From Collins Radio 1974 catalog #74: A round-up of broadcast compressors from Collins and CBS. Models covered: Collins 26U-3 limiter, 26J-3 compression amplifier, CBS 4100, 4450A. and 4110, 4000A limiters; CBS 4500 dynamic presence equalizer; and CBS 710 ‘automatic loudness controller,’ which I imagine is some sort of LFKS-type limiter?
Also – a bonus – from the same era – second-hand limiter/pre-amp price list from the same era. RCA BA2Cs for $20? Yes I will take 30 please. How about a General Electric BA-5 for $75?
Big scans so… follow the link for the info…
2 replies on “Broadcast Compressors etc. Circa 1974”
Wow – item AA for $2200. Totally upside down from today.
If I recall correctly those Collins 26U-3 and 26J-3 are based on the 741 op amp, and compression is simple manipulation of the feedback path around the 741. I’ve never seen either one show up for sale….not that I would look either.
I had these on a station I engineeered. They were dreadfully noisy, even by the standards of the mid-70s, and they had quite nasty and obvious distortion on peaks. I was so frustrated by them that I designed and built my own limiters, which we installed late at night to avoid the ire of the managers, and evade the senior engineer. In the following days, many listeners and staff commented on how much better the station sounded!
I found one of the prototypes when I cleared out some of my old gear. It still worked, which was a pleasant surprise. More recently, I’ve been designing much more modern designs (though staying in the analogue domain), and now use only PWM for voltage-controlled attenuation. It confers a number of advantages, including easy channel matching, low distortion and no noise.
Haven’t things moved on over the last fifty years?