[BC] processing way back when

[Robert Orban]

At 10:03 AM 12/19/2006, Mark Humpfrey wrote:
>Not the first limiter, but possibly the first "look-ahead" limiter was
>the General Electric BA-5-A, which is shown in my 1947 GE broadcast
>audio catalog.
>
>According the the catalog blurb, its initial development was done by
>the CBS technical staff, and it included a delay line in the signal
>path, to "delay the signal until bias generator circuits have time to
>reduce the required amplifier gain", and also had a dual-time-constant
>release "anti-pump" circuit.

When I was working at a summer job at WPAT in 1968, they had one of those 
on their AM TX (an old Federal 5 KW with a separate vault for the mercury 
vapor rectifiers and mod transformer!). The GE had LOTS of tubes. IIRC, the 
audio was modulated as RF to permit gain control in the RF domain without 
thumps. As far as I know, they also used an RF delay line for the audio. I 
can attest that the unit had good peak control, probably thanks to its 
look-ahead design.

My recollection was that the GE unit sounded good by itself. Later that 
summer, they added a tube-type Audimax to the chain.

The Chief Engineer at the time was Paul DiSavino (sp?) who later left the 
station and started a used broadcast/pro-audio equipment dealership.

Bob Orban