Recreating a legendary filter

With the V Collection we aim to allow all musicians access to the sounds of legendary, but too often, inaccessible instruments. Our quest has led us to take full advantage of advances in science and technology.

As a recreation of one of the most appreciated analog synthesizers ever made we devote to the Mini V all the attention required to make sure it meets the high expectations musicians place on it.

Ready to learn more about the latest major improvement to the Mini V software and the man who handled this ambitious project?

The software revolution behind Mini V

TAE® technology - the lifeblood of Arturia’s virtual instrument family - is a constantly evolving, expanding system designed to accurately replicate the sound and feel of analog components and circuitry.

With every advance we make, our software instruments become more organic and vital, giving you the most authentic analog hardware sound but with all the benefits and convenience of software. One of our most popular and critically acclaimed instruments is the Mini V: a meticulously reproduced emulation of Dr Bob Moog’s classic 70s monosynth. The original instrument is now part of music history, and consequently very expensive and difficult to obtain. Mini V puts the iconic sound and power of that legendary synthesizer into the hands of a new generation of musicians, producers, and sound designers.

Meet Stefano d’Angelo, DSP Engineer with Arturia.

With Arturia since April 2015, Stefano is part of the technical engineering team which aims to improve the current DSP code of our award-winning virtual instruments, develop new algorithms based on cutting edge virtual analog modeling, and - whenever no available method provides satisfying results - advance the research even further. Let’s hear more from the man himself:

Thanks to Arturia’s dedicated team of engineers and programmers, Mini V has seen several transformations since its original release, edging closer and closer to emulated perfection every time.

“I started playing piano before learning how to read”

“I could trace my passions for music and technology back to very early childhood. I started playing piano before learning how to read, which I did by using a Commodore 64 before going to primary school. My formal training includes a Master of Science degree in Computer Engineering at Politecnico di Torino, Italy, in 2010, and a Doctor of Science (PhD) degree in Electrical Engineering from Aalto University, Finland, in 2014.”

Having studied the technology of analog circuitry and DSP in detail, with a thesis dedicated to the components of Dr Robert Moog’s game-changing monosynth, Stefano literally wrote the book on analog emulation.

After finishing his studies d'Angelo decided it was time to apply his academic expertise to real-world products. He soon started working in the talented, passionate team at Arturia: one of the few music technology companies capable of accepting real challenge, and meeting it head on.

Climbing the ladder

The famous filter of Bob Moog’s original monosynth is one of the instrument’s most iconic features, and has been copied numerous times by hardware and software creators for the best part of half a century.

Until now, these replica filters haven’t ever truly captured the musical essence of the original. Thanks to Stefano and the tireless efforts of the Arturia tech team, the code has finally been cracked.

“While I feel confident to say that the majority of subtractive synths around include a 24 dB/oct. lowpass filter with resonance of some sort, the ladder filter on Robert Moog’s 1970 monosynth is special in that it has a distinctive timbre and peculiar control characteristics.”

“In order to let you get a glimpse of its salient sonic features, I need to say a few words about the core circuit. The heart of the filter circuit is functionally equivalent to a series of a saturating amplifier and 4 identical saturating lowpass stages. On one hand the lowpass filtering part indiscriminately attenuates the signal spectrum past the cutoff, and on the other the saturation part adds only frequency content that is harmonically related to the input, thus enhancing the “overall musicality” of the signal, if used properly.”

“The global feedback allows for complex behavior and richer tone”

The system also includes a global feedback path, whose gain is controlled by the “emphasis” knob. When this is set to the minimum, the “cutoff frequency” knob is solely responsible for the actual cutoff of the filter. Otherwise, as the “emphasis” increases, resonant behavior is introduced and becomes progressively more apparent. Meanwhile, the actual cutoff first decreases sensibly, then it slowly increases up to the point in which the filter goes into self-oscillation. In other words, the global feedback allows for complex behavior and richer tone, thus enhancing the musical qualities of the filter even more.

While the dependency of the actual cutoff on both knobs is sometimes regarded as a misfeature, and even more so if you consider that the passband gain also decreases with increasing “emphasis”. This arrangement however makes the position of the cutoff slope exclusively dependent on the “cutoff frequency”, a remarkable and unique property that is too often neglected.

Unlocking the analog code,
one component at a time

“My mission was to make the Mini V filter whistle and scream like the original.”

In Arturia’s continuing quest to ensure the most authentic, organic analog sound, we strive to capture and reproduce every nuance of the original hardware.

Precisely modeling a system which contains both nonlinearities (saturation) and dynamic effects (filtering) is among the hardest tasks in music DSP, and indeed it is one of the main subjects of most recent virtual analog research in universities around the world.

The previous implementation tried to address both the linear and nonlinear aspects of the filter at the same time, but it did so in a suboptimal way so no two were 100% correct. This was very evident when the filter was set in self-oscillation mode: if you kept the emphasis high enough and tried to sweep the cutoff, you could see that the amplitude of the sine wave generated by self-oscillation was very far from constant, and at the lowest cutoff settings it would just die out.


Applied science

Representing the nuances of an analog component as a mathematical equation is one of the greatest challenges in the world of digital signal processing. These often take the form of many nonlinear differential equations that are difficult to express in closed-form.

Despite being practically unsolvable, algorithms exist that can express these equations numerically. These methods require some fairly intense processing power, and so aren’t suitable for the real-time calculations required for virtual instruments.

To work around this issue, researchers in the field have developed several techniques to cope with the equations hidden within each analog component. However, no single solution is considered to be both general and optimal, and so each case needs special handling.

“I have even seen seasoned researchers getting scared when looking at the math behind it”

“Some of the techniques that tend to yield good performance in modelling linear systems are called “delay-free loop methods” or “zero-delay feedback” (ZDF) methods. Nonlinear extensions to those exist, but they are usually quite CPU intensive. Therefore, I had to develop a special nonlinear ZDF method that reproduces the linear response of the circuit, while also very closely models its saturating behavior, and only using very few computation resources. I successfully accomplished that, but I will not go into the details as I have even seen seasoned researchers getting scared when looking at the math behind it.”

Learn more (Articles 5 and 6)

The end result

“I was able to reproduce the linear behavior of the filter with practically 100% accuracy, and also the nonlinear part is extremely close to the original.”

"All of that without increasing CPU usage. The new filter is also much more stable, and can sustain extremely fast modulations.”

This breakthrough in the reproduction of analog components is the very bedrock of our exclusive TAE® technology, and gives you, the musician, access to some of the world’s most iconic instruments. Sounds that cut through the mix. Sounds that are a joy to perform. Sounds that will shape the future of popular music.

Thanks to Stefano’s expertise, the technical skill of his teammates, and Arturia’s company-wide vision, this labor of love makes Mini V the most breathtaking, authentic emulation of Bob Moog’s classic 70s monosynth on the market.

From science to music

Beyond the scientific achievement, the improvements to the Mini V filter are an exciting step forward for the musician.

As well as giving the filter an unparalleled fidelity, it now self-oscillates linearly throughout the audio spectrum. Musicians can now take full advantage of the self-oscillation for sound-design, for instance when using it as a supplementary oscillator to beef-up a vivid lead or a nasty bass.

Mini V’s filter now has superior clarity in the upper register and the ability to withstand audio-rate modulations of the cutoff frequency. This powerful addition will inspire adventurous synthesists seeking harsh, cutting sounds.