Mesa-Boogie 400 User Manual

Strategy 400 Stereo

Operating Manual

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CONGRATULATIONS AND THANK YOU!
You've just become the proud owner of the world's most musical power amplifier: The

Strategy 400™ Stereo. All of our efforts have been directed at making this a special piece of
equipment -- a fine hand-made musical instrument -- that we hope you'll enjoy and treasure
for many years to come. Your total satisfaction is our highest priority and we appreciate your
good word-of-mouth referrals. So when people compliment you on your sound, you can
smile knowingly and hopefully you'll tell them a bit about us.

VACUUM TUBE AUDIO
People who don't know about MESA/Boogie are usually surprised when they learn that we

make amplifiers using vacuum tubes. They think tubes are some obsolete relic of a primeval
electronic age, long ago faded from earth. And that's largely true-- but with two notable
exceptions: TV picture tubes and Audio.

Have you ever heard of a tube amp claiming to have "that great transistor sound"'? Neither
have we. So here's a clue that many knowledgeable types -- even the latest MOS-FET
designers -- hold good tube sound as the standard for comparison. And now, with the
introduction of the Strategy 400 Stereo, a new, higher level of musical performance has
been made available -- and at a very affordable price when compared to the few fabulously
expensive "esoteric" tube.

DESCRIPTION AND FEATURES
The Strategy 400 Stereo is a modern, all-tube power amplifier-hand-built in the musical

instrument tradition. Producing 200 watts of mid-band power-- the Strategy excels in
playback systems-especially home stereo--and is unequaled for musical instrument
performance including guitar, bass, keyboards and electronic drums. In all of these
applications the Strategy will deliver state-of-the-art performance and almost certainly sound
much better than whatever is presently being used. You will enjoy an outstanding musical
richness that is the result of year's of careful design and refinement spanning the range from
individual components to overall concept.

INPUT CONNECTORS
Each channel of the Strategy includes a 1/4 inch input jack plus a female 3-pin XLR

connector. The XLR is wired as an unbalanced input with pin 2 hot and pins 1 and 3
grounded. An additional 1/4 inch jack offers access to both channels simultaneously and is
labeled "Parallel Inputs A+B". Located on the rear deck of the chassis, this is a mono jack
with a built-in switch so that a single mono cable will drive both channels of the amplifier. It is
vital when using this jack that both channels be connected to separate speaker loads or
damage to the output tubes and/or transformers may result. You can listen to each channel
individually by using the Standby switches although a slight distortion may occur when
using the Parallel Input Jack if one channel is operating and the other channel is standing
by. When both channels are ON, this slight distortion will go away entirely.

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INPUT CIRCUITRY
The Strategy 400 Stereo offers extremely sensitive input circuitry: 0.2 volts will produce full

power when the Level control is turned fully up. This means you can actually plug in many
signal sources directly without needing a preamplifier. The output from virtually any effect
unit is strong enough -- as is any keyboard, CD player, cassette deck... even electric bass
plugged in direct produces full power with incredible tone. Electric guitar needs more tone
shaping to sound right but can still be plugged in direct for testing purposes. When using the
Strategy with a preamp you should turn down the Level controls for best signal-to-noise
performance and easy controllability from the preamp knobs. With the MESA/Boogie Quad
preamp, settings from 2 to 5 are recommended for the Strategy Level controls. With the
Level set at 7, input sensitivity is reduced to 1 volt for full power out. With the Level at 6, 2
volts are needed; and at 5, 3 volts of signal deliver full power. Input impedance of each
channel is 75K ohms which becomes 37.5K when using the Parallel Input jack, still high
enough to be perfectly compatible with virtually any signal source.

OUTPUTS
Each channel of the Strategy 400 offers two 8 ohm plus two 4 ohm quarter inch jacks for

connection to speaker cabinets. Unlike transistor amps, the 400 will produce full power at
either 4 or 8 ohms, and mismatching of speaker impedance will not cause damage or severe
loss of power (extreme mismatches will decrease tube life however). Avoid running either
channel without a proper load or damage may result. When using more than one speaker
cabinet on a single channel, remember that the total impedance goes down as more
cabinets are hooked up. For example, if you use one 8 ohm cabinet, use one of the 8 ohm
jacks. But if you use two 8 ohm cabinets on the same channel, they will be operating in
parallel and the total load will be 4 ohms. Therefore plug each cabinet into a 4 ohm jack.

LED POWER INDICATORS
The output power of each channel of your Strategy 400 is continuously monitored by simple

LED indicators. Reflecting the logarithmic relationship of loudness and power, the first LED
comes on at 12.5 watts (-12 db); the second at 50 watts (-6 db) and all three at 200 watts.
Due to the 400's large dynamic headroom and predominately second-order harmonic
distortion, it is quite possible to light up all three LED's very strongly before objectional
clipping distortion is heard. A more complete explanation of distortion appears later in this
manual.

POWER AND STANDBY SWITCHES
AC Mains power is turned on via the Power switch and indicated by the pilot light. Before

switching on the power, place the other two front panel switches in the Standby position.
Allow 20 to 30 seconds of warm-up time before switching the Standbys to On. This helps
extend tube life by preventing a high-voltage turn-on surge, however, all amplifiers are
tested to withstand this extra stress in case you neglect to follow the best procedure.

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