TONESTAR 2600 is an ARP® 2600-inspired synth voice 31 years in the shaping, pre-patched like Pearlman's prodigy, and fully #OutsToOuts modular, allowing for highpass/bandpass/notch filter tones, and bristling X-mod effects. Connect CV / gate and twist 'n' switch, or pull its tones and voltages apart one 3.5mm cord at a time. 26 knobs, 7 switches, and 21 jacks make for complex and satisfying signal flow, color and collisions. If it gets reedy, route the triangle wave 'round the VCF, and keep it boomin'. See the Outs-to-Outs / Interesting Patches .pdf for a demonstration of awaiting creations.
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Knowledge from circuit designer
Tim Caswell
The VCO is the same affair as the Oscillation, the Boomstar, and the Omega. It's kind of a combination of Arp®,
Oberheim® and Moog® circuits (sort of a greatest hits), time-tested, very stable—very good tracking over a very
large range; certain parts have to be hand selected to achieve that level of exacting performance.
Editors Note: This module is a TONESTAR—its own thing—and not a 2600 clone attempt;
nevertheless, the Tone☆ tugs lovingly at times on the sleeve of the 1970's era classic.
Envelope FYI: The Tonestar Sustain control replicates the behavior of the 2600 and Odyssey: after the initial
Decay, it continues to move (sink) very slowly, adding a little extra texture to the sound. It's technically a
flaw, but after digging out my Odyssey, it is for sure a desirable "quirk", and the perfect companion to the
4072 filter
(which we mistakenly titled a 4075
in the Boomstar Modular
line).
Another bit of fun: The LFO is voltage controlled, so you can envelope, LFO, or otherwise modulate both the
rate and the depth; the ADSR amount is also voltage controlled, so it can be manipulated by MIDI dynamics,
MIDI volume, an LFO, etc. Greg
[St. Regis] has decreed that anything must be patchable to anything, so some technically wrong patchings
(for example, pulse wave out to ADSR out) may often produce unexpectedly interesting, x-mod/notch
filtering—quite pleasing effects.
The Tonestar was Greg's concept, but as I understood it, the goal was a single oscillator, 2600 VCF,
pre-patched and yet fully modular classic synth voice, at a specific size, wielding every trick we could
cram in. Main use would be as a go-to bassline/lead tool, or a premium quality, entry-level, complete synth
module, for root-to-leaf sound design, and multiform analog exploration/expression.
,
7 switches 
,
21 jacks 
FREQUENCY
– Oscillator frequency attenuator.PULSE WIDTH
– Variable pulse wave width control.OCT
– +1/-1 octave switch. LFO (^)
– Triangle wave low frequency oscillation to pulse
width control.FREQ/PW
– Oscillator frequency, or Pulse (square wave) width to ADSR
modulation routing switch. Center off.GLIDE
– Slew generator control.MOD (ADSR)
– Oscillation modulation via ADSR control. TRIANGLE*/NO VCF
– Triangle to VCA switch—bypasses VCF. SAWTOOTH
* – Sawtooth wave attenuator.SQUARE*
– Square wave attenuator.SUB
– Square wave Sub Oscillator attenuator.TRIANGLE*
– Waveform output.SAWTOOTH*
– Waveform output.SQUARE*
– Waveform output.MIX
– Composite waveform output.1V/O
– One volt per octave control voltage input. TUNE
– Master fine tune (approx. -5/+ 5 semitones).MOD IN
– Modulation CV input. Normaled to ADSR; ADSR is replaced when alt. source connected.NOISE
– White noise generator output.LEVEL
– Noise attenuator.FREQUENCY
Frequency, or cut-off attenuatorRESONANCE
– Resonance, or Q attenuator.TRACK
– Keyboard/voltage tracking attenuator.DRIVE
– Oscillator output to filter input attenuator.FREQ/RESO
– Filter Frequency, or Resonance to LFO modulation routing switch. Center off position.ADSR
– Filter to ADSR envelope attenuator. MOD (LFO)
– Filter to LFO attenuator. EXT IN
– External audio input. FIL OUT
– Filter audio output. MOD IN
– Frequency or Resonance modulation CV input.TRIANGLE/SQUARE*
– Waveform select switch (triangle core).DPTH (OSC)
– LFO to Oscillator control.SPEED
– Speed or rate attenuator. DEPTH
– Control voltage Input.TRIANGLE*
– Triangle wave output.SQUARE*
– Square wave output. SPEED
– Speed or rate CV input.ATTACK
– Attack stage control.DECAY
– Decay stage control.SUSTAIN
– Sustain stage control.RELEASE
– Release stage control.DRONE/MASTER
– Indefinite/instant sustain, and master mode for ADSR routing switch: fuses VCF envelope with VCA envelope. Center off.ATTACK
– Attack stage controlRELEASE
– Release stage control.GATE IN
– External gate input.MOD IN
– Allows for dynamic modulation of the ADSR, eg., if you want
the amount of modulation added to/determined by a external source, jack in; or if you prefer, modulation
input to the ADSR routing—use with velocity, or a sequencer: the sequencer could isolate the ADSR amount
the amount to a single step in the phrase for example. Exciting. A second external envelope can provide
an interesting effect, or the AR (in the box patching).ADSR OUT
– ADSR output. AR OUT
– AR Output.FEEDBACK
– Oscillator/filter feedback loop control.VOLUME
– Master volume control.VCA CV
– Amplifier control voltage output.IN/MIX
– VCA mix input switch switch (normalled jack). When set to IN, external audio
replaces filter output to VCA; when set to mix MIX, filter output is fed along with the filter audio to VCA.VCA IN
– Audio input.OUTPUT
– Main output. 
