The HP40 is a high pass filter based around the SSI2140, the successor to the legendary SSM2040. The 2040 is the best sounding filter chip that came out of the 19070s and the 2140 takes the original design and adds CV controlled Resonance. The HP40 is a small format filter that does not cut corners. The Input is set up like the Dual SeM20, when the indicator line is straight up the input is at full, anything past that will over drive the input. The Frequency CV responds to both positive and negative voltages while the Resonance CV is 0-10V. The HP40 will track 1V/Oct with internal temperature compensation. There are 3 output types and 4 outs; 12 and 18db have one output each and there are 2 24bd outputs. While using the 24db output you can take the second and send it to the LP40 to create a variable band width Band Pass while still using the 24db High Pass. The HP40 is a unique filter. There have been very few High Pass filters over the years, let alone ones that resonate. The High Pass filters in the Roland polys were crucial their sound and with the HP40 those types of sounds are easy to make. But the real magic of the HP40 happens with you turn up the Resonance and let it go; from fragile and brittle leads that vanish into the air, to sweeps and hollow thumping kick drums the HP40 is in a class by itself.
