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Scanner - 4U Four Channel Scanning VCA PCB & Panel | Hollasynth

Scanner - 4U Four Channel Scanning VCA PCB & Panel | Hollasynth


The Hollasynth four-channel scanning VCA + Mixer in Loudest Warning 4U format. This is a PCB/Panel set in the 4U: Loudest Warning format.

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Brand Hollasynth

The Hollasynth four-channel scanning VCA is a version of Jurgen Haible’s Interpolating Scanner idea, in 4U Serge-compatible format, complete with a beautiful front panel by Loudest Warning

It is a four-channel voltage controlled crossfader. As the scan CV is swept from 0V to 5V, the mix output fades from channel 1, through a mix of channel 1 and 2, to channel 2, then fades to channel 3 and finally channel 4. In addition to the main mix output, there is an individual output for each channel. Front panel knobs provide an offset and attenuversion on the scan CV.

The gain of each channel is also individually controllable, so the module can be used as a four channel VCA as well. A switch allows the scanning control to be disabled so that only the VCA CV affects channel gain. Finally there are attenuator for the gain CV and initial gain knobs on the front panel.

What can I do with it?

Probably more than I can! But try some of these:

  • Crossfade between the wave shapes of a VCO for voltage-controlled morphing, e.g. from sine to saw to triangle to square and back. Like this.
  • Crossfade between up to four audio sources under voltage control. Like this.
  • Voltage controlled CV mixing. The inputs and outputs are DC coupled so you can use the module to mix and morph between CV sources
  • Voltage controlled signal switching. By appying stepped CV to the scan input, e.g. from a sequencer, you can switch between signals rather than fading… if you get the CV set up just right!
  • Audio Waveshaping. Patch fixed voltages or LFOs or whatever you like into the signal inputs. Send an audio rate 0-5V sawtooth into the scan CV. Use the mix output as am audio signal. Like this. Or like this. (Thanks, Loudest Warning!)

How does it work?

The scanner contains four linear VCAs, one per channel, based on the LM13700 IC. Each VCA is controlled by the sum of two CVs: the direct VCA CV and the scanning CV. The scan CV is provided by a version Don Tillman’s beautiful scanner implementation, used with his kind permission. (But please don’t bug him if you have issues with the module!)


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Brand Hollasynth
HP 4
Additional Resources Hollasynth GitPages

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