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Synthesis Technology E300 Ultra VCO (silver)

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The Synthesis Technology E300 Ultra VCO is an analog oscillator based on the MOTM-300 5U module, with an updated design engineered in collaboration with Dave Rossum of Rossum Electro-Music.

The E300 uses modern temperature-controlled exponential converters without the expensive MAT-02EH + Tempco found in the MOTM-300. It also incorporates variable HFT (High Frequency Tracking) for a wider, more accurate 1V/Oct input. The SYNC circuit is a simpler hard sync type, with accurate detection of any waveshape/frequency used. There is an added -1OCT/-2OCT sub-octave squarewave output, which is phase-aligned with the sawtooth.

The VCO core is a new sawtooth-based circuit with improved linearity and a unique saw-to-triangle converter with no glitch in the transition peaks.

Just like the MOTM-300, the E300 is designed to be the best tracking analog VCO available (over 10 octaves) with the lowest temperature drift (typically less than 0.1Hz over a 24hr period).


Height 3U (128.5mm)
Width 14hp (70.8mm)
Depth 32mm
Power 16-pin Eurorack (55 mA from +12V, 40 mA from -12V)
CV Range 10Vpp (-5V to +5V)
Audio Output 10Vpp nominal +-0.35V
Frequency Range 15Hz to 19KHz (no CV input)


COARSE/FINE Sets the initial VCO pitch with no CV applied
PULSE WIDTH Modifies the width of the PULSE output
FM 1/2 Attenuators for the FM inputs. FM 1 can be switched between EXP (exponential) and LIN (linear) FM. FM2 is linear.
SUB SWITCH Controls whether the sub-oscillator output is 1 or 2 octaves below the initial oscillator frequency.


1V/Oct 1 volt per octave control for the initial VCO pitch
FM 1 VCO frequency modulation input with attenuator Can be switched between EXP (exponential) and LIN (linear) FM using the toggle switch.
FM 2 VCO frequency modulation input, exponential FM, with attenuator.
Sync Reset VCO frequency when input signal exceeds +1.7V
PWM PULSE width modification input, with attenuator.
SINE, TRI, SAW, PULSE The primary outputs of the oscillator
SUB The sub-oscillator output. Can be switched between 1 or 2 octaves below the initial oscillator frequency.
_hp 14