[net.audio] Compressing/Limiting Amplifier

review@drutx.UUCP (Millham) (04/26/85)

If anyone can remove themselfs from the exciting, year-old
discussion of how terrible CD's sound (I have a Fisher, and haven't
listened to a record since buying it), I have a question.

I would like to build/buy either a Compressing or Limiting stereo
amplifier. Is there anything on the market at a reasonable price? If
not, does anyone know how to build one?

I need this to operate a small 15 watt FM stereo transmitter. My
current setup overmodulates, especially when talking. For this use,
which is better, compression or limiting, or both?

Thanx,

--------------------------------------------

Brian Millham
AT & T Information Systems
Denver, Co.

...!inhp4!drutx!review

newton2@ucbtopaz.CC.Berkeley.ARPA (05/01/85)

I can't believe it-- a question about *audio* instead of bombast about
bullshit!

Let me just brush the dust of centuries off this tablet-- there! OK, first of course
you'll want to gang both stereo channels (so your precious stereo image doesn;'twander when one channel's gain changes WRT to the other).

Second, just what are you doing with a 15 watt FM transmitter? If it's a translator
or repeater, fed by a broadcast program, the modulation should already be limited,
so I'd guess you'd only "need" a safety limiter to guard against improper
gain-setting. Come to think of it, you said "when I'm talking", didn't you?
So I'd advise first of all a clipper (or limiter, to use the polite term)
to avoid wasting all your dynamic range on the useless fricatives and glottal
stops (git th' tar 'n' feathers, boys, he's a-stompin on our dy-namic range..).
If that doesn't allow a decent average loudness without instantaneous overmod,
you might consider adding compression to taste. If you're using the US standard
75 microsecond preemphasis, you might give some thought to a frequency-sensitive
compressor that is less tolerant of spectral components most likely to overmod-
ulate. The late and apparently unlamented Dolby FM system will reward study.

Yours for less crap about imaginary problems and their illusary solutions,

Doug Maisel