The Bug Box
Six bug boards, one unit, a speaker, a line out and ten patch jacks · By Onion Madder · Mess O' Pedals
Six of the stripboard builds on this shelf are going into one enclosure: the Hive, Dragonfly, Cicada, Grub, Firefly and Hornet. The Bug Bus runs them all off one wall wart, the Bug Mixer turns four of them into one signal, the Hornet turns that into sound, and a line-out jack sends it somewhere else. Then the part that makes it an instrument rather than a crate: ten 3.5 mm jacks, wired so the box plays with nothing plugged in and a patch cable changes what it does.
What is in the box
| Board | In the box it is | Bus output |
|---|---|---|
| Hive Drone | Six drone voices. Audio out to the mixer | HIVE |
| Dragonfly VCO | The pitched voice. Audio out to the mixer, and the one board with a control input | DRAGONFLY |
| Cicada NAND | Four gated voices. Audio out to the mixer | CICADA |
| Grub Divider | Seven octaves down from whatever clocks it. Audio out to the mixer | GRUB |
| Firefly Sequencer | Eight steps of control voltage and a clock. Makes no sound itself; it plays the Dragonfly | FIREFLY |
| Hornet | The speaker amp. Its input is the mix | HORNET |
| Bug Bus | One wall wart in, seven supplies out, master switch and power LED | - |
| Bug Mixer | Four level knobs into one signal, out to the Hornet and to the line jack | MIXER |
What a normalled jack is
A normalled jack is a jack with a switch inside it. With nothing plugged in, the switch is closed and the signal goes where the box wires it. Push a plug in and the switch opens: the built-in path breaks and the cable takes over. That is the whole trick behind a synth that makes a noise with no cables in it and does something different with them. The jacks that have this are the switched 3.5 mm ones - Thonkiconn PJ398SM is the Eurorack standard and costs pennies - and they have three lugs: T for the tip, S for the sleeve, and a third, the normal contact, that touches the tip lug only while the jack is empty. The default source goes to the normal lug; the destination goes to the tip lug. Outputs do not need the switch and get a plain jack, or a switched one with the third lug left empty.
Mono cables. These are all mono 3.5 mm sockets and want mono patch cables, the Eurorack kind. An aux cord works in a pinch, but it is stereo: its ring sits connected to nothing and picks up hum along the way.
The patch map
Every jack on the box, left to right as they would sit on the panel. Normalled from is what feeds an input when it is empty. Plug in and is what a cable does.
| Jack | Carries | Normalled from | Plug in and |
|---|---|---|---|
| HIVE OUT | The Hive's audio | - (an output) | The Hive goes down the cable too. It stays in the mix |
| CICADA OUT | The Cicada's audio | - (an output) | Same |
| DRAGONFLY OUT | The Dragonfly's audio | - (an output) | Same. It also keeps clocking the Grub |
| GRUB OUT | The Grub's audio | - (an output) | Same |
| DRAGONFLY IN | The Dragonfly's control input - its IN pad, the one the mode switch hands the pitch to | FIREFLY CV OUT. With the mode switch over, the sequencer plays the VCO | The Firefly is cut off and whatever is on the cable plays the Dragonfly instead: another oscillator, a pedal, an outside sequencer |
| GRUB CLK IN | The Grub's CLK_IN pad - the thing it divides | DRAGONFLY OUT. The VCO clocks the divider, so the Grub is seven octaves under the Dragonfly | The Grub divides the cable instead - the Cicada, the Firefly's clock, anything square |
| FIREFLY CV OUT | The sequencer's CV_OUT pad, 0 to about 8V in steps | - (an output) | The sequence leaves the box. It still feeds DRAGONFLY IN unless that jack has a cable in it |
| FIREFLY CLK OUT | The sequencer's CLK_OUT pad, the clock through 1K | - (an output) | A gate for something else, in the box or out of it. Into GRUB CLK IN it makes the Grub tick at the sequencer's tempo |
| HORNET IN | The amp's input, through its volume pot | MIX, the Bug Mixer's AMP pad | The mix is cut off and the speaker plays the cable: one bug on its own, or something from outside |
| LINE OUT | The Bug Mixer's LINE pad, through its 1K | - (an output, switched) | The mix leaves the box. Its switch contact sits in the Hornet's speaker lead, so a cable here mutes the speaker |
The four OUT jacks and the mixer. Each board's output goes to its mixer level pot and to its OUT jack, both, always. That is on purpose: an output does not break anything, it is just available. If you would rather a cable in HIVE OUT took the Hive out of the mix, use a switched jack there and put the mixer pot on the normal lug instead of the tip.
With nothing plugged in
The Firefly steps its CV into the Dragonfly, so the Dragonfly plays a sequence when its mode switch is over and a drone from its own knob when it is not. The Dragonfly clocks the Grub, so the Grub is seven octaves under whatever the Dragonfly is doing. The Hive and the Cicada drone on their own. All four audio boards meet at the mixer, the mixer feeds the Hornet, and the Hornet feeds the speaker. Turn the box on and it plays. The line out carries the same mix, and the moment a cable goes into it the speaker goes quiet.
Levels, unmeasured. Everything in this box is a square wave near the full 9V, sitting on 0V. Inside the box that is fine: the Grub's clock input and the Dragonfly's control input are both built for exactly that. Out of the box it is hot and off-center for real Eurorack, which wants plus and minus 5V. If that day comes it is a resistor and a cap at the jack, later.
