~ajxs

Korg Volca FM Review

2020.10.15
A review of KORG's modern FM module, in which we discover how embarrassingly little research I put into my equipment purchases.
TL;DR: A fantastic idea, hampered by a terrible, short-sighted implementation. The Volca FM amounts to little more than an expensive toy. Not cheap enough to be good value, not good enough to be valuable. The Volca FM is truly a disappointment given KORG's history of creating fantastic synths.

It's not often that I get the least bit excited by new synthesizer releases. The most modern synth I own, and incidentally the only synthesizer in my studio that I purchased outright from a store, is a MicroKORG. A synthesizer which is now old enough to vote.

While the analog fetishism of my peers proceeded steadily towards the boutique territory of eurorack modules, I spent my formative years of synthesizer addiction as a student, relegated by my dismal budget to the benighted world of second-hand studio equipment. The remainder of my equipment had made its way into my hands, in a variety of interesting conditions, through the kind of resourcefulness usually associated with post-Soviet economies. I had made a habit of keeping a keen eye on auction sites, trading posts and pawn shops for the odd bargain. In the intervening years my collection of synthesizers has grown to encompass an increasingly obscure array of second-hand vintage curiosities.

In the exciting days of the mid 'two-thousands' I could only dream of participating in the blossoming Moog resurgence, getting my grubby novice hands on one of DSI's new Evolver synths, or touching the beautiful MS20 reissues that so beautifully furnished the tables of synth shops, and my dreams. Truly, I had contracted the dreaded Gear Acquisition Syndrome. However, in what was perhaps a fortuitous case of 'The fox and the grapes'1, my austere budget had cultivated in me a perverse taste for the undisputed pariah of the synth world: digital.

In what can only be described as the bitter hangover from the late 80s halcyon days of FM, the synthesizers that had done so much to define an entire era of music2 roared at full throttle into the rubbish heap of history. By the two-thousands Yamaha's mass-produced DX series of synthesizers could be purchased for a song. In what I would call one of my life's more serendipitous moments, an unexpected series of events put me home early from work at just the right time to watch the clock ticking on an eBay auction for a Yamaha DX7. I walked away the proud and curious owner of a DX7. A beautiful love affair blossomed from that day on, played out over the airwaves in harsh, metallic tones.

High hopes

My initial hope for the Volca FM was to act as a stand-in for the time-honored but physically bulky DX7 that was so dear to my heart. Which had admittedly spent the last few years languishing in storage, freeing up space on the keyboard rack for more recent acquisitions. The promise of a pocket-size six-operator FM-synthesizer patch-compatible3 with Yamaha's flagship FM synth was just too promising for me to ignore. I set out to the music store with grand visions in my mind of breathing new life into my old DX7 compositions: Re-recording the industrial basses of my youth in modern high-fidelity; Metallic FM bells ringing out in beautiful clarity; Fantasies of composing darkwave on European inter-city trains with this pocket-sized battery-powered FM module tucked safely in my suitcase. Maybe these lofty aspirations of mine had set me up for a stern disappointment. There's one born every minute, I'm told.

Unboxing

Unboxing the device itself was a positive experience. I liked the size and feel of the device in my hands. I've never been much for novelty when it comes to input. At the risk of betraying a lack of imagination on my behalf, I'll admit right now that MIDI is perfectly adequate for my needs. Having said this, I found the small touch-pad keyboard to be a surprisingly fun and engaging novelty. When the thrill of bashing out FM bass with my fingertips began to subside I figured it was time to attach the device to a computer and get to work. That was where the reality of this device's shortcomings came crashing down.

The first moment of confusion came quickly: The device features no velocity sensitivity. By which I not only refer to the device's surprisingly novel physical input mechanism, but also to the device's MIDI implementation. The device simply does not acknowledge NOTE ON signal velocity via MIDI at all. Huh?
For me, this was an instant dealbreaker. How did this device get off the drawing board without implementing one of the most fundamental features of the MIDI standard? Apparently, the device does support velocity being manually set via the use of MIDI CC commands, as specified in the device's MIDI implementation chart4. This mimics the internal mechanism used by the 'velocity' fader on the device's front-panel to set note velocity globally.4 All of this begs the question: who is this synth intended for? It's also worth noting that the device is limited to a fairly unimpressive 3 notes of polyphony.

The Volca FM's DAC and amplifier sound cheap, but capable. The device's output manages to best the circuitry in the original for clarity and brightness in the high end, which is not an enormous feat given its vintage. The overall quality is not impressive, however. It sounds flat and dull overall compared with other modern devices. The device's LFO is horribly clicky, even by the standards of DX7's notorious envelopes.

