Unpacking the 2800E reveals an unusual looking power amplifier. The amplifier is finished in either a chrome plate or bright dip finish. Small portions of the heatsink are visible on either side and the top cover wraps around the sides of the unit with two cutaway sections for the heatsink. It also has a Plexiglas window allowing a small portion of the printed circuit board to be seen. Centrally located is a fan that provides forced air-cooling. The 2800E is physically quite large, measuring approximately 12.75" (width) x 15" (length) x 2" (height). It is not heavy for its size, probably a function of having a fan to aid in the cooling process, and all of the input and output connections are located on one end of the unit. There are hefty connectors for both loudspeakers, and the power inputs, which appear to be gold-plated. Other controls and connectors include RCA left and right inputs, gain adjust, low pass and high pass frequency controls and a switchable bass boost feature. Included together with the amplifier is an owner's manual that adequately describes how the unit works. Also included are four mounting screws along with two Allen wrenches.
The 2800E is a two channel stereo amplifier that is rated at 2 x 200W, although there is no mention at what load impedance or DC input voltage. The internal crossover is selectable as high pass, low pass or full range mode. High pass is adjustable from 120 Hz to 750 Hz; low pass from 30 Hz to 120 Hz; but there is no mention of the order of the filters, i.e. the slope. The manual also states that the power supply is regulated. Two 30A fuses provide protection. Internal protection includes over current and thermal.
Popping out the retaining screws allows the top to be removed exposing the electronics. Internally the 2800E is as unusual as the outside. The fan and heatsink modules occupy about one half of the internal space. The remaining half contains actual electronics. The 2800E is essentially split into two distinct sections along its length. The right side containing power supply circuitry, and the left side and front center section the audio circuitry. The input to the power supply has some filtering in the form of a choke and capacitor as well as reverse polarity protection in the form of diodes. Without dismantling the amplifier the choice and number of power supply switching devices cannot be determined. The power transformer is well-sized and neatly wound. The PCB appears to be gold-plated copper with a clear solder mask. On the audio side of the board you can see that the layout was accomplished neatly with a fair amount of attention to detail. Again because of the physical construction the number and choice of the output transistors cannot be determined. There are only two short flying wires used that are not conducting power or audio signals. Good use of copper buss bars is made where necessary. On the power supply side there is 6600uF of input capacitance and for the audio sections there is a total of 13200uF of reservoir capacitance. There is one vertically aligned daughter board that carries the power supply controller and associated circuitry. While the fan is relatively large, 80 x 80 x 25 mm, it is unclear how effective it can be since it draws air in from the top of the unit and exhausts straight to the bottom of the case. There appears to be little in the way of airflow management, where there would be some means of ensuring that the cool air actually flows over the heatsink fins. Overall the internal design of the 2800E is fairly well done, showing the use of decent quality components and layout technique.
Comments: As can be seen from the power output numbers the 2800E is actually an unregulated design. However the amplifier does make respectable power output; it is either higher or lower than claimed depending upon how you look at it. The results for damping factor and THD are indicative of a high feedback design; DF is high and THD is very low. The bass boost circuit appears to offer +15 dB of boost at 55 Hz, slightly different from the claimed numbers; but it's nothing much to worry about - if you need more than 15 dB of boost at 55Hz then something else is wrong! As for the crossovers on the 2800E - neither the frequency ranges nor filter alignments are accurate. In fact the Q of the filters appears to change significantly as the frequency control is rotated, changing from under damped to over damped response. This is can certainly detract from the overall sonic quality in some instances. The actual response curves can be seen in figures (3) & (4). Overall bench performance was fine with the exception of the crossover filters.
ConclusionThe 2800E from an overall standpoint is an interesting design cosmetically as well as from an engineering standpoint. It is relatively well built and has decent electrical performance, aside from the performance of the crossovers. From a sound quality standpoint the unit faired quite well. There are no real weaknesses. The bass sounds have a tight and dry feel to them, and are not quite so effortless and deep sounding as some other models. Midrange and treble sounds are detailed and quite articulate, sometimes bordering on a cold and non-involving nature. It is fair to say that the nature of sound is one intrinsic of a high feedback design. Not a bad package.