Designed for 500 series rack enclosures, the Heritage Audio 73EQ JR is a full-featured line input module that shares the 3-band equalizer, the transformer-coupled line preamplifier, and the Class A transformer-balanced output stage of the classic 1073 module. This combination allows the module to capture a full transformer-based Class A sound without the need for external preamps.
The equalizer section of the module features the same Baxandall-type high and low shelf filters found on the 1073, but with the addition of a high frequency selector switch. You can select four different frequencies of 10, 12, 16 or 20 kHz. The low frequency shelving EQ has a selectable frequency of 35, 60, 110, or 220 Hz. The mid frequency has a dual inductor-based ±18 dB peaking filter with a fixed Q and selectable center frequencies of 0.36, 0.7, 1.6, 3.2, 4.8, and 7.2 kHz. An EQL button allows for the equalizer section to be turned off and on.
The output stage is a Class A singled-ended design driven by a 2N3055 high headroom amplifier. To improve the performance of the module within a 500 series enclosure, the unit utilizes an internal slow turn-on +24V power supply for lower inrush current. The module is finished with Carnhill transformers and Marconi-style knobs for a classic tone and user interface experience.