Mesa Boogie Stereo Amplifier D 180 User Manual

D-180 Amplifier  
Operating Manual  
1
 
EFFECTS LOOP  
Two pairs of Send and Return jacks are provided, one pair on the front and one pair on the  
back of the D-180. So whether you use effects devices on the floor or built into a rack,  
patching with your D-180 is convenient and precise. The sophisticated Effects Loop circuitry  
of the D-180 works extremely well. A low impedance "send" amplifier assures high  
intercompatibility plus low noise. A unique Blend control located on the upper rear amplifier  
chassis (where it won't get-broken or damaged) enables you to mix "dry" and effected  
signals. With the Blend knob set at 10, all signal will pass through the accessory effects; set  
at 5, about half of the D-180 signal will pass through the effects and half will go direct. Set at  
0, the effect patch points are fully bypassed. Zero is the recommended setting when no  
effects devices are patched into the loop. The Effects Send level has been padded at the  
rear panel jack to accommodate low-headroom effects devices. The front panel Send jack is  
unpadded.  
The Effects Return jack offers access directly into the D-180's power stage, and about .775  
volts (or 0 dBv) is required to drive it to full power when the Master is set at ten. This exactly  
matches the input sensitivity of the M-180 basic power amplifier (no preamp or control  
sections) so, by driving the M-180(s) from the Effects Send of the D-180, automatic level  
balancing will be maintained between all amplifiers. But if distortion from the D-180 is being  
used, or if heavy effects processing is in the loop, the 600 ohm balanced out or the Slave  
Output would be preferable. These features are described below.  
3
 
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.  
4
 

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