Hi-Fi Phono Preamp

This project was born as a gift to my twin brother who is a major vinylphile. I wanted to throw something together for his (our) birthday to give to him to replace the internal phono stage built into his turntable that he was using. I had considered the Marantz circuit as well as a design using a 6DJ8 but having just restored a Dynaco PAS 3 preamplifier, I had two extra PCBs for the power supply and had plenty of 12AX7 tubes lying around (12AX7s are just the best).

Given my part surplus and familiarity with the PAS 3 circuit I decided to build the RIAA-EQ amplification stage outright. I made designs for just the phono stage but wanted to add more knobs and a line output so I decided to just build an entire modified PAS 3 and house it in a custom acrylic enclosure. The final design has three inputs (1 phono, 2 Auxiliary), uses 4 12AX7s, and a Hammond 290AX transformer that provides more current and won't get as loaded down as the original Dynaco PA-115.

Below is documentation of the design process of the enclosure and circuit. Beyond that is soon to be the build process and Bill of materials (hyperlinked to purchasing links). Glamour shots are to come on the next page.

Enclosure Design:

Circuit Schematics: