dbx 117/118/118 series
I've owned all 3 of these fine units, and they are magic.
dbx-117 is a basic unit, with big knob calibrated from infinity compression (with built-in -50dB gain limit) thru 1:1, up to 1:2 expand. The small knob is level match. The switch is for response time only (medium/slow).
dbx-119 is a more flexible unit,big and small knobs are functionally same as in 117, but the switch does something entirely different. UP runs the unit in "Threshold" mode (very fast), allowing Peak Limiting/Expanding. DOWN runs the unit in Linear Mode, at medium speed.
dbx-118 is the home stereo choice. Operation is simple, with big & small knobs and slide switch functioning same as the 119. A dbx type II NR system is on-board, and jack-wired for stringing the 118 between tape deck and home stereo. The variable COMP/EXP is routeable (by silver push switches), to place the C/E ahead or behind the tape deck. An optional silver push switch tailors the TypeII NR for those old (and impossible to find) dbx records.
117/118/119 have no power switch, but they draw only a couple of watts, so don't worry about the "Green Factor".
All three use "mono" detectors. That means that the units are intended to process both stereo channels together as a stream.
117 has no indicator light, at all.
118 has two L.E.D.'s for threshold above/below.
119 has one red L.E.D. which brightens as the threshold is driven harder. (I've seen a 119 with a calibrated scale meter on the top, but I think it was a custom mod, not production).
My personal experience: I have used balanced mics, thru x-formers, directly into 117 & 119(linear mode), set for 1.4:1 comp, and fed to tape deck. Playback is 1:1.4 exp, then EQ, and re-record to mixdown deck. (mastering deck, with 50dB S/N and dbx loop, provides a performance range window of 70dB. I never had to watch the meters, and recorded master at -6 peak. Stage Recordings Were Excellent.)
