MATRIXSYNTH: Orpho VLPF - Eurorack Vactrol Low-Pass-Filter

Tuesday, June 11, 2024

Orpho VLPF - Eurorack Vactrol Low-Pass-Filter

video upload by HOX808

"The Orpho VLPF is an active low-pass filter module for modular synthesizers in the Eurorack format. It is a fully resonant low-pass filter that uses vactrols as controlling elements for the filter frequency and resonance. The two potentiometers for frequency and resonance set the desired filtering. The more they are opened, the more light falls on the two LDRs. By changing the control voltage, frequency, volume, and resonance change simultaneously. The potentiometers allow the adjustment of the light impact to achieve fine gradations. The two LEDs are exposed to provide a visual representation.

A fully resonant filter shows significant amplification at its resonance frequency, leading to a sharp peak in the frequency response. The quality factor (Q-factor) determines the sharpness of this resonance: a high Q-factor implies a sharp resonance, while a low Q-factor results in a more damped resonance. Fully resonant filters can also tend to oscillate in the absence of an input signal when set to maximum amplification, a phenomenon known as self-oscillation.


A vactrol is a combination of a light-dependent resistor (LDR) and a light-emitting diode (LED) housed in a common, light-tight enclosure. Increasing the LED brightness decreases the resistance of the LDR. This can be used for various circuits that rely on variable resistances. These components are known for their "soft" sound, as they are linear elements that do not cause distortion.

Module Overview:

- VLPF with vactrol control
- Fully resonant filter
- Self-oscillation possible
- High-quality potentiometers
- CV input
- Two LEDs behind the front panel for visual representation
- Amazing organic sound, ideal for drum snappy sounds and bongo sounds

Enclosure and Power Consumption:

The VLPF is 3U high, 8HP wide, and 18mm deep. Power consumption: +12V, -12V | 40mA."

No comments:

Post a Comment

Do not insult people. Do not ask if listings are still available. Click through auction links to check yourself. Posts and pics remain for historical purposes only. To reduce spam, comments for posts older than one week are not displayed until approved, usually same day.


Switched On Make Synthesizer Evolution Vintage Synthesizers Creating Sound Fundlementals of Synthesizer Programming Kraftwerk

© Matrixsynth - All posts are presented here for informative, historical and educative purposes as applicable within fair use.
MATRIXSYNTH is supported by affiliate links that use cookies to track clickthroughs and sales. See the privacy policy for details.