zerosum inertia zi54 price : $500.00

this is the 54 mkii.
originally produced by metasonix with permission granted to zerosum inertia to put back into production and make available once again.
the circuit design is based on the wien bridge circuit created by max wien.
metasonix applied that concept along with ideas of his own to create an experimental musical instrument for eurorack modular synthesizers.
the best way to describe the function of the 54 is an audio processor that can also be a sound generator.
when used as an audio processor it can be used as a bandpass filter and distortion device.
when the resonance is at about 10 o clock it will oscillate to become a sound generator and add resonant squeal to the filter frequency.
this version has the feedback loop and cv for the drive control.
in this version, when the switch is in the upward position pointing north that routes the output of the 54 back into the freq cv which creates instability and more gain. think of it as a color switch or a wild card.

the drive cv is there to add choppy amplitude modulation.
this input feeds control voltage into the grid of the 6ak5/5654 pentode and is done with the tube and sounds different on every unit due to the unique nature of the vacuum tube.
this cv input is unlike any other vca you have encountered and is not meant to be a precise voltage controlled amplifier. it is there to add rhythmic amplitude modulation and trem effects.
there are no exponential converter chips or otas used.

the freq cv is done with a 5c3/2 vactrol and does the classic splats and bonks when fed a sharp snappy plucky envelope.
it is best to use a modulator with a variable curve and onboard processing to dial in the best curve and behavior of the modulation.
vcs and maths works very well with this circuit and all other vactrol based cv circuits.
hitting this with creative rhythmic pulses creates the classic lazer zaps and liquidy bubbley goopy sounds found in electronic music classics.
vactrol cv is a slewed unique indescribable experience for the experimental musician.

the sound is all coming from a 19kg8 and 6ak5/5654.
the 19kg8 is a tube containing a triode and a pentode which is where the filtering and oscillation happens.
this tube is responsible for the freq and res controls.
the 6ak5 or 5654 which is the miltary version of the 6ak5 is responsible for the clipping and overdrive and amplification effects.

recommended starting positions for the knobs are with freq at about 2 o'clock, res at about 10 o'clock, drive and output at about 3 o'clockand the toggle switch down/south.
slowly turn the the freq knob then slowly turn the res knob to get a feel of how they interact with eachother.
then increase the drive knob and ovserve how the foldover and clipping distortion.
now flip the switch up/north and observe how much the sound changes when turning the drive and out level knobs.

this module requires 400 ma of + and - 12v.
make sure you have a high quality power supply and are leaving headroom and not using it to the full capacity.
linear power supplies are recommended and what the module has been tested and used with.
22hp wide.
33mm rear depth.