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PHOBoS | NANDulator


What is a NANDulator?

The NANDulator is a simple digital circuit capable of producing rather complex squarewaves. It is designed to be used as a little synthesizer producing a wide array of sounds, varying from simple drones to noise, Atari Punk Console like sounds, bleeps and blips and it can even produce vowel like sounds. What sets it apart from more conventional synths built around the same chip (4093 QUAD NAND) is that it incorporates a very unique design which makes its behavior rather chaotic and unpredictable and it is the main reason it can produce such a wide array of sounds.

How does the NANDulator work?

The NANDulator has 3 squarewave oscillators that are combined together to produce a rather complex square-wave signal. The two main oscillators (A & B) are similar but use a different set of timing capacitors for a wider frequency range. These oscillators are the main core of the NANDulator and responsible for its complex nature. Each oscillator is actually a combination of 2 different oscillators built around a single NAND gate. Sections A1 and B1 are oscillators with a fixed frequency but variable duty cycle. Sections A2 and B2 are oscillators with a variable frequency but have a fixed 50/50 duty cycle. Because these sections (A1 + A2, B1 + B2) are both built around single NAND gates (D & C) they interact with eachother which makes the resulting output signal very unpredictable.

These already complex signals produced by the 2 main oscillators are 'mixed' together with another NAND gate (A) to produce an even more complex squarewave signal. This signal is then used to modulate a third oscillator built around another NAND gate (B). This oscillator also has a variable frequency and a fixed duty cycle but it has a much larger range than the two main oscillators and the effect it produces can sometimes sound very similar to a filter.

The output signal of this third oscillator is then attenuated and can be further adjusted with the LEVEL pot. (P6) before it is buffered by a transistor. A capacitor (C6) provides AC coupling and the two 470 ohm resistors protect the output against shorts to GND. (which also happens when a mono jack is plugged into the Line Out socket)

The slide switch (S2) can be used to mute the sound but when it is muted it can be bridged by the momentary button (S1). This makes it possible to manually produce bursts of sound.

How does the mini 8x8 LED Scope work ?

The mini 8x8 LED Scope uses 2 decimal counters (IC2, IC3) to control an 8x8 LED matrix. The outputs of one counter are connected to the rows (anodes) and the outputs of the other counter are first inverted (IC4) and then connected to the columns (cathodes). Because only one output of each counter will be high at a time only one LED will light up. However, the CLK inputs of these counters are connected to the outputs of the main oscillators and because these oscillate at a high (audiorate) frequency it will appear as if more LEDs are on at the same time. Because the output of the main oscillators isn't a regular squarewave and the frequencies can differ from each other all kinds of interesting patterns emerge that are in sync with the audio.

What is the function of the mini 8x8 LED Scope?

The LED scope is a fun visualizer that does not function as a regular oscilloscope. Instead it shows the correlation between the frequencies of the 2 main oscillators (A & B). Therefor the visuals can vary from simple moving or static lines to very complex chaotic patterns. It can be helful as a tuning aid but it is mainly intended for visual entertainment. In other words, it just looks very cool.

Does the NANDulator produce a Stereo signal?

No, the NANDulator itself produces a mono signal but both a stereo or mono jack can be plugged into the Line Out socket. When a stereo jack is used both the Left and Right channels will receive the same signal.

What is the level of the Output signal?

The NANDulator produces an AC coupled (complex) squarewave signal with a maximum level of roughly 3.5Vpp (Pro line level). But it can be adjusted to a lower level.

What is the recommended Supply Voltage?

The NANDulator is designed for a 9-12V DC single supply voltage but it should also work on 5V and possibly even lower. However, on a lower supply voltage the frequencies of the oscillators will be higher and the LEDs will be less bright. It has a 2.1mm socket for a wallwart supply but could be powered from a single 9V battery as well. And although the used chips should be able to handle a maximum voltage of up to 18V it is advised not to exceed 12V. Also the Capacitors supplied with the NANDulator Kit have a maximum rating of 16V.

Is this some kind of alien technology?

The circuit is designed by PHOBoS and it is has been speculated that he is not truly human, so it might as well be alien. The full capabilities of the NANDulator are yet to be discovered and there is a possibility that it can cause alterations to the very fabric of space-time itself.
Engine TypeDigital
Engine Detailed3 OSC, Square
Key typeN/A
Extra infoDIY
Legend: Obvious Y: Yes, N: No, N/A: Not Applicable
VCO Voltage Controlled Oscillator DCO Digital Controlled Oscillator
LFO Low Frequency Oscillator Sub Sub Oscillator
VCF Voltage Controlled Filter VCA Voltage Controlled Amplifier
Velocity As with a piano, the harder you hit a key, the louder the sound, unlike most organs which always produce the same loudness no matter how hard you hit a key. Aftertouch Pressing a key after you activated it. Channel Aftertouch, no matter which key, it will send a Channel message. Poly Aftertouch, sends the pressure per key instead of the whole channel.
Values for OSC, LFO, Filter, Envelope are per voice unless stated otherwise.

Manuals, patches etc.


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