Mosquito 556

The Atari Punk Console on an NE556, soldered down · Ten strips by eleven holes · By Onion Madder · Mess O' Pedals

The Dead-Bug Mosquito is the one bug in the series that never got a permanent home - the Hive, Cicada, Grub, Dragonfly and Hornet all made it onto stripboard, and the noise box that started the whole thing did not. This is it: an NE556 as the Atari Punk Console, on ten strips by eleven holes, with the values from Paul In The Lab's two-555 APC - 470K pots, a 10n cap on the oscillator and a 100n on the one-shot. Timer A runs free, its output triggers timer B, and timer B's one-shot is the sound. The output leaves through a 10 µF cap to a volume pot, a CV jack bends the pitch through a 100K into pin 3, and the sync out keeps an empty pad so it can be added without a redraw.

The Mosquito 556 layout drawn as a stripboard diagram, titled Mosquito 556, 11 by 10 stripboard. Ten orange copper strips lettered a to j run left to right with eleven columns numbered above them. A pale rectangle marked IC1 NE556 sits across strips c to i, with gray X marks under it where the strips are cut. Left of the chip three small outlined resistors stand in one column, R1, R3 and R4 from the top, with the green ceramic cap C1 below them; a long dark blue link right beside the chip runs from strip a down to strip i, a shorter one between the resistors and the chip runs from strip d to strip h, and one at the left edge runs from strip g to strip j. Two dark blue links run down under the chip from strip b. Right of the chip a green cap C2 runs from strip a down to strip e, a second green cap C3 stands at the top right corner between strips a and b, the resistor R2 stands between strips f and g, and a pink circle, the electrolytic C4, sits between strips h and i. Gray X marks near the ends of strips a, f and i are the cuts that make the pad islands. Holes carrying wires off the board are labeled in the margins: PITCH_A, GND, 9V, PITCH_W and CV_IN down the left, GND_JACK, SHAPE_W, SHAPE_A, VOL_T and SYNC down the right. Beside the board on the left are the pitch pot marked 470K, the DC jack, the power toggle and a quarter-inch jack for CV in, with wires to their pads; on the right the output jack, the shape pot marked 470K and the volume pot marked B10K. A parts list and an Off the board list run underneath. Below the board the same board is drawn a second time from the solder side, mirrored, with the column numbers running right to left, every solder point as a dark dot, the cuts as X marks, the chip as an outline with pin 1 boxed and the pads labeled on the margin they now sit nearest. — The revision, 10 strips by 11, as the layout file draws it: every part, link, cut and off-board pad, and the panel parts beside it with a wire to every hole they land in. The lower drawing is the solder side, mirrored - the side you actually work on.

The 10 by 11 board wired up loose on a dark desk mat in front of a lilac practice amp, not boxed. The small piece of stripboard sits in the middle with the NE556 standing in its center, small yellow ceramic capacitors, a few resistors, one small electrolytic capacitor and green wire links. Blue, yellow, green, black, orange and white wires run from the board to three pots with bare shafts, one at the left, one at the top and one at the right, and to a panel DC jack at the left with a right-angle power plug in it. A lit LED with a resistor on one leg lies at the foot of the amp. A blue cable is plugged into the side of the amp. — Mine, built and working on this layout, still on flying leads: the three pots, the DC jack and an LED that is not in the layout file. Pitch and shape are 500K, not 470K, and the power switch is left off for now.

What you'll need

tap to expand / collapse

1× NE556 dual timer, 14-pin DIP - spot it: NE556 on top, not 555; a notch or dot marks pin 1. Two 555s in one package, which is the whole trick of the circuit
3× 1K (brown-black-red, R1, R2 and R3) - R1 and R2 are the stops, one in series with each pot on the supply side, so a knob turned to the end never puts a discharge pin straight onto the supply. R3 is Paul's 1K, from pin 1 to pins 2 and 6. All three stand up
1× 100K (brown-black-yellow, R4) - the CV input, from pin 3's strip to the CV_IN pad. It stands up
1× 10n ceramic (103, C1) - timer A's timing cap, the pitch. It stands left of the chip, near the bottom
2× 100n ceramic (104, C2 and C3) - C2 is timer B's timing cap, running from the right of the chip up to the top strip; leave its leads long. C3 is the supply decoupling, standing between the top two strips in the corner
1× 10 µF electrolytic (C4) - the output DC blocker. Spot it: stripe marks the negative leg. Its plus goes on pin 9's strip; it stands up
Stripboard, 10 strips × 11 holes or larger, and solid wire for eight links. J3 and J4 run under the chip, so they go in before the chip