Talking to the outside world

The device features only a single MIDI input socket. MIDI output, or through-routing are not possible on this unit. Dumping SysEx data from the device to external storage is not possible. The Volca FM includes two 3.5mm mono jacks for the purposes of manually synchronising patch data with another Volca FM unit. It however does support the receiving of SysEx patch data via the MIDI input port. This begs the question of why KORG added two extraneous audio jacks for synchronisation purposes, where a single extra MIDI jack would have afforded the device complete SysEx I/O functionality5. From a unit-cost perspective this would surely be a cheaper approach, not to mention a reduction in the extra firmware complexity required to encode and decode the patch data in KORG's SYRO format.6

Korg's listed specifications for the device suggest compatibility with the original DX7's patch format3. While I was able to load my original DX7 patches onto the device via SysEx, many of them did not produce sound when loaded. After some experimentation it appeared that there is a bug in the implementation of the operator envelopes. Altering the envelope values appeared to resolve this to some extent. However even with considerable effort I was still unable to load many of my DX7 patches.
There's also a noted bug in the implementation of the LFO's, discussed in detail here [7]

Deconstructing the Volca FM for fun and profit

The device itself is powered by a Cypress FM4 ARM Cortex M4 processor11. Since the FM's release KORG has issued several minor firmware updates, which are transferable to the device in audio format6 via the sync input. An extremely skilled engineer by the name of Pajen was clever enough to use KORG's own tools to decompile the firmware blob from KORG's proprietary SYRO6 format into a plain ARM binary. In a stroke of luck, it turned out the decoded binary output did not feature any encoding or obfuscation. This allowed Pajen to reverse-engineer the firmware in IDA to the degree that it was actually possible to correct some of the Volca FM's outstanding bugs, in addition to extant bugs in other Volca devices. Additionally, he was also able to perform the herculean task of implementing proper MIDI NOTE ON velocity functionality in the device. Sifting through 256kb of unannotated embedded assembler is certainly a feat worthy of respect. He has released several unofficial firmware updates for the devices. Information on the latest of which can be found here: [8] Additional information on the reverse-engineering process can be found in this Gearslutz thread: [9].

Conclusion

Ordinarily I preach a pragmatic, ascetic philosophy on the nature of gear festishism: That a skilled practitioner can produce good music10 on just about any terrible gear. This device has perhaps been sent here to test my faith. Korg has missed a valuable opportunity to design a series of professional, portable devices with serious musical value. I would have suggested removing the induction keyboard, step sequencer and other gimmicks. Trade in the sync ports for a combination MIDI out/thru port, which would maximise compatibility with other devices and permit chaining multiple Volca devices together in a standard fashion. A dedicated Volca control companion unit featuring a keyboard and sequencer could have better fulfilled the need for portable control of the Volca series. Ultimately this is a synthesizer designed for the small-souled bugman. It's ultimately no more than a toy. It's a disappointing waste of a potentially amazing concept by KORG. An even bigger disappointment is that this ill-conceived unit will contribute to the already burgeoning problem of landfill. Destined to rot to our collective societal loss, next to all of the other forgotten plastic children's toys.


  1. "Who needs analog anyway when you can have bell tones like this?"
  2. Madonna - Papa Don't Preach (Instrumental Cover with DX7, TR-707 and Juno-106) - Youtube
  3. KORG Volca FM Specifications
  4. 'Volca FM and velocity' thread - KORG forums.
  5. From a firmware-development perspective, SysEx is cheap. Much cheaper than the encoding/decoding of KORG's proprietary SYRO audio format, clearly. The transfer of SysEx patch data does not require compliance with any standard. Typically SysEx binary patch data represents a direct dump of the in-memory data structures used by the device.
  6. KORG SYRO is a codec for encoding binary data into audio using QAM (quadrature amplitude modulation). In their own words: "Like the old dial-up modems!"
  7. Volca (sample) firmware hack? - Gearslutz - Post #156 by Pajen
  8. Volca FM firmware 1.09 [UNOFFICIAL] - Reddit
  9. Volca (sample) firmware hack? - Gearslutz
  10. What I actually mean here is Industrial music. A genre that characteristically cultivates the kind of hostile aesthetic to which terrible gear can more readily contribute.
  11. It's worth noting that newer synthesizers are beginning to use newer architectures like ARM. I'm more accustomed to peering under the hood of Japanese synthesizers and seeing Renesas chipsets implementing Hitachi's ubiquitous H8 architecture. Even as late as 2000, KORG was using H8 based CPUs in synths such as the MicroKORG. The KORG Kronos even features an Intel motherboard, in addition to an ARM processor, and an H8 processor. Additionally, firmware updates being distributed in the form of binary downloads, rather than EPROM, makes reverse-engineering of firmware much easier to accomplish using easily accessible tools. It's also worth noting the absence of dedicated DSP hardware in these synthesizers.