We build the Bastl Skis Dual Decay VCA DIY kit. This neat little all-in-one decay envelope generator and VCA is a very handy tool for your Eurorack Modular. Plug in a sound source, trigger the skis channel, and dial in a decay time to get the volume shaped sound at the output.
The Bastl Skis DIY kit is a complete package. It even comes with solder. It’s an easy and inexpensive build suitable for beginners.
This is version 1.2 which has the new aluminum panel instead of wood. You can get the assembly manual here. Or just follow along with the build below 😊
Empty the bottom board bag in a container.
Do the same for the control board.
Let’s fire up the soldering iron 🔥
Bast Skis Bottom Board
Let’s start with the bottom board first. It is wise to clean the PCB with isopropyl alcohol (I use the 96% kind) before soldering any of the components.
We start with the resistors. There are five different values on the bottom board. Use a multimeter to keep them apart.
We solder the 14 resistors of 100k Ohm in place.
These are followed by the 4 10k Ohm resistors.
Then a batch of 12 times 1k Ohm.
And 2 resistors of 47k Ohm.
Finally, we place 2 resistors of 4k7 Ohm on the bottom board.
Solder the two N4148 signal diodes in place.
Place the two N4007 power diodes to prevent blowing up components by reversing the power polarity.
Ad one 16 pins socket for the LM13700 Dual Operational Transconductance Amplifier (OTA)…
… and another 14 pins sockets for yet another TL074.
Solder the eight 100nF caps in place. You recognize them by their ‘104’ marking.
Add the batch of four 10nF capacitors. No more caps to solder.
Then we solder the two 2N3906 PNP transistors…
… and finally four BS170 Small Signal N-channel MOSFET transistors.
Prepare a 2×5 male header for the power connector on the back of the bottom PCB. Solder it on the front.
Do the same for 2×2 and 3×1 male headers like this.
Lastly, solder the two 2×1 male headers in place.
Place the two 1uF capacitors. Be sure to take care of the correct polarity. The white strip on the caps housing should match the negative on the PCB. The long leg should match the positive side.
Do the same for the four 10uF capacitors. Solder them in place.
The final components on the bottom PCB are two protective PTC fuses. Solder them on the spots marked with PTC.
Done. We’re making progress here 😃
The controller PCB has only four 1k Ohm resistors. Solder them in place.
Mount the two BS170 MOSFETs and be sure to match the flat side with the flat side on the PCB silkscreen.
Headers and Spacers
Two connect the bottom PCB to the controller board, we need to prepare two 8 pin headers and two 10 pin headers. Both male and female. Place the male header on the bottom board and the female headers on the back of the controller board. Don’t solder yet.
Mount the spacers on the controller board. Carefully connect the two boards, mount the spacer to the bottom board with the screw and fixate the boards with some painters tape. Now solder both female and male header to their boards. This way we know the headers will fit correctly after soldering.
The result after finishing the board connectors.
Place the two 500k potentiometers, ten jacks, two LEDs (long leg is the positive side), and two switches on the controller PCB. Don’t solder yet.
Carefully mount the front panel and hand screw the jacks and potentiometers to it. Be sure the switches are correctly placed. They need to be flat on the back of the front panel. Finally, solder the components to the controller board.
Be sure to put the TL074 and LM13700 chips in their sockets (watch out for the placing of the dent). Connect the front panel with controller board to the bottom PCB. Screw the spacer to the front panel and we’re done!
Your Bastl Skis Eurorack module is ready for some DUAL Decay VCA action 😍