HackMe Electronics Rockit Manual

1.Summary

Rockit is a monophonic, digital and analog hybrid synthesizer. Rockit can make one sound at a time, but it has the capacity to make very simple sounds to very complex and dynamic sounds. Sound generation begins with digital synthesis, moves through analog amplification, analog filtering, and comes out a product of both the digital birth and the analog processing. The digital synthesis is comprised of two oscillators with independent waveform selection. These oscillators can be mixed or played independently and the second oscillator can be detuned from the first in note steps. The analog amplification stage has independent envelope controls for a complete ADSR envelope generator. Rockit’s filter section is an entirely digitally controllable analog filter, meaning all filter parameters are explicitly accessible internally, via knobs and switches, and externally, via MIDI. In addition, Rockit has two Low-Frequency Oscillators for modulating various synthesizer parameters at controllable rates and amounts.

Rockit offers 18 knobs and 8 switches for controlling both the digital synthesis and shaping the analog processing. Rockit is enabled to store and recall 16 patches, storing all knob, switch, and LED settings. Rockit also has a Drone and Loop feature that allows for independent play. For inputs and outputs, Rockit has an audio output and an audio input which routes into the analog filter. Rockit has MIDI In and Out capabilities with all settings accessible via MIDI controller channel numbers. All knob movements are transmitted to the MIDI output on the appropriate MIDI channel number.

2. Oscillator Section

        Rockit has two oscillators. Each oscillator has 16 possible waveshapes. These waveshapes are generated by playing back single cycle wavetables. Some of the waveshapes are pure playback of a simple wavetable, such as a Sine wave or a Square wave. Some of the waveshapes are modulations, manipulations, and combinations, of multiple wavetables in order to make more dynamic waveshapes. Some of the manipulations are timing based and others are based on which portion of the ADSR envelope is presently being played. Which waveshape is selected is shown on the LED display for 5 seconds after the knob was last moved.

The waveshapes are:

0.Sin

1.Square

2.Saw

3.Triangle

4.Square/Saw Morphing Back and Forth

5.Triangle/Saw Morphing and Phasing

6.Triangle/Square Morphing and Phasing

7.Square with Phasing Pulse Width

8.Sin modulated Square

9.Ramp modulate Square

A.Slow Square Phasing Pulse Width

b.Triangle attack, followed by a noise pulse, Square with a pitch down over time

C.Triangle attack, phasing Square for decay, and Ramp for release

d.Hard sync sin

E.Noise

F.Raw Aliasing Square

The Oscillator Mix knob controls which oscillator is being heard. Turning the knob hard left will play Oscillator 1 by itself. Turning the knob hard right will play oscillator 2 by itself. And with the knob at 12 o’clock, oscillator 1 and 2 will be mixed equally.

The Oscillator 2 Detune knob shifts the frequency of oscillator 2 relative to Oscillator 1. This knob is bidirectional, with both up and down capability, and “0” with the knob at 12 o’clock. Turning the knob to the left lowers the frequency of Oscillator 2 and turning the knob to the right increases the frequency of Oscillator 2, relative to the frequency of Oscillator 1. The amount of detune is fixed in note steps. For example, if Oscillator 1 is played at middle C and the detune is turned to the right two steps, Oscillator 2 will play two notes above middle C at middle D. The total range is 16 notes steps up and 16 note steps down. This allows for full octave ranging of the two oscillators.

3. ADSR Amplitude Envelope Generator

        

The amplitude envelope generator controls the level of a note being played back over time.

The Attack knob controls how fast a sound increases in amplitude.

The Decay knob controls how fast a sound decreases in amplitude.

The Sustain knobs controls the level that a sound decreases to during the Decay phase and the level that a sound is held at if the note is held.

The Release knobs controls how fast a sound decreases in amplitude after a note is released.

Since the envelope generator is an analog function, though digitally-controlled, there are some nuances to be aware of. The note attack begins as soon as a note is played, but at some of the longer settings, it may take several seconds for the sound to reach appreciable amplitude. It will be audible, but quiet. The sustain is capable of being turned to zero, which in combination with a very short decay and attack can make very short popping noises and percussive sounds. The release can swing from very short, but not actually zero, to very long. If another note is pressed during the release phase, the envelope does not start over from zero, but begins the attack phase increasing from where it is. If it were to begin again from zero, audible pops and clicks would be heard where the signal level was discontinuous.

4. Analog Filter

        

The analog filter is a two-pole filter with low-pass, band-pass, and high-pass modes. The filter type is selectable with the Filter Type switch and the lit LED indicates which mode the filter is in. The Frequency knob controls the filter cutoff frequency, turning the knob left decreases the filter cutoff frequency and turning it right increases the cutoff frequency. For instance, with a low-pass type filter selected, turning the knob to the right allows more higher frequency signal to pass through the filter and turning it left decreases high frequency content. The Filter Resonance, or Q, knob controls the gain of the filter around the filter cutoff frequency. It’s effect can range from subtle to pretty extreme. Turning the knob to the right increases the resonance or Q of the filter, leading to a characteristic emphasis on the filter cutoff that yields a “wah” type effect.

The Envelope Amount knob controls the amount of the envelope applied to the filter. This knob is bidirectional, with 0 being at the 12 o’clock position. Turning the knob to the left will cause the filter cutoff frequency to be modified in the negative direction and turning it to the right will cause the filter cutoff frequency to be modified in the positive direction. The further the knob is turned, the larger the effect of the envelope will be. The Attack knob controls how quickly the filter frequency will get to the maximum of the envelope. The Decay knob controls how quickly the filter cutoff frequency will return from the maximum of the envelope. The Sustain knob controls where the envelope will stop progressing if a key is held. And the Release knob determines how quickly the filter cutoff frequency returns to the initial value set with the Frequency knob.

