Eurorack Modules
The bug boards, in a rack, and the supply that feeds them. Drawn and checked; the Output Rack and the battery bench supply built and working, the other modules not yet.
The stripboard shelf has six boards named after bugs that were always going to end up in one box together. These are the same boards as Eurorack modules: in every one but the mixer, the built board sits inside the layout hole for hole - same strips, same cuts, same parts - and a rack block is bolted onto its right-hand end. The block is the same idea six times over: a 2×5 header for the rack's power cable, a diode on each rail so a backwards cable does nothing, a 78L05 making the chip its 5 V, and a TL072 on the real ±12 V doing the rack-level work - summing, buffering, taking a gate or a clock in through a 100K. The exception is the Dragonfly, which had to become a 1 V/oct oscillator and got a new control path around its old chip.
The seventh board is not a bug. The LFO Rack is the stripboard shelf's Utility LFO drawn again for the rack's ±12 V: a triangle, a square and a sine, each on its own jack, from one TL074.
The eighth is the Envelope Rack, and it is the other way around from the bugs: the AD/AR Envelope I built, hole for hole, needs nothing from the rack but +12 V, so its block is a header and two links - no regulator, no second chip.
The ninth is for the bench, not the rack, and it is built and working. The Battery Breakout puts two 9V batteries on the same 2×5 header the modules take, so a module can be brought up and heard before there is a case to plug it into.
The Switchboard Rack is a built board that is not a bug: the Switchboard, hole for hole, with my growl toggle and starve pot on its panel and the rack block on ten strips under it.
The Opto Duet CV Rack is the same idea for my built Opto Duet CV: the board hole for hole, knobs where its two eyes were, and the rack block under it.
And the Output Rack is the way out: rack level down to a level a pedal, an amp or a line input will take, on a 3.5 mm jack with a volume knob. It is built and working.
As on the stripboard shelf, the layout file is the build document: download the
.json, open it in Copper Bottom, and the editor walks
you through the board and checks it. Each guide also carries a 1:1 drill template for a blank
3U panel, drawn for 9 mm pots and Thonkiconn jacks. Every module here but the Output Rack is Unverified
- drawn, checked in the editor, and not yet proven on a bench - and each page says which of its numbers is
a datasheet's and which is a guess. Build one, and the banner comes off. The size on every card
is strips by holes.
All 13 boards
Battery Breakout
A bench supply for bringing a module up before there is a case. Two 9V batteries in series make ±9 V into the same 2×5 power header the modules take: nothing to plug in backwards at the wall, not much current into a short, and every module here already has a diode on each rail. An LED on each rail says its battery is in the right way around, and one toggle switches both rails together. With the layout file and the netlist.
Output Rack
The way out of the rack. A rack signal swings about 10 V peak to peak, which slams a pedal and clips most line inputs, so this brings it down to about a fifth through a divider, buffers it with a TL072 on each side of a log volume pot, and sends it out of a 3.5 mm jack through a cap that blocks any DC. Mono, one knob, 6 HP. With the layout file, the netlist and the panel drill template.
Hive Rack
The six-voice Hive Drone as a Eurorack module. The built board hole for hole, and beside it a rack block: the 2×5 power header, a diode on each rail, a 78L05 for the chip and a TL072 that sums the six voices onto a virtual ground - which is also the fix for the Hive's old output stage. Six pitch pots and one jack on a 10 HP panel. With the layout file, the netlist and the panel drill template.
Dragonfly Rack
The Dragonfly VCO as a Eurorack oscillator that tracks a keyboard: the 4046 and its timing cap are the built Dragonfly's, and pin 11 now gets its current from a two-transistor exponential converter - a TL072 sums the 1 V/oct jack and the pitch knob through a scale trimmer, a second half serves as the reference - with a second TL072 putting the square out at ±5 V. The drop bend survives as a range switch. Pitch, 1 V/oct, out and drop on a 6 HP panel. The one module on this shelf that is a new circuit around the old chip.
Cicada Rack
The four-voice Cicada NAND as a Eurorack module, with a gate jack for every voice so a clock or an LFO can play the gates the toggles used to. The built board hole for hole, the kill toggles still there, and beside it the rack block: power header, a diode per rail, a 78L05 and a TL072 summing stage. One voice per row on a 12 HP panel. With the layout file, the netlist and the panel drill template.
Grub Rack
The seven-octave Grub Divider as a Eurorack module: patch any square into the clock jack and seven toggles pick which octaves below it come out. The built board hole for hole, the volume pot now a level knob into a TL072, and the rack block beside it: power header, a diode per rail, a 78L05. Seven toggles, one knob, two jacks on a 10 HP panel. With the layout file, the netlist and the panel drill template.
Spider Rack
The eight-step Spider Sequencer as a Eurorack module. The built board hole for hole, and at 5 V its steps come out at the 0 to 5 V every rack sequencer speaks; a clock-in jack normalled to its own 555 so a cable takes over the clock, a TL072 buffering the CV out, and the rack block beside it. Nine knobs, eight LEDs and three jacks on an 18 HP panel. With the layout file, the netlist and the panel drill template.
Mixer Rack
A four-channel Eurorack mixer on the real ±12 V: four level pots as dividers into a TL072 unity summer, the other half inverting it back into phase, out through 1K. The one module on this shelf drawn fresh rather than grown from a bug board, because a bipolar supply makes a half-rail reference unnecessary. One channel per row on an 8 HP panel. With the layout file, the netlist and the panel drill template.
LFO Rack
A utility LFO for the rack, the Utility LFO's circuit drawn again for ±12 V: one TL074 integrating and comparing for the triangle and square, scaling the square to ±5 V, and rounding the triangle into a sine with gain. Each wave on its own jack at rack level, a rate pot, a range toggle for ten times slower and a rate LED, on an 8 HP panel. With the layout file, the netlist and the panel drill template.
Envelope Rack
The AD/AR Envelope I built, hole for hole, with a power header on its end. It was already a one-supply circuit on a rail-to-rail op-amp, so the rack's +12 V runs it as it is: no regulator, no second chip. Attack, release, a toggle for AR or AD, a button to fire it by hand, an LED, and a 0 to 8 V envelope out, on an 8 HP panel. With the layout file, the netlist and the panel drill template.
Ladybug Rack
An envelope follower for the rack, the Ladybug's four stages drawn again for ±12 V on one TL074: audio in, a CV out from 0 to about 10 V that follows how loud it is, and an inverted CV out that falls as it rises. Sensitivity, attack and release, and an LED, on an 8 HP panel. With the layout file, the netlist and the panel drill template.
Switchboard Rack
The Switchboard as a Eurorack module: four 40106 voices that a counter and a mux switch into tone, rest, tone, rest. The built board hole for hole with the rack block under it: a clock-in jack normalled to its own clock, so a rack clock can take over the steps, the starve pot and the growl toggle from my bench build, and a TL072 for the level. Three knobs, a toggle and two jacks on an 8 HP panel. With the layout file, the netlist and the panel drill template.
Opto Duet CV Rack
The Opto Duet CV as a Eurorack module: two 555s that play each other, an engine flashing an LED sealed to a photocell in the voice's timing. The built board hole for hole with the rack block under it: tempo and pitch pots where the eyes were, the two CV jacks as built, and a TL072 taking the voices to rack level where the speaker was. Two knobs, an LED and three jacks on an 8 HP panel. With the layout file, the netlist and the panel drill template.