Troisi 512 EQ with power supply

Offered is a matched pair of the exceptionally rare Troisi 512 Parametric Equalizers, housed in a Fredenstein powered 500-series rack.

Designed and introduced in the early 1980s, the Troisi 512 is a sophisticated analog equalizer that combines musicality with precise control. Each module features three fully parametric bands with continuously variable frequency, gain, and bandwidth (Q), allowing both broad tonal shaping and highly surgical corrective equalization. In addition to the parametric sections, each module includes independent high-pass and low-pass filters along with a notch filter, making the 512 particularly effective for resonance control, room correction, and difficult problem frequencies.

Unlike many vintage equalizers that are valued primarily for coloration, the Troisi 512 was engineered for transparency and precision. Its flexible topology makes it equally at home for tracking, mixdown, and mastering applications where exact frequency control is required without sacrificing musicality.

Both modules have been professionally serviced, including replacement of all electrolytic capacitors and installation of Burr-Brown audio op-amps, improving long-term reliability while lowering noise, increasing headroom, and enhancing overall clarity. The modules operate quietly and perform exactly as intended.

The equalizers are in excellent cosmetic and functional condition and are fully compatible with the API 500 Seriesformat. The included Fredenstein powered rack provides a reliable, ready-to-use platform.

Troisi equipment was produced in relatively small numbers, and the 512 is rarely seen on the secondary market. Finding a serviced pair in this condition is exceptionally uncommon, making this an excellent opportunity for engineers, collectors of vintage professional audio equipment, or studios seeking a unique and highly capable analog parametric equalizer.

This version emphasizes the design philosophy, filtering architecture, and sonic performance in language that will resonate with professional engineers and serious vintage audio enthusiasts.