PreSonus Studio Channel Vacuum-Tube Channel Strip High-voltage Class A 12AX7 vacuum-tube mic/instrument preamplifier Gain, Tube Drive, HP filter, -20 dB pad, phantom power, polarity reverse3-band EQ features variable-Q on mid-band w/ peak/shelving on high- and low-bands Variable VCA compressor with Auto Attack/Release and Soft/Hard Knee 3-band EQ with parametric mid and semi-parametric, shelving/peak low and high bands Instrument, line, and mic inputs 1U 19 rack-mountable, rugged steel chassis