Krackle Krusher Synth

The Krackle Krusher is an ode to the Crackle Box of the 1970s paired with a hand sketched silkscreen. At its heart is a LM709 OpAmp, originally designed by Bob Widlar, which, when launched in 1965, was sold out for two years. The LM709 era OpAmp is unique in that it lacks frequency compensation, creating the crackle sound that makes this synthesizer so awesome. Because it uses capacitive touch pads, this instrument produces a different sound from musician to musician.

Unfortunately I couldn’t get ahold of a LM709 and had to make do with the identical B109D. The Krackle Krusher has it’s own custom PCB designed with Patchr.io paired with a hand drawn silkscreen. It features an 8 ohm speaker to generate just enough of a crunching squeal to complement a good jam sesh.

Components of the Krusher

If you bought the Krackle Krusher Kit on Etsy you should have all the components you need to get started. You will have a bag containing the PCB and an Acrylic back; a bag containing the battery holder and speaker; a bag containing standoffs, screws and nuts; and a bag containing all the components you need! We did not include a 9V battery with the kits, you will need to snag one from your favorite battery snagging spot.

Before we get started, I always suggest laying out all the components to make sure you have everything you need to get started. Hopefully this will help fast track you to crackling sonic bliss.

You will need hot glue or double sided tape to attach the speaker to the Krusher. Otherwise we will be using your standard soldering iron, wire cutters and screw driver to assemble this little box of Krackle.

Building the Krusher

It's that time, the moment you dreamed of, the very moment you will build your Krackle Krusher, transporting you to a cosmic crunching kaleidoscope of capacitive Krackle Krushing contentment.

We will start by soldering the components to the PCB. When in doubt... the labels are on the back side of the PCB...

A few things to note:

• The on/off switch can be placed either on the top side or bottom side of the PCB, its personal preference.
• We suggest leaving the speaker and battery holder to the last steps.
• The speaker cables and battery cables will be inserted from the bottom side of the PCB to the top side and soldered on the top on the PCB.
• I've added this image to note the polarity of the speaker:

Place the speaker within the circle on the backside of the PCB. You can use either hot glue or double sided tape to adhere the speaker to the PCB. I suggest using hot glue if that is handy:

Next we will use 4 screws and 4 nuts to mount the 9V battery pack to the acrylic panel:

Finally we will use the standoffs, four screws and four nuts to attach the acrylic back to the PCB. **Don't forget to put your 9V battery in the holder before attaching the acrylic back**

Wrapping it All Up!

There it is, your very own Krackle Krusher. I've attached the Gerber files if you would like to order your own! Otherwise, I'd suggest heading to Patchr.io to design your very own Krackle Krusher PCB in a fun form factor.