Audio research d 90b brochure

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D-9OB AMPLIFIER

When designing a high performance power amplifier, the
engineer is faced with four primary criteria; 1) audio
quality, 2) construction quality, 3} power and 4} cost.
Audio Research successfully blends these criteria into an
ideal combination in the D908 vacuum tube stereo
power amplifier.

With over twenty years of design experience, the D908
incorporates the summed knowledge of both classic and
contemporary vacuum tube technology.

As in