This site is dedicated to everyone interested in Serge Modular Music Synthesizers
Audio Interface - $1700 USD*
Audio Interface

Features and Notes

Preamp Detector (PRNV)

The PREAMP DETECTOR (PRNV) allies a Serge detector with a multi-purpose preamp suitable for a wide variety of inputs. The LO-Z input accepts high output microphones in the 200 to 1000 Ohms range (such as most electret microphones), with a sensitivity suited for close-mitring applications such as instrument or voice pickup. The HI-Z input accepts transducers such as guitar pick-ups and contact microphones. It is also suited for amplifying low level signals from tape machines, tuners, etc. Detector and Preamp can be switched to work separately or coupled. Sensitivity for the various microphones and audio sources can be adjusted over a very wide range using the Preamp's gain control. Please note that it will not cut the gain to zero, however.

Resonant Equalizer (EQ)

The RESONANT EQUALIZER (EQ) is a unique ten-band filter designed specifically for electronic sound synthesis and processing. Except for the top and bottom frequency bands, all other bands are spaced at an interval of a major seventh. This non-standard spacing avoids the very common effect of an accentuated resonance in one key, as will be the effect from graphic equalizers with octave or third-octave spacing between bands. Spacing by octaves will reinforce a regular overtone structure for one musical key, thereby producing regularly spaced formants accenting a particular tonality. The Resonant Equalizer's band spacing are much more interesting, producing formant peaks and valleys that are similar to those in acoustic instument sounds.

There are three equalized outputs, two which mix the alternate filter bands, and one which is a mix of all filter bands. The upper "COMB" outputlet passes the outputs of frequency bands at 61 Hz, 218 Hz, 777 Hz, 2.8Khz, and 11 Khz. The lower "COMB" output mixes the other bands (29,115,411,1.5K,5.2K).

This equalizer is different from other equalizers in that the bands can be set to be resonant. When the knobs are in the middle position, the response at the main EQ Output is flat. When the knobs are positioned between the 9 and 3 o'clock position, up to 12 db of boost or cut is set at the band. If the knob is set beyond the 3 o'clock position, the band will become resonant, simulating the natural resonance of acoustic instrument formant structures. Below the 9 o'clock position, increased band rejection is achieved.

Dual Universal Slope Generator (DSG)

The DUAL UNIVERSAL SLOPE Generator (DSG) is the ultimate patch-programmable control voltage generator in the Serge system. At least one (DSG) is recommended for almost every Serge system. and in most cases, a number of these are desirable. People familiar with our previous series of "slewing" modules know about the importance of this kind of function in a large patchable synthesizer system. For those unfamiliar, it is advised that the various applications as outlined here and in the Serge Owner's Manual are studied. The uses of this module are numerous, some duplicating functions found on other synthesizers, some totally unique to the Serge system. Most systems require a number of control voltage generators to control the various signal processors and modifiers. Sources of trigger, pulses (clocks), control voltage processors (portamento's), regular repeating voltages (LFO's) are standard synthesizer requirements. The Dual Slope Generator is the main module providing these functions in the Serge system.

The Universal Slope Generators are unity gain voltage followers with voltage controllable slopes. The range of control is exponential, extremely wide, and the Rise and Fall times can be controlled independently. The range of the Slope Generator is from sub-sonic to high audio frequency. Trigger inputs and trigger outputs allows each section of this dual module to function as a transient (envelope) generator, pulse delay, or in a "cycling mode" (to produce an LFO or clock). Since the Rise and Fall times are voltage controllable, this adds another dimension to the above functions. Two VC inputs are available, one is calibrated at 1 volt per octave (within about 3%), and the other is fully adjustable in the negative and positive direction. This VC input can control either the positive slope (rise), negative slope (fall), or both. The linearity and accuracy of the slewing amplifiers allows them to be used in the most exacting applications, such as processing the output of a keyboard or sequencer to produce portamento functions. Note that this portamento function has a separate rate control for rising notes and falling notes... An interesting portamento effect. Among the functions which one Slope Generator can be patch-programmed to perform are the following:

  • VC Transient Envelope Generator. The envelope is simply started With a trigger, or may be used with a gate input to obtain a steady-state sustain level on the envelope. This envelope will repeat if the END trigger output is connected to the TRIG IN input.
  • VC LFO. Patched as mentioned above, a wide-range, low-cost, space-efficient Low Frequency Oscillator can be patched when needed. The Slope Generator is often used as an LFO since it is more cost effective than a regular oscillator switched to a low frequency range. it has a built-in LED to show its current output level, and it has a synchronized trigger output. The waveform can be set from saw to triangle, and the rising ramp can be voltage controlled independently of the falling ramp.
  • VC Portamento device. The accuracy of these devices makes this portamento function useful with keyboards and for generating control voltages of arbitrary shapes and times with computer control. Analog control of slopes allows the computer to do less "number crunching", and frees the processor from time-consuming routines that are more easily handled in this low-cost multifunctional hardware.
  • Envelope Follower (Detector). The decay rate is voltage controllable with the unique function that under voltage control, the response may be moved from positive peak detection to negative peak detection.
  • VC Pulse Delay (Monostable). When the unit is triggered, it will produce an envelope set by its Rise and Fall knobs (and VC's) and then the END pulse will go high. This may be used to trigger another Slope Generator, ADSR, or advance a sequencer.
  • Sub-Harmonic Series Generator (Divider). If a series of triggers are applied to the TRIG IN jack that are faster than the total rise plus fall time, then the unit will divide the incoming triggers by a whole number. This allows the user to program synchronized rhythmic relationships (such as 2 against 3, 13 against 11, and so on). If the Slope Generators are set to audio frequencies, and the incoming triggers are in the audio range, then the output will be the sub-harmonic series. This is similar to the "hard sync" sound found in other synthesizers (and is the main reason that it is not included on Serge VCO’s).
  • Audio Oscillator. The range reaches 4000 Hz, and the waveform has variable symmetry (saw to triangle).
  • Non-Linear Audio Processor. The slew limiting is voltage controllable, so a sawtooth wave input will progressively be transformed into a triangle wave. This aspect allows the Unit to be used as a low-fidelity VCF!

VCA / Comparator (VCOM)

This is a module comprised of a single VCA from the Dual VCA (2VCA) and the Comparator section of the ÷ N Comparator (NCOM).

Additional note:
The Audio Interface is available with Hi-Z Balanced Input [DID] by means of 'XLR' and/or 1/4" t-r-s via the M-boat rear panel. (Lo-Z input transformer is also available)

*Plus $150 with XLR Input - plus $150 with Lo-Z Transformer input added
Thanks to Ty Hodson for pulling M-Class module information together from various sources. Other references include "Introduction of the Serge Modular Music System" by Rich Gold, Darrel Johansen, and Marina LaPalma
 ASR Quan  Audio Matrix Mixer
 Audio Interface  Control Generator
 Bi-Filter  CV Matrix Mixer
 Creature  CV Processor
 Dual NTO  Dual ADSR
 Dual 'Q' Filters  Dual Oscillator
 Gator  EQ Shift
 Klangshifter  Hex VCA Mixer
 Mayhem  Klangzeit
 Sequencer-A  Multi Filter
 Stereo Mixer  SQP Sequencer
 Triple Oscillator  Quad Slope
 Wilson Analog Delay  Wave Processor