## Thursday, 17 October 2019

### Dual LFO/VCO

This is an upgrade for the NLC thru-hole dual LFO and the thru-hole dual VCO.
The circuit is based on the thru-hole dual VCO but can be switched to operate in 3 ranges; 15Hz-10kHz, 1 minute per cycle to 25Hz (approx) and down to 20 minutes per cycle for the slowest.

Both have CV inputs with attenuating pots and sync inputs. The sync is quite hard and attempts to momentarily ground the timing capacitor, how successful this is depends on what else is going on. At slow LFO rates it works more like a wave-shaper.

The outputs are sine, stepped, square and triangle. The stepped outputs are S&H circuits sampling the sine-waves. They are clocked by the other oscillator, there is no external clock input :)

There is provision to install 1k tempco resistors if you want to try for 1V/oct tracking. Don't expect good tracking over more than 2 octaves tho, there are no matched transistors onboard. If such niceties are not so important, simply leave off the 1k tempcos and install regular 1k 0805 resistors on the bottom of the engine PCB.

PCB set = USD20
panel = USD20
Assembled = USD180

## Saturday, 7 September 2019

### Mobius PiLL

This is a chaotic noise module, it is generally not very nice unless you are into noise. In which case, hello!!

There are several papers describing ways to couple PLL (phase locked loop) ICs to create chaos. I have been sitting on a stack of them for years but found the actual circuits quite limited in a synth.

Eventually it clicked that the low-pass filter needed to be a bit fancier than a pot and a capacitor, so this version gets two Buchla style low pass gate/filters.

The circuit contains two PLL chips and two low pass filters. The PLLs are voltage controlled together, the filters are controlled individually.

Normally in a PLL circuit, the output of the phase detector goes thru a low pass stage and then the output of this is used to control the VCO. In this version, the low pass filter outputs are fed to the non-inverting input of an op amp for it's own VCO and the inverting input of an op amp for the other VCO. Maybe the pic describes it best, this is from Intermittent Chaos in a Mutually Coupled PLL’s
System (Shirahama et al), tho I have seen similar circuits in other papers.

It doesn't need an input signal to lock to, it can run on its own, but it can be fun to give it a signal anyway. The other inputs are for Freq CV, LPG1 CV and LPG2 CV. Two of the outputs are from the LPGs and two are from the PLL VCO, these two are pulse/squarewaves, very nice for feeding into filters.

The PLLs and filters are all vactrol controlled but the PCB is a unpatented NLC black-box design, so no need to buy any expensive vactrols.

PCB set = USD23
Panel = USD22
assembled = USD200

## Tuesday, 20 August 2019

### Sloth DK

6HP Sloth DK

For those that have not seen the Sloth before - this module is a simple chaos circuit that puts out 3 slowly varying and never repeating CV signals. It is not random as the chaos occurs within a bounded region and generally moves in or between two strange attractors or wells.

It is really slow and can take from 8-20 hours to complete a chaotic orbit.
Generally the output signals range between +/-4V, tho mostly around +/-2V.
The middle output is simply a mix of the two main outs, passing through the pot to attenuate the signal if you wish (and it helps hold the PCB to the panel). It is a little hotter and more complex that the individual outs.

There are no inputs and no way to control it.

The large capacitors sticking through the panel never see more than +/-0.15V in normal use. Nevertheless you probably should not take the module out of the case and rest your tongue across their leads.

PCB = USD12
Panel = USD20
assembled = USD100

Build guide on wiki

flamingo situation.......

### 1U Signum

In the simplest sense, this is a switching module. It is a little different though because it has 3 states rather than just on/off:
${\displaystyle \operatorname {sgn} (x):={\begin{cases}-1&{\text{if }}x<0 amp="" if="" text="" x="">0.\end{cases}}}$

In this case, the module uses approx 1V, rather than 0V, as the switching point, so that it can be controlled by gates. It is simple to bring it back to 0V for those who think it should be.
Also the '0' state is really a result of the diode voltage drops rather than any circuit design trickery.

The signal on the bottom input is fed to the switch of the Switch jack (oh yes) so the incoming signal can switch itself without any help.
The three states actually mean there is a flat spot at the switching point, so the circuit can be used for audio but at slow rates there is a click, so it is far better suited for CV processing.

This circuit originally was used as the nonlinear element in the Primal Hyperchaos and two of them in the Hyperchaos Deluxe. I quite like it on its own, so the Signum Hyperchaos brought the signum section to the panel where it could be used as a stand-alone module. This version drops the chaos and just has the Signum.
The switching is done by diodes rather than a dedicated IC.

The panels are available in white/gold and black/gold in both Pulp Logic and Intellijel formats. Please specify which colour and which format you want when ordering.

Also the PCBs are the same for both panel formats and use a standard Eurorack power connector. There is no provision for the Pulp Logic 3 pin power connector.

PCB and panel set = USD10
Assembled = USD55

Build Guide on wiki

### VCAs

This 8HP module contains 3 VCAs and a fuzz/distortion. The VCAs are similar to the ones used in the NLC Cluster; simple OTA based but work very well.

The fuzz/distortion is part of the bottom VCA and is a typical diode based affair, on the PCB the space for these are thru-hole so you can install Si or Ge diodes or LEDs. Turn the Fuzz pot to 0 if you just want VCA.

PCB = USD18
Panel = USD20
assembled = USD160

### Beat Freq

The idea for this module came from a schematic that has been floating around the web for years - 'beat frequency indicator'
The idea is to feed the circuit two signals and depending upon which one had the higher frequency the ring of 4 LEDs would light up in a clockwise or anti-clockwise direction. The speed of rotation would indicate how close or disparate the frequencies are. If the signals have the same frequency then just one LED is lit.

The original circuit used 74xxx series ICs for the logic, so it was simple enough to find the CMOS equivalents (sort of), then add gates corresponding to the LEDs and use the spare outputs of one chip to feed pots to make sequences. Then for good measure a discrete XNOR circuit was added to give a pseudo ring-modulator output based on the 2 incoming signals.

In operation this module is quite unique; the CV signals return to 0 between each step, the length of each step can vary depending on the incoming signals. Gates come in spurts. The circular LED display jerks around, sometimes it completes several revolutions confidently and then stutters between two stages, sometimes it shimmers on one spot.

At both audio rates and clock rates, this module is quite unpredictable but always seems to be putting out useful signals.

PCB = USD18
Panel = USD20
assembled = USD160

Build guide on NLC wiki

This video is from the 1st version proto-type, tho little was changed in the production version -

## Monday, 12 August 2019

### 1U 6HP Difference Rectifier

Those that build a lot of NLC modules will know this is one of my favorite circuits. The diff-rect has appeared on the Neuron, 1050 mix/sequencer, triple Sloth, GENiE and 8 of them make up the Let's Splosh.
It is great for mixing audio and/or CV signals to get all kinds of unexpected and interesting results. This page from 2012 on my old Pinky site has some more details.

The panels are available in Pulp and Intellijel formats and in white/gold or black/gold, please specify when ordering.
Please note, the PCBs only have eurorack 10 pin power connectors, not the Pulp Logic 3 pin type.

PCB & panel set = USD10
assembled = USD55

Build guide on wiki