Dorrough 10-A, Instruction Manual, Page: 4 / 19

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To install your DORROUGH Loudness Monitor, perform the procedures
described in the following sections.
Unpacking
Your DORROUGH Loudness Monitor was carefully packed at the factory.
Take a moment to examine the unit for any signs of shipping damage. If
damage is evident, retain the carton and notify the transit carrier and your
local distributor about your claim.
Once you are satisfied with the physical integrity of the unit, proceed with
Initial Set-Up to align the meter to match your operating level requirements.
Initial Set-up
You can set the operating level either on the bench or at the installation
location. For set-up at the installation site, refer to the section on Mounting
Considerations prior to performing the following procedure.
1. Plug the AC cord into a convenient AC line and observe that the display
becomes backlit.
NOTE: If you do not see this action, make sure the AC line has power and the
Power Switch (recessed in the back panel) is in the ON (up) poasition, or test the
internal 0.25 A fuse for continuity.
2. While observing polarity, feed a 1000 Hz sine-wave at a standard operat-
ing level (i.e., -10, +4, +8, etc.) into the left input, as shown in Fig. 1.
3. Adjust the input level control (Fig. 1) on the rear panel for an indication
of “0” on the meter scale. This step applies to all models.
NOTE: The peak excursion and the persistence amplitude are equal under
steady state sine-wave conditions.
4. Next, remove the signal from the left channel and feed the signal in the
same polarity to the right input, making the same adjustment.
5. Following the adjustments for both the left and right inputs, feed the
signal to both inputs simultaneously. The summing amplifier will
algebraically add the two inputs for an indication of +6, as read on the
PEAK scale. This action applies only to an "A" Type meter; a "B" Type
meter would be "off scale" for the same summing condition.
INSTALLATION
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