HERITAGE AUDIO SYMPH-EQ Asymptotic stereo bus equalizer

Heritage Audio has successfully replaced the Baxandall topology with a functional, much more musical equivalent implemented in a 1U master bus/mastering rack space.
The asymptotic stereo equalizer gets its name from the shape obtained by different frequency range curves:
- The amplification or cutoff amplitude grows until the asymptotic value is reached, keeping the ultra highs and sub-bass always under control.The sound can only be described as tight, smooth and natural. This use of parallel equalization to achieve the desired response curves results in exceptionally low phase deviation and artifacts. An intelligent circuit arrangement allows a maximum boost/cut of 10.5 dB in 0.5 dB steps. The main rotary switch sets 1dB steps while the 0.5 knob adds half a dB to the main reading. The CUT knob turns the increase into a decrease. Six strategically selected frequency choices per band are available (8, 10, 12, 15, 20, and 24 Khz on the upper range, and 470, 360, 220, 110, 60, and 20 Hz on the lower range).
In order to properly control sub- and ultra-high frequency content, additional high-pass and low-pass filters have been added on two concentric rotary switches at 12 dB/octave. 5 more OFF frequency choices are available on each (10, 12, 18, 22 and 30 Khz on the low pass, and 160, 82, 47, 20 and 15 Hz on the high pass). It features the same exclusive Oxford-built Carnhill input transformers found in the Successor.
The outputs are driven by Class A Type 73 output amplifiers, built with the same Carnhill output transformers as the rest of the family. Most importantly, and this is where the Symph EQ really shines, is that it has built-in Mid Side (M/S) capabilities.The secondary filter automatically transforms to an elliptical topology when M/S is engaged.