Opus 5.0 – A Modern Mullard

Opus 5.0

The Opus 5.0 a modern Mullard amplifier using 2 KT88 output tubes per channel. The circuit was designed by SGregory and DIYAudio friends. I contacted him 3 years after he designed the amplifier and he told me it is has main amp and he uses it daily. That is a stable, dependable amp. Just what I needed to satisfy my tube audio curiosity once and for all.

The chassis is made from 1/4″ aluminum sheet and 1/8″ aluminum angle stock. I covered the amp with leather and added aluminum corner posts and meter surround. I have always liked the look of meters and the amp front panel needed something, at least to my eye. These are mono block amps, each one measures 13″ x 16″ x 9″ and weighs 40lbs.

I am building each channel differently. I want to hear the difference between the 2 constructions. The other channel uses circuit boards designed by Pete Millett another very generous DIY audio person. He sells his boards on eBay and the projects are described on his site pmillett.com

Here is the bottom plates drilled for tubes, capacitors and holes for the transformer wires.

Bottom plate




Components installed



Bottom view



More to come


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