Streams Magpie plate

Dual dynamics gate

Streams provides two channels of extremely flexible signal dynamics manipulation.

Each channel consists of an analog voltage-controlled filter and amplifier (VCFA). The response curve of the amplifier section is continuously variable from exponential to linear. The amplifier gain is directly controllable from a CV input, through an attenuverter. But what makes Streams truly unique is the multi-purpose EXCITE input. The signal routed to this input is analyzed by a micro-controller and converted into internal control signals for the VCFA, making Streams a very versatile module:

Envelope mode: the EXCITE input works as a trigger input, triggering an internal AD envelope routed to the gain and the filter cutoff (in variable amount). This makes it immediate to shape the output of a complex oscillator into notes.

Vactrol mode: the EXCITE input is processed by a digital model of a resistive opto-isolator (Vactrol), controlling the gain and the filter cutoff (in variable amount). The digital emulation allows the modification of properties of opto-isolators - such as response time - which are otherwise difficult to control.

Follower mode: the envelope and cutoff of the EXCITE signal is measured, and applied to the signal on the VCFA input.

Dynamics processor mode: the VCF is disabled, and the VCA is used to control the dynamics of the input signal. An intuitive control scheme allows the compressor to be used either for peak reduction/limiting operation; or for boosting signal levels with soft-limiting. The EXCITE input works as a sidechain.

Each channel input is normalled to +5V, allowing the module to be used for applications such as:
* CV exponentiation.
* Envelope generation.
* Signal slew-limiting with the vactrol model.
* Filter control and auto-wah.

In addition, Streams' LED display can be used as a bargraph to monitor signals on any of its inputs and outputs.

Inputs/outputs
* Multi-purpose EXCITE input.
* DC-coupled Audio/CV input (normalized to +5V constant voltage).
* VCA gain CV (normalized to +8V constant voltage).
* Output.

Controls (per channel)
* Digital control mode selection.
* Response time / compression threshold.
* Modulation amount / compression ratio and makeup gain.
* VCA gain CV input attenuator.
* VCA exponential to linear response curve.

Technical characteristics
* Analog signal path.
* All inputs DC-coupled.
* 12-bit, 31kHz EXCITE signal acquisition (for metering and following).
* 16-bit, 31kHz control voltage generation.
* Cortex-M3 ARM processor.
* Open-source hardware and firmware.
* 12-HP.
* Easy firmware updates through an audio interface.
* Current consumption: +12V: 100mA ; -12V: 30mA.

http://mutable-instruments.net/modules/streams