Handcrafting Synthesizers Since 2004

Bananalogue Serge VCS Voltage Controlled Slopes Module


Serge VCS FracRak Format




Serge VCS Euro-rack (Doepfer) Format



The Serge VCS module from bananalogue.com is an extremely versatile control voltage generator and audio source. In the early 1970s, Serge Tcherepnin developed the Positive Slew and Negative Slew modules for the original Serge synthesizer. In time these merged into the classic Dual Universal Slope Generator. The Bananalogue VCS is an adaptation of Serge's original circuit with a few new features.

Control Panel

The VCS is a unity gain voltage follower. The rising and falling slopes are independently and jointly voltage controllable over a wide range.



A Trigger input. Trigger fires envelope, gate sustains level
B Input.
C Cycle switch. Connects "End Out" to "Trigger"
D AC Out. AC coupled output.
E Output LED
F Output.
G Both. VC control both Rise and Fall
H Exp CV. Approximately 1V/Oct scaled input.
I Rise knob. Manual control of rise time.
J End Out. Outputs a trigger pulse when the envelope completes a cycle.
K Fall knob. Manual control of fall time.
L VC Rise. Voltage control of Rise
M VC Rise Knob. Attenuates VC Rise amount. Pull the knob out for non-linear slopes.
N VC Fall. Voltage control of Fall
O VC Fall Knob. Attenuates VC Fall amount. Pull the knob out for non-linear slopes.

Patch & Sound Examples

The VCS is an extremely versatile module, creating and modifying CV and audio. Here are some examples:

VC Transient Envelope Generator

A pulse at the trigger input will start the envelope, or a gate input will sustain the level and the envelope will fall when the gate goes low. Rise and fall are independently and jointly voltage controllable, with variable linear and exponential wave shapes.

VC Portamento

Voltage is slewed according to the rise and fall times.
SOUND SAMPLE

VC LFO

When the cycle switch is thrown, the trigger input is connected internally to the end trigger output, creating a VC clock with variable waveform and independent rise and fall times.
SOUND SAMPLE

VC Oscillator

While not as wide ranged, or accurate as a dedicated oscillator module, the VCS is still an excellent audio source. The Exp CV input is scaled approximately to the 1v/oct standard. The Output wave can be swept from triangle to saw with linear and non-linear waveforms. End Out also produces a pulse waveform.
SOUND SAMPLE A
SOUND SAMPLE B

VC Non-Linear Audio Processor (Low-Pass Gate)

If an audio rate signal is slewed, the module responds like a VCF, and a rough VCA. The signal is low-pass filtered down to silence, similar to a low-pass gate.
SOUND SAMPLE

Envelope Follower

Positive and negative peak detection envelope follower.

VC Pulse Delay

Trigger input starts the envelope and a trigger will be produced again at the ”End Out” when the envelope completes its cycle.

Sub-Harmonic Generator

If a series of triggers are applied to the VCS faster than the total rise and fall times, the module will divide the incoming signal by a whole number. In the audio range the output will be the sub-harmonic series.
SOUND SAMPLE


User Submitted Patch & Sound Examples

The following examples were kindly provided by VCS user Ingo Zobel. The front panel settings are given, with a brief mp3 clip. Thanks Ingo!

Triangle VCO

8 note sequence from an analog sequencer at the Exp CV input.
cycle = on
rise = 12 o'clock
fall = 12 o'clock
both slopes linear
Signal from the AC Output

Skimmed Sawtooth VCO

8 note sequence from an analog sequencer at the exp cv input.
cycle = on
rise = 12 o'clock
fall = 12 o'clock
vc rise = fully ccw exponential
vc fall = fully cw exponential
Signal from the AC Output

Narrow Pulse VCO

8 note sequence from an analog sequencer at the exp cv input.
cycle = on
rise = 12 o'clock
fall = 12 o'clock
vc rise = linear
vc fall = fully cw exponential
Signal from the End Out

