Mesa/Boogie II operating instructions Rear Panel Features

REAR PANEL FEATURES

FUSE Should your .50 Plus blow its fuse, be sure to replace it with a 2.5 Amp Slo-Blo type. Should the fuse repeat its blowing, check for a bad power tube. Often it will light up red hot all over the large metal plate inside. Repeated instantaneous fuse blowing indicates a bad rectifier diode or a shorted filter capacitor. Any of these events is very uncommon in the .50 Caliber Boogies.

GROUND This switch is often helpful in reducing buzzes which originate in the AC power wiring outside the amplifier. Leave the switch in its center OFF position unless position A or B definitely helps. This usually occurs only when the ground pin on the AC plug is being defeated via a ground-lift adapter at the wall socket.

DIRECT This feature provides a variable strength signal output originating right from the output transformer. Thus, good tone is supplied, all Effects and Reverb are included, and there is absolutely no loss of the Boogie's tone when running from the Direct Output to a mixing board or another amplifier. But bear in mind that speakers themselves exert a tremendous coloration to the tone, primarily by rolling off the highs very steeply above 5 to 6 kilohertz. Consequently, many players will still prefer the recorded sound of a microphone "listening" to the speaker.

In some sophisticated set-ups, players run their Boogie'sDirect Out into an effects rack, and then from the last effects device into other external amplifiers. But such a set-up cannot route the last effect output back into the original Boogie. Also note that a speaker or load resistor must remain plugged into a speaker jack at all times, even when using the Direct. Otherwise the amplifier will operate improperly and damage may result from running without a load. Suggested value of the load resistor is 8 ohms, 50 watts minimum.

EFFECTS SEND & RETURN These jacks provide a low-noise patch loop within the 50's preamp for connecting external accessories. Compatibility is quite good with most line-level or rack-mount devices, although some will require you to trim down their input attenuators to prevent overload. (Pedal-type effects are designed to handle the low-level signals emanating directly from your guitar; therefore this type of device should be connected “in front” of the amplifier, rather than in the Effects Loop.)

Some manufacturers offer rack-mount multi-effects units for guitar which include compression, distortion, overdrive, etc. Although a good-quality compressor can be used effectively in your Boogie's Effects Loop, we do not recommend the use of multi-effect "guitar processors" in the Loop, as their inputs are often too sensitive and their added gain stages will tend to contribute some noise. If you wish to use this type of device with your Boogie, it should be patched in between the guitar's output and the amplifier's input.

The Send jack can also provide an external “preamp, out” signal without breaking the signal path that leads to the .50's power section and speaker. If you're using the Send as an output but you still want to hear the internal speaker, turn up the Master. If you don't want to hear the .50's power amp and speaker, turn the Master to zero. (Remember to leave the speaker - or a load resistor - connected to one of the speaker jacks).

Plugging a signal from another source into the Return jack provides direct access to the .50's power amp section. Remember to adjust the Master to an appropriate setting for best signal-to-noise ratio.

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