Music and Synth DIY

Eurorack, SMD, Synth DIY

DIY Mutable instruments Streams clone (finished)

OK, so I’ve had this PCB in a draw for a long while because the LED bargraph driver has been a victim of the chip shortage.

Streams is a dual low-pass gate , VCA/VCF and dynamics processor, amongst other things.

It can be a dual mono or stereo linked compressor with sidechain input, it can be a VCA with linear/exponential response, an envelope follower with spectral content CV output, and a Vactrol emulation.

As builds go, it’s about the same difficulty as Clouds, Rings etc. It’s mainly 0603 surface mount components. Apart from the MCU and the DAC, the only other fine pitch IC is the aforementioned bargraph driver.

The only potentially tricky bit is this little bargraph PCB. Here’s how I approached it.

  1. Drag solder the driver chip.
  2. Solder the 0603 decoupling caps and the LED resistors
  3. Push the LEDs into place. There’s a flat edge marking the correct orientation on each footprint.
  4. Align that with the panel

5. Solder LEDs in place and cut the legs.

6. Cut a double 2.54mm pitch header and solder one pin, connecting the surface mount header on the main board to the bargraph pcb, then check the panel orientation again. Finish soldering the header. I found the height of the SMD header and this one fit exactly. Note I had to bore the tactile switch holes in the panel a bit, as the buttons were getting stuck.

Without bargraph PCB
with bargraph PCB

To flash it, you either need to compile the code from the MI Github via the MI development environment, or grab a pre-compiled bootloader.hex and streams.hex file (from here).

I used an ST-Link with Olimex JTAG adapter and utility software via the mini JTAG connector on the back. The red stripe on the mini JTAG cable goes to the small dot on the PCB.

As usual, if you’re getting the “cannot connect to target” error, chances are you need to reflow the STM.

PCBs & MCU –

Mutated panel –