On Sun, 14 Jan 2007 22:28:56 -0500, "Jimmie D"
wrote:

+++From my experience compression is more to allow consistent modulation when a
+++change in voice, such as the difference when I talk on the radio and my wife
+++talks. IF she tries without readjusting the mike gain she may not be heard.
+++
+++Clipping really removes audio not needed for effective modulation and
+++amplifies that that contains the most intelligence. This often shows up on
+++the rx S meter as less than an S unit change over an unclipped signal but
+++sounds like 10db or more increase.I dont have a clipper except for this
+++peice of junk I threw together the other day but when I did have one the
+++reaction was usually" wow how big is that amp you just turned on."
+++
+++On SSB average power out of a 100 wat tx on voice may be only 12 watts
+++average add a clipper and you can increase that to 80
+++
+++My preference is a clipper with some AGC action to keep the average output
+++level faily constant.
*************

Again I reiterate that both audio clipping and audio compression
attempt to to the same thing, that is to reduce the peak to average
power in an audio signal.

Compression techniques are basically a variable gain stage in which
the gain is contrtolled by the input signal power. Therefore as teh
input is low the gain is high. As power increases the gain reduces.
This raises the average audio power while maintianing the peak power.
Compression suffers from attack time and decay time issues. Set the
decay to slow and the gain does not return to higher levels fast
enough to amplity lower power signals. Set the decay time to fast then
the compressor becomes ineffective. The attack time issues are even
more critical in their adjustments.

A clipper works by removing the power above a certain threshold. That
power does not just go into oblivion. Instead the power goes into
harmonics of the audio frequencies that make up the power signal.
Therefore with clipping the peak to average is reduced by moving the
power in the peaks of the audio power signal into the harmonics of
that signal. There filtering will attenuate the harmonics to restore
the original bandwidth. You need sufficient filtering with clipping
somewhere in the amplifier chain before that audio power signal
reaches the modulated stage.

The major issue of audio processing to decrease the peak to avergae
power is not to do so much that you over stress the average
characteristics of the modulated stage and any subsequent amplifier
stage. Also do not confuse PEP (Peak Envelope Power) with Peak to
average. They are two different identities.

A clipper with some form of agc is eesentially a clipper/compressor
combination. Another best unto itself.

james