Thursday, 31 May 2018


The second kit from Befaco I built is the Rampage.

And it is not for the faint of heart.

Befaco Rampage

The kit is good quality (as was the A*B+C).  However, with 227 parts (about 560 pins to solder), 3 connectors and around 40 jacks, pots and various switches, I wouldn't quality it as easy.

Rampage kit

I chose this module as an alternative to Make Noise's Math, one of the most recommended module in forums.  With some exceptions, Rampage fills the same roles.  Moreover, it is available as a kit which fulfills my desire to build my synth as much as I can.

Main board close-up

According to Befaco website :
"The module is built around two voltage controlled integrators. Integrators (also known as Lag Processors or Slew limiters) allow you to process your voltages, converting sharp square waves in ramp-like waveforms.
These lovely devices can, for instance, convert a gate signal into a simple envelope, or achieve a “portamento” or “glide” effect when applied to pitch CV."

A properly patched Rampage can assume more than 20 different functions : envelope generator, oscillator, comparator, polyrythmic gate generator, trigger delay, etc…

Before mechanical assembly
Assembly instructions are similar to the previous kit : same advantages, same drawbacks.

With a kit of that size and density, you have to be systematic in order to make sure to be "good first time".  Debugging such a circuit afterwards was not in my intentions.

Calibration of the triangle shape
I estimated that the two Schottky diodes of the kit were too large for the PCB footprint and I replaced them by some in my stock.

I also found an oddity in the presence of a solder joint below one of the potentiometer.  I reckon there should be enough room between the back of the pot and the joint when the pot is tightly attached to the panel, but I decided to mask it anyway with some insulation tape.

Better safe than sorry.

Still, I implemented the mod presented in this Muff Wiggler thread to ensure reliable gates by soldering 1M pull-downs resistors at the outputs.

Additional pull-down resistors

Finally, a photograph of the Befaco boys in action and a bit of sound.

Befaco boys in action

Here above, Rampage channel A is programmed as an LFO which frequency is determined by the output of the S&H and cadences the patch.  Channel B is the envelope triggered by channel A and whose attack is also determined by the ouput of the S&H.
A*B+C plays the role of the VCA.   The sound source is the pink noise from the S&H module.
The sound is coming out via Rings (whose parameters are, ... guess what ? ... controlled by the output of the S&H) and the phaser.
Additional effects : NI Supercharger, TAL Reverb II & LoudMax

Friday, 11 May 2018

A * B + C

To complete my synth, I recently bought 2 DIY kits from Befaco.

The first one is called A*B+C.

Finished module

The kit is  good quality and rather simple.

Before soldering

The A*B+C is a dual, four-quadrant multiplier with VC Offset.

It can perform different operations on its inputs :
- amplifier and inverter of A input.
- VCA on A, with envelope CV on B.
- VC offset generation with C input.
- attenuation/inversion of C input
- ring modulation of audio signals in A and B.

Moreover, the output of the the first channel is normaled to the mixer of the second channel.  So the module can serve as CV/audio mixer.

Before assembly

Assembly instructions are good but could have been clearer, especially for the final assembly.
A couple of photos wouldn't have been too much.  But I didn't encounter any major issue.

My only gripe was about some parts that had a larger size than their footprint on the PCB.  I had to replace the two Schottky diodes with those I had in stock and solder 2 couples of resistors vertically. One resistor even had to be soldered on the other side of the board.

Once again, nothing major in my view.

Profile view.  You can see the vertically mounted resistors

Finally, the module suffers from a high level of background noise as indicated in this Muff Wiggler forum thread.   Anyway, it does not seem prohibitive.   There is a suggested mod but it looks like it modifies the potentiometers behaviour, so I didn't want to perform it (and I didn't have the necessary 1/8 W resistors).   Time will tell.