Studio Technologies 220 2013 - Manual (Page 12)

Issue 5, February 2013 Model 220 User Guide
Page 12 Studio Technologies, Inc.
headsets, which he did by the veritable
“boatload.” Why? Because these usually
broke soon after going into service! He
knew that on a regular basis he’d receive
orders for more of them. Had these us-
ers, from the beginning, purchased only
premium-quality headsets, their total cost
of ownership would have been much less.
Enough said…
Headphone Output
The Model 220’s headphone output is
compatible with stereo or mono head-
phones, headsets, or earpieces. Connect-
ing devices with a nominal impedance
of 100 ohms or greater is preferred. This
shouldn’t prove to be an issue as essential-
ly all contemporary devices already meet
this condition.
Devices are connected to the headphone
output by way of a ¼-inch 3-conductor
phone jack located on the Model 220’s
back panel. As is standard for stereo head-
phones, the left channel is connected to
the “tip” lead of the ¼-inch headphone
jack. The right channel is connected to the
“ring” lead of the jack. Common for both
channels is connected to the “sleeve” lead.
Devices with ¼-inch 2-conductor “mono”
plugs can also be used with the Model
220’s headphone output. In this arrange-
ment only the tip lead (left channel) will be
active. The 2-conductor plug will physi-
cally connect (“short”) the ring lead (right
channel) to the sleeve lead (common).
Technically this won’t damage the cir-
cuitry associated with the right-channel
headphone output. (100 ohm protection
resistors are electrically in series with the
headphone output circuits.) However,
energy will be wasted if an audio signal
coming out of the right channel goes into
a “dead” short. There is a simple solution
to this issue. No audio source should be
assigned to the right-channel headphone
output. Refer to the Configuration section
of this user guide for details.
Main Output
The main output is intended to be the
“on-air” signal that connects to the input
of an audio console. The output is trans-
former balanced with a nominal signal level
of –2 dBu. The actual level will depend on
the gain setting of the microphone pream-
plifier, sensitivity of the microphone, and
how loudly the talent speaks into the micro-
phone. The transformer used in the main
output is intended for professional broad-
cast applications. It has a low source im-
pedance and can drive lengthy cable runs
with no difficulty. It is capable of driving 600
ohm loads but performs best with loads of
2 k ohms or greater. (This should not prove
to be an issue as virtually all contemporary
audio equipment has a relatively high input
impedance.) As the secondary winding of
the output transformer connects directly to
the main output connector, care should be
taken so that DC voltage is never present
on the interconnecting cable.
The main output is interfaced by means
of a 3-pin male XLR connector located on
the Model 220’s back panel. The intercon-
necting cable’s mating connector (female)
should be wired so that signal high (+ or
hot) is on pin 2 and signal low (– or cold)
is on pin 3. The cable’s shield can be con-
nected to pin 1, but it will have no function.
To limit the chance of grounding interaction
between the Model 220 and connected
equipment, pin 1 on the main output’s
connector is isolated from any point in the
Model 220. The fact that pin 1 “floats” will
minimize the chance of hums, noises, or
buzzes being present on the equipment
connected to the main output.