5. Low-Frequency Oscillators - LFOs

Rockit has two Low-Frequency Oscillators, LFOs. The purpose of the LFOs is to modulate various synthesizers parameters in order to make dynamic, but controllable sounds.

The two LFOs share controls and only one can be active at a time. Which LFO is active is determined by using the LFO Select switch. When the LFO 1 LED is lit, all the LFO controls effect LFO 1. When the LFO 2 LED is lit, all the LFO controls effect LFO 2. This is true for the LFO Rate, LFO Amount, LFO Shape, LFO Sync and the LFO Destination.

 Each LFO has 6 possible destinations, meaning 6 different synthesizer parameters that the LFO can modulate. The destinations for LFO 1 are: Amplitude, Filter Frequency, Filter Resonance, Filter Envelope Amount, Oscillator 1 Pitch, and Detune. The destinations for LFO 2 are: Oscillator Mix, Filter Frequency, Filter Resonance, LFO 1 Rate, LFO 1 Amount, and Filter Attack.

Each LFO has a Rate, Amount, Shape, and Sync parameter. The Rate parameter determines the speed of the LFO oscillator, how quickly it modulates the destination parameter. The Amount parameter determines how great of an effect the LFO has on its destination parameter. The Shape parameter determines the waveshape of the LFO. The waveshapes are very similar or the same as the oscillator waveshapes. The Sync parameter causes the LFO to be retriggered when new keys are pressed, or notes received.

6. Patch Save and Recall

Rockit has the ability to store up to 16 patches, meaning it can store the position of all the knobs, switches, and LEDs for up to 16 different sounds. The LED display indicates the currently selected save/recall location. The display can change to display which waveshape is being selected by the oscillator or LFO, but after 5 seconds it returns to show which save/recall location is presently selected. To save a patch, use the Select switch to determine which save location you’d like to use, 0-F. Then, press the Save switch, to store the current Rockit state in that Save location. To recall a patch, use the Select switch to determine which location you’d like to use, 0-F. Then, press the Recall switch, to activate that saved patch. The knob and switch settings are maintained until that knob or switch is used, or that parameter is changed via MIDI. This is true regardless of the current state of each knob.

7. Drone/Loop

Rockit is equipped with a special drone and loop feature. The intention of this feature is to allow Rockit to be played as a standalone instrument. Pressing the Drone/Loop switch once activates Drone Mode. Pressing it again activates Loop Mode. Pressing it again returns Rockit to normal operating mode.

In Drone mode, Rockit plays a continuous tone without any envelopes. Since the ADSR envelope knobs aren’t used, they have a dual purpose. The Attack knob controls the pitch being played. The Sustain knob controls the level of the sound being played. All the other knobs, except for the Filter Envelope, behave normally. In this mode, Rockit still responds to MIDI to trigger the LFO Sync parameter.

In Loop mode, Rockit plays much like in Drone mode except that it is storing a 16 step loop. The loop will play back knob movements. The Attack knob and Sustain knob work as in Drone Mode. But in addition to that, the speed of the playback loop can be changed with the ADSR Release knob. In this way, it is fairly easy to generate repetitive and expressive sounds. Each knob has it’s own storage of 16 positions through the loop. The recording of each knobs movement begins with the time it’s touched until the loop comes back to the point it started recording, unless that knob continues to be moved.

8. MIDI Control Channel Numbers

        Every parameter of Rockit is accessible via MIDI. The control channel numbers for Rockit software version 1.01 are listed below. If you find that these are off by 2 numbers, you may have software versino 1.00. The behavior of the knobs regarding MIDI is that if a parameter is set by MIDI, the software will ignore the position of the affected knob until that knob position is changed.

PARAMETER                MIDI CONTROL CHANNEL#                RANGE

 PITCH WHEEL                0                                0-127

 MOD WHEEL                        1                                0-127

 LFO_SHAPE                   2                                0-127

 FILTER_ATTACK                    3                                0-127

  ADSR_SUSTAIN                    4                                0-127

 OSC_1_WAVESHAPE           5                                0-127

 FILTER_RELEASE                    6                                0-127

 FILTER_Q                            7                                0-127

 ADSR_ATTACK                   8                                0-127

 OSC_DETUNE                   9                                0-127

 FILTER_SUSTAIN                    10                                0-127

 FILTER_ENV_AMT                    11                                0-127

 ADSR_DECAY                   12                                0-127

 OSC_MIX                           13                                0-127

 FILTER_FREQUENCY            14                                0-127

 FILTER_DECAY                    15                                0-127

 ADSR_RELEASE                    16                                0-127

 OSC_2_WAVESHAPE           17                                0-127

 LFO_RATE                            18                                0-127

 LFO_AMOUNT                   19                                0-127

 LFO_1_RATE                   20                                0-127

 LFO_2_RATE                   21                                    0-127

 LFO_1_AMOUNT                    22                                    0-127

 LFO_2_AMOUNT                    23                                0-127

 PITCH_SHIFT                   24                                0-127

 AMPLITUDE                   25                                0-127

 LFO_1_DEST                   26                                0-127

 LFO_2_DEST                   27                                0-127

 FILTER_TYPE                   28                                0-2

 LFO_1_WAVESHAPE           29                                0-127

 LFO_2_WAVESHAPE           30                                0-127

 LFO_SEL                           31                                0 OR 1

 LFO_SYNC                            32                                0 OR 1

 PORTAMENTO                   33                                0-127

 OSC_PITCH_SHIFT           34                                0-127