This all-analogue processor is designed to massage, mangle and mutilate your audio.
The filter/distortion effects unit can be a bit of a misunderstood beast. You won't often see them amongst the racks of compressors and EQs in a professional studio. To be fair, there aren't that many around, at least not in a rackmount format. Quite often they are made by smaller manufacturers. Long-discontinued examples can reach cult-like status (and prices) — the Schippmann Ebbe und Flut and Mutronics Mutator are prime examples. And yet, in the studio, they can offer both tonal and dynamic shaping that would otherwise take two or three different effects units to achieve. The Iotine Core 4 is the latest contender in a cult class of analogue processors.
Packed into a 3U rackmount box, the Iotine Core (I'll drop the 4 for simplicity) is a fine-looking effects unit. At its heart are three interconnected channels, comprising multi-mode filters, distortion circuits and VCAs. Two of the channels are almost identical and are designed to be used as dual-mono parallel processors. The third channel, used in parallel or series with the others, also contains a multi-mode filter as well a frequency divider and multiplier. Finally, two modulation sources, in the form of an envelope follower and an audio triggered envelope, are available for filter and amplitude modulation.
Contrary to current trends, the Iotine Core doesn't have a modular-friendly arrangement of inputs and outputs on the front panel — there is one front-panel socket, which I'll discuss later, but in general everything is designed with rackmounting and permanent patching (either directly to your mixer and sound sources, or to a patchbay) in mind. At the rear, there are: two mono balanced inputs, which can be routed to various key points in the signal path using front-panel switches; four balanced outputs, which provide flexibility to route audio from each of the three channels, or from a summed Mix output; and, finally, two unbalanced inputs, which allow you to patch signals directly into the envelope and envelope follower trigger circuits. All audio connections are on quarter-inch jacks. The power supply is internal and all that's needed is a standard IEC power lead. Yay!
The two main channels are identical except for their saturation circuits, which I'll come to in a moment. A two-way switch toggles the channel input source between the two audio-input jacks on the rear. This allows quick switching between a dual-mono configuration and parallel processing of a single signal, and by patching the output of one filter to the input of the other, it's possible to have the channels operating in a serial configuration too. An input amplifier allows you to boost or attenuate the signal before it goes into the filter, and a pair of helpful LEDs shows you when a signal is present and when the filter is beginning to soft limit.
The 12dB-per-octave resonant multi-mode filter can be switched between low-, band- and high-pass using a three-way switch. The filter isn't self-resonant. Cutoff can be modulated by either the envelope or the envelope...