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5.0 OPTIONS AND MODIFICATIONS
This chapter describes available BMX III options and modifications. Included are sections describing
phantom microphone powering, +4 dBu to +8 dBu conversion, stereo Sends, input module steady CUE
indication, using Send circuits for Telco operations, and the Talkback/Intercom Module.
5.1 PHANTOM MICROPHONE POWERING
The BMX III is equipped with a +48 volt "phantom" power supply for the powering of condenser
microphones connected to the Microphone Input Modules. This "phantom" power is available
whenever the MICROPHONE toggle switch on the BMX III power supply is placed in the ON position.
All necessary modifications to the Microphone Input Modules have been accomplished at the factory
(see note below), so condenser microphones may be connected just like any other microphone.
NOTE: To power microphones connected to the A input, jumper wires have been installed between
points E1 and E3 on the Microphone Input Module PC assembly. To power microphones connected to
the B input, jumper wires have been installed between points E2 and E4 (reference the schematic located
in Chapter 7 for more information).
5.2 OUTPUT LEVEL CONVERSION (+4 dBu to +8 dBu)
All consoles are set for a +4 dBu output level at the time of factory test, unless a +8 dBu level is specified
at the time of order. In order to convert a +4 dBu console operating level to +8 dBu, it will first be
necessary to change resistors on the Control Room Monitor Module and Telco Mix Module PC
assemblies as follows:
1.
Change 4.32K ohm, 1% resistors R5 and R105 on the Control Room Monitor Module PC
assembly to 10K ohm, 1% (PR&E #1-1002). This change provides a gain match between
the Monitor Selector and the SOLO bus levels.
2.
Change 5.1K ohm, 5% resistor R51 on the Telco Mix Module PC assembly to 3.0K ohm,
5% (PR&E #2-302). This change rectifies the Telco Meter Output for +8 dBu operation.
Once these resistors have been changed, align the console to the +8 dBu operating level in accordance
with the following procedures:
STEREO LINE INPUT MODULES
Apply a 1 kHz test signal at +8 dBu (600 ohm source) to both the left and right module inputs. Adjust
the module GAIN TRIM controls for a -10 dBu output at the module Patch Sends.
STEREO LINE OUTPUT AMPLIFIER
Apply a 1 kHz test signal at -10 dBu (600 ohm source) to both the left and right Patch Returns. Adjust
the module GAIN TRIM controls for a +8 dBu output into a balanced bridging load.
PACIFIC RESEARCH & ENGINEERING
89
BMX SERIES III CONSOLE
REVISION C
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