Classic Audio Products Of Illinois FC526 XFMR by kokkobil3
The FC526 is an audio limiter by CAPI Gear.
It's sold as a kit, with all parts needed for the kit included apart from the doa (you need at least 1, but if you want to have it all discreet you need to get 3) which can be bought as kits or already soldered and tested.
Two different output audio transformer can be bought, I had the Litz one and the Ed Anderson one is available.
The kit is not simple to build if you are unexperienced with a soldering iron, but the instructions are very detailed and even if I had practically no experience in building circuits, it was good working from the very first power up.
The calibration is not simple too, but it can be done with a soundcard and a tester, and once you read the guide and understand the process is not that difficult anymore.
Soundwise I was expecting a lot, and it oustand my expectations.
The machine is features a 1176/1178 inspired gain reduction system (featuring the famous ABI setting) with API style signal path and output transformer.
At normal limiting ratios (2:1,4:1,8:1,12:1,20:1) is very musical and transparent, and it's particulary good in treating voices.
When you start to play with the ABI settings it really gets to that 1176 vibe. Superb drum slammer, amazing as a parallel compressor.
Attack and Release time does perfecly their jobs and are quite versatile.
Big plus are the sidechain filter (an hipass filter on the sidechain that helps a lot when you compress bass heavy busses, like the drum bus), and the ability to bypass just the gain reduction so you still benefit of the plus of the signal flow (DOA+transformer, with input and output level).
A version with 2 IC opamps+ 1 DOA instead of all discrete 3 DOA is available.
A must have in every 500 rack!