Features
It was nice to see that Autotek went the extra mile and included features like balanced inputs and zero to 180-degree phase adjustment on the 1400.1D. This unit also uses a well-placed variable 13 to 250Hz, 24dB lowpass crossover as well as a variable subsonic filter up to 35Hz. Rounding it off, the preamp features is a 0 to 18dB bass boost at 45Hz. Autotek also included an illuminated remote control to mount within arm's reach of the driver.
Cosmetics
Keeping with the high-class Euro-style design that Autotek fans have clamored over, the new Mean Machine amplifiers are sleek and still manage to portray the hidden power inside. With its brush-finished stainless steel cowling covering its more than 10 pounds of black extruded heatsink, the amplifier has a classy look and yet the heft to let you know that it can deliver. The illuminated Autotek logo top center is subtle, with an even blue light when the unit is powered. The top cover is reversible for installations where you want two amplifiers side by side; however, I'm not certain whether this is forbidden, as the warranty language is vague on the topic. The controls are clearly labeled on one endplate while the power and speaker terminal blocks as well as fuses protrude through the other.
Design
Pulling the cover off, one will see the huge power supply and clean overall layout. All of the power devices are mounted with spring clips to the heatsink with an insulator tape and thermal grease -- a mounting method we really like to see. Given the temperature stresses an amplifier undergoes while in use, it is hard to maintain even distribution of pressure between the power devices and the heatsink using a solid mounting option with screws or bars. Spring clips remove this problem. Other thermal measures were taken for the fuse holders. By using fewer larger fuses and bussing the current with large wire instead of using circuit board traces, a few watts of heat were saved rather than being generated in the amplifier.
Power connections for the amp accept 4-gauge power and ground. According to our IASCA handbook, this is a little small for the total fuse rating of 160 amps. In fact, the handbook and "The rec.audio.car FAQ" site both recommend ought-gauge wire for runs up to 22'. Of course, this would be worst-case scenario, and it is likely that you won't be able to power this amp to its maximum capabilities for extreme amounts of time; but it you were to, both the 4-gauge wire and terminal blocks could feel the heat. At 5 percent distortion we measured 170 amps of current.
The speaker terminal block is set up to allow two parallel connections with 8-gauge wire. What I found frustrating is that the power, remote and speaker terminals require three different sizes of hex drivers to tighten. Fortunately, Autotek provides these with the amplifier, but it can be annoying to have to find one again to adjust a cable.
On the preamp side, RCA inputs connect with pass-through output RCAs for daisy chaining amps together. This is also where the remote and balanced input connectors are located. The balanced inputs connect through a 6-pin connector which, in my opinion, would not be capable of staying connected if used while the amp is mounted to a sub cabinet.
The power supply consists of dual transformers controlled by a single PWM chip to keep them in phase with each other. They easily supply the power the amplifier needs. Taking up nearly two-thirds of the interior there is still not a huge amount of capacitance on the input to the supply or on the outputs. Being a Class D amplifier and an unregulated supply, these are design decisions made solely on putting in what is needed for a strong, reliable product. This also keeps the size and price down, making this a relatively small amplifier considering that it produces nearly two kilowatts of power.
Amplification of what Autotek refers to as "Super D-Class" is carried out by a pretty standard Class D chipset, the HIP4080A. While this is a relatively new chipset for Class D amplification in the car audio market, it has been around for a number of years, so most of the bugs have been worked out of it. This has permitted Autotek to claim the benefits of its high-speed conversion, accuracy and low distortion. As stated by Autotek, "Super D-Class amplifiers offer higher current capacities and more precise digital to analog conversion, resulting in very low distortion levels, even at high listening levels. Super D-Class possesses a significantly greater efficiency rating than analog and lesser D-Class designs from our competitors." We'll see if these claims are true in just a bit.
The main power supply is not synchronized with the Class D switching portion of the amplifier. This doesn't affect the efficiency or performance of the amplifier, but it does lead to some odd effects if your speaker and enclosure have a large frequency-response range. For fun we did hook it up to a fullrange speaker, without any audio, and the difference in switching frequency from the supply and the Class D section make for a good science fiction sound effect. This is not a problem or an issue for an amplifier that won't be hooked up to a speaker with such a response, but a fun thing to try nonetheless.
The majority of the components in this amp are pretty generic. The frequency control pots use detents which some people like and others don't. The capacitors are really being pushed in this design -- now it won't really effect the performance, but I don't really like to see a large number of 85C electrolytic capacitors as the amplifier could exceed this temperature in places, creating a problem.