The Fool’s Paradise

A tragicomic musical set in a Lilliputian hellscape.

Oh Korg! with one hand you blessed us, and with the other you ground our noses in despair. (this post contains a LOT of complaining)

This system is a very large-scale modular analog expansion for the Korg Volca Modular. There are 2 of these star-crossed hobgoblins embedded in this modular analog. The patching for the entire system is the frail & frangible Dupont pin connector that Korg implemented.

The Fool’s Paradise is an orgy of juxtaposition. Its design is the most vexing project I ever waded into… voluntarily. The designers of the Volca Modular became a diabolical Greek -chorus in the traumspiel of its construction. I addressed them often, and many-times, out-loud, using a lot of very fundamental Anglo-Saxon terms, in the process.

In the cold light of hindsight. I’d love to report that this caper had a unequivocally happy ending. I really would… But I purposefully held-off naming this instrument until months after I finished with it. I felt like I needed some distance from the roller-coaster course of its development in order to regain some perspective, lest I name it something obscenely pejorative. The bottom line is that I cannot say that If I knew what I was in for that I would do it again. I want to state unequivocally that the result sounds as good as I’d dared to hope, but getting to that result was more hassle than it should have been. One always learns from challenges no matter how much expertise or talent one possesses. And I did learn a lot from building the Fool’s Paradise. But too many of the issues were caused by byzantine & recondite choices by the Korg designers. This vexation was compounded by the fact that too many of these obstacles required inordinate effort just to discover them, much less address them.

I am generally scornful of contemporary (2021 AD) commercial synthesizers. Much of this scorn is admittedly rooted in my stubborn adherence to DIY principles. One of things that alarms me most is surface-mount fabrication. In terms of manipulation , a surface-mount PCB is a Lilliputian chamber of horrors. Surface-mount is designed to be fabricated by robots. It is not meant for human hands to touch. I’m not naive. I realize that through-hole fabrication is a low-lying atoll in an inexorably & rapidly rising sea of surface-mount, and I also realize that this unhappy trend is not Korg’s fault. But it damn-sure made all the other issues in expanding the capabilities of the Volca Modular more difficult by a full order of magnitude. (well…. that, and the fact that there are no available schematics!)

With all that vitriol on the table-

The Korg Volca Modular is an astonishingly powerful and beautiful sounding analog synthesizer and at least half of that astonishment is that it costs $200. There is no mistaking that the intent of it’s design is a ‘tribute’ to Don Buchla’s justly venerated Music Easel. (Ye Gods! just look at the COLOR choices). In my opinion, the ‘source’ section of the Volca Modular , a triangle-wave VCO, FM-pair with an embedded wave-folder is worth $200 by itself. Another very attractive feature (that I did NOT expect to enjoy) is the boingy digital effect at the end of signal chain. My crankiness about an all-analog signal chain is well known, but this digital effect was very well chosen to complement the sound of the all-analog hootenanny upstream. It sounds great. And let’s face it there was no way that Korg was gonna shoehorn an Easel-like spring-reverb tank in a pocket-sized $200 box.

On the down side:

the Low Pass Gates on the two Volca Modulars both manifest a THD in excess of 20%. Mind you, they don’t sound bad. But they definitely don’t sound like the optical LPG in a Buchla Easel or a 292. Given the narrow power-rails and the surface-mount space constraints I think it is a safe bet to surmise that whatever resistive component Korg used, it was not an optical component. This deficiency prompted me to put an LPG with a genuine vactrol first on my list of additions.

There’s no lag processor (!) This omission is just silly. A lag processor requires only one pot, one capacitor, and one opamp stage. Now, I’ve noticed Korg publishes expert tips from their technical staff, and in one of these exegeses, one of these august boffins, presumably with his arm in a cast from patting himself on the back for his cleverness, breathlessly holds forth with an account of how to create a lag processor on the Volca Modular. His solution requires the dedication of the Sample-Hold Module AND one of the two function generators(!); Two vital elements of any complex patch, JUST TO PRODUCE PORTAMENTO. Nope! I’m callin’ shenanigans. The scheme works. But that’s a ludicrously disproportionate allocation of resources. Like using a howitzer as a flyswatter, or excavating a subway to your mailbox so you don’t have to get wet retrieving the mail on a rainy day. I added a a lag knob. It required the aforementioned 3 components, and 9 minutes to install.

This one is admittedly a bit esoteric, but it’s shockingly obtrusive if you intend to use the Volca Modular modularly. The CV input that controls the ‘source’ (VCO-Pair) pitch responds as expected from +3.3v to +0.25v, then, at any voltage BELOW +0.25v the VCO’s CV ignores whatever is coming in the CV socket and responds instead to the default CV input which is the CV from the on-board sequencer. Whiskey!-Tango!-Foxtrot! Korg??? A VCO-pair that sophisticated that can’t respond to a negative CV? In my book, that’s a downright failure in the design. At very least, an additional un-defaulted (un-normalled) CV input should have been provided on the VCO-pair for a parameter as fundamental as VCO pitch.

Now…Korg certainly didn’t intend the Volca Modular as any kind of DIY platform; They did not intend that their little Easel ‘tribute’ would require any outside help, so the onus of adding capabilities to this gadget is ENTIRELY on me; My Fault.

