Rossum Trident - Multi-Synchronic Triple Analog Oscillator Ensemble

Multi-Synchronic Triple Analog Oscillator Ensemble

The latest brainchild of synth pioneer Dave Rossum, TRIDENT is a 100% analog, triple oscillator module that opens up a universe of dynamic timbral textures.

At its most basic level, TRIDENT is three precision audio VCOs, each sporting a unique variety of control voltage inputs. 

The main or “Carrier” oscillator provides its three waveforms simultaneously. The two Modulation Oscillators each have a single output and a waveform selector. The Modulation Oscillators also have a voltage controlled Symmetry parameter which varies the duty cycle of the triangle wave output from sawtooth to triangle back to time reversed sawtooth, and also varies the sawtooth output to have an upward or downward kink in the middle, as well as controlling pulse width when the pulse waveform is selected. 

And while each oscillator can be used independently if desired, it’s when they’re combined into a synchronous ensemble that the real sonic magic happens.

That magic is what we call Zing Modulation. Each of the Modulation Oscillators can modulate each of the Carrier outputs in an amount controlled by the Zing parameter. Zing Modulation is mathematically akin to ring modulation, but due to the synchronization of the oscillators (when an oscillator’s Sync button is on), the aharmonic sum and difference sidetones of ring modulation transform into complex but purely harmonic overtone spectra, which vary dynamically and dramatically with the frequency and waveshape modulations of the modulation oscillators.  Each change in the Modulation Oscillator parameters – Frequency, Symmetry, Waveshape, Zing, and (in the case of Modulation Oscillator 2) Phase – will have a different effect on the timbre of each of the three Carrier waveshape outputs.

When the modulation oscillators are set to track the carrier oscillator, the waveshape will remain constant as the carrier frequency changes.  In this case the overtone structure is determined by the settings and CV modulations of the modulation oscillators.  If instead the modulation oscillators do not track the carrier, some of the overtone structure will vary relative to the carrier frequency.

What all this means is that whether you take advantage of Trident’s unique synchronous modulation capabilities (which you, of course, should), or just treat it as three superb, wide-range analog oscillators, TRIDENT offers a vast variety of dramatic sonic textures.

TRIDENT features include:

– Three precision analog oscillators with dedicated 1V/Octave inputs and coarse control ranges of 20Hz to 20kHz and modulated ranges of 0.01Hz to 25 kHz.

– Main Carrier oscillator with simultaneous triangle, sawtooth and pulse waveforms, with exponential and linear frequency modulation and pulse width modulation.

– Main Carrier oscillator hard sync input 

– Modulation Oscillator 1 with selectable triangle, sawtooth and pulse waveforms with exponential frequency modulation, variable symmetry and symmetry modulation, and variable Zing level and Zing level modulation.

– Modulation Oscillator 2 with selectable triangle, sawtooth and pulse waveforms with exponential frequency modulation, variable symmetry and symmetry modulation, variable Zing level and Zing level modulation, and variable phase and phase modulation.

– Both Modulation Oscillators with independently selectable options to sync to the Main Carrier oscillator and track the Main Carrier oscillator

– Trident, like all Rossum Electro-Music modules, features solid construction, with thick aluminum panels, solid aluminum knobs, and quality components throughout. 

TRIDENT is 30HP wide and 25mm deep.

Power requirements (max):  290mA +12V, 270mA -12V. Reverse polarity protected.

