A little blast from the past. This was found in a transmitter manual at one of the sites we take care of:
I thought I would scan it and make it available here. As luck would have it, there is also a corresponding piece of equipment to go along with it. I had never seen a “CCA Optomod” (.pdf) before I was working at one of the radio stations in Trenton, Florida. This unit was rescued from under a pile of garbage out in the lawn shed. It was full of mud was nests and mouse droppings. Needless to say, it required a bit of TLC to return it to operation. I replaced the electrolytics, cleaned it up and ran some audio through it. It is probably as good as the day it left the factory. Bob Orban made some really good stuff in his day.
The original Optomod 8000 was an evolutionary design that made FM radio processing what it is today. The idea of combining broadband limiter, AGC and stereo generator in one box was a radical departure from the norm. The audio limiter functioned as a 15 KHz low pass filter and broadband AGC.
The stereo generator used very modest amounts of composite clipping to reduce overshoot and transients. Many people disparage composite clippers. If done correctly, it is transparent to the listener and increases perceived loudness by stripping off modulation product that is non-productive.
Some thirty five or so years later, there are still many of these units in service in various stations around the world.
As this is an older design than either the Gates Sta level or the Collins 26U, it may not be as useful to tube audio enthusiasts.
The main issue with the Gates and Collins unit is the GE 6386 remote cutoff triode used, which were great tubes, but very difficult to come by these days. This design calls for a 1612 or 6L7, which is a pentagrid amplifier. Feedback is provided by the screen of the following stage, a 6SJ7GT. Anyway, perhaps it will give somebody some idea on how to make a good tube compressor limiter.
This is the finished product from an earlier post. Currently, it it the studio for WAJZ in Albany, but that is not permanent. The SAS studio goes together fairly quickly, as most of the trunking between the TOC and studio is done over the SAS data channel.
The studio monitors (Tanoy Reveal) are set on little posts under the computer screens. I like this set up as the DJ’s are less likely to rock the house if they decide to crank up the volume on their favorite tune. I am also kind of digging the lack of a table top equipment pod. That takes up a lot of counter top space and always seems to be in the way. There are two CD players rack mounted below the counter (lower left), which are almost never used.