Off the board

2× 470K pots - pitch and shape, Paul's value. Wired as variable resistors: the wiper and one outer lug, the third lug left empty. Their 1K stops are on the board. Mine has 500K, and it works
1× 10K pot, the volume - spot it: B10K. Wired as a divider: all three lugs. Lug 3 to VOL_T, lug 1 to GND_JACK, wiper to the jack
1× 1/4″ jack for the output - or a small 8 Ω speaker straight off the volume wiper, the way the dead-bug build plays
1× 1/4″ jack for CV in - tip to CV_IN, sleeve to GND_JACK
1× SPST toggle for power, in the positive leg between the DC jack and the 9V pad
1× DC jack or 9V battery snap - a 9V battery, or at least two vape cells in series
An upright 125B - the drill template further down

The layout file is the guide

Like the 555 theremin and the Opto Duet, the build document for this one is the file itself: ↓ Download Mosquito_556.json - import it into Copper Bottom and the editor gives you the board picture, the placement walkthrough, the electrical checks and a printable build sheet, all from the same file. No coordinates are written out on this page on purpose: the editor is the viewer, and a number typed twice is a number that can drift.

Strip a is ground and strip b is V+, so the decoupling cap stands between them, and J1 takes ground down the column beside the chip to pin 7. Strip j is the trigger bus. Timer A's output leaves pin 5 on the left of the chip and timer B's trigger is pin 8 on the right, and no single strip joins them - so J6 takes OUT A down the left edge to strip j and J7 drops pin 8 straight onto it. The SYNC pad sits at its right end. Four cuts away from the chip make the pad islands: PITCH_A at the left end of strip a, CV_IN at the left end of strip f, SHAPE_A and VOL_T at the right ends of strips f and i. On strip f the cut under the chip sits one hole further right than the rest, so J3 lands on pin 4's side.

Pin 11 is left open, the way Paul leaves it on his board, and there was no hole left for a pad on it. Copper Bottom's checks flag it as an orphan, a strip with one thing on it; that warning is expected here.

The netlist

Quoted verbatim from the layout file. It was written from the board, so checking the board against it can only pass - what it is for is carrying the circuit somewhere else, and telling you what each strip is supposed to be doing while you stare at it.

# Mosquito 556 - written from the board # 10 strips of 11 holes, 16 parts, 1 chip, 11 cuts # # The Atari Punk Console on an NE556, on the values from Paul In The Lab. # Timer A runs free: the pitch pot and R1, its stop, from V+ to DIS, R3 from # DIS to THR and TRG, C1 to ground. Its output triggers timer B down the bus # strip. Timer B is the one-shot: the shape pot and R2 from V+ set its width, # C2 to ground. OUT B leaves through C4 to the volume pot. CV_IN reaches pin 3 # through R4. Both resets are held high and pin 11 is left open. V+: @9V C3.A IC1.10 IC1.14 IC1.4 J3.A J3.B J4.A J4.B J8.A J8.B R1.A R2.A GND: @GND @GND_JACK C1.B C2.B C3.B IC1.7 J1.A J1.B PITCH_A: @PITCH_A R1.B DIS_A: IC1.1 @PITCH_W R3.A TIME_A: IC1.2 C1.A IC1.6 J2.A J2.B R3.B CV_A: IC1.3 R4.A CV_IN: @CV_IN R4.B OUT_A: IC1.5 @SYNC IC1.8 J6.A J6.B J7.A J7.B TIME_B: IC1.13 @SHAPE_W C2.A IC1.12 J5.A J5.B CV_B: IC1.11 SHAPE_A: @SHAPE_A R2.B OUT_B: IC1.9 C4.A VOL: @VOL_T C4.B

The off-board wiring

Ten pads leave the board. One of them, SYNC, is for an extra and stays empty on the base build.

Pad	Goes to
9V / GND	The supply. 9V through the power toggle from the DC jack or battery snap; GND to the jack's sleeve or the snap's black lead
PITCH_A / PITCH_W	The pitch pot, as a variable resistor: one outer lug to PITCH_A, the wiper to PITCH_W, the third lug empty. PITCH_A is the end of R1, the stop from V+; PITCH_W is pin 1. Which outer lug decides which way the knob turns; swap them if it feels backwards
SHAPE_A / SHAPE_W	The shape pot, the same way: one outer lug to SHAPE_A, the end of R2, the wiper to SHAPE_W, on pins 12 and 13, the third lug empty
CV_IN	The CV jack's tip. R4 on the board takes it on to pin 3. The jack's sleeve goes to GND_JACK
VOL_T	The volume pot, lug 3 - the top of the divider. The output arrives here through C4
GND_JACK	The volume pot's lug 1 and both jacks' sleeves. The volume wiper goes straight to the output jack's tip and never touches the board
SYNC	Empty. Timer A's raw output at the pitch rate, a short drop once a cycle rather than an even square on these values - a 1K to a jack tip makes it the clock out the dead-bug page describes

Built, and heard

The first board, 10 strips by 16, was built on the bench in September 2026 straight off its file, kept here as Mosquito_556_v1.json, and it works. That board has 1M pots, 10n on both timers, the fixed 1K on the supply side of the pitch pot and no CV jack. In the photo every off-board part is still on flying leads: the three pots, the toggle and the jack. The lit LED is not in the layout file and the pad table above does not describe it. Not boxed yet.

