3. INPUT LEVEL CONTROLS

The amplifier is equipped with separate input level controls for each

channel. Before turning on the M25 for the first time, make sure all

level controls are in their normal full-clockwise position.  With the

input levels set to the maximum position, the gain is exactly

conforming to THX Ultra

2

™ 

standards.

Under some circumstances, other settings may be useful for:

• Level-matching - In systems that incorporate speakers of varying

efficiencies, it may be necessary to reduce the settings of some

controls to achieve proper channel-to-channel balance.

• Extended volume-control range - Many stereo systems have so

much voltage gain that the speakers (or your ears) are over-driven

at any volume-control setting higher than 11 or 12 o’clock position

of the volume control. As a result you can use only the lower half

of the volume control’s range, where adjustments are imprecise

and channel-balance errors tend to be greater. If all input level

controls are reduced, you can turn up your preamplifier’s volume

control, making effective use of most of its range. (Suggestion:

Adjust the input level controls so that your preferred maximum

sound levels occur at about 2 or 3 o’clock on the volume control.)

As an added benefit, this procedure suppresses any noise produced

by the preamp’s high-level circuitry (e.g. any residual hum or hiss

that does not go away when the Volume is turned down).

4. SPEAKER CONNECTIONS

This amplifier is equipped with special high-current binding-post

speaker terminals. Connect the loudspeakers with heavy-duty (16-

gauge or thicker) braided wire. Connections may be made in any of

three ways. [See Figure 2.]

• Strip off a half-inch (1 cm) of insulation from each speaker wire. In

each conductor, twist the thin strands of wire together. Unscrew

the knob, insert the bare wire into the opening at the base of the

binding post, and tighten the knob until it grasps the wire securely.

Check to be sure that there are no loose strands of wire touching

the chassis or an adjacent terminal.

• Spade lugs. Unscrew the knob, insert the U-shaped spade lug

behind the bushing, and tighten the knob until the spade lug is

secured.

• Install banana plugs on your speaker wires, and plug them into the

end of each binding post.

NOTE: 

Speakers must operate in phase with each other in order to

produce a proper stereo image and to reinforce rather than cancel

each other’s output at low frequencies. When connecting speakers,

take care that the red (positive) terminal on each loudspeaker is

connected to the corresponding terminal marked red (positive) on

the amplifier.

5. AUTO TRIGGER ON/OFF

Set the Auto Trigger switch to the ON position to activate the 12V-

trigger. By connecting the 12V-trigger, the M25 can be remotely

switched to On and Standby and vice-versa. When set to the Off

position, the 12V-trigger input is not active.

NOTE: 

With the Auto Trigger switch set to the ON position and the

12V-trigger input connected, the M25 will switch from Off to

Stand-by when the Power Switch on the front panel is pressed. For

normal operation, ensure the switch is in the OFF position or that

the 12V-trigger input socket is not connected.

6. 12V-TRIGGER INPUT

For external Power on/Stand-by switching, connect the 12V-trigger

output of a source component to this DC input jack. The center pin is

the live or + connection, the outer sleeve of the input jack is the 12V-

trigger - or ground connection.

NOTES: 

The M25’s 12V-trigger will work within a range of 6 to 15 V

DC level and typically draws less than 10mA of current. Check the

specifications of the 12V-trigger source to ensure it is compatible

with the M25’s 12V-trigger input. Do not exceed the

recommended voltage as this may cause damage to the M25.

7. SOFT CLIPPING

When an amplifier is driven beyond its specified power output it

normally produces “hard clipping” or distortion of the signal. Such

hard clipping, in addition to sounding unpleasant, can damage the

speakers in the system. The NAD Soft Clipping circuit gently limits the

output waveform, minimizing audible distortion and reducing the

change of speaker damage when the amplifier is overdriven. We

recommend that the Soft Clipping switch on the back panel of the

M25 be left in the ON position when system is being operated at levels

that might exceed the amplifier’s power capacity. The LED on the front

panel indicates if Soft Clipping has been engaged.

8. FUSE HOLDER

There is a fuse holder nearby or next to the AC-line cord. In the

unlikely event a fuse may need to be replaced, unplug the line cord

from the wall. Then remove all connections from the amplifier. Only

replace the fuse with the same type, size, and specification.

9. GROUND CONNECTOR

The M25 is provided with a GROUND terminal on the rear panel. This

terminal is connected directly to the chassis of the M25. In the event

of radio hum or radio interference, this terminal can be connected to

a ‘true earth’ such as a copper plated rod driven several feet into the

ground.

8

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