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UNIVERSAL AUDIO Model 175 B LIMITING AMPLIFIER
OPERATING INSTRUCTIONS
UNIVERSAL AUDIO INC.
Model 175 B
LIMITING AMPLIFIER
The Universal Model 175 B is an extremely versatile professional quality peak
limiting amplifier designed for use in the recording, broadcasting and motion
picture industries as well as other high quality audio systems. The 175 B is a
true limiting amplifier capable of high gain, low distortion, linear amplification
at levels below the threshold of limiting and with excellent limiting
characteristics and negligible increase in distortion at levels above.
The model 175 B is designed to be mounted in a standard 19" rack. The unit
requires only 3½" of rack space, and the front panel is hinged to provide
accessibility to the inner components. The highest quality military type printed
circuitry is combined with 1% precision resistors and over rated components
throughout to insure maximum performance and reliability. Plug-in type "FP"
electrolytic capacitors are used for ease of replacement.
The 175 B has a self contained power supply, a VU meter that is switchable to
indicate input or output level as well as gain reduction in dB, and input and
output attenuators graduated in 2 dB steps, with vernier adjustments in excess
of 2dB for each step.
The limiter is provided with input and output jacks on the front panel as well as
a terminal strip on the rear of the unit for interconnecting the amplifier with a
system. The terminal strip also provides for connecting a remote VU meter if
desired.
Separate adjustments of the attack and release times are provided on the front
panel as well as a limit defeat switch mounted on the rear of the attack control to
allow for the wide variety of program material that the 175 B will be expected to
handle. Checking the unit for balance, or rebalancing may be accomplished
without the need for test equipment, because an internal signal for balancing is
provided on the position of the test switch. Screw-driver adjustment holes are
provided on the front panel so that the VU meter may be easily observed with
the panel closed during balancing.
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Summary of Contents for Universal Audio 175 B
- Page 1 The model 175 B is designed to be mounted in a standard 19” rack. The unit requires only 3½” of rack space, and the front panel is hinged to provide accessibility to the inner components.
- Page 2 The input and output attenuators are both adjustable from 0 to 40 dB. For this reason the 175 B may be utilised at any point in the system where input signal level is between -24 dBm and +13 dBm. The attenuators are adjusted for proper operating levels as follows: a.
- Page 3 UNIVERSAL AUDIO Model 175 B LIMITING AMPLIFIER g. Decrease attenuation with the output attenuator until the desired output level is observed on the meter. h. Return the meter switch to GR position to verify amount of limiting during operation. Note: The output level may be increased 6 dB by replacing the output attenuator with Langevin model AT 601 attenuator.
- Page 4 UNIVERSAL AUDIO Model 175 B LIMITING AMPLIFIER BALANCING ADJUSTMENTS Inherent stability eliminates the need for frequent balancing of the 175 B. However, if thumping is noticed or components are replaced, the unit should be balanced as follows: a. If using TEST 1 position, remove any input signal from the amplifier.
- Page 5 UNIVERSAL AUDIO Model 175 B LIMITING AMPLIFIER NOTE: The absolute minimum meter deflection should be in the order of -20 dB. If the two sections of the 6BC8 are not reasonably symmetrical, optimum balancing cannot be obtained. NOTE: The fastest attack or release time is attained by turning the control full...
- Page 6 UNIVERSAL AUDIO Model 175 B LIMITING AMPLIFIER PERFORMANCE SPECIFICATIONS FREQUENCY RESPONCE: Without limiting: ± 1 dB, from 20 cps t0 20 kc With 5 dB limiting: ± 1 dB, from 20 cps t0 20 kc MAXIMUM POWER OUTPUT After output attenuator with limiting switch off to prevent limiting at +24 dBm less than 1% THD from 50 cps to 15 kc.
- Page 7 UNIVERSAL AUDIO Model 175 B LIMITING AMPLIFIER...