Audio Processors

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 instrument 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) lets pass the outputs of frequency bands at 61 Hz, 218 Hz, 777 Hz, 2.8 kHz, and 11 kHz. The lower (↓ COMB) mixes the other bands (29 Hz, 115 Hz, 411 Hz, 1.5 kHz, 5.2 kHz).

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.

Ring Modulator (RING)

The RING MODULATOR (RING) is a brand new design which incorporates greatly improved specifications. Features include the following:
  • A VERY CLEAN SOUND down to very low signal levels (unlike conventional modulators where distortion increases at low levels). 
  • NO SQUELCH CIRCUIT IS REQUIRED due to the low noise characteristics, therefore annoying signal dropouts and “pumping” effects are totally absent. 
  • INTERNAL WAVESHAPING OF CARRIER to add to modulation effects 
The sum total of these design improvements is a Ring Modulator capable of treating the most subtle acoustical signals, without the coloration typically associated with even the best previously available ring modulators. The versatility of the Serge Ring Modulator is enhanced by the added feature of voltage and manual control of the entire spectrum of modulation possible: from zero modulation (i.e. the original, untreated input signal) through amplitude modulation to full ring modulation. This allows many shadings of effect, manual or automatic with voltage controls. The ability to control the Carrier level manually and through voltage control allows the output to be level controlled as well. Through the use of an internal signal processor for the Carrier, additional effects can be produced by waveform modification of the carrier signal. When the module is set to full Ring Modulation from the lower knob or voltage control the output signal contains the sum and difference frequencies of the Signal Input and the Carrier Input. If both signals are pure sine waves (only one frequency component), the output will be a composite signal consisting of two frequency components: the sum and the difference frequency of the Signal and Carrier. If the Carrier level is increased beyond the mid-position, then the carrier waveform will become slightly rounded, and new frequency components will be produced. Each of these new components will also modulate with the Signal input to produce a sum and difference frequency, and the output signal will become richer in harmonics. This effect is unique to the Serge Ring Modulator, and allows another dimension in timbral modification. Although this module may be one of the most sophisticated in the SERGE system, it only takes up one inch of Panel space. (Recommended as companion modules placed near the RING MODULATOR are the various Preamps and VC Oscillators.)

Frequency Shifter (FRS)

The FREQUENCY SHIFTER is an advanced model with several improvements over existing designs:
  • Greatly improved signal-to-noise ratio
  • Extremely high carrier frequency rejection
  • A very clean sound down to very low signal levels (unlike conventional shifters which have increasing distortion at low levels) 
  • No squelch circuit and, therefore, no annoying dropouts or "pumping" action in the sound
These improvements have so improved the quality of the sound, that even the most subtle natural sounds can be processed. Apart from its effect, the FREQUENCY SHIFTER does not intrude with extraneous noises or distortions. The FREQUENCY SHIFTER does not transpose. Rather it shifts each harmonic of the signal by a fixed value equal to the shifting frequency. Thus, as the shifting frequency becomes larger, the relationships between overtones are altered, and timbres change dramatically.

Uses of the FREQUENCY SHIFTER abound. It can be used to frequency modulate natural sounds (from musical instruments, for example), to produce the "Leslie effect" of rotating speakers, and to synthesize other phase shift and vibrato effects. In concert halls, frequency shifters are often Used to control feedback. It performs special effects on human speech, excellent for "computer-like" or "alien-type" speech. One of its most dramatic effects is frequency shifting of an echoed sound, where delayed signals get successively fed back and shifted up or down to produce incredible arpeggios of multiple echoes. Such an effect can be produced with the FREQUENCY SHIFTER and a reverb chamber or tape delay. Quite similar (and other rather far-out) effects can be produced with the use of the Analog Delay module.

...[This] basic unit features a built-in oscillator (with 0 and 90 degree outputs) whose sine wave outputs provide for the smoothest and cleanest shifting... Additional features ... include output VCAs for both the UP and DOWN shifted signals, and an Output providing a COMPRESSED version of the input.

Frequency Shifter (ext. carrier) (FRSX)

The FREQUENCY SHIFTER is available in two versions... Available (at higher cost and only on on special request) is a version which accepts any external shifting signal. This version may be of interest to musicians wanting to shift the sound of one instrument by another, say the flute by a tuba. Both modules take up 3 inches of panel space, with one of the inches left blank (as shown) or filled by 1 inch modules which do not require a PC board. The CONTROL MODULE and the ADAPTER modules are examples of this type of module.

