With the Erica Synths Fusion VCF you get a voltage controlled filter based on a tube. In this bandpass filter, the tube functions both as a preamplifier and feedback loop. The Fusion VCF tube can also be used as a mixer with the two audio inputs. One of the two CV inputs for the cutoff is adjustable with an attenuator. The Erica Fusion VCF can be integrated into any Eurorack modular system, but requires an additional 6V AC power supply for the tube heater, such as the Erica Synths Fusion 6VAC PSU.
Erica Synths Fusion VCF v2