A precise, fully discrete recreation of one of the most sought-after operational amplifiers in recording history.

The SA-25 is a true 1:1 replica of the legendary Huntingdon-era 2520 discrete operational amplifier, originally found in early API consoles from the 1970s. Built around a fully discrete 9-transistor design, the SA-25 faithfully captures the architecture, performance, and sonic character that made the original 2520 a cornerstone of classic analog recording equipment.

Each unit is carefully engineered to deliver the unmistakable tone associated with early Huntingdon 2520 op-amps—punchy, fast, and harmonically rich, with a forward midrange and tight low-end response. This signature sound has been integral to countless classic recordings and remains highly sought after by engineers and producers who value authentic vintage character.

The SA-25 is used across our product line, including the SA-4000, 25609, 312+, and 312-5T, ensuring consistent performance and tonal integrity throughout. It is also fully compatible as a drop-in upgrade for a wide range of OEM equipment and DIY projects, offering a straightforward way to enhance sonic performance with true vintage accuracy.

Each op-amp is built with premium-grade components, fitted with PCB pins for easy installation, and rigorously tested to ensure reliability and consistency. Backed by a 3-year warranty, the SA-25 delivers both the sound and dependability expected from a world-class discrete op-amp.