OH -D33R Preamps

The OH-D33R is a DIY, op amp–based microphone preamp designed for easy assembly and serious sonic character. Inspired by the legendary ISA-110 mic preamp, it captures the spirit of classic British console sound while embracing modern accessibility. Whether you're a home recordist, a boutique builder, or a curious tinkerer, the OH-D33R delivers clean gain, flexible tone, and a rewarding build experience—no soldering required. Thoughtfully laid out and grounded in pro audio tradition, it’s a clever deer in a forest of clones.

A close-up of a printed circuit board with electronic components and a white line drawing of a deer's head with antlers.

The Tone is in the Antlers

The OH-D33R isn’t just easy to build—it’s packed with the features you’d expect from a serious studio tool. At the front end, a 1 to 5 input transformer provides natural saturation and a healthy gain boost, setting the stage for detailed, musical recordings. A switchable low-cut filter helps tame rumble and tighten up your sound, while onboard phantom power ensures compatibility with your favorite condenser mics. Need to track instruments? The OH-D33R includes a selectable DI input for clean, punchy direct tones. All of this is wrapped in a smart, affordable design that makes high-end sound approachable for any builder.

Disassembled electronic circuit board with various components on a blue grid cutting mat.
Close-up image of a green printed circuit board with various electronic components, including capacitors, resistors, connectors, and a black rectangular chip. The circuit board has labels for different sections and connection points, with white dashed lines indicating different areas.