The Heritage Audio Symph Eq is a dual-channel Asymptotic EQ with Mid/Side mode offering precise shelves and 2-pole HPF and LPF controls.

The Heritage Symph EQ takes its cue from the legendary Baxandall topology but uses a more modern and clever implementation. This new asymptotic topology provides surgical yet musical curves with super low phase deviation and artefacts.

Asymptotic EQ: A Modern Take on Baxandall

The Symph EQ shares the main principle with Baxandall topology with offering Low and high shelves to add more weight and air to the music. These pleasing curves with the low cost of Baxandall circuits made it a favourite on Hi-fi systems. 

However, Asymptotic EQ provides the same benefits while keeping the sub and high regions controlled. By using parallel EQs to obtain the desired response curves, the Symph EQ manages to offer a tight, sweet and natural sound resulting in extremely low phase distortion. 

Surgical and Musical EQ.

The Symph EQ offers boosts and cuts of up to 10.5dB in 0.5dB steps. Gain is achieved by a combination of the 1dB/step rotary switch and a 0.5 button which adds 0.5dB to the selected value. A cut button modifies the boost into cuts. Each band offers a generous choice of centre frequencies ranging from 20, 60, 110, 220, 360, 470Hz for the low shelf and 8, 10, 12, 15, 20 and 24 kHz for the high shelf.

Furthermore, the Symph EQ adds additional controls for the extremities of the frequency range with both high- and low-pass filters accessible on dual concentric rotary switches. These filters both share a 12dB/oct slope and include a choice of 5 frequencies (Low: 15, 20, 47, 82, 160Hz / high: 10, 12, 18, 22, 30kHz). Each filter also includes an OFF position.

Full of Mojo and M/S processing

The Symph EQ also includes the same exclusive Carnhill transformer found on the Successor and Class A amplifiers based on the 1073-type designs, including Carnhill St Ives output transformers. These contribute greatly to the sonic characteristics of the Eq imparting it its musicality and superlative sound.

Finally, an M/S mode lets you process the centre and sides independently, sculpting the width of your music and brightening a mix without affecting the vocals. 

In M/S mode the Side HPF becomes elliptical like in vintage disk cutters EQ to minimise low-end stereo information while maintaining precise frequency response.