The May '78 Preamplifier

Details on this preamplifier will be added over time. First, the line stage — the specifications achieved are shown below:

The design was made very similar to the “Otala” designs. It was a single-power-supply design — note the input and output capacitors. It was designed to replace our old, completely single-ended preamplifier, which was never a big hit.

At Electrocompaniet this preamp was named “Model II”. It was designed in the period January to July 1978 — I don’t remember why it ended up being called the May ‘78 preamp.

Original design notes (kuriositet)

The original handwritten design notes from 1978 have survived, covering more than what’s shown above: the line amplifier (two revisions), the phono equalization amplifier (including RIAA time-constant calculations and component-level schematics), the moving-coil head amplifier, and the shared power supply system.

Line Amp & MC Amp — original design notes (PDF, scanned, 1978)