The Folcrom RMS216 is a 1RU passive summing unit with standard D-Sub connectors providing 16 balanced inputs on the back and two XLR connectors for balanced outputs. Each input can be assigned to Left, Right, Center or Nothing via a line of 32 latching switches on the front. Since the summing is passive, it needs makeup gain after the fact, via a stereo mic preamp that you provide (although anything with enough gain will do). Fear not, it's not that radical-only about 32 dB of gain is needed in my experience. A great many of our favorite consoles employ passive summing with makeup gain, not to mention some killer outboard gear (Pultecs, anyone?), and no one loses sleep over it. Plus, by the time you're mixing, the preamps are just sitting there anyway, right? The beauty of this arrangement is how easily you can mess with your mix's character by swapping out different ones.
I'm pretty fortunate to go to work on an SSL 9000J every day, so my first test with the Folcrom wasn't even as a mix buss. I run four parallel-buss compression chains in addition to the stereo on the desk-this arrangement is a huge part of my mixing. I figured it would be a great test to sum all of these through the Folcrom and into a pair of SSL channels. We (myself and my assistant, Quick Lee) set the unit up, matched levels with tones, and listened to a just-completed mix. I liked it better-just slightly, mind you-probably because we were swapping eight channels of SSL electronics for two, but I preferred it. Great. So I filled up the other eight inputs with static effects that I don't automate on returns, and I let it ride. It's still there, and I've used it every day for months.
In fact, the Folcrom is a great problem solver. Warm up digital reverb returns with a Folcrom and tube preamp hang. Extend the inputs on your console for monitoring, keyboard submixes, whatever. You can link two of these together, with a quick tweak on an internal jumper, for 32 channels of fun. Rad.
I went out of town for a bit, and when I got back, someone had trashed the back of the rack that the unit was in. We lost a few channels on it, so we took it apart to see what had gone wrong. Inside, the unit has two circuit boards joined together-not the most reliable of setups. The D-Sub connectors were snap-ins, which is where our failure occurred, and I noticed that the resistors weren't precision and the switches weren't sealed. I broached all these concerns with Justin (the designer) and discovered that I was the proud owner of an original production run, long since gone. The current units use much heavier-duty, bolt-through D-Subs and a single circuit board. The switches are gold-plated but not sealed, so you can clean them. The resistors are hand-matched to 0.1% tolerance. The lime-green box is built like a tank. Problems solved.
We then took stems of previously mixed material and original raw tracks and compared summing with digital, analog, and the Folcrom. This is where this box's strength comes in. Rather than being locked into one specific tonality, I was able to mix and match from a wide range of preamps to get a pretty crazy array of sonics-from SSL to vintage Neve to a pair of RCA BA-6A's. I've always preferred the sound of analog summing to digital, and this was no exception. 16 channels through the Folcrom/SSL sounded very close to the J's mix buss. It was a blast changing preamps, and I was surprised at the sometimes unexpected differences between them. It's great to have this much control, and it's the only summing option I know of that makes this possible.
Two other points worth mentioning. If there's a maximum input level this thing can handle, I never found it. I pounded it and never clipped it. Since it's all passive, extreme levels would equate to heat, but it never got there. Also, because there are no caps in the unit, it's conceivable that any phantom power from a mic preamp would travel back through the unit to your D/A, which is not good. Don't do that.
If you want to get your geek on, Fred Forssell dropped the science on passive and active summing in a great web paper (www.forsselltech.com/summing%20buss.htm). One disadvantage of passive summing, says Fred, is noise. Helsing Audio assured me that given recent resistor design improvements over the last 20-30 years, this is not a problem (sorry Fletch). I found the unit to be as quiet as an open grave.
I know someone who paid $25,000 to make a passive summing box with several amplification options in it. With the Folcrom, you can have the same thing, with a virtually unlimited range of preamp options, and still have enough money left over to buy an entire recording studio. It's worth looking into. I'm not giving mine back. ($1000 MSRP; www.helsingaudio.com, www.rollmusic.com)