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A rare Optonica SM-4646 integrated amp!

A long-dead division of Sharp Electronics in Japan, this extremely rare amp was their attempt to break into the HiFi market. Too little and too late (and not enough marketing) this brand never really caught on, which is sad as the build quality and sound reproduction is really quite excellent. A customer sent this in to be restored. It was in working condition, but being 40+ years needed some love. It uses "power-packs" as the outputs instead of discreet transistors. Each power pack is 2 transistors and a few resistors. These are no longer manufactured, but there are some workarounds in case they ever fail, robust as they are. The power packs are actually re-branded Sanken S-100W units.

A neat feature is the fact that this is a dual-mono power supply inside. 2 transformers (1 per channel) for two power supplies. It has an additional transformer for the pre-amp so, really, 3 transformers! This is a HEAVY machine! Each giant filter capacitor is actually 2 capacitors in one unit. So, 4 x 6,800uf (microfarads)!

Pictures below are before any work had started.


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