I built the 10 by 11 revision above too, in October 2026, and it works: it sounds like an APC. I used 500K pots for pitch and shape instead of the 470K the file asks for, and added an LED, which is not in the layout file: a 2.2K from power to the LED, and the LED to ground. The power switch is left out for now, and the CV jack is not fitted yet, so the CV input is untried.

The built board on a dark desk in front of a pink keyboard, wired but not boxed. A small rectangle of orange stripboard in the middle carries the NE556, small capacitors, resistors, one electrolytic capacitor and blue link wires. Three pots hang off it on flying leads: one to the left on yellow, blue and black wires, one above on white wires and one to the right on blue, green and yellow wires. A blue toggle switch lies at the lower left on orange and black leads. A lit LED on red and black leads sits beside the left pot. A black jack lies at the right edge on a yellow and a black wire. — The first board, 10 strips by 16, built and working, September 2026. It is Mosquito_556_v1.json, on the older values and with no CV jack - not the drawing above. Everything off the board is still on flying leads: the three pots, a toggle and a jack. The lit LED is not in either layout file.

Don't eyeball the holes. There is a 1:1 drilling template for the 125B - the box drawn unfolded, so you wrap the sheet around it and every hole lands by folding instead of by measuring. Face plus four walls, true-size circles with a punch dot in the middle. The walls are blank; everything is on the face.
↓ Same box, jacks on top (PDF)
The second sheet keeps every control where this one has it and moves the jacks - power, CV and audio - to the top wall, so the cables leave upward. Two ways to drill one box; pick one.
Drawn for the layout file's parts and nothing else: pitch, shape and volume down the left, the power toggle and the CV input on the right, DC and the output jack along the bottom. Nobody has drilled this one yet.
Print at 100% / “Actual size”, never “Fit to page” - check the bar measures exactly 4″ before you touch a drill. The face is 66 by 121 mm but only 42 mm of it is drillable once the lid lip is clear, which is why everything sits in a column.

How it works, in one breath

Two timers, one chasing the other. Timer A is an astable: the pitch pot, R1 and R3 charge C1 toward two thirds of the supply, then the timer discharges it through R3 alone, back to a third, and around it goes at a rate the pitch pot sets. Charging goes through the whole pot and discharging only through the 1K, so pin 5 sits high for most of each cycle and drops for a moment - and that short drop is what timer B wants on pin 8, its trigger. Timer B is a monostable: every time the trigger falls it puts out one pulse whose width is R2 plus the shape pot charging C2, and then it waits for the next fall. When the pulse is shorter than the pitch period you hear the pitch; when it is longer, timer B misses triggers and you hear the divisions and the beating between them, which is the Atari Punk Console's whole personality. C4 takes the DC off pin 9 and the volume pot hands what is left to the jack. A voltage on pin 3 moves the two levels timer A charges between, so the CV jack bends the pitch. R4, at 100K, means a source plugged into the jack nudges pin 3 rather than taking it over.

The stops are not optional. Each pot runs from the supply to a discharge pin, so at zero ohms the timer's discharge transistor would pull the supply straight to ground once a cycle. R1 and R2 are the floor under the knob, which is why each pot is wired as a two-lug variable resistor and not a divider. R3 is a different job: it is Paul's, and the oscillator needs it at every setting, because C1 discharges through it.

Things to try

None of these have been tried on this board.

Sync out. A 1K from SYNC to a jack tip is timer A's clock, to run the Grub or the Spider off this box
A second one-shot. The dead-bug page's NE555 voice 2 hangs off the same trigger; SYNC is that node, so it wires up from the pad
Other timing caps. A bigger C1 pushes the pitch down into clicks and rhythms, a smaller one (1n) up into whistles; C2 does the same to the one-shot's width
The first board's values. 1M pots and a 10n for C2, what the built board in the photo runs, fit this layout part for part. The oscillator would still be wired Paul's way

Circuit is Forrest Mims's Stepped Tone Generator, the Atari Punk Console. The values on this revision are Paul Stevenson's, from his two-555 Atari Punk Console layout on Paul In The Lab; the stops, the CV input and the layout are Onion Madder's, drawn in Copper Bottom. The first board followed the Dead-Bug Mosquito.