Integrated Amplifiers

NAD M3 Integrated Stereo Amplifier

ARTICLE INDEX

The Design

The M3 is officially classified as dual-mono rather than stereo, because each amplifier has its own separate power supply. This is not a defining feature, but rather, is just one item that does separate it from other integrated amplifiers. By having the two channels configured as dual-mono, this greatly reduces crosstalk between channels.

The preamplifier section uses JFETs in Class A operation. Volume, Tone Control, and Tilt utilize precise 0.1% tolerance resistors that are controlled by a digital circuit. This eliminates wiring that would otherwise have to go to the front panel and back to the circuit board. I know you might be thinking at this point, “But I thought that tone controls worked best if left in the digital domain.” Well, remember, the M3 is a totally analog product. There is no DAC input because the M3 doesn’t have a DAC, USB or otherwise, nor does it have A/D conversion. The only digital circuit is the one that switches the various precision resistors in and out of the analog circuit for volume, tone, and tilt control.
The output stage monitors the load impedance to prevent distortion levels from going too high, and thus, the amplifier tends to deliver volume levels that belie the 180 watt output spec.

The front panel (see large version of picture at the beginning of the review) has an On/Off power button and volume control knob. Underneath the LED display panel are buttons labeled “Listen” (You then select the input that you want from the remote control), “Record” (Sets the input to be sent to the Record output jacks on the rear panel), “Mode” (Stereo, Left, Right, Mono), “Balance” (Left vs. Right Volume), “Tone” (Tone Controls), “Biamp” (uses selectable crossover frequencies of 40 Hz, 60 Hz, 80 Hz, or 100 Hz,  if you want to drive the tweeter and midrange driver of a speaker with one of the power amplifiers, and the woofer with the other channel), and “Speakers” (A, B, A+B). The fact that you can connect two sets of speakers to the M3 is reflected by the fact that it is rated into 3 ohms – very unusual for a product of this type and price point.

The inside of the chassis wastes no space, and you can see the two separate power supplies along the sides at the bottom. The heat sinks are very large, and the unit got pretty warm during use. I would guess it is biased about 10 watts per channel into Class A.

 

 

As you can see in the photo below of the rear panel, it is packed with connections, including the various pairs of RCA analog inputs, one set of XLR inputs, and also IR connections and trigger for remote turn/on of other amplifiers (which you would need if you use the M3 in Biamp mode). The Main In/Pre Out has removable U-shaped connections for ease of using the M3 as a bi-amplifier.

 

 

The XLR inputs are fully balanced, to deliver Common Mode Rejection, i.e., electrical noise that is picked up by the interconnect. The balanced +/- input pins feed into identical 100k//100pF discrete buffers and then to a discrete differential amp with unbalanced output  to the rest of the unbalanced preamp. There is a trim pot that adjusts common mode rejection to > 70dB. I used the XLR input for most of the bench tests.

The M3 package includes two remotes, one with all the buttons, and a small one that has the most often used buttons. They are luminescent in the dark but are not illuminated by back lighting.