Trident Specifications

CARRIER OSCILLATOR 

Controls 

Coarse Frequency

Fine Frequency 

Pulse Width 

Sync In 

1x 3.5mm mono socket 100kΩ Input Impedance 3.5V Rising Edge Threshold 

1 V/OCT CV 

1x 3.5mm mono socket 100kΩ Input Impedance 

Attenuverted Exponential FM CV 

1x 3.5mm mono socket 100kΩ Input Impedance 

Attenuated Linear FM CV 

1x 3.5mm mono socket Min 80kΩ Input Impedance 

Attenuverted Pulse Width Modulation CV 

1x 3.5mm mono socket 100kΩ Input Impedance 

Audio Outputs 

3x 3.5mm mono socket 1kΩ Impedance 

MODULATION OSCILLATOR 1 

Controls

Coarse Frequency

Fine Frequency

Symmetry

Zing Level 

Sync On/Off

Track On/Off

Output Waveform 

1 V/OCT CV 

1x 3.5mm mono socket 100kΩ Input Impedance 

Attenuverted Exponential FM CV 

1x 3.5mm mono socket 100kΩ Input Impedance 

Attenuverted Symmetry Modulation CV 

1x 3.5mm mono socket 100kΩ Input Impedance 

Attenuverted Zing Level CV 

1x 3.5mm mono socket 100kΩ Input Impedance 

Audio Output 

1x 3.5mm mono socket 1kΩ Impedance 

MODULATION OSCILLATOR 2 

Controls 

Coarse Frequency

Fine Frequency

Symmetry

Zing Level 

Phase

Sync On/Off

Track On/Off

Output Waveform 

1 V/OCT CV 

1x 3.5mm mono socket 100kΩ Input Impedance 

Attenuverted Exponential FM CV 

1x 3.5mm mono socket 100kΩ Input Impedance 

Attenuverted Symmetry Modulation CV 

1x 3.5mm mono socket 100kΩ Input Impedance 

Attenuverted Zing Level CV 

1x 3.5mm mono socket 100kΩ Input Impedance 

Attenuverted Phase Modulation CV 

1x 3.5mm mono socket 100kΩ Input Impedance 

Audio Output 

1x 3.5mm mono socket 1kΩ Impedance 

POWER REQUIREMENTS 

+/-12V (+/- 2.5%) via 16-pin, Doepfer-style connector 

CURRENT DRAW 

290mA +12V, 270mA -12V (maximum) 

DIMENSIONS 

30HP (W); Panel to power connector (with connector plugged in) 25mm (D) 

SUPPLIED ACCESSORIES 

1x 16-pin, Doepfer-style cable
4x M3 screws
4x M2.5 screws
4x Nylon washers 
1x Quickstart Guide 

Dave Talks About What Inspired Him to Create Trident

Since we launched Rossum Electro and produced our first module (Evolution), folks have been bugging me to build an analog VCO. In their day, the E-mu Modular VCOs were the most stable and had widest range of any of that era. But I waited for inspiration to strike, and it did, twice!

So what is “Zing Modulation” anyway? In thinking about what makes an interesting timbre, I have always felt ring modulation (actually, “four quadrant multiplication”) held a prime spot, but it’s limited in usefulness because it produces frequencies that are not harmonically related to its inputs. This is due to the trigonometric identity:

2 x sin(A) x cos(B) = sin(A + B) + sin(A – B)

where A and B are frequency components of the ring modulator inputs.

But I realized that if the two inputs could be forced to be periodic with the same frequency, this limitation would disappear. To understand why, just realize that there is no “memory” in a ring modulator – if you start over from the same spot and give it the same waveforms, it will produce the same output every time. So the output of two inputs that have the same period must itself be periodic at that same frequency, which means all its frequency components must be harmonics of that frequency. And it’s fairly easy to arrange two oscillators to be precisely periodic – it’s called hard sync*. Bingo!

But because of that crazy trigonometric identity, there are going to be zillions of harmonic components, all adding together in weird combinations of phases, and these will vary in interesting ways depending on the exact details of the incoming waveshapes. Below are some examples of the bizarre waveshapes coming out of Trident. The yellow waveshape is the carrier oscillator with Zing modulation; the green is the original carrier waveshape. The blue and red traces are the modulation oscillators.

The second inspiration was to build a VCO that would provide interesting yet precise control of the waveshapes. The circuitry underlying Trident’s symmetry control was remarkably challenging. Varying the symmetry of a triangle wave from sawtooth, through triangle, to inverted sawtooth has been done many times before, but doing so in a fully analog, voltage controlled manner that has absolutely no effect on the underlying frequency is extremely challenging. Add to that challenge the requirement for the waveforms to be visually perfect up to 20kHz – now that would be fun (i.e. really hard)! I had to throw away an entire prototyped design because it wasn’t quite accurate enough at the highest frequencies. The final circuit is the only time I’ve ever had to specify a capacitor as small as 0.5pF to get the precise results I wanted. Here are some of the pure waveshape ‘scope photos. The top photo is the shapes at about 250 Hz, below it are the shapes at about 20kHz!

Finally, I realized that I’ve never seen anybody play with the phase relationship between hard synced oscillators. Combining that with Zing modulation gives even more voltage controlled timbral variation. These waveforms differ only by the phase of the MOD 2 oscillator!

* I’m pretty sure I was the person who first coined the term “hard sync.” I didn’t invent hard sync; I think that honor goes to Serge Tcherepnin. When I heard about it and how great it sounded, I immediately implemented it. But E-mu modular VCOs already had one form of sync, so we needed another name to distinguish the two. Hence “hard sync” and “soft sync”.

Trident Quick Start Guide (PDF)

Trident Manual (PDF)