The configuration of the Orban 422 A Compressor is a bit interesting for a dynamic processor, but is nonetheless simple to use. For parameters it has knobs for input attenuation, ratio, attack, release, gate threshold, output, gain, and de-ess. The unit also has metering for gain reduction and output level. A manual would definitely be very hard to find, but one isn't necessary anyway.
The Orban 422 A Compressor definitely isn't the best sounding compressor in the world, but it also isn't the worst. It doesn't have a lot of punch or clarity, but will do the basic job. I've used the 422 for compressing a whole slew of different drums, but for nothing else. While I liked the amount of control that I have over your sound, it doesn't excite your original sound like some compressors do. It is nice to be able to de-ess with it, and it's best feature is the fact that it is pretty versatile. However, the sound just doesn't blow me away and I would rather use compressors that do.
The Orban 422 A Compressor is a really a rare piece of gear. After using it in a recording studio I went to do some research about it to see if I could find out a thing or two about it, but really didn't find much. However, everything about it is pretty self explanatory when it comes to actually using it. I wouldn't recommend trying to seek out of these, as it just isn't worth it, but if you do come across one at a very cheap price, I'd at least recommend taking a second look.