Unlike the article we published in Tape Op #45, which outlined a very simple mod for the 3630 compressor, this kit is a complete overhaul. Considering the low initial cost of the compressor and the low cost of this kit, this is a killer deal for recordists with more time on their hands than money in their pockets. After completing this mod, I can say the sonic improvement is substantial, but we'll come back to that later.
I've built several PAiA kits and found them to be a bit frustrating. The manuals were never that clear, and the end result never blew me away sonically. The old adage that you get what you pay for comes to mind. By contrast, the Black Lion kit was a huge improvement. The parts were very clearly labeled, and the instructions were super easy to follow. As a bonus, the manual clearly explained not only what was going on, but also why parts were being replaced and how they affected the sound and performance of the compressor.
I have to admit that I've been sitting on this kit for over a year, hoping to find the time to do the mod and write this review. Publishing a magazine and running a studio doesn't leave me much time for soldering, and this review would still be unwritten if it wasn't for Chris Woodhouse, a great engineer (A Frames, Team Sleep) who's been working in my studio and helping me with tech work. I dropped this in Chris's lap, and a day later it was done. Now Chris is not a trained tech but is definitely above average in his soldering and electronics skills. It took him about 10 hours to do the mod. I'm guessing it would have taken me 16-20 hours. Serious solder whizzes might be able to do it in 4-6, and if you've never picked up an iron, proceed with caution and plan for a week or so. Chris reported that doing the mod went without a hitch and that the instructions were super easy to follow. This kit completely overhauls the 3630 without changing its underlying design, which makes me wonder why the 3630's audio circuitry is pretty well designed but utilizes such crappy components! First, the input stage is hot-rodded with two hand-selected op-amps, metal-film resistors, and silver mica capacitors. Next, the VCA circuit is overhauled with new VCA chips, resistors, and audio-grade capacitors that replace the stock electrolytics. During this part of the mod, you are given the option to set up the 3630 (via two trimpots) for transparency or second- harmonic crunch at heavy compression settings. Next, the Level Detect Circuit is modded followed by a change to the soft/hard knee circuit and switch. Finally, the rectifier that converts the wall wart's AC to DC is improved by swapping out the stock diodes for fast-recovery diodes that diminish AC ripple and residual noise.
We opted for the "transparent" mode, and in listening tests against a stock 3630, the Black Lion 3630 blew away the stock one. The difference isn't subtle. It's immediately apparent. I was able to determine which unit was modded in a blind comparison test. Every aspect of the modded unit's sound-low end, midrange and top end- was greatly improved, and the unit had a fuller frequency response. Imaging was better as well. The stock 3630 just sounded kinda cheap and lo-fi compared to the Black Lion unit.
You could obviously go further with the 3630 mods if you wanted to. We discussed adding a switch to enable the simple change we discussed in Tape Op #45. You could also mount pots on the back of the unit to replace the trimpots in the VCA circuit, allowing user-control of the second-harmonic distortion. Congratulations to Black Lion Audio for doing such a fantastic job on this kit. They've basically turned a cheap compressor into something very useful. ($115 direct; www.blacklionaudio.com)