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858 Dual Mono Power Amplifier

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Power amplifiers form the decisive link between the low signal voltages emitted by the source and the high level of power required by the loudspeaker. Highly conflicting requirements make designing an amplifier like this a real challenge: on the one hand, rendering the most subtle details and while remaining true to the timbre; on the other hand, absolute forcefulness and authority even when mastering difficult loads. A challenge we have been rising to, again and again, for more than 20 years now.

The 858 Dual Mono Power Amplifier is the best amplifier which Lindemann has ever produced. A quantum leap in a lengthy development process. The perfect synthesis of technology and sound. The decisive advantage is provided by a precise combination of three complex types of technology: The 858 showcases the circuit design principle of the “single ended push-pull” amplifier, which has been derived from valve technology, and is being employed for the first time ever in a fully-symmetrical transistor amplifier with current feedback. This means that the 858 masters all varieties of music, from mellow to militant, and its unmitigated aplomb and naturalness are immensely satisfying.

Dual mono configuration

Dual mono configuration

The 858 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 800-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

Symmetrical signal processing

Both channels of the 858 are configured in full symmetry. 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!

„Current mode“ amplifier

„Current mode“ amplifier

The real highlight of the 858 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.

Intelligent quiescent current adjustment

Intelligent quiescent current adjustment

The complete 858 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.

Push-pull output stage

Push-pull output stage

Each channel of the output stage of the 858 is equipped with 16 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.