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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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