[BC] nominations for best sounding AM in your area?

[Dana Puopolo]

As Chip well knows, processing is like a dance. Practically anyone can dance,
but only a few can dance really well.

My philospohy is this:

First thing is either wideband or a maximum of two band AGC. For two bands, I
cross over at between 100-200 Hz. I set my AGC to be slow-and use about 8-12
db. It's sole purpose is to fix the level errors the jocks do (a 'jock
watcher'). A Compellor or rechipped/recapped CRL SPP 800 works perfectly
here.

Next comes the multiband compression. With analog a maximum of 4 bands
please-with digital six is okay. Analog crossovers are usually single pole due
to group delay/phasing issues. Digital crossovers can be more bands and
steeper slopes because digital filters don't have the phase distortion that
analog filters do. Speeds are either program dependent or medium slow to
medium fast-depending upon format. Usually about 6-10 db of gain reduction is
plenty. This compressor does two things. It does much of the dynamics
reduction (loudness) and also provides dynamic source to source consistency
(the 'sound signature' of the station). Unlike the first stage, it's really
easy to screw up this stage. Again, the four band CRL APP units or Glen
Clark's Texars work well here. Next we have the limiter. For AM, this is where
any assymetry begins. For FM this is usually a high frequency limiter where
the 75 us pre-emphasis gets changed depending on content. It's important to
not use this stage very much-only a few db at most. Modern digital limiters
use what's called 'look ahead' technology. This allows the limiter to do just
that-to look ahead a small amount of time to actually know in advance how much
it will be needed/used. Our next stage is the wideband clipper. This is where
some loudness happens and the rest of the AM assymetry is done. I prefer
what's known as 'soft into hard' clipping, where you first soft clip the audio
a db or two (resulting in mostly even order harmoncs) and then follow up with
a 'brute force' clipper (which is there to make you LOUD-but also can be
easily over used. Again, I like the approach that Glen Clark used in his audio
clipper where he used a VCA to control the clipper drive based upon a user's
setting. This way the clipper could not be overused. After this comes the low
pass filters-15 kHz for FM and 10 kHz (or less) for AM. For FM there's uusally
a stereo generator here (which also has the 15 kHz filters built in). Then
things go off to the STL. At the transmitter there's one final hard clipper
whose purpose is to strictly control any filter overshoots in the system. For
FM I use a heavily modified Mod Sciences unit. For AM you can use a biased
diode clipper set assymetrically. 

My favorite integrated analog processors are the Optimod FM 8100 (with Zero
card) and the
Optimod 9100B. Both of these can work great if upgraded (better negative power
supplies, better caps and opamps, etc).  

Today's digital processors can also sound great if properly set up. I've heard
great things from most Orban, Omnia, Inovonics, Arianne and other brands of
digital processors. Some of the software audio processing programs can sound
amazingly good at a really cheap price (I use the 30 dollar Breakaway Home on
my office PC to process all my streams-and they sound incredible!). The free
Stereo Tool program can slso be made to sound really good.

Now as Bryan Ferry sings: "don't stop the dance!"......

-D 

 
From: Broadcast List USER <Broadcast at fetrow.org>

Sorry, but compression does not sound bad.

CLIPPING sounds bad.  Very hard limiting sounds bad.

Compression sounds bad on things like voice, with noise in the  
background, like a mic in a noisy studio.

Compression makes radio listenable in noisy conditions like in cars.

Frankly, if you ask the public, audio processing, that would be  
compression and moderate limiting, sounds GOOD.  I have at least twice  
written about an SBE/AES meeting in DC where the golden ears liked  
processed audio better than their own records.

--chip