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Dixon Systems
Stereo Rack Monitor
Model RM-35
Owner’s Manual
Dixon Systems
Model RM-35
1-1 Description:
Dixon System’s RM-35 is a self contained, rack mountable, stereo amplifier and
speaker monitor system designed to compliment the NM-250 Newsroom Mixer. The unit
employs a high quality stereo audio amplifier driving two three by five inch shielded
speakers, each in it’s own acoustically treated ‘enclosure’. The result is exceptional
audio quality, very low distortion and outstanding stereo separation. The shielded
speakers, along with the toroidal power transformer in it’s power supply, eliminate the
concern about placing the unit in close proximity to video and computer CRT monitors.
There is only one control on the front panel. This allows the operator to switch
between ‘Stereo’ and ‘Mono’ mode to check phase and mono compatibility. This is
done with true L+R summing and with no change in volume. LEDs indicate Power and
Stereo or Mono mode.
**(The RM-35 is also available with the gain control mounted on the front panel when
it’s not used with the NM-250.)
The RM-35 can be used in newsrooms and editing suites or with modulation
monitors and logging systems. It’s a valuable accessory in a wide variety of facilities
and installations.
1-2 Features:
The RM-35 uses 2 premium quality shielded speakers, each in it’s own ‘enclosure’
inside the unit. The stereo amplifier and power supply are in the center of the unit. To
keep things clean and quiet, 1% low noise metal film resistors are used in the signal
path of the amplifiers. The result is clean, very low distortion audio and a better stereo
image. Audio inputs are on the rear panel and are the ‘combo’ type which accept either
XLR or quarter inch TRS connectors. The gain control is also located on the rear panel.
(See ‘Set Up”)
1-3 Technical Description:
The input stage of the RM-35 is a 5532 configured as a differential amplifier. This
permits either a balanced or an unbalanced source. The unit is designed for a nominal
+4 dB input level. The input stage then feeds a resistive network and an analog switch,
a 4053, followed by a summing amplifier, again a 5532. Gain is set in the following
stage, another 5532 and the output stage is a typical NPN/PNP driver/output pair. The
amplifier drives a pair of 3" by 5" speakers, each in it’s own compartment or ‘enclosure’
which has been acoustically damped. This results in better audio and less vibration of
the enclosure itself.
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Dixon Systems
Model RM-35
1-4 Unpacking and Inspection:
Carefully examine the contents of the shipping carton for any sign of physical
damage which could have occurred in transit.
IF DAMAGE IS EVIDENT, DO NOT DESTROY ANY OF THE
PACKING MATERIAL OR CARTON AND IMMEDIATELY NOTIFY
THE CARRIER OF A POSSIBLE CLAIM FOR DAMAGE. SHIPPING
DAMAGE CLAIMS MUST BE MADE BY THE CONSIGNEE.
1-5 Mounting:
The unit should be mounted where convenient to the operator, ideally at approximately
ear level for best fidelity and stereo image. It’s excellent magnetic shielding means it
can be placed close to CRTs without concern.
1-6 Heat Dissipation:
The RM-35 will operate satisfactorily over a wide range of ambient temperatures.
If installed in an area with high heat producing equipment, adequate ventilation should
be provided to prolong the life of components. Heat generated by the amplifier is
dissipated into the center compartment of the unit. The lid is vented and there should
be some space between the RM-35 and whatever is mounted above it. With normal
use, no other special considerations for cooling are necessary.
1-7 General:
The RM-35 is ruggedly constructed and should provide years of trouble free use with
normal care. All parts are conservatively rated for their application and workmanship
meets the rigid standards professional users expect.
No special preventive maintenance is required.
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Dixon Systems
Model RM-35
1-8 Set Up:
The RM-35 can be set up in a few easy steps. Once the unit has been inspected,
slide and secure the monitor into the rack. Connect the audio signals via XLR or
quarter inch TRS connectors. Plug the unit into the AC mains. (The RM-35 operates
from 110VAC - 60Hz power.)
Adjust the volume control on the rear panel. The RM-35 is designed to be driven by
a balanced source at a nominal +4 dB level. When used with the NM-250, the volume
control on the RM-35 should be at approximately ‘one o’clock’. If used with another
audio source, be sure the monitor is not over-driven. AVOID CLIPPING! Audible
distortion (or other nasty things) will occur.
Best performance is achieved when using balanced, shielded cable; however
satisfactory results can sometimes be realized without it. The design of the input stage
permits unbalanced sources to be applied to the balanced inputs. The drawings below
show both balanced and unbalanced connections. (Only one channel is shown.)
Balanced
Unbalanced
Note: When using balanced line, only one end of the line should be grounded. This
will help avoid ground loops. As shown above, the ground would be connected at the
‘send’ end and not connected to the RM-35.
1-9 Amplifier Specifications:
Input Impedance:
Load Impedance:
Maximum Output Level
Gain:
40kOhms
8 Ohms
> 1 W per Ch. RMS
Adjustable
Frequency Response:
Total Harmonic Distortion:
Noise:
< .5 dB 20 Hz to 20 kHz
Better than .5%
Better than 90 dB
110 VAC/ 60 Hz 15 W
Power Requirements:
1-10 Schematic Diagram:
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Dixon Systems
Model RM-35
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Dixon Systems
Model RM-35
1-11 Notes:
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