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GRP Synthesizer A8 User Manual

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A8 USER'S MANUAL
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Summary of Contents for GRP Synthesizer A8

  • Page 1: Voltage Controlled Low Frequency Oscillator

    Grp Synthesizer A8 USER’S MANUAL www.grpsynthesizer.it...
  • Page 2 Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 3: Table Of Contents

    FRONT PANEL CONNECTIONS CV-Gate-Trigger Sequencer Filter Main Out REAR PANEL CONNECTIONS Power MIDI Audio Future Upgrades A8 AUDIO AND MODULATION ROUTINGS SOUND SOURCES AND SOUND MODIFIERS PATH VOLTAGE CONTROLLED OSCILLATOR 1-6 Frequency Control Grp Synthesizer A8 User’s Manual V. 2.06...
  • Page 4 LOW FREQUENCY OSCILLATOR 3 Frequency and Frequency Range Waveshape Output Control Modulation Routings LOW FREQUENCY OSCILLATOR 3 REFERENCE Frequency Waveshape Controls Output Controls Destination Controls ENVELOPE GENERATORS Common behaviours and controls - Trigger Mode Grp Synthesizer A8 User’s Manual V. 2.06...
  • Page 5 PW SEQ ENA(ble) F(i)LT(er) SEQ ENA(ble) Column A Section - Column B Section Clock & Clock Divider Step Repeat & Loop Sequencer mode Manual controls Sequencer remote connections and controls on the front panel Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 6: Foreword

    • The Grp A8 Synthesizer is an heavy synthesizer: place it on a suitable solid surface or table. • The Grp A8 Synthesizer can be very LOUD: please, be careful with the big volume knob on the lower right of the front panel.

  • Page 7: Setup And Connections

    Connections In order to get started with your Grp Synthesizer A8, you will need some connections: • Suitable AC powering. Make sure (twice) that the power available in your country matches the correct position in voltage switch 110-220V on the rear panel.

  • Page 8: Front Panel Audio Connections

    In details, there are connections for: • LOWER SECTION Connections: Trig Input (0/+5V), Gate Input (0/+5V), CV Input (1V/Oct). • UPPER SECTION Connections: as above. • LOWER and UPPER Connections: as above, in common for both sections. Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 9: Overview

    OVERVIEW The Grp Synthesizer A8 is a complex, but not-so complex analog machine dual structure/bitimbral, with an integrated Step Sequencer. Each part (Upper or Lower section) is a complete and independent analog synthesizer fitted with three VCOs each with separate SubOsc, one Ring Modulator, one Audio Mixer, two dynamic VCFs, one Fixed Filter Bank, one VCA, three EGs, one LFO.

  • Page 10: What Is Inside The A8

    - work in cross audio rate modulation between VCOs on VCOs and VCOs on VCFs. The above (simplified) picture shows the interactions between the different components of the A8. Feel free to experiment with different sections of the synthesizer; first, with Upper/Lower synth parts, then, with Step Sequencer.

  • Page 11: Basic Operations

    Before turn on, please CHECK THE CORRECT AC RATING. Tuning the instrument The Grp A8 is an analog synthesizer but, despite this, the VCOs inside stays in tune pretty well. For tuning the instrument to concert pitch, you should work in the Tuning-Portamento module on the left part of the front panel.

  • Page 12: Mode Selection

    Interface on the front panel. As we’ll see later, the MIDI Interface reacts to Start, Stop and Continue RealTime Commands: those will be routed to the internal Step Sequencer for normal transport functions. Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 13: Cv Offset

    It is possible to add an octave offset on the CV received at the analog control inputs; in this way, you can match the octave played by A8 with the range of your external analog controller. Grp Synthesizer A8 User’s Manual V. 2.06...
  • Page 14 VCOs on 8’ and impart a CV Offset with value U3 and/or L3. If you impart a CV Offset with value U2/L2, you’ll play a lower octave (e.g.: like if you have selected 16’ on VCOs). If you impart value U4/L4, you’ll play a higher octave (like if you have selected 4’ on VCOs). Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 15: Front Panel Connections

