Studio Technologies 60A - Manual (Page 17)

Model 60A/61 User Guide Issue 1, June 2003
Studio Technologies, Inc. Page 17
connecting an audio source with a +4dBu
nominal level can lead to distortion (“clip-
ping”) of the signal. In this fault condition
the user might hear a harsh “clicking”
sound in the audio, especially when peak
levels occur in the program material. To
remedy this problem simply use the appro-
priate switch on the Model 60A’s back
panel to configure the input for +4dBu
operation. The distortion will go away and
the gain structure of the StudioComm
system will be correctly established.
Technical Notes
Definition of Level—dBu and dBV
Whenever possible, Studio Technologies
has opted to use the dBu designation as
it seems to be quite rational. Using dBm
was fine when all audio line outputs were
terminated with 600 ohm loads. In this way
it was easy to say that 0dBm is 1 milliwatt
dissipated in the known load (i.e., 0dBm
across 600 ohms will measure 0.775V).
In contemporary situations an output is
rarely terminated with 600 ohms; generally
10k ohms or higher. The dBu designation
is better because it refers to dB referenced
to 0.775V, with no reference to load im-
pedance. This takes into account today’s
audio scene where signals have a low
source impedance, and a high input
impedance. The dBu designation is
becoming the standard for the professional
audio industry.
The Model 60A Central Controller is de-
signed to interface with audio signals that
have nominal signal levels of +4dBu or
–10dBV. You might wonder why dBV
came into the picture. Most people don’t
realize that equipment that utilizes “–10”
levels usually mean –10dBV, which is
substantially different from –10dBu
(–10dBV = –7.78dBu). The dBV designa-
tion is simply a different way of measuring
signal level and is often used when deal-
ing with portable or consumer audio equip-
ment. The dBV designation refers to dB
referenced to 1.0V, rather than dBu which
refers to 0.775V.
“Hot” Disconnection of the Model 61
Control Console
Should you need to relocate the Model
61 while your StudioComm system is
operating, there is no reason why you
can’t disconnect the 5-conductor cable,
move the unit, and then connect it again.
No clicks, pops, or other noises will occur
when the Model 61 is disconnected and
then again connected.
Cue (Talk to Phones) Noise
During field trials of the Model 60A and 61
one item came up for discussion: “thumps”
in the cue function. A brief discussion may
be useful. The circuitry in the Models 60A
and 61 that support the cue function is
reasonably quiet, not adding appreciable
“clicks, pops, or thumps.” However, me-
chanical noise being picked up by the
Model 61’s microphone can be an issue.
If the cue button is pushed using a rela-
tively light “touch” no objectionable noise
will be generated; pressing the button with
“gusto” will cause mechanical noise to be
transferred into the microphone. While the
Model 61’s microphone is of good quality,
shock mounting it was not possible using
a cost-effective method. The fact that the
Model 61 is physically small and the button
is relatively close to the microphone adds
to the difficulty. (Note that most all record-
ing consoles, both small and large, share