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.

Vactrol:

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.

https://www.orpho.de/vlpf/"