Studio Technologies 60 - Manual (Page 15)

Issue 2, March 1998 Model 60/61 User Guide
Page 18 Studio Technologies, Inc.
Troubleshooting
Intermittent Audio Connections
Should you experience audio connections
that seem to be “flaky” or intermittent
carefully check the ¼-inch plugs that are
used to interface the installation with the
Model 60. The ¼-inch phone jacks used
on the StudioComm products are of very
high quality, conforming to the industry
standard EIA RS-453. Some ¼-inch plugs
do not meet this standard, specifically
in the shape of the tip conductor. In rare
cases you may have to replace plugs
on interconnecting cables or headphones
to remedy an interconnection problem.
Switchcraft No. 280 (2-conductor)/No. 297
(3-conductor) or Neutrik NP2C (2-conduc-
tor)/NP3C (3-conductor) phone plugs will
function correctly.
Clicks in the Audio
As covered in the Configuration section of
this guide, the four stereo line inputs can
be configured for +4dBu or –10dBV opera-
tion. Setting an input for –10dBV, while
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 60’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 be-
coming the standard for the professional
audio industry.
The Model 60 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 dealing
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