Erica Synths Bullfrog Highpass VCF Voice Card expands the sound processing capabilities of the Bullfrog by adding a high-pass filter. This allows for exploration of high-frequency and bandpass filtering. The card features typical VCF controllers - CUTOFF frequency, RESONANCE, and the level of the controlling CV. A CV source switch enables selection from three sources: Envelope Generator 2, Sample & Hold LFO - a pulse generator in the Sample&Hold "module." The Bullfrog Highpass VCF Voice Card includes internal audio connections to simplify patching.