Mackie M800 FEATURE DESCRIPTIONS, LET’S TWIST A GAIN, Note:

FEATURE DESCRIPTIONS

			LET’S TWIST A GAIN
GAIN/dB			These are completely independent volume
	3v		controls for each channel. Instead of having an
16	18	20
			arbitary scale, they are carefully calibrated:
		2v
14		22	• The inner ring graphic is labeled in dB,
12		24
			though this indicates the amplifier’s voltage gain,
6		26	think of it as increasing decibels from off to 28.
00		28	• The outer ring shows the input sensitivity
		1v	in volts. This is the amount of voltage required
SENSITIVITY		1.23v (+4dBu)

from a mixer to drive the amp to it’s rated power output (225 watts into 4 ohms). With the control fully clockwise, it will require an input level of 1.23 volts rms to reach rated power. This is equivalent to putting in a signal level of +4 dBu.

If you have the knob set at 3v, it will require 3 volts from your mixer to reach full power. This will rob the mixer of headroom, because it takes extra voltage to drive the amp. Rotating the knob to 2v means you will need 2 volts from your mixer, which improves the mixer head- room. Rotating the GAIN control all the way clockwise provides the best mixer headroom under normal operation.

Note: The calibration marks only apply to stereo or mono operation using speakers of 4 ohms impedance.

Like all amplifier controls, you’ll typically determine the optimal settings during installation or sound check, then leave them alone, using your signal source (mixer/preamp) to control listening levels as you work. Or play.

You may wonder why we didn’t use just one stereo control to control both sides. That’s in case your application requires a left/right imbalance (due to an irregularly shaped room), an irregularly shaped friend, or if you’re using the two sides for completely different purposes (such as monitor in CH 1 and side-fill in CH 2).

Here are some more examples of how you might use the GAIN controls:

•When you are in a small room where loud volume is not required, having the amp gain controls turned fully clockwise would require you to keep the mixer faders down exceptionally low. In this case, first set the mixer faders to unity gain, adjust the mixer’s input trim controls to optimum, then rotate each M•800 GAIN con- trol until the desired volume is obtained.

•If you have high efficiency speakers and a high gain preamp, you may hear “hiss” in your speakers. This can be fixed by turning the GAIN controls down a few notches.

•If you are not blessed with a mixer or

preamp, it is possible to connect a source com- ponent directly to the amplifier. For example, you can connect a CD player directly to the in- puts. You MUST make sure that the amplifier GAIN controls are turned down before you start the CD, then bring them up to a nice level. This direct connection only applies to line-level components. It does not apply to turntables, microphones, or instruments, as these need preamplification and equalization.

The GAIN controls differ in operation be- tween stereo, dual mono, and bridged modes:

STEREO and MONO:

Each control is independent; CH 1 GAIN only changes CH 1, CH 2 GAIN only changes CH 2.

BRIDGE:

Only the CH 1 GAIN control will work because the CH 2 control is bypassed internally.

FULL SYMMETRY DUAL DIFFERENTIAL HIGH CURRENT DESIGN PROFESSIONAL POWER AMPLIFIER

CH	GAIN/dB
1		3v
	16	18	20
			2v
14			22
12			24

626

00	28
	1v

SENSITIVITY 1.23v (+4dBu)

SIG OL	OL
–3	–3
–6	–6
–9	–9
–20	–20
CH STATUS
1&2
NORM	HOT

GAIN/dB		CH
	3v	2
16	18 20		ON
		2v
14		22
12		24
6		26	OFF
00	28
	1v
SENSITIVITY	1.23v (+4dBu)		POWER

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