Oberheim SEM

The Oberheim Synthesizer Expander Module was one of the world's first self‑contained synthesizer modules, developed so that owners could play sequenced lines without tying up valuable synths such as Minimoogs or ARP2600s. But, right from the start, there was something a bit special about the SEM, so it wasn't a total surprise when Tom Oberheim used it as the basis of all manner of instruments including dual‑ and four‑module synths (the '2‑Voice' and '4‑Voice'), a 4‑Voice expander, and a huge eight‑SEM dual‑manual polysynth (the '8‑Voice'). Even today, vintage Oberheims that are not based on SEMs are judged by how well they emulate the SEM sound, hence the reverence the OB1 and OBX command, and the lesser esteem bestowed upon the OBXa and OB8.

Consequently, there's a thriving market for second‑hand SEMs and SEM‑based synths, but Oberheim himself wasn't interested in resurrecting the design until pressure from Roger Linn and a bunch of end‑users at an event in Barcelona caused him to re‑think. Today, thanks to them, the SEM is back in production, and Oberheim claims that, "the new SEM is pretty much the same as the original... in fact, I made the circuitry as close to the original as possible.” There was an easy way to check this; I took one of the SEMs out of my 4‑Voice and removed the review unit from its case. Superficially, they appeared somewhat different, but after a few seconds' inspection it became apparent that, despite the use of surface‑mount components and hugely improved board quality, much was the same. I wondered if they also sounded the same...