Saturday, 29 February 2020

Mammouth VCO

Here is my second module from Mammouth Machine : a VCO (Voltage Controlled Oscillator) to take the place of the oscillator of the DIY Doepfer based module that I plan to relegate in a box.  Having two oscillators will allow either to enlarge the sound palette (via mixing or FM), or to have two separate synthesis voices.

Finished Module
Not much more to add than for the ADSR assembly from the same producer.  Same workmanship, same (splendid) wooden, laser-cut face.  I applied the same 2 coats of transparent matte varnish.
Small detail: this kit included the flat cable to connect the module to the bus board.  Curiously, this was not the case for the ADSR.
On the bench

I did have two little problems, though.

Ongoing calibration.
First was with the kit: I received two electrolytic capacitors of 4.7uF instead of 47uF.   With another type of module, I would have smiled and soldered the 4.7uF capacitors, but a VCO needs all the power supply stability it can get.  Maybe 4.7uF is enough.  Nevertheless, I decided to replace these capacitors with the closest value I had in stock.  No 47uF in the drawer, the 100uF are too big.  Remain two 22uF capacitors which fit like a glove.

Then, a small omission in the manual: I couldn't find out how to use the tuning trimpot to calibrate the module, when it's obviously the V/oct scale adjustment, which is critical and not that easy to adjust.
Luckily I had a little help from Bob to do the calibration.

First rows.

And now, as promised, a little bit of sound :

There are two synth voices in this track.
For the first one, the two, slightly detuned, square waves from the VCO are mixed, then sent to Ripples, whose frequency is modulated by the ADSR output.
For the second voice, the sine of the Doepfer oscillator is directed to Rings, then the phaser.
The whole is mixed in the output module.

Rampage generates the two main envelopes. One triggers the other and vice-versa.  The random outputs of the Sample&Hold and the Turing Machine are used to control the rise and fall times as well as the Rings parameters.
Notes are randomly drawn by the Turing Machine and calibrated by the 2hp Tune module.

DAW: Reaper
Usual Suspects : TAL Reverb II, TAL Chorus-60

Saturday, 22 February 2020

Mammouth ADSR

ADSR module
I finally decided to replace the Doepfer DIY-based module with separate elements. First, because the quality of the electronics is not up to my (modest) expectations: the oscillator is quite poor and keeps detuning, the VCA does not close completely and is influenced by the LFO, the envelope generator is not very reactive. I'll regret the filter though. Separate elements in kit will also save me some space: my realizations are not very dense.

Since I'm lucky enough to have a local producer, I went to Mammouth Boutique, in our good old town of Liège.

This ADSR module is the first module from Mammouth Machine I built.

Kit is of quality : bulk components in bags, super clear PCB indications, online manual but very well done.  Only caveat for english speaking people : manuals are in french.

The kit

Bob helps to fix the switch
The components are loose in the bags and are not identified other than by their marking, whereas other suppliers offer specific labeling.
But there is nothing wrong with that.  The information on the PCB and in the manual is very clear. A small cheat sheet comes in the kit with resistor values color coding and capacitor indications. With a little care, everything goes well. Nevertheless, I tested every resistance with an ohmmeter, but that's what my perfectionist side is all about.

The face is made of wood, laser cut. The wood is untreated, I decided to delicately apply two thin coats of transparent matte varnish to ensure a certain durability over time.


No particular remark on this kit, everything went perfectly.

[edit Feb 29, 2020] After my first tests, I noticed a residual voltage (about 60mV) after the end of the envelope.  This leaves a VCA a bit open and I could hear a faint noise.  It does not look to be problematic in real conditions though.