Phase Shifter (PHA)

The VC Phaser (PHA) is perhaps the lowest noise and lowest distortion phase shifter available today. As an aid to recreating some of the subtle properties of phase delay in acoustic sounds, three separate outputs are provided with 360 degree, 720 degree, and 1080 degree of voltage controllable phase shift. A MIX output combines the 1080 degree phase shift with the input signal to produce the multiple notch filter effect that is usually associated with phase shifters. The VC Phaser's log-conforming characteristics and the manual and voltage controls enable ultra-smooth, precisely centered sweeps of phase shift for both spatial effects and timbral modification. For high-density systems a 2'' DUAL PHASER (2PHA) is available.

Dual Phase Shifter (2PHA)

Incomplete information here, but see PHASE SHIFTER (PHA).
Triple Waveshaper (TWS)

The TRIPLE WAVESHAPER (TWS) is a non-linear modifier which can transform a sawtooth wave into a sine wave. This module incorporates three independent waveshapers for modifying synthesizer waveforms or for processing signals from preamplified instruments. Although originally designed as a waveshaper for our early oscillators, this module has been found to be an excellent modifier of electronic and acoustic sounds, and is highly recommended for subtle timbral modifications beyond the range of simple oscillator/filter patches.

Wave Multipliers (VCM)

For generating and modifying sound, the typical synthesizer patch is VCO-VCF-VCA, linked in series, with suitable control from keyboard, sequencer, or computer. The VCO generates the raw sound, the VCF dynamically varies the timbre (sound quality). and the VCA controls the amplitude and produces the envelope on the sound event. The Serge Modular WAVE MULTIPLIERS (VCM) provide a new link in this chain, representing an advance in synthesizer technology. In this typical patch, the Wave Multiplier could be placed just before the VCF. Like the VCF, the Wave Multiplier affects the timbre. Unlike the VCF, whose action is a subtractive process of filtering frequencies from the input waveform, the Wave Multipliers are able to dynamically process the input waveform to produce new harmonically-related overtones. This function should not be confused with Ring Modulation, since it is a non-linear process using a single audio input. Although it is possible to describe the effect of a VCF by saying the sound gets “bass-heavy”, makes a “wah-wah” effect, or sounds “thin”, describing the sound of a Wave Multiplier is much more difficult. The input sound comes out richer in harmonics, somewhat similar to pulse-width modulation and to linear frequency modulation, but with a new characteristic timbre. The nearest we can come to describing the unique sound qualities (there are three different sections) is to say that they alter the timbre in exciting new ways, producing interesting alternative forms of signal processing which are unique in the Serge Modular Music System. Since there are three entirely separate and different types of Wave Multipliers in this module, an enormously varied palette of new effects can be synthesized.
  • The uppermost section is the simplest of the three multiplier sections. but it has two switchable effects. With the switch set at the “HI” position, the module functions to “square-up” an incoming signal. This is not the same as a simple comparator squaring function, though, since there is a rounded flattening of the signal peaks: an effect somewhat similar to overdriving a tube amplifier (except that in this version the process is voltage controllable!). With the switch in the “LO” position, the module is a linear gain controlled VCA. This is useful for various functions such as amplitude modulation and for gating signals into the other sections. 
  • The middle Wave Multiplier provides a sweep of the odd harmonics (1, 3, 5, 7, 9, 11, and 13th) when a sine wave is applied to its input and the knob is turned up or a control voltage is swept from low to high. This effect is similar to overblowing a wind pipe closed at one end, and thus the module can be used to produce the sounds of various wind instruments. A second input is included to allow two signals to be mixed before processing, a technique that we have found to be very usable. This module can be used to explore timbral areas beyond the range of ring modulation because there are more varied harmonics than the sum and difference tones. 
  • The bottom Wave Multiplier performs non-linear waveshaping known as full-wave rectification, but with sophisticated level-compensating conditioning as well. Actually the circuit uses three full-wave rectifier sections linked in a very refined controllable format. Each section can double the frequency of a sine or triangle wave applied to its input. Thus sweeping the VC input over its range will produce a smooth timbral transition using the even harmonics (second, fourth, and eighth). Many other partials are present in this basic sound, however, and the sonorities are very rich and varied. A notable feature of this multiplier is that the full-wave rectification is not accompanied by a reduction in the output amplitude. There is no alteration of the essential level of the sound. There are two inputs to provide mixing before processing, and two outputs. One output is a “squared up” version of the other. This output resembles voltage controlled pulse width modulation (only much more interesting). 
The Wave Multipliers are among the most powerful timbral modifiers available on any analog music synthesizer. The rich varieties of inter-patch possibilities are nearly inexhaustible, and these possibilities combined with the flexibility of other Serge modules will provide unique synthesis tools for the person who is eager to experiment with entirely new classes of sounds. The Wave Multipliers provide what has too often been lacking in electric musics: a means of generating sounds as complex and dynamically variable as those found in acoustic sound sources. Yet these are also precision modules which respond accurately to control voltages, so they may be used to give repeatable results in the most exacting analog or digital applications.

