Mesa/Boogie II User Manual

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MESA/BOOGIE
.50 CALIBER PLUS
OWNER OPERATING INSTRUCTIONS
MESA/BOOGIE
The Spirit of Art in Technology
CONGRATULATIONS! You've just become the proud owner of the boldest sounding, easiest
operating 50-watt amplifier there is… and you're sure to enjoy it!
GREAT SOUND
. Many months of patient, painstaking R&D were spent in developing the .50 Plus's
special, high-gain "personality". We tuned (and retuned) its preamp section to make it capable of
monstrous, fat lead tones while still offering plenty of crystal-clear headroom for rhythm. Its power
section has been fitted with 6L6 tubes in a specially modified (and patented) circuit that offers fluid
dynamic response with plenty of “give”. And a custom-designed vintage Celestion speaker - made
exclusively for MESA/Boogie - provides a perfect blend of full-bodied clarity and warm “crunch”.
GREAT SIMPLICITY
. One of the .50 Caliber's greatest virtues is its incredible simplicity of operation.
It's nearly impossible to come up with a bad sound or a wrong setting. And here to help you get
started is a brief explanation of your new amp's features and controls.
FRONT PANEL
FEATURES
INPUT JACK This ¼” guitar jack is the instrument input to your amplifier. Patented “Dual Mode”
circuitry makes this single jack work for both Rhythm and Lead… providing very high headroom for
sparkling clean Rhythm, and super high gain for monstrous Lead playing. Be sure to use a
good-quality, shielded guitar cord.
FOOTSWITCH JACK
This ¼” jack connects to the Lead/Rhythm footswitch via the unshielded cable
provided. When the red LED on the footswitch box is illuminated, the .50 Caliber is in the Rhythm
mode… red equals Rhythm. Stepping on the button switches the amp into the Lead model and the
LED goes out.
Should you lose or forget your footswitch you can activate the Lead mode by pulling out the "Pull
Lead" switch on the Volume knob.
VOLUME (GAIN)
This control is active in both Rhythm and Lead modes. It establishes the amplifier's
overall sensitivity to your guitar's output, and must be mixed in conjunction with the Master(s). In the
Rhythm mode, the maximum clean setting is usually around 6 (varies with stronger or weaker
pickups) and most players find their favorite cleanest, brightest spot between 3 and 5. But if you want
some breakup in the Rhythm mode, turn the Volume up high.

Mesa/Boogie II Specifications

General

Brand	Mesa/Boogie
Model	II
Category	Musical Instrument Amplifier
Language	English

Summary

Front Panel Features

Input Jack

Guitar input jack using patented "Dual Mode" circuitry for Rhythm and Lead.

Footswitch Jack

Connects to the Lead/Rhythm footswitch; red LED indicates Rhythm mode.

Volume (Gain)

Sets amplifier sensitivity and must be mixed with Master for overall output.

Master Controls

Master

Regulates power amplifier level and overall loudness, works with Lead Master in Lead mode.

Lead Master

Affects only Lead mode, works in series with Master for loudness and effects send.

Treble

Powerful tone control that affects Bass and Middle; balance is key for clean tones.

Tone and Effects Controls

Bass, Middle

Tone controls are interactive and must be set together for optimal sound balance.

Reverb

Features a 3-spring Hammond-Accutronics reverb with all-tube send/return.

Presence

Adjusts extreme high frequencies for overall brightness and tone clarity.

Graphic Equalizer

Expands tonal flexibility with a three-position EQ switch and popular "V" setting.

Rear Panel Features

Fuse

Replace blown fuse with 2.5 Amp Slo-Blo; check for bad power tubes if it repeats.

Ground

Helps reduce buzzes from AC wiring when the ground pin is lifted.

Direct

Variable strength signal output from the output transformer, includes effects and reverb.

Effects Send & Return

Low-noise patch loop for external accessories and preamp output.

Connectivity and Usage Notes

Speaker Jacks

Provides 8-ohm and two 4-ohm speaker jacks for various cabinet configurations.

EQ Footswitch Jack

Connects the optional EQ Footswitch for remote Equalizer switching.

Caution

Proper balance of Volume and Masters is crucial to avoid feedback and tube stress.

Maintenance

Addresses noise issues by suggesting preamp tube replacement (V1, V2, V3, V4).

Sample Settings

Using the Lead Master

Use the Lead Master to fine-tune Lead mode loudness relative to Rhythm.