Mesa Boogie Bass 400 Plus User Manual

MESA/BOOGIE

MESA/BOOGIE

BASS 400 PLUS
OPERATING INSTRUCTIONS

CONGRATULATIONS! You've just become the proud owner of the world's finest bass
amplifier. When people come up to compliment you on your tone, you can smile
knowingly... and hopefully you'll tell them a little about us! This amplifier has been
designed, refined, constructed and tested to deliver maximum musical performance of any
style, in any situation. And it is very easy to operate.

INTEGRATED SYSTEM
The idea behind this amplifier is to assemble all the elements of a custom rack system
into one perfectly matched unit. Your Bass 400
different) bass preamps, plus a versatile tone control network, an adjustable Effects Loop,
a seven-band Graphic Equalizer, and special driver and buffer circuits feeding a highly
dynamic, twelve-tube power amplifier. All were created especially for bass.

Plus includes two separate (and slightly

The Spirit of Art in Technology

WHY VACUUM TUBES?
Most musicians know that tube amps are unbeatable for guitar… but what about bass?
Isn't it better to have a big, clean, high-power transistor amplifier? We don't think so. And
our proof is that your Bass 400
solid-state systems costing two to three times as much! In our years of research we have
made some surprising discoveries: the best sounding power amplifier for bass is quite
different than the one we use for guitar. And is very different than the best power designs
for keyboard or stereo fidelity. Transistor systems are designed primarily for "laboratory
conditions", not the real world of live music. Your Bass 400
difference: you'll hear knockout punch (without the farting attack) and clear, distinct pitch
(without boominess or mud).

CHANNEL ONE
Input 1 and Volume 1 offer a high-headroom preamp that you might find preferable for
active type basses. The gain is slightly lower than Channel 2 and the tonal personality is
slightly different. The Pull Bright switch built into Volume 1 can be great for funk bass, as it
accentuates the harmonics above the Treble control region.

Plus will offer superior tone and more usable power than

Plus will demonstrate the big

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CHANNEL TWO
Input 2 and Volume 2 recreate the classic sounds of the D-180, predecessor to your Bass

400. The gain is slightly higher and may be better suited for traditional basses than
Channel One. But be certain to sample both channels because their tonal personalities
are both very usable with very interesting differences. It is even possible to preset the two
channels and footswitch between them using our separate A-B Footswitch Box.

TONE CONTROLS
The Bass 400

Plus uses traditional type tone controls which have been especially tailored
for bass, and whose ranges can be extended by use of the “Pull Shift” switches. The
Treble control, when set high, becomes the most powerful of the three. At settings of 7
and above it will minimize the effect of the Bass and Middle, but they will become the
stronger controls when the Treble is below 5. Most players find a “sweet spot” between 2
and 5 where the tonal balance is just right for them. Pulling out the Treble Shift alters its
frequency center-point downward, toward the upper mid-range. (And since there is more
musical energy at these frequencies, your amp will seem to get a little louder as well.)
Using either Bright switch injects an extra dose of high treble. The Bass control is
wide-ranging and using the Pull Shift can boost its power. Your Bass 400

Plus (especially
when used with our speaker cabinets) can produce more true fundamental tone than just
about anything else. Its bottom-end response is truly "profound" and yet it avoids
boominess and muddiness. The Middle control is the subtlest of the three. Its purpose is
filling the gap between the treble and bass frequencies. Spice according to your liking.

MASTER
The Master control comes after the Effects Loops and after the Graphic Equalizer. So its

best use is as a sensitivity control for the Effects Return and/or the power amplifier
section. Full undistorted power is developed at settings around 5. There is rarely any
reason to run the Master above 6 or 7, as higher settings merely increase noise without
improving power or tone.

EFFECTS LOOP
Two pairs of Send and Return jacks are provided; one on the front and one on the rear of

your Bass 400

Plus. So whether you use effects devices on the floor or in a rack, patching
with your Bass 400 is clean and professional. 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 control at 10, all signals will pass through the
accessory effects. Set at 0, the Effects Loop is fully bypassed, as it should be when no
effects are used. Most players find an ideal setting between 2 and 5.

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