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THE DELTAMAX™ SYSTEM
AMPLIFIER/CONTROLLER CALIBRATION
AMPLIFIER CALIBRATION PROCEDURE
Maximum performance of the DeltaMax™ controller
protection circuitry occurs, under the most severely
over-driven conditions, when the voltage gain of the
amplifiers fall in the range of 27 to 35 dB (with 32
dB being optimum). This gain range is typical of
most high-power amplifiers and can easily be ad-
justed by simply adjusting the level controls on the
amplitier.
The procedure for calibrating an amplifier to have
32 dB of gain is as follows:
1.
With the amplifier turned on and without speak-
ers hooked on the amplifier output, apply 0.5-
volt rms 1,000-Hz sinewave signal to the input
of the amplifier.
2.
Adjust the amplifier level control until the output
of the amplifier measures 20 volts rms.
NOTE: If the amplifier will be operated in the
mono-bridged mode, it should be calibrated
when wired in the mono-bridged configuration.
CONTROLLER CALIBRATION PROCEDURE
This procedure is for calibration of the DMC
controller's internal amplifier limit circuits to the ac-
tual clip level of the power amplifiers. Calibration is
set by the LF and HF Amplifier Calibration trimpots
on the front panel.
Before plugging in the ac power cord, be sure the
controller is wired for the correct primary (mains)
voltage.
Disconnect the speakers and remove the security
cover from the controller by removing the two
screws on the front panel of the controller. Perform
the following procedure:
1. Connect the controller to the low- and high-fre-
quency power amplifier channels as detailed in
the INSTALLATION section.
2.
Besure the controller LF and HF Sense Inputs
are connected to the correct amplifier outputs
and the speakers are disconnected from the
amplifier.
3.
Setthe low- and high-frequency amplifier gain
controls for 32 dB voltage gain, or as close as
possible to 32 dB (this is optimum, but it can be
in the range of 27 to 35 dB). See the AMPLI-
FIER CALIBRATION PROCEDURE section.
4.
Tum the LF and HF Amplifier Calibration
trimpots on the controller to full counterclock-
wise. Press the Cal/Clip Limit switch to its re-
cessed Cal/Clip position with a screwdriver or
other suitable tool.
5. In order to prevent thermal! limiting from occur-
ring while calibrating the amplifier limit levels,
insert a shorted '/4-inch phone plug (tip-sleeve)
10.
13;
Amplifier/Controller Calibration
into the Gain control bus jack on the back of
the controller. The Thermal Limit LED may still
come on but no gain reduction should be indi-
cated.
Send a 500-Hz sinewave test signal to the con-
troller input.
Adjust the signal source level until the low-
frequency amplifier begins to clip (you may
turn up the LF Output Level on the controller if
necessary to get the amplifier to clip). Clipping
is noted by the clip indicator on the power
amplifier or by monitoring the output with an
oscilloscope. Now, turn the level down until the
clip light just goes out (or until the clipping dis-
appears on the oscilloscope).
Turn the LF Amplifier Calibration trimpot on the
controller clockwise with a screwdriver until the
LF Amplifier Output Limit LED comes on. Note
that the slot of the trimpot is pointed at the
approximate power rating of the amplifier for an
8-ohm load as denoted by the calibrated mark-
ings on the front panel of the controller. Note
also that this is the maximum amount of power
capable of being delivered to a single driver in
this amplifier configuration.
The LF section of the controller is now calibrat-
ed. The LF Output Level trimpot may be adjust-
ed as necessary for the desired frequency
spectrum balance without affecting calibration.
Change the input test signal to a frequency of
5,000 Hz.
Adjust the signal source level until the high-fre-
quency amplifier begins to clip (you may turn
up the HF Output Level on the controller if nec-
essary to get the amplifier to clip). Now, turn
the level down until the clip light just goes out
(or until the clipping disappears on the oscillo-
Scope).
Turn the HF Amplifier Calibration trimpot on the
controller clockwise with a screwdriver until the
HF Amplifier Output Limit LED comes on. Note
that the slot of the trimpot is pointed at the ap-
proximate power rating of the amplifier for an 8-
ohm load as denoted by the calibrated
markings on the front panel of the controller.
Note also that this is the maximum amount of
power capable of being delivered to a single
driver in this amplifier configuration. If the
power rating of the high-frequency power am-
plifier is much greater than 250 watts (and,
hence, the HF Amplifier Calibration trimpot on
the controller is set much greater than 250
watts), then an additional margin of safety for
the high-frequency driver can be obtained by
setting the HF Amplifier Calibration trimpot to
250 watts.
page 12
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