, flanger-like modulation. The reverb adds to the "crystal clear" sound, which is gradually moving across the stereo field. The algorithm's pronounced character can be tamed via the BASE and DEPTH settings.
• DOWN: Broken Tape Reverb. A slow descent into eternity, which has somehow been recorded on an old VHS tape. This peculiar sonic character stems from a combination of unorthodox techniques, such as out-of-phase filters and deep reverb modulation. The pitch shifting section creates a sort of "echo" with characteristic artifacts. Finally, LFO3 in stepped random mode imitates a broken tape mechanism with different settings for each of the two channels.