Power
One wall wart, 9V center positive, into the Bug Bus. Everything hangs off the bus's outputs, one pair of twisted wires per board, the Hornet on the unfiltered one. The master toggle and the power LED are the bus's. No batteries: on their own these boards already run a 9V down to where they sound wrong, and six of them together would do it in minutes.
The panel, roughly
Counting the guides: about 28 pots (six on the Hive, three on the Dragonfly, four on the Cicada, one on the Grub, nine on the Firefly, four on the mixer, one on the Hornet), about 15 toggles (four Cicada gates, the Dragonfly's mode, the Grub's seven octaves and its reset, the Firefly's step count, the master power), ten jacks and a DC inlet, nine LEDs (eight Firefly steps and the power light), and the speaker. At a comfortable knob spacing that is about 12 by 8 inches of panel, which is a steel chassis with an aluminum top or a wooden box with a plate for a lid, not a die-cast pedal box. The drill sheet gets drawn against the actual enclosure, not before it: a template that is true size for a box you do not have yet is a way to ruin two things.
What to order
Five of the six bug boards are already built. What the box still needs is the Firefly, the Bus, the Mixer, and everything that mounts on the panel. The enclosure and its cover come from Amplified Parts; everything else is a Tayda or Thonk order, and the two-vendor split is a feature - the wait is the time to draw the panel properly.
| Part | How many | For |
|---|---|---|
| Hammond 1444-29 chassis, aluminum, 12 × 10 × 2″, and its 1434-29 cover plate with #6 self-tapping screws | 1 each | The box. Amplified Parts |
| 3.5 mm mono switched jacks - Thonkiconn PJ398SM from Thonk, or Tayda's PJ-301M, the same jack | 9, plus spares | Every patch point but the line out |
| 1/4″ mono switched jack | 1 | LINE OUT - a guitar cable into an amp or a pedal, and its switch contact mutes the speaker |
| 3.5 mm mono patch cables | 5 or more | Playing it |
| DC jack, 2.1 mm, panel mount | 1 | The Bus's IN. The 12V wall wart already on the bench is fine: the Hornet's LM386 is happy to 12V and nothing else cares |
| Speaker, 8 Ω, 0.5W or more, 2 to 3″ | 1 | The Hornet. Its diameter sets a hole on the panel, so decide it before the drill sheet |
| B100K pots | 8 | Firefly steps |
| B1M pot | 1 | Firefly rate |
| A100K pots | 4 | Mixer levels. B100K works, log feels right |
| A10K pot | 1 | Hornet volume, if the built board does not have one yet |
| Knobs | about 28 | One per pot on the panel. Count the built boards' pots before ordering; small knobs, the Firefly's two rows are on 25 mm centers |
| Mini toggles: SPST | 2 | Bus master power; Firefly step count (or a wire) |
| Momentary pushbutton, normally open | 1 | Grub reset, if it is not already on the built board |
| 5 mm LEDs, one color | 9, plus spares | Eight Firefly steps sharing one resistor, so they must match; one power light |
| 5 mm LED panel holders | 9 | Optional; a 5 mm hole and a dab of glue also works |
| M3 nylon standoffs, 8 or 10 mm, with M3 × 6 screws and nuts | 24 standoffs, 48 screws | Eight boards, three each, bolted to the cover plate with the parts facing up - the screw heads end up under the box where nobody sees them |
| Rubber feet | 4 | The cover plate |
| Stranded hookup wire, several colors, and heat shrink | - | Seven twisted pairs from the Bus, and everything else |
| Stripboard | one large piece | 16 × 30 for the Firefly, 4 × 46 for the Bus, 11 × 22 for the Mixer - one 100 × 160 mm board cuts into all three |
| CD4017, NE555, TL072 | 1 each | Firefly, Firefly, Mixer |
| 1N4148 | 8 | Firefly steps |
| 1N5817 | 2 | Firefly and Bus supplies |
| Resistors: 10R × 6, 1K × 2, 2K2 × 2, 10K × 2, 22K × 1, 100K × 7 | as listed | Bus, Firefly, Mixer |
| 100n ceramic | 7 | Firefly 2, Mixer 5 |
| Electrolytics: 2.2 µF × 1, 10 µF × 3, 100 µF × 7, 220 µF × 1, 470 µF × 1 | as listed | Firefly, Mixer, Bus |
The boards bolt to the cover plate, not the panel. That is the one change from a first thought of adhesive standoffs under the top: a nylon standoff and two screws costs pennies at Tayda, and the heads land on the underside of the box. It means the boards face up toward the panel and the pots come down toward them, so on a 2″ deep chassis a board cannot sit directly under a pot - the drill sheet will place the board footprints as well as the holes, for exactly that reason.
Things to try
- Sequence the Grub. FIREFLY CLK OUT into GRUB CLK IN, and the divider ticks at the sequencer's tempo while the Dragonfly plays the notes
- One bug, loud. Any OUT into HORNET IN puts that board alone on the speaker, at the Hornet's volume, while the mix still goes out the line
- Outside in. A pedal or a phone into DRAGONFLY IN with the mode switch over, and the VCO goes hunting for it
- A mix input. The mixer page shows how a fifth channel is one more strip. Bring it to a jack and the box can mix something that is not a bug
The boards are the six guides linked above. The bus and mixer are this shelf's. The patch map is Onion Madder's, drawn up on paper before the box, so the wiring exists before the holes do.