by John Simonton
When we went on-line in the mid-90s I was very surprised by the interest in the Voltage Controlled Synth Modules that we manufactured during the ’70s and early ’80s. If you’re not familiar with them there are some pictures in the photo album.We were often asked if these modules would be reissued. For a time, I considered simply doing this and the FracRak was designed as an improved packaging system for these resurrected devices. But along the way the idea of putting a good bit of work into simply redoing, got to be less interesting than trying some new things.
The PAiA 9700 series takes a different approach in several ways. First, these are double or even triple versions of conventional modules. Also, since having lots of modulation sources is key to interesting sounds, Envelope Generators that double as Low Frequency Oscillators are an integral part of each module. Normalization of these high level functions is carefully optimized to allow complex voices with few patch cords while still allowing individual elements to be used independently.
The first module released was the midi2cv8 MIDI to CV converter which serves as both controller and power supply in systems such as the P9700S. Several of it’s operating modes are tailored to controlling modular systems either as a single complex voice or as groups of simpler polyphonic and polytonic voices. It also set the design style for the rest of the modules.
Then we released the 9730 Dual VCF w/Modulator. Two identical filters with Lo Pass, Band Pass and Hi Pass outputs are normalized as a single 24dB/oct element. but can also be used as two independent filters for a large variety of complex 12 dB/oct and 24dB/oct responses. Corner frequency range is 10 octaves from 16Hz to 16kHz with the two Fc inputs to each filter scaled 1V/oct. The built-in AR/ASR/Gated LFO modulator is normalized for Fc modulation.There are more details including photos and .wav files on the 9730 page.
Third was the the 9710 VCA/Mixer/Noise Source. Light years beyond the traditional VCA, the PAiA 9710 combines 3 VCAs (one is also a Balanced Modulator), a White Noise Source and full function ADSR/LFO Envelope Generator. The unique normalization produces a powerful processing element that can be used as VCA/Balanced Modulator with manualy or Voltage Controlled Panable sub-mix input, or as a Voltage Controlled 3-input mixer or as three totally independent VCAs and EG. There are more details on the 9710 page.
The fourth module was the 9720 Dual VCO w/Modulator. Two independent VCOs that between them have Ramp, Triangle, Sine and Pulse waveforms. Pulse width is controllable by panel control or CV. Each oscillator has two 1V/oct. scaled Pitch CV inputs and a chromatic range of 10 octavs from 16Hz to 16kHz. One VCO has a linear FM input and the other has a sync input and 3 octave transpose switch. Pitch knobs set initial pitch over a 3 octave range. The built-in modulator provides AR/ASR and Gated LFO functions and is normalized for PWM or vibrato (Pitch shift). Here’s a preliminary 9720 page.
The 9770U Power Wing is a zero-space power supply for systems that do not have a midi2cv8 or other power souce. In the 9700 series, power is distributed as unregulated bipolar 18VDC to the modules which have local voltage regulation where needed. Signal ground and power grounds are separate lines for star grounding.
Other Techie stuff
Module Control Voltages are nominally scaled 1 V/Oct but can be calibrated for 0.8 V/Oct to 1.2V/Oct. and are chromatic over a 10 octave range from about 16Hz to 16kHz. Operation outside this range is possible (VCOs can go down to 1Hz or lower) but with reduced pitch accuracy.Typical audio and conrol signal levels are 5V p-p.
Patching is by 1/8″ phone plugs and jacks. Some builders like “banana” jacks and plugs because they stack. But they don’t switch and this is important because of the normalization of these high level functions. With Phone jacks you can over-ride or extend the normalization just by jacking-in and stackable connectors can’t do this at any reasonable cost. Some builders prefer larger 1/4″ phone jacks, but the complexity of these modules and the number of jacks on a typical panel won’t allow this in the FracRak format.
Electronic parts kits are available without any jacks, so you can use your own choice. Otherwise, the electronic kits for each module are complete with all electronic components, controls, knobs, wire, circuit board, etc. All 9700 series circuit boards are tin-lead plated and solder masked on FR-4 material. Most are double-sided with plated-through holes.The FracRak accessory kit available for each circuit includes Panel, Jacks, Switches and other mechanical parts required to build a complete FracRak format module.
This comprehensive MIDI system includes a midi2cv8 MIDI to CV converter, 9710 VCA/Mixer/Noise Soure, 9720 Dual VCO w/Modulator, 9730 Dual VCF w/Modulator, FracRak Case and patch cord set. Everything needed for a complete MIDI controlled modular synthesizer system with extraordinary power and flexiblity. The discounted package price saves you more than $25 on the purchase of the individual kits and panels.