Mesa/Boogie D-180 - Manual (Page 4)

REAR PANEL FEATURES
SPEAKER JACKS
Two 4 ohm and two 8 ohm jacks are provided. Unlike transistor amplifiers, the D-180 will
produce its full power at 4 and 8 ohms. Furthermore, speaker impedance mismatching is not
harmful to the D-180 and perceived loss of power is minimal. When using more than one
speaker cabinet, remember that total load impedance goes down as more cabinets are
hooked up. For example, if you use one 8 ohm speaker cabinet, use one of the 8 ohm jacks.
But if you use two 8 ohm cabinets, they will be operating in parallel and the total load
impedance will be 4 ohms. Therefore, plug each cabinet into a 4 ohm jack. If you want to use
two 2x15 cabinets where each individual speaker is rated at 8 ohm , the best results will be
achieved by wiring the speakers inside each box in series. Then each cabinet will become
16 ohms and they should be plugged into an 8 ohm jack.
SLAVE LEVEL, SLAVE OUTPUT & 600 OHM BALANCED OUTPUT
Signal is taken right from the speaker terminal - so that it captures the full sound of the
D-180 - then it is linked through the Slave Level Control to both the Slave Out jack and the
600 ohm Balanced transformer and XLR connector. This enables precise level matching for
best sound and lowest noise where any variety of receiving electronics might be used - from
additional power amplifiers to mixing boards. Full compatibility is assured because all
combinations are possible. For example, the M-190 matching full-featured power amp has a
balanced input capability and for installations where one or more of these are located a
great distance away from the D-180, the balanced interconnect system would be
advantageous. Same with long cable runs to the PA and monitor boards: the D-180's
balanced output will provide an ideal low noise signal and totally eliminate microphone
leakage. Use of a line level input at the board is recommended. For devices that lack
balanced input systems, the 1/4" Slave Output jack is provided. Remember that in using
either the 600 ohm Balanced Out or the 1/4" Slave Out, you should first adjust the D-180
front panel for desired performance, then increase the Slave Level control as you play to get
an appropriate mix into the following equipment.
GROUND SWITCH
A three position ground switch is provided to help in reducing buzzes which originate in the
AC power. It is advisable to leave this toggle switch in the center OFF position unless
selecting position A or B reduces buzz. With the Ground Switch in its center position, any
residual shock between the D-180 and other equipment (microphones, guitar amps, etc.)
cannot possibly be originating in the D-180.
FAN SWITCH
Normally the fan should operate in its LOW speed because cooling is adequate and dust
build-up is minimized. If fan noise is objectionable - in a recording studio for example -
turning the fan OFF will not cause overheating unless the D-180 enclosure is in a confined
space. Use the fan’s HIGH speed setting when the D-180 is in an equipment rack with other
units and free air circulation is reduced.
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