    1. • EXT CLOCK: a train of pulse (0/+5V) received at this port will advance the Step Sequencer; it will function only if the Step Sequencer is set to EXTERNAL CLOCK SELECT position. Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 16: Filter

    • MONO OUT: summed signal of Upper and Lower Part. • PHONES: headphones stereo output. • LEFT - RIGHT LOW LEVEL OUT: low impedance stereo output. • LEFT - RIGHT HIGH LEVEL OUT: high impedance stereo output. Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 17: Rear Panel Connections

    • LEFT+RIGHT MONO OUT: doubles the front panel mono output. Future upgrades • HOST: this port is for future upgrades to the internal MIDI Interface firmware. At this very moment, it is disabled. Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 18: A8 Audio And Modulation Routings

    Then, we’ll follow the modulation sources and their applications on the audio circuit. SOUND SOURCES AND SOUND MODIFIERS PATH The above scheme is an over simplified view of the audio path for both Upper and Lower A8 Sections. As you can see, the signal produced from VCOs, SubOSCs, Noise Generator (in common for both sections) and Ring Modulators is treated thru the dual VCF section and then equalized with the Fixed Filter Bank;...

  • Page 19: Voltage Controlled Oscillator

    VOLTAGE CONTROLLED OSCILLATOR 1-6 The six VCOs comprised in A8 Synthesizer are, more or less, all equal; minor differencies are found in the FM/PWM Sources and Hard Sync capability. The VCO behaviours are organized in three main stages: Frequency Control and Frequency Modulations, Waveform Selection and Pulse Width Modulation, Output Leveling and Suboscillation.

  • Page 20: Waveform Control

    FM 2 buss works only in Exponential mode and can be connected with LFO 1 or 2; while this kind of circuit can be found useful mainly for vibratos, don’t forget that in A8 Synthesizer, the LFOs goes fairly high in the audio range.

  • Page 21: Output

    Input (for audio rate/low freq linear/exponential frequency modulation), to theFilter(s) Cutoff (for the audio rate/low freq exponential frequency modulation) and to the common Sample & Hold section (like the other possibile S&H sources). Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 22: Voltage Controlled Oscillator 1-6 Reference

    4, VCO 5, VCO 6, S&H, EG7+ (positive-going only), EG7- (negative-going only), SEQ, AFTERTOUCH, MODULATION WHEEL, Key VELOCITY. • AMT: The Pulse Width Modulation Amount from the selected source; operating range 0-10. • SUB VCO: Selection for frequency dividing factor; operating range: -1 OCT/-2 OCT. Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 23: Ring Modulator

    While each Upper and Lower MIXER has a separate NOISE Level control (as seen two pictures before), the colour noise will be the same in both parts of A8 Synthesizer. You can choose the type of noise (Low Frequency, Pink, White Noise) with the Noise Colour control located into the SAMPLE &...

  • Page 24: Voltage Controlled Filter

    Both Filters has indipendent three FM busses: one for Keyboard Tracking, the second for Envelope Generator, the third for a selection of different modulations and (as on the rest of A8 structure, there is a fair amount of modulation sources for Cutoff Frequencies).

  • Page 25: Voltage Controlled Filter 1-2 Reference

    6, EG 1, EG 4, EG 6, EG 7 (only positive-going), NOISE, S&H, AFTERTOUCH, MODULATION WHEEL. • FM 24 dB AMOUNT: the amount of modulation from the selected source routed to Cutoff Frequency. Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 26: Controls For 12 Db/Oct State-Variable Filter

    Hz, 700 Hz, 1 kHz, 1.4 kHz, 2 kHz, 2,8 kHz, 4 kHz, 5.6 kHz. • High Pass Level @ 7 kHz. • Bypass On/Off: you can entirely bypass the Fixed Filter Bank. Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 27: Voltage Controlled Amplifier

    Linear or in Exponential shape to the external CVs: you can choose which one is the best for your needs. Each VCA Section in the A8 Synthesizer contains two cascaded amplifiers: the first one is involved in the complex Main Mix / AutoPan structure which we’ll talk later; the second one is the “official” VCA who drives the articulation of the Upper/Lower Part(s).

