The 4027 VCO is a 10HP Eurorack filter adaptation of the colorful VCO-2 tone source from the ARP 2600 synthesizer.   You know…that all analog, all discrete components, SAWTOOTH core packed with the SINE, TRIANGLE, and PULSE w/ PWM!  If you’re looking for warm, fat analog synthesizer tones – 4027 VCO is the one for you.

In bringing that special tone to life the 4027 VCO keeps the circuit as close to the original as possible: a matched transistor pair, an Interfet premium dual FET can (because that beautiful Sine is worth it), temperature compensation resistor for tuning stability, low ESR styrene oscillation capacitor, 5-NPN monolithic substrate transistor array, precision Tune and Tracking trimmers, and the 70s spec op amps which are still being offered today.  The 4027 VCO has requisite LDO voltage conditioning to isolate the oscillator tuning from your systems power rails. While each module is fully tested and calibrated, it may need minor TUNE trimmer correction after warm-up to account for variances in different systems. This limited quantity module is lovingly hand-crafted in the USA. 

Waveforms: SINE (-4v to 4v), TRIANGLE (-4v to 4v), SAWTOOTH (0 to 6v), PULSE (0-6v) w/ PWM
Three 30mm throw Illuminated Bourns slide pots - Frequency, Fine Tuning, and Pulse Width
Three 20mm throw Alpha CV slide pots
CV1 input: Wide Frequency Modulation (FM)
CV2 input: Reduced Frequency Modulation (Vibrato, FM)
Keyboard (KBD) V/Oct input.
Multi-turn Trimmers: Tune, Tracking
Single-turn Trimmers: TRI Symmetry + DC Offset, SINE Purity + Gain
CV Frequency Range: C1 –C8 when Initial Freq. is fully decreased
No-Input Freq. Range: 10-550Hz
Slim design makes it skiff/boat-friendly.
Includes a 10-pin to 16-pin Eurorack ribbon connector 

4027 VCO Pairs Well With…
  • GSE Tonus VCF
  • GSE 4023 VCF
  • GSE Spring Tank Reverb Driver
  • another 4027 VCO
  • Delta Sound Labs Mobula

10HP Module width
24mm Module depth
78mA on +12V
24mA on -12V
0mA on 5V (not used)

ConditionBrand New (New)
Brand New items are sold by an authorized dealer or original builder and include all original packaging.learn more
  • 4027 VCO
Made In
  • United States


Oklahoma City, OK, United States
Joined Reverb:2016

Reverb Gives

Your purchases help youth music programs get the gear they need to make music.

Carbon-Offset Shipping

Your purchases also help protect forests, including trees traditionally used to make instruments.

Oops, looks like you forgot something. Please check the fields highlighted in red.