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• Review

Audio Realism's Bass Line has quietly become the industry standard TB-303 emulation over the last few years, offering everything Roland's original classic ever could and then some.

Now, with Bass Line Pro, the Swedish company have given their already rockin' synth a massive shot of steroids, beefing it up into a far more versatile semi-modular machine with a supercharged 303 at its heart.

An intriguing development in the history of the acid legend – I wonder what Tadao Kikumoto would make of it.

Overview

To be honest, for the most part, the 303 heritage of ABL Pro (as its creators call it) is relegated to the six-knob panel in the middle and the step sequencer, and even those have been upgraded.

The sequencer features virtual CV output, variable gate time and a three-octave keyboard for convenience.

While the Envelope Modulation can be shaped via the synth's Main Envelope Generator (MEG), the Decay knob has been traded for a filter tracking control, and the Accent parameter has separate decay and volume controls to the right.

It is possible to 'do' traditional 303 business to a certain extent with ABL Pro by just using one oscillator, setting some of the surrounding parameters to specific values (given in the manual and one of the presets) and not straying from the central controls.

However, elements of the core engine (the accent circuit and filters, for example) are different to those in the original Bass Line, so Audio Realism make it clear that if you're after a 303 emulation, that's the better option.

With that out of the way, then, ABL Pro is a two-oscillator, two-envelope, single-filter, single-VCA, single-LFO semi-modular subtractive synth with a graphical CV cable patching system like that in Reason and Arturia's Moog Modular V.

As well as making noise on its own, it can also be used to process external audio signals, and a 2x oversampling filter mode is included for this purpose.

The interface looks great, with nifty swinging cables and beautifully rendered knobs, though at times it can feel quite cramped and confusing, with many of the CV sockets bereft of legending and the knobs in the Voltage Processor section being absolutely miniscule.

The sockets problem is at least alleviated by the ability to choose sources and destinations by right-clicking on them, but they could do with icons or single character labels at least.

The two oscillators are both identical and offer five different waveforms (sawtooth, square wave, pulse, triangle and sine), sync of oscillator 2 to oscillator 1, frequency modulation of oscillator 2 by oscillator 1 and ring modulation.

It's also possible to bring a third oscillator into play, as the LFO (or Modulation Generator, as it's been dubbed) can be cranked up into the audible frequency range while still being used to modulate multiple targets.

And for added dirt, a noise generator is also built in, which can be set anywhere between red, pink and white noise, that particular control sports a CV input for modulation by all manner of sources.

Before the two oscillators reach the mixer, their waveshapes can be touched up with the Shape control, which is also CV modulatable. In the same section, bass boost can be applied to the oscillators and the overall volume can be adjusted.

The low-pass filter sports three different settings: 18dB/octave, 24dB/octave and the aforementioned 2x oversampling 24dB/octave.

Both the 24dB models are self-oscillating and absolutely scream, while the 18dB might have been adjusted from the original Bass Line model, but still sounds fabulously squelchy and '303-esque.'

The cutoff can be modulated by the LFO, its own ADSR envelope, and (via CV cabling) note pitch, velocity and anything else with a CV output socket.