TC Works Spark

The FX Machine in Spark can host VST effects plug‑ins as well as Spark Modular modules.

TC have come up with a new twist on the analogue synth emulation theme by providing modular oscillator, filter and envelope blocks that can be combined with VST effects. Paul White tries a few variations.

TC's Spark Modular is an add‑on package that works with TC's existing, Mac‑only Spark or Spark XL editing software to provide analogue‑style virtual synth building blocks, which can be combined like a build‑your‑own synth kit. Spark's FX Machine is a 4 x 5 matrix with comprehensive signal routing into which effect plug‑ins and Spark Modular synth components can be loaded. The fact that Spark Modular works within the FX Machine means that you're not restricted to using its supplied modules in your synth designs: these may be combined with other VST plug‑ins (including other VST Instruments) to form more complex synthesizers. As with all plug‑ins, they may be used in multiples. As the Spark FX Machine can be used within other VST‑compatible software as a plug‑in in its own right, any synth created using Spark Modular can be treated just like a single VST Instrument.

Minimum hardware requirements are a 233MHz Mac G3 or higher running OS 8.5 or later, though latency figures will tend to be better on a more powerful machine such as a G4. The minimum RAM requirement is 128Mb and users still running Spark v1.5 will find that the installer software automatically updates Spark to v1.6. No further authorisation is required if the host version of Spark is properly authorised. Registered Spark users get a significant discount when buying Spark Modular. Although Spark has to be registered to use it for longer than 21 days, apparently some buyers still haven't registered! You should also note that using the synth modules from within Spark requires OMS to be installed, though if the FX Machine (containing a synth setup) is loaded into a VST‑compatible sequencer program, it can be accessed just like any other virtual instrument.

Building A Synth

TCF is a filter module based around a variable‑resonance low‑pass filter plus an adjustable high‑pass filter.

The modules are loaded into the FX Machine just like any other plug‑ins. The most vital of all the building blocks is the TCO master oscillator module, as that's where the raw sound comes from (though you could use the filters and envelopes to treat external sounds or other VST Instruments). The visual representation is much like a hardware modular synth component with the possible exception of the 'virtual biscuit' on the lid! This is apparently a MIDI indicator, and as MIDI data is received, it is gradually eaten away leaving only crumbs: MIDI bytes, no doubt! Double‑clicking the crumbs restores the biscuit. Having got the important stuff out of the way...

The TCO module is monophonic and comprises two main oscillators plus a sub‑oscillator, with a choice of analogue‑style waveforms. Oscillator 2 can have pulse‑width modulation applied, and there's a menu for setting up controller assignments that affect the oscillator modulation or pulse width. Oscillator 2 can be detuned, in coarse or fine steps, relative to Oscillator 1, global portamento can be applied, and the three outputs can be balanced via a mixer. Oscillator 2 can also be used to ring modulate Oscillator 1, or be sync'ed to it. In sync mode, any wheel or envelope pitch changes apply only to Oscillator 2, so as to produce the classic screaming sync sound.

Although the Spark Modular oscillator module is monophonic, the method of calculating the waveforms is quite processor‑intensive as it doesn't rely on samples but rather calculates the waves in real time. This is claimed to eliminate aliasing and to produce a more analogue sound. It certainly sounds smooth, but I can't help wondering whether a standard sample waveform mode should have been included as a switchableoption for those short on DSP power.

TCF is a filter module based around a variable‑resonance low‑pass filter plus an adjustable high‑pass filter. Filter slopes of 12, 18 and 24dB per octave can be selected, and the cutoff frequency can be modulated by envelope, key tracking or a choice of modulation sources, accessed via the Edit menu. The filter has its own ADSR generator which can modulate the filter frequency in either a positive or negative direction, and the envelope can be triggered in either single or multi mode. In single mode, no retrigger is allowed until the first key is released.

Handling the amplitude shaping is the TCA module, a classic ADSR envelope shaper that also has Drive and Level controls. Drive produces distortion that can either be hard and nasty or more polite, thanks to the option of TC's proprietary SoftSat algorithm. As with the filter section, both single and multi triggering modes are supported, and an Edit menu allows various controllers to modulate the signal level.

Completing the set are the sequencer (see box below), and a virtual keyboard which allows you to test the sounds without having to patch in your real keyboard.

Vast Possibilities

The TCO module is monophonic and comprises two main oscillators plus a sub‑oscillator, with a choice of analogue‑style waveforms.

Taken in isolation, none of Spark Modular's building blocks does anything much out of the ordinary, but being able to combine them in different ways within the FX Machine (and being able to use the same component more than once) opens up a vast number of possibilities. For example, you could split the signal and feed it through two or more TCF filters with different settings and mod rates, you could use two or more detuned oscillators layered together as the sound source, or you could place other VST processing plug‑ins within the synth's signal path. I had a lot of fun putting the Spectral Gate from Logic Audio between the oscillator and filter, and using reverb or chorus/flange to add complexity to the sound from the oscillator prior to the envelope shaper can also be interesting. The possibilities are innumerable, yet anyone who's ever played with an analogue synth will find it easy to set up. This flexibility is the real strength of the product and is the reason it may appeal to more sophisticated sound designers as well as musicians.

As I said earlier, Spark Modular is pretty greedy on processing power considering it's essentially a monosynth, but I suspect TC thought the sacrifice was worth it to provide a smoother, more analogue‑like waveform. Providing you have a reasonably powerful computer, you can use Spark Modular sparingly within a composition without wasting resources . The world probably has enough 'me too' analogue synth substitutes, so it's good to see that TC have managed to put a new spin on an old idea.

Built‑in Sequencer

Spark Modular also comes complete with a 16‑step sequencer that can either free run or lock to the MIDI tempo of the host software. The play direction can be forward, backwards or alternating; there's a Swing control to add a groove feel to the result, and individual notes may be accented. Any note can be applied to any step and Glide can be used to recreate all those bilious dance sounds of yesteryear. There's even a Flam effect for analogue drum sequences as well as the ability to change note lengths and to switch into a legato mode. Depending on your processor power, it's possible to combine more than one sequencer with multiple synth modules to create more complex patterns — very useful for creating drum loops. During testing, the sequencer worked fine, but as Logic doesn't yet support the sending of tempo information to third party plug‑ins, I was unable to test the Sync To Tempo facility.