HiPass is a quad fixed frequency high pass filter. The two first sections are 3-pole filters (-18dB/oct) cutting at 30Hz. This removes low frequencies generated by resonant filters, FM synthesis and DC offsets from your audio signals. Use them to process the main stereo output from your modular system and remove non-audible signals that limit your headroom! The bottom two sections are 3-pole filters cutting at 100Hz. They are designed to work exactly like the low-cut sections on your favourite mixing desk.