RCA BA-103A mic preamp. The other API. Early 70's preamp from custom series BC-100 consoles, which mainly went to TV installs. What we have here is a re-badged API 2520 (most likely an API 'Melville' version based on date, also as evidenced by the measured thickness relative to the Melcor version in the earlier RCA's) driven by a UTC A-24, nested in an A-33 magnetic shield (lots of ebay claims about A-24 in various RCA modules; pretty sure they are getting that info from my posts, and not from having taken apart themselves. The line modules instead have A-20's!). I've replaced the axial electrolytics on the daughter card, and it works fine. Sounds like an API, but with UTC sound characteristic. Has 3 mic inputs that feed a switch, so you could theoretically wire 3 mics, and switch between them for comparison. MIC gain is in (3) 10 dB steps, and the HI section is a separate 20K bridging input for line use. I've sorted out a plan to make it work as (5) 10 dB MIC gain steps, to keep switch original, or you could replace it with a standard API style fully variable gain pot such as this pretty easily. My reverse engineered schematic and connector info will be supplied. Runs on standard bipolar +/-16VDC. It's so painfully almost a 500 series module, but the UTC makes it slightly wider, and it's longer. I have several of these wired to 500 series extender connectors and sitting loosely in my 500 rack ATM. If you're pervy enough to track down 8 more of these, the 9 will sit beautifully as a solid full rack face on an RCA 3RU shelf. The connector is about impossible to find, but it's very easy to solder directly to the one on the module. Or, bust it for the early 2520, UTC A-24, and Urei knob. It's your conscience, not mine.
SOLD.
SOLD.
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