Iron Ether - Pithoprakta - Trigger / Gate Sequencer

Published on Dec 29, 2015 simon

"Here's an overview of the soon to be released Pithoprakta by Iron Ether, the renowned purveyor of stunning effects pedals.
This is Iron Ether's first foray into making Eurorack modules... and it's a belter.
Please note, this video features the pre-production panel, it will look different to the finished article.

I kept everything pretty simple throughout so that it's easy to tell what's going on, and for the main part I just used it to trigger the drums of my old Syncussion DRM-1.

0:00 - Triggering drums.
2:48 - Triggering drums, with CV control over Probability.
3:06 - Triggering drums, with CV control over Probability, and CV control over Looping.
4:10 - Triggering envelopes for Akemie's Castle, and CV out to Akemie's Castle.
4:58 - CV out to oscillator.
5:45 - CV out to oscillator, and triggering drums.
6:57 - Gates mixed, quantised and sent to Oscillator.
7:54 - Gates mixed, quantised and sent to Oscillator, and CV out to filter cutoff.
9:00 - Clocked at audio rate with 8 outputs sent to a 8 way switch.
11:30 - END"

"Pithoprakta is a probabilistic gate/trigger sequencer, able to create 8 channels of gates or triggers whose probability/density can be defined by the panel controls and/or CVs. The looping function will loop up to 64 steps, the loop length being CV-controllable in powers of 2, and an external gate signal can be used to enter/exit looping seamlessly.

The Probabilities of Channel 1 and 8 are defined directly by the panels controls/respective CV inputs. The other 6 channels' probability levels are interpolated from these two values, so if channel 1 is at 10% and channel 8 is at 80%, channel 2 is 20%, channel 3 is 30%, etc. The thinking behind this is that it allows you to have 8 channels with different probability, or the same if you choose, which can be controlled by just two modulators, rather than requiring a separate modulator for each channel - good for smaller systems or if you just don't want to tie up a ton of modulation sources just to control this one module.

Div mode clocks the 8 outputs, each with a different division of the input clock - divide-by-two down to divide-by-sixteen. The upper 4 channel outputs are "on beats" and the lower 4 channels are "off beats," allowing the user to easily create drummer-like rhythms which evolve over time or improvise infinitely.

Once loop mode is active, the Probability controls become "probability of change," in other words they control the likelihood that a given step of the loop will be overwritten, rather than whether that step is on or off. To keep from deleting the loop as soon as one enters looping mode, the probability controls are ignored when entering loop mode until the user turns them down to 0% and back up.

Ideas for usage
Create rhythms that sound like an improvising human drummer, without resorting to preset sequences. Beats can evolve over time in a way you control.

In div mode and with looping off, it functions as a clock divider, with probabilistic skipping.
8 channels of random triggers or gates with CV-controllable density - clock it fast and try using them to gate WMD Digital VCAs for low-level granular synthesis.

Record two gate sequences from another module into Pithoprakta by sending them into the probability CV inputs. You'll get six new sequences from outputs 2-7, each resembling the "parent" rhythms to a varying degree.
Use it as an evolutionary algorithm that's very open and low level - with 8 outputs and 6 inputs, everything is exposed so it can work well in more experimental use cases.

Mult the gate outputs to a CV mixer, to generate up to 64 step CV sequences with direct control of the probability of change over time.

Can be clocked up to 1000 Hz, so it works as an 8 channel audio source, with various flavors of digital noise and octave generation, morphable with CV.

Physical details/specs
16 HP
Full size attenuators for all three CV inputs
Potentiometers are metal shaft, bolted to panel, 100,000 cycle life
Very skiffable due to single-PCB parallel construction
Reverse polarity power protection, full over/under voltage protection on all CV/gate inputs
Jumper selection for internal/external 5v
Header for the 8 outputs allows for future expander connection"