Low Pass VCF + VCA Response

Analog sequence is now sent to a VCO. Sawtooth output goes to the VCS Input. A slow triangle wave from an LFO goes to the VC Both input.
cycle = off
rise = fully ccw
fall = fully ccw
both slopes linear
Signal from the AC Output

High Pass VCF + VCA Response

Same patch as above, but this time the slow triangle LFO is patched to VC Fall only.
cycle = off
rise = fully ccw
fall = fully ccw
vc rise = linear
vc fall = 9 o'clock exponential
Signal from the AC Output

Sync + Low Pass + VCA

Analog sequence is sent to two slightly detuned VCOs. As above the sawtooth of VCO1 goes to the VCS Input. The squarewave from VCO2 goes to the VCS Trigger Input. The slow triangle LFO goes to the VC Both input.
cycle = off
rise = fully ccw
fall = fully ccw
vc rise = 1 o'clock linear
vc fall = 1 o'clock linear
Signal from the AC Output
Same as above, with Cycle switched on:
Signal from the AC Output

VC Waveshaper

VCO Sawtooth to VCS Input. A triangle wave from the same VCO is patched to the VC Both input.
cycle = off
rise = fully ccw
fall = fully ccw
both slopes exponential, starting fully cw
First the VC Fall knob is turned from fully cw to fully ccw. Then the VC Rise knob is turned from fully cw to fully ccw.
Signal from the AC Output

Animated Wave

2 VCOs are slightly detuned, the sine from VCO1 is fed to the VCS Input while the sine from the second VCO is fed to the VC Both input.
cycle = off
rise = fully ccw
fall = fully ccw
vc rise = fully cw exponential
vc fall = fully ccw exponential
Signal from the AC Output

VC Slew Limiter

Standard slew with equal rise and fall times:
Audio source is a VCO pulse wave. Pulsewidth is modulated by the sinewave of another VCO. The Analog sequencer CV goes into the VCS Input. VCS Output is fed into the 1v/oct CV input of both VCOs. Slew time is modulated by a slowly increasing positive control voltage at the VC Both input.
cycle = off
rise = 2 o'clock
fall = 2 o'clock
vc rise = fully cw linear
vc fall = fully cw linear
Signal from the external VCO pulse output
Same patch as above, but the VCS is in Cycle mode. The voltage at the VC Both input goes from -5 volts in the beginning to +5 volts at the end.
Signal from the external VCO pulse output

VC LFO

VCS Output modulates the cutoff frequency of Low Pass Filter.
cycle = on
rise = 3 o'clock
fall = 3 o'clock
both slopes linear
Signal from the Low Pass filter output

VC Envelope Generator

Audio source is a filtered VCO pulse wave. The pulsewidth is modulated by the sinewave of another VCO. Filter cutoff is modulated by the VCS Output. The VCS is triggered with each note. A second sequencer row goes into the VC Fall input for increasing the decay time on three of the eight notes in the sequence.
cycle = off
rise = fully ccw
fall = 2 o'clock
vc rise = fully cw exponential
vc fall = 1 o'clock exponential
Signal from the VCF output

VC Pulse Delay

Audio source is a filtered VCO pulse wave. The pulsewidth is modulated by the sinewave of another VCO. The filter is a multimode filter in lowpass mode. Two adsr envelopes are used for cutoff modulation. Every note triggers the first envelope and also the VCS. The second envelope is triggered by the end out of the VCS. In the first half of the recording the filter is modulated by the first envelope only. In the second half you hear a modulation from both envelopes.
cycle = off
rise = 10 o'clock
fall = 2 o'clock
both slopes linear
Signal from the VCF lowpass output

VC Envelope Follower

The audio source is an analog drum machine, coming into the system through an external input module. From there the audio signal is fed into the VCS Input and a lowpass filter. The cutoff of the filter is modulated by the VCS Output. A variable control voltage at the VC Both input is used to modulate the slew time of the envelope follower. The voltage is slowly increasing from -10 volts in the beginning to +10 volts at the end.
cycle = off
rise = 9 o'clock
fall = 12 o'clock
vc rise = half past 1 linear
vc fall = half past 1 linear
Signal from the VCF output