The heat-sink fins for the output transistors extend out from the sides of the chassis and wrap around the back.

The heavy-duty power cord plugs into a recessed socket on the rear.

There is also a rear monostereo pushbutton switch that converts the left- and right-channel amplifiers into one bridged mono amplifier rated at 450 watts into a single 8-ohm load.

The MOSFET output transistors (six per channel) are also immune to thermal runaway, eliminating the need for protective circuits to guard the output devices against destruction from excessive current.

A useful feature is the Soft Turn OnOff system, which monitors the regulated low-voltage power supply.

When the amplifier is turned on, its circuits are disabled until the system determines that voltages are normal; then it activates the amplifier through a small MOSFET switch in its input stage.

When the amplifier is switched off, the system rapidly cuts off the amplifier circuits before the power-supply voltages begin to collapse.

The result is a complete elimination of thumps and noises from the speakers when the amplifier is turned on or off.

The case is extensively perforated with ventilating slits and, like the heat sinks and front panel, is finished in black.

An optional rack-mount version has a silver-finish 19-inch front panel slotted for an EIA-standard rack or installation in a cabinet.

In later listening tests we found that it ran nearly as hot as it did during bench testing, suggesting that its operating conditions may have been closer to true Class A (in which the power dissipated in the amplifier is relatively independent of signal level) than to Class B.

Noise was very low, and frequency response was almost perfectly flat across the audio band, dropping off by less than half a decibel at 100 kHz and 2 dB at 200 kHz.

Most amplifiers using Class AB output-stage biasing show a steady increase in distortion at low levels as power is reduced (especially below 1 watt).

The Hafler amps distortion, however, was not only low at any level short of clipping but was still decreasing as the power dropped below 1 watt, where it had already fallen to 0.0025 percent into 8 ohms and 0.004 percent into 4 ohms.

This may or may not have any relationship to the Model 9300s sound quality, but it is certainly evidence of careful and thorough circuit design.

The same thoroughness was apparent in the owners manual, which included not only complete electrical and mechanical specifications, drawings of the front and rear panels, and useful suggestions on installation and operation, but also a parts list, a drawing of the main circuit board with part-number IDs, an electrical schematic diagram, and a functional block diagram.

Clearly, it is a class act, especially among amplifiers in its price range.

Hafler P3000 Transnova Pdf