Tuesday, 4 September 2018

Venus Cloud City

I took the opportunity of August's KVR Music Cafe contest to put the last upgrade on my small modular synth to good use.

The piece combines 6 tracks, out of which 4 are from the modular.
The first part is made entirely by the modular.  Then, enter the drums, made of TR-808 samples from NI and a synth pad from Korg Wavestation softsynth.
The main melody is played by the Korg SQ-1 in random mode and relies heavily on Rings.
Winds track consists of three sounds recorded separately and stacked.  They are made thanks to a white noise source, the filter from the DIY-101 module and the phaser.
Bass drone and the other bass pattern use the Doepfer VCO and the filter.  Rampage was used as  envelope generator.  The  movements effects on the bass drone are performed thanks to TAL Filter 2, great little toy.

DAW : Reaper
Synth : Modular Synth Suitcase, Korg Legacy Collection Wavestation, NI Kontakt 808 kit
Effects : ReaEQ, ReaXComp, NI Supercharger, TAL Dub II, TAL Filter 2, TAL Chorus-60, Voxengo OldSkoolVerb, Thomas Mundt LoudMax,

Photo : HAVOC project NASA / SACD

Saturday, 1 September 2018

DIY-101 synth voice - part 2

This is the second part of the making of my Doepfer DIY synth based module.  You can find the first part here.

Finished module in action.
Now is the time for some cabling.

There are 7 connectors on the circuit, numbered JP1 to JP7.  Moreover, I have to connect the 5V and common ground.
With the synth, I  ordered the set of dedicated flat cables to ease the interconnection.

I started with Ground, 5V and all connections that were not linked to a specific connector.

Before cabling connectors.
Pin 1 above
Then I did cable connector after connector, cutting the wires, splitting the flat cable, stripping with my nails and finally soldering … One wire at a time, in order not to lose track. 
I started with JP2 and JP3, as I reckoned they connected mostly to pots and jacks below the circuit and that would prove difficult if I finish with them.
All ground pins on those connectors were ignored as I chose to have a common ground from the 5V power connector.

Pin 1 below

Thanks to the schematics from M-19, I noticed the dot indicating the first signal (red line) on the connector was sometimes above or below in the Doepfer documentation tables.   I fell in the trap on my first schema.

Ongoing cabling

I also verified twice each wire connection before soldering.  And I did well. I noticed a couple of mistakes on my schematics this way.  I annotated my drawings along the way.
Annotated schematics

Bob checks a solder joint

 Bob managed to get some useful Quality Control time. 

My first tests showed I made some minor mistakes :
- switches pins are reversed with regards to the switch handle position;
- a couple of signals were wrongfully soldered on the switch pin of the jack, instead of the tip;
- I detected one or two bad solder joints that escaped Bob's control.

Here is the finished product.


Bob fixes knobs.

Finally, I let Bob place the knobs.

Tuning the VCO proved problematic.  Even after I let the board heat up for 20 minutes, I really had a hard time approaching the 1V/oct slope.
I'm not 100% sure yet, but the VCO is not very stable and slowly drifts, even with the tempco option installed.  Is the circuit defective ?  Is the design problematic ?  Was it damaged during my early tests with a home made power supply ?  I don't know.  The rest works like a charm.

Tuning the beast

Finally, all the Eurorack power flat cables I got for my DIY modules were 16-pin to 16-pin.  And JP1 is aligned in a way it is not possible to use a 16-pin connector properly.

I had to divert the 10-pin to 16-pin cable from Rings to put the module in place.

Time to buy some 16-pin to 10-pin cables next time I guess.

Finally in place.   Ready to wiggle.