The 885 Integrated Power Amplifier is showcasing itself as the latest integrated amplifier in the 800 series. It is also represents a pinnacle in the consistent technological evolution, and our thriving art, of designing and constructing amplifiers.
It was the AMP1, launched in 1993, which was the first amplifier not to be based on the widespread “operational amplifier” principle, but rather the principle used by the current feedback amplifier (“current mode amplifier”). The 885 is now opening a whole new chapter: the circuit design principle of the “single ended push-pull” amplifier, which has been derived from valve technology, is being employed for the first time ever in a fully-symmetrical transistor amplifier with current feedback. The expert combination of these three sophisticated technologies yields a decisive advantage in audio quality. This means that the 885 masters all varieties of music, from mellow to militant, and its unmitigated aplomb and naturalness are immensely satisfying. Let yourself be astonished!
The 885 is comprised of two entirely separate amplifiers which are housed together in one unit. The only connection between the two channels is at the power socket. Each channel is equipped with a 500-watt transformer all of its own. The brilliance of the resulting channel separation ensures an exceedingly vivid stereo sound and generously-phased spatial reproduction.
Symmetrical signal processing
Both channels of the 885 are configured in full symmetry. Asymmetrical input signals are also converted into symmetrical signals and adapted to the ideal level using a symmetrical volume attenuator, a standard used in studio technology. The high level of common mode rejection attained using this circuit principle allows a far higher dynamic scope than otherwise possible with asymmetrical circuits. This is an extremely important prerequisite for rendering high-resolution music recordings!
Push-pull output stage
Each channel of the output stage of the 885 is equipped with 8 high load-capacity power transistors. In contrast to standard amplifiers, these transistors are not housed next to each other, but rather in the form of exceptionally low-induction H bridges. This effectively prevents any losses due to eddy currents in the high-frequency range. The result is a exquisitely fine and transparent playback, even at low volumes.
Intelligent quiescent current adjustment
The complete 885 has been produced using “thermal track” power transistors. These transistors feature a diode on the transistor chip which immediately senses the temperature, and instantaneously adjusts the quiescent current to the correct level. This eliminates any quiescent current problems typically encountered by “class AB” power amplifiers.
“Current mode” amplifier
The real highlight of the 885 is its amplifier circuit. The fully symmetrical design featuring current feedback is based on an idea originating in the era of the valve amplifier: the “single ended push-pull” amplifier. Utilizing highly linear, special transistors from Japan allowed this principle to be successfully applied to a “current mode” amplifier. The radical reduction in the number of components required, as well as the extremely short signal paths it results in, paves the way for a tremendous increase in audio quality. Meticulous selection of components as well as close-tolerance thin film resistors and low-loss film capacitors contribute the rest, making a previously unparalleled playback quality possible.