Masters Research

CMOS synth update

After further exploration of the cmos chips, additional components were added to the circuit. 

A 40106 provides six oscillators using various different capacitors to give a variety of frequency ranges. The input and output pins of each oscillator were soldered to headers, allowing the frequency to be set by altering the resistance between them. Modulation inputs were also included for frequency modulation of the oscillators. Several R2R ladders and a second 4040 were also added for creating intervals and harmonic divisions.

In addition to this, a 4070 was used to provide four XOR gates, creating an effect similar to ring modulation. The added harmonics produced by this chip create a range of rich textures and noisy sounds, especially when the four gates are chained sequentially.

After playing with this chip I realised that more complex and interesting routings could be possible if I had duplicated the outputs. This was solved by adding rows of connected headers, duplicating the signal, allowing for the splitting of signal paths and creation of parallel layers.

Two passive mixers allows for polyphonic layering of sounds. Each mixer has four inputs and four duplicates of the mixed output. The use of two separate mixers allows for the creation of sub mixes and feedback.

The eight touch contacts allow for gating and manipulation of signals, providing human controlled variation of resistance. However, the performer cannot remove the hand to manipulate other parameters whilst retaining the connection. This could be solved by using either a sample and hold circuit to retain values when removing the fingers, or a flipflop gate to create a toggle like behaviour for the contacts. This could also be solved by resting conductive objects over the contacts or using magnetic patch cables.

Four patchable LEDs were also added for providing visual feedback. They can be routed to display specific outputs or visualise signal flow whilst patching. The decision to make the visual feedback optional helps retain the unpredictable nature of the instrument's interface whilst shifting focus toward the sound.

The use of linear pots compliments working with low frequencies, pulses and rhythms. The squashed range makes it harder to control higher frequencies accurately and consistently. This is particularly interesting as the reproducibility of actions reduces as the values of the slider get higher.

The combination of XOR gates and unconnected wires tends to create dense, rich layers of noise  accentuated by the distortion of the amplifier circuit and small speaker.

When using unconnected wires the movement of cables and proximity to the circuit becomes amplified and starts to influence the sound.

In this way, the unpredictability of the circuit is often not random but is intrinsically linked to the environment. This gives the instrument a sense of presence and life as it reacts to the changes in its surroundings. 

Once a patch reaches a certain stage of complexity the significance of the individual connections, components and actions become blurred and difficult to navigate. At this point, the performer has to rely on intuition and awareness, reacting to changes in the system spontaneously. 

The process of building and exploring this circuit has facilitated thinking about the layout and mapping of modular interfaces. This involved the creation of different sections that provide specific functions and contemplating their possible uses and combinations