So I will suspend my editorializing for a bit and expose what I added:

The More exotic additions are:

-A triggered function that produces a wiggling voltage that decreases or increases in both amplitude and frequency over the period of the function. All of the parameters are voltage controlled, and it can retrigger itself.

-a version of Grant Richter’s experimental take on the Oberheim Xpander’s tracking generator. Among several mods I made was a manual slide pot so that I could sweep the function over it’s length in a perverse emulation of a DJ using a turntable to scratch. This controller is described in more detail here.

-(though not really exotic) a Low Pass Gate that uses the original-gangsta Vactrol as a resistive element, ala Buchla.

-2 Sawtooth VCOs with onboard Animators

2 Divide-by-CV Pulse & Staircase generators

-‘Heretical Resonator’, an analog resonator with VC phase & cutoff Frequency

Plus the more mundane cast:

4 External CV scaler/limiters

1 DC-coupled mixer

4 AC-coupled mixers

Lag Processor

2 Complex multi-output Random CV generators

VC-crossfader & VCA

4 VC-LFOs

6 CV processors (offset + scaling)

a voltage meter that flags voltages above 3.3v or below -3.3v

Construction/Physical Form Factor & Interfacing

The Volca Modular uses unshielded Dupont pin jumpers for patching. This approach definitely makes for an easy fabrication and saves a lot of panel space & a lot of cost. I realized these same advantages in making my expansions. I also realized the DISadvantages. The Dupont ‘jacks’ (basically just a stiff pin crimped to a wire) are downright eager to bend and break. And when they break, rest assured they will break off IN THE SOCKET and you will have to tweeze them out with a sewing needle. The sockets are undifferentiated black holes in black plastic housings, a microscopic 2.5mm (0.1-inch) apart. This rig will travel to all gigs with a STRONG clip-on light source. (and I will travel with the STRONG reading glasses).

I decided to emulate Korg’s physical design for much of the expansion; using PCB-mounted pots and pin-sockets, even a few illuminated shaft pots of my own.

The currently dominant form-factor in modular analog synthesis is the eurorack standard of 3.55mm (1/8-inch) jacks and a signal tolerance that is roughly 20 volts wide (+10v to -10v). The Volca Modular eschews all of that. (see this review in ‘the Outside World’ sidebar at the bottom) The Volca Modular uses Dupont pins and a specified signal tolerance of 6.6volts (+3.3v to -3.3v) Korg does provide a pair of interface features that will scale one 3.55mm CV & one Gate to a level it can tolerate. But that’s it.

Translating the 3.55mm 2-conductor jacks to the 1-conductor Dupont pins is not effortless, but it is trivial compared to scaling a 20-volt operating environment like eurorack to a 6.6-volt one. And the consequences for a slip-up are pretty dire. Squirting a voltage that exceeds the Volca Modular’s limits can very definitely do permanent damage. And these tiny surface-mount Volcas are not designed for component-level repair. This meant that every circuit I wanted to add to the system had to either operate between +3.3v & -3.3v rails or it had to be designed to ensure that no output ever exceeded those limits even in fault modes. I vastly underestimated how troublesome and involved that is.

I am, by now, a veteran of the school of hard knocks and I am made more bitter by the gratuitous obsoleting of technologies long before their full potentials are known. I’m well aware that that’s the way the technology cookie crumbles and I’m sure there are a lot of modern technicians who will sneer at me for saying so, but here goes anyway…

+/-3.3v is too narrow to do analog audio.

Korg pulled it off, but just by the skin of their teeth, in my humble opinion. For instance, my random voltage schemes rely on a true analog noise source and that circuit requires a 10-volt potential to avalanche the junction. So I made a design decision to build my expansions around my familiar standard of +/-12v rails and take all the above & beyond measures to absolutely constrain the outputs. That’s what made this project a constant pain in the ass.

The thing sounds very VERY good. It Better! ….considering the contortions I endured to build it.

This is my soapbox. So in the interest of catharsis, I’m going to end this post with a sort of a ‘truth & reconciliation’ session at the end of a long & bitter struggle; my personal accounting for who’s to blame for what. Spoiler alert! Korg gets most of the blame – but then, I did bring this on myself… and this should be read as it was written – with tongue firmly in cheek!

-Korg made the Volca Modular just sophisticated and tempting enough that it could not be simply ignored. So it’s Korg’s fault that I bought two of them.

-It’s Korg’s fault that the normalling scheme is nothing other than in my way. If they insist on using a connector without a mechanical override. They should have forgone normalled paths altogether.

-It’s my fault the expansion is so electrically fragile and convoluted. I don’t know how to do my act without at least 10 volts to work with.

-Imposing a DIY expansion on the Volca Modular is my fault but the absence of any bona-fide technical documentation on it is Korg’s fault. Korg released schematics for the original Monotron before it was in the stores. I realize that the Volcas are treated differently by Korg but that difference is nothing other than the evil work of marketing. And marketing is a bigger threat to humanity than climate change.

It’s Korgs fault for relying on the unreliable Dupont connectors for patching. That was a bridge too far in terms of cutting cost.

So with plenty of blame to go around, when the dust settled I ended up with very luggable munchkin-sized modular that has to be handled with extreme care but sounds GREAT in the big speakers.

That ain’t ALL bad!