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The Symph EQ is Heritage Audio's take on the classic Baxandall shelving EQ topology, reworked into what they call an "asymptotic" equalizer, where boost and cut amplitude grows toward a fixed ceiling as you turn the control up, rather than climbing indefinitely. This keeps the extreme highs and lows under control even at higher boost settings, while using parallel equalizing to keep phase deviation low. It's built as a one-rack-space master bus and mastering tool, with the same Carnhill Oxford input transformers used in Heritage's Successor compressor, and 73-style Class A output stages driven by matching Carnhill St Ives output transformers.
The high and low shelving bands offer a maximum of 10.5dB of boost or cut in precise 0.5dB steps, with six selectable frequencies per band. Separate 2-pole high-pass and low-pass filters are available to control frequency extremes independently of the shelving bands. The standout feature is built-in Mid/Side (M/S) processing, letting you EQ the center and sides of a stereo mix independently, useful for things like brightening a mix without hardening vocals, or tightening low end in the sides without weakening a centered kick or bass. When M/S mode is engaged, the side channel's high-pass filter automatically switches to an elliptical response, the same technique used in vintage disk-cutting lathes.
Key features
- Asymptotic shelving EQ (updated Baxandall topology), high and low bands
- Built-in Mid/Side (M/S) processing alongside standard L/R stereo mode
- Elliptical side-channel high-pass filter automatically engaged in M/S mode
- Separate 2-pole high-pass and low-pass filters, 5 frequencies each plus off
- Custom Carnhill Oxford input transformers, Carnhill St Ives output transformers
- 73-style Class A output stage
- Individual hard bypass per channel
- Fully manufactured in the EU
Specifications
| Input Impedance | 10kΩ bridging, transformer balanced |
| Output Impedance | Less than 75Ω, transformer balanced (600Ω load) |
| Maximum Output | Greater than +26dBu into 600Ω |
| THD | <0.025% @ 1kHz, <0.05% @ 100Hz |
| Frequency Response | 20Hz (+0.3dB) to 20kHz (-0.2dB) |
| Noise | Less than -89dBu, EQ flat |
| High Shelf Frequencies | 8, 10, 12, 15, 20, 24kHz |
| Low Shelf Frequencies | 20, 60, 110, 220, 360, 470Hz |
| Shelf Boost/Cut | 10.5dB max, 0.5dB steps |
| High-Pass Filter | 15, 20, 47, 82, 160Hz (12dB/octave) |
| Low-Pass Filter | 10, 12, 18, 22, 30kHz (12dB/octave) |
Please allow ~10-14 days for delivery.