Wilson Analog Delay (WAD)

The Wilson Analog Delay was specifically designed to allow internal functions such as filtering, feedback, and delay to be determined by the user as a patch programmable function. Features of the Wilson Analog Delay include the following:
  • VOLTAGE VARIABLE DELAY OVER A VERY WIDE RANGE, from a minimum of .0005 sec. to greater than one half second ** 
  • Availability of the TWO DELAYED OUTPUTS (A & B), one which is twice the delay of the other. 
  • A FLANGING OUTPUT with a control to set its depth 
  • A 1 VOLT PER OCTAVE (V/OCT) OUTPUT to permit controlling external VC filters easily. 
  • THREE INPUTS, each with its own gain control and specific function. IN-1 is the main audio input for internal or external signals. IN-2 is suitable for audio, but also for the input of control voltages to be delayed. IN-3 is connected via a switch to provide feedback selectively from either the "A" or "B" delay outputs, or from the AUX jack. This channel features a processing-type control to scale and invert either the feedback from "A" or "B" or the AUX signal. 
  • An INNOVATIVE NOISE-CANCELLATION CIRCUIT which produces a very clean sound, as opposed to the "muffled" quality of more conventional analog delays. 
These features provide an amazingly varied palette of effects. Here are some of the possible ways to use this module:
  • "GLIDING" FREQUENCY SHIFT effects (the frequency shift effect is never steady, but is a function of envelopes varying the delay rate). 
  • STRAIGHT DELAY (perceived as fast repeats as in the delay between two tape recorder heads). 
  • ECHO CHAMBER EFFECTS, where the delayed signal is fed back into the Analog Delay's input. (The switchable AUX input is particularly valuable for this type effect, especially if an external VCA is inserted into the feedback loop, allowing voltage control of the number of echoes as well as their rate of occurrence). 
  • DELAY AND ECHO OF CONTROL VOLTAGE ENVELOPES (via IN-2). Though the maximum guaranteed delay is .5 second, in practice the delay will go to more than 5 seconds for low frequency signals such as control voltages. 
  • MODULATION EFFECTS resulting from the modulation of the input signal by the clock internal to the Analog Delay. 
** The first question often asked about the Analog Delay is how long a delay can it do? The answer to this question is fairly complex. Quite a long delay can be performed by the module. However, as delay becomes longer, the bandwidth of the signal which can be processed by the Analog Delay becomes more restricted. As an example, if it is desired to delay a signal consisting of a sine wave at 440 Hz (concert "A"), then better than a half second can be gotten quite cleanly. The same note with a lot of harmonics, say a square wave at 440 Hz, if delayed at a half second, will produce a very modulated output (if the Analog Delay's built-in filters are opened wide) full of extraneous signals, or will lose its overtones because the filters will remove them. (This is why many other delay modules have a dulling effect at long delays). The moral to this story is that one function which the Wilson Analog Delay will not do, is to reproduce the full effects of tape delay (i.e. "echo-plexing") without appreciably changing the signal being delayed. But tape delay is a stock effect, usually available to most synthesists (but which can be used with other voltage-controlled functions such as filtering, phasing, frequency shifting, etc., for more sophisticated effects). The forte of this module is its ability to transform signals and control voltages in an incredible number of ways.

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