  • Page 28: Main Mix / Auto Pan

    • (Auto Pan) UPPER ON: this switch enable the LFO pan modulation for the Upper signal. Controls for the Lower Section: • VOLUME: as above. • PAN: as above. • (Auto Pan ) LOWER ON: as above. Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 29: Controls For The Auto Pan Section

    • the couple of VuMeters has a fairly limited visual dynamic range (-14/+3); so, if you want to see needles dancing, you’ll be probably forced to set an high out level. Beware! The A8 Synthesizer can be very LOUD. Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 30: A8 Modulation Sources And Control Modifiers

    Note To be fully honest, there is a sixth kind of audio rate modulation source into the Grp A8 Synthesizer: you can use (…you should try it!) the VCO signals for lin/exp (cross) modulate the frequency of VCOs and Filters.

  • Page 31: Modulation Sources

    • Filter 24 dB Ext CV In. • Filter 12 dB Ext CV In. Modulation Destinations Here is a list of the available modulation destinations: • VCO 1 PWM, Linear Frequency Modulation, Exponential Frequency Modulation. Grp Synthesizer A8 User’s Manual V. 2.06...
  • Page 32 • VC LFO 1 Frequency, Output Shaping. • VC LFO 2 Frequency, Output Shaping. • LFO 3 Output Shaping. From here, we’ll explain the behaviour of the different modulation sources and modifers available in the synthesizer. Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 33: Frequency Control

    (sine, triangle, sawtooth, ramp, square) and, thanks to the analog nature of the LFO circuit, is it possible to modulate the shape/simmetry of the square wave, obtaining all the desidered Pulse Widths. Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 34: Hard Sync

    LFO. There are several shaping sources, enclosed a dedicated Envelope Generator for modulation fade in/fade out, comprising MIDI Key Velocity, Modulation Wheel position, Channel Aftertouch value, the other VC LFO value, the auxiliary Envelope Generator 7, several other EGs available in the A8 structure.

  • Page 35: Voltage Controlled Low Frequency Oscillator 1-2 Reference

    2; LFO 1, (available only in VC LFO 2), from LFO 1; SEQ, the Step Sequencer Clock Generator; MIDI 1/1, sync the LFO cycle on every 4/4 bar of external MIDI Clock; MIDI 1/4 sync the LFO cycle on every quarter of external MIDI Clock. Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 36: Shaping Controls

    Waveshape As on other great mono machine of the past, the A8 Synthesizer offers in the LFO 3 two main waves, triangle and square, that can be freely altered from the user. On this way, you can obtain all the intermediate values from sawtooth - triangle - ramp and all the different pulse widths, starting from square wave, till 1% to 99%.

  • Page 37: Output Control

    You can choose if have permanently on the CV outputted from LFO 3 or re-shape its amplitude scaling with Modulation Wheel position or Channel Aftertouch value. As you can imagine, this is appliable only when the A8 Synthesizer is under MIDI control. Modulation Routings The LFO 3 outputs eight different amounts of the same CV (same waveform, same frequency) towards the available Upper and Lower destinations.

  • Page 38: Envelope Generators

    ENVELOPE GENERATORS The A8 structure contains seven indipendent EGs positioned in logical points of the signal flow; in addition, each EG output is available in the modulation source list of the instrument: • Envelope Generator 1: controls, with separate bipolar amounts, the cutoff frequencies of Low Pass and State Variable Filters in Upper Section.

  • Page 39: Common Behaviours And Controls - Gate Source Select

    The structure of the envelope is straightforward and, as you can see from the above scheme, is it possible to mimic the classic “clipped decay” envelope from historical vintage mono synths or, if needed, obtain several kind of articulation contours. This kind of envelope has three separate control outputs: Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 40: Six Stage Envelope Generator (Env 1/ Env 4) Reference

    • R(e)TR(i)G position: when the envelope is retriggered, it will restart from the current value. • TRIG OFF position: the envelope ignore triggers and works only with Gate. • RESET position: if the envelope is retriggered, it will forced to restart from level zero. Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 41: Activity Led

    In spite of EGs 1 / 4, the EGs 3 / 6 lacks the dedicated Amount controls: every kind of attenuation should be done directly at the modulation destination stage. SIX STAGE ENVELOPE GENERATOR (ENV 3 / ENV 6) REFERENCE You can refer to the previous reference description. Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 42: Four Stage Envelope Generator (Env 2 / Env 5) Reference

    • R(e)TR(i)G position: when the envelope is retriggered, it will restart from the current value. • TRIG OFF position: the envelope ignore triggers and works only with Gate. • RESET position: if the envelope is retriggered, it will forced to restart from level zero. Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 43: Activity Led

    • KYBD S&H position: the envelope is fired from Gate On received thru MIDI Interface or from the analog Gate Input ports OR from the Clock signal emitted from Sample & Hold module. • SEQ position: the envelope is gated from the Step Sequencer. Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 44: Trig Switch Parameters

    Noise Generator with three different colours. As told before, the Noise signal is available to the audio chain of the A8 Synthesizer thru both the audio pre-filter Mixer (Upper and Lower); obviously, there is only one Noise Generator, so once you choose the its colour, you’ii get the same audio result in Upper and Lower section.

  • Page 45: Input Source Selection

    The most common input source, for a standard Sample & Hold module, is the Noise Generator, in addition, the A8 Synthesizer offers the two main LFO signals (don’t forget to analyze in deept the possible interactions between clock frequencies of LFO-input source and S&H…), and the audio rate signals of all six audio VCOs.

  • Page 46: Noise Generator Controls

    Glide is full cw, you’ll get a smoothed output. Noise Generator Controls: • NOISE COLOUR: you can choose between White, Pink and Low Frequency Noise. Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 47: Step Sequencer

    STEP SEQUENCER The A8 Synthesizer contains an integrated Step Sequencer that can be used either on Upper/Lower internal sections or on external analog equipment. The Step Sequencer has two Columns A and B, each one with 8 steps, that can be freely configured for work in 8x2 parallel or 16x1 serial fashion;...

  • Page 48: Column Parameters

    CV output, the A8 Step Sequencer has a selectable Hold mode that can be used for latch (e.g.: for freeze) the CV value contained in the last active step, prolonging it over all the subsequently paused (e.g.: with no Gate Out enabled) steps.

  • Page 49: Step Sequencer Reference

    (1/12V). • QUANTIZER B: same as above for Column B. VCO SEQUENCER ENABLE Each VCO can be assigned to Column A, Column B, Off (no sequencer enable) thru a dedicated three-position switch: Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 50: Pw Seq Ena(Ble)

    • OFF: the Cutoff Frequencies of the Upper VCFs are free from Step Sequencer. • B/B (inverted label): o if the MODE switch is on 8x2, this position assigns the Cutoff Frequency to Column B only; Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 51: Column A Section - Column B Section

    /8 /4 /2 0 x2 x4 x8: the dividing/multiplying positions for analog clock sources (all except MIDI); at central 0 position, the Divider is bypassed; at /2 position, the Step Grp Synthesizer A8 User’s Manual V. 2.06...

  • Page 52: Step Repeat & Loop

    CV output of the sequencer (e.g.: a S&H module or similar). Into the A8 Step Sequencer, you can freeze or prolong the CV value from Gate-active step over all the subsequent Gate-inactive steps.

  • Page 53: Sequencer Mode

    • GATE OUT COLUMN A - COLUMN A+B - COLUMN B: the Gate Output for the single Column A or B and for the two Columns A+B combined in series (16x1 steps). Range: 0/+5V. Grp Synthesizer A8 User’s Manual V. 2.06...
  • Page 54 LOOP ON MODE for Step Sequencer. This external input is parallel with the hardware LOOP SWITCH on the front panel. Note If you want to remotely control LOOP ON, don’t forget to turn off its hardware switch on the front panel. Grp Synthesizer A8 User’s Manual V. 2.06...
  • Page 55 © ® 2010 Manual: Enrico Cosimi Grp Synthesizer di Iannotti Rossana Via Formello, 17 - 00040 Monteporzio Catone (RM) P.IVA 10681631007 Grp Synthesizer A8 User’s Manual V. 2.06...
  • Page 56 Grp Synthesizer A8 User’s Manual V. 2.06...

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