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AM-55 / Sep 2015
A M - 5 5 G U I
Internet connectivity allows processors in even the most remote locations to be easily
adjusted via a remote GUI. In most cases, the need for the processor to be at the studio
“…so it can be accessed…” is a thing of the past.
When audio levels in the plant are properly calibrated, there is no need for an AGC
in front of an STL path because almost all processional broadcast gear that may be
in‑line between the console and the STL will have as much if not more headroom than
the broadcast console. If non‑broadcast or semi‑professional gear is in the audio path,
it should be replaced.
There may be some cases where, no matter what, an outboard processor is needed
or desired and three of these situations follow.
•
Ratings Encoders
– We’ve found that ratings encoders need a “steady diet” of
incoming level in order to be function properly. Improper levels, especially those
that are too low, can be problematic for stations that are automated where a hu
‑
man can’t make compensating adjustments to source levels on the console. While
our i
AGC can easily compensate for audio levels more than 10dB different from
source to source, a 10dB drop in level at the input to the ratings encoder (which is
prior to the processing) will not keep a ratings encoder happy over the course of a
3‑4 minute song. It may even set an audio alarm and email and page the s tation’s
staff.
The BEST way to address the level consistency problem in a facility is to make sure
there are standards in place for getting proper levels recorded into the playout system and
refrain from using outboard pre‑processors. Unfortunately, that isn’t always practical,
so if a station feels they must use outboard pre‑processing ahead of the AM‑55 we
suggest bypassing the i
AGC option in the AM‑55. The
i
AGC was meant to measure the
dynamic range in real time of the incoming audio, including any dynamic range issues
with board work or audio levels that did not match. If there is an aggressive leveling
device in front of the i
AGC, it can alter the measurements and cause the
iAGC
to fight
with the pre‑processor.
• Reverb – Reverb was originally used as a way to increase modulation density on
older AM transmissions when the audio processing of the day simply wasn’t so
‑
phisticated enough to do it. The effect of reverb not only did the trick, it also added
a pleasant sonic texture to the audio, one still desired by many stations today. The
challenge for most reverbs is that variations in their input levels can have a very
large effect on how they sound on the air if installed directly into the program chain.
A pre‑processor is traditionally used ahead of a reverb unit which will protect it
from generating excessive reverb if (when) its input levels are too high. The use of a
pre‑processor ahead of a reverb also helps sustain the reverb effect.
As in the case of adding pre‑processing to boost encoding levels in a Ratings Encoder,
the same steps should be taken to adjust the AM‑55 to “mate” with the outboard processor.
If reverb is side‑chained into a microphone processor and not directly in the audio path,
and no outboard AGC is deployed, no special adjustments of the AM‑55 need to be made.
• Analog Telco STL or Aural STL – Older analog telco lines sometimes need some
pre‑processing in order to keep signal to noise ratios high. Some users have indicated
the need for pre‑processing before an aural STL to prevent overshoot. Again, if you
feel the need to use a pre‑processor in either of these situations, adjustments to the
AM‑55 should be made in concert with the suggestions above.
