Mesa/Boogie MARK 1 owner manual Rear Panel

REAR PANEL: (Continued)

EFFECTS LOOP & LEVEL CONTROL: This control and the two adjacent 1/4” jacks comprise the Effects Loop of the MARK I. When Effects devices are connected to the Loop, they are inserted between the pre-amp and the power section and loss of gain and signal strength due to impedance or input voltage mismatch is minimized.

The FX LEVEL Control can increase or decrease the signal strength from

FX	LEVEL
	1	0
		10
	2		9
	3		7	8
FUSE	4
	5	6

3A GRND SLAVE

drive an Effect when you change to INPUT channels.

unity gain present at the SEND and RETURN jacks. This is useful when

OUT	trying to match an Effect that has a very sensitive input, or a line-level
	Effect that requires a relatively large signal for its input. Because the
IN	MARK I has two distinct channels ( each with very different gain struc-
	tures ), very different signal levels will appear at the FX SEND jack. De-
LOOP	pending on the situation, you may find that an Effects input setting that is
	perfect for INPUT 2 will clip badly when you change to INPUT 1. Like-

wise, a setting that is perfect for INPUT 1 may not allow enough signal to 2. Use the EFFECTS LEVEL Control to compensate for the difference when switching

NOTE: This is another reason why we don’t advertise the MARK I primarily as a footswitchable amplifier.

The EFFECTS LEVEL Control can serve another purpose that could be called a “juicy” secret. By simply connecting a short shielded cable to the SEND and RETURN jacks and increasing the FX LEVEL Control, more gain can be introduced into the pre-amp. This creates many possibilities for lead sounds in both channels. INPUT 1 becomes a high gain dream using this little control, while INPUT 2 boasts truly useable lead or crunch rhythm sounds. Using the FX LOOP in this manner combined with the TWEED position on the POWER switch transform a “vintage” circuit into a modern Gain machine - with sound and feel that must be experienced to be believed!

NOTE: When using the FX LOOP to achieve additional gain, avoid high settings of the VOLUME, TREBLE, PRESENCE and FX LEVEL simultaneously. Extreme settings of all these controls at the same time puts undue stress on the pre-amp tubes and can cause the pre-amp to oscillate. An oscillation with these controls “maxed - out” is normal and is “setting - correctable”.

SLAVE: This 1/4” jack and its Level Control ( located under the chassis ) provide a “direct” signal that originates from the speaker jack. This signal is “padded” so that by using the Level Control, the proper level for Slaving to power amplifiers or mixing boards for live reinforcement can be achieved. Some players prefer using a microphone for tonal coloration and to ensure reproduction of the

speaker’s characteristic sound. Remember that the slave signal, though originating from the speaker jack, does not actually “see” the
						speaker, so any high frequency roll-off or other speaker coloration that you are
						used to hearing will not be present in this signal. Compensate for this at the mixing
	FX LEVEL					board or slave amplifier that you are using by rolling-off slightly the EQ Band that
	1	0			OUT
						deals with the highest frequencies ( 5K and above ), to simulate the sound of the
		10
	3			8
	2		9
FUSE	4		7			amplifier’s internal combo speaker. Lead sounds especially will require this high-
	5	6
						frequency roll-off to avoid sounding thin and scratchy through the slave output.

IN

3A GRND SLAVE

a microphone right up to a speaker - extreme

NOTE: Once you have used the SLAVE to capture a signal from the amplifier, you cannot route that signal back into the amplifier. The effect is similar to holding

feedback will result.

REMEMBER...A SPEAKER OR LOAD RESISTOR MUST REMAIN PLUGGED INTO ONE OF THE SPEAKER JACKS AT ALL TIMES OR SERIOUS DAMAGE TO POWER TUBES AND THE OUTPUT TRANSFORMER MAY RESULT.

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