Sony AC-148A
A phantom power supply that never got top billing - but without it, a small fleet of Sony's best condensers stayed silent.
Overview
The AC-148A is easy to overlook in a pile of vintage gear until you actually need it. It is a phantom power supply, and Sony's own literature rated it at 49 V.D.C. ±1 volt. That is the standard phantom voltage, held to a tight tolerance for feeding a capacitor capsule. It has built-in connectors for two microphones, and Sony's documentation notes it can power up to ten additional microphones through external adaptors. For a small studio or a location rig running a handful of condensers, that makes it a distribution point rather than a single-mic afterthought.
Look at what it was built to feed and the purpose is clear. Sony's period advertising listed the AC-148A alongside its professional condenser line, and several of those mics carried a footnote insisting they "must be powered by Sony AC 148A or equivalent power source." The C-37P variable-directivity studio condenser and the C-500 studio standard both carried that requirement. So the AC-148A was the enabling hardware for Sony's condenser catalog. The microphone got the headline and the power supply did the unglamorous work behind it.
Sony's advertising pegged the AC-148A at $99.95. That's not pocket change for 1972, and this was professional-application gear sold through the Sony/Superscope Special Applications dealer network, not a consumer trinket. The same ad spread listed the C-37P at $325 and the C-500 at $395, so the supply sat at roughly a quarter to a third of the microphone it powered.
The period press covered the C-37P's launch with real enthusiasm. Recording-Engineer (April 1971, p.31) reported that the C-37P was an improved version of the earlier C-37A, with the key change being a new low-noise FET amplifier yielding a 130 dB dynamic range. The same item noted the noise floor had dropped by 10 dB, from 34 dB SPL equivalent on the C-37A to 24 dB on the C-37P. The overload point climbed by 20 dB, from 134 dB to 154 dB SPL equivalent. Those are the microphones the AC-148A was built to serve, with 49 volts of phantom power and no noise contribution of its own.
Collectors chasing Sony's condenser microphones eventually run into the AC-148A whether they planned to or not, because the mics won't operate without it or a documented equivalent. It's a support component, priced and sold as professional gear, built to a tight voltage spec, and able to distribute phantom power to a small fleet of microphones. There's no cult around the AC-148A the way there is around the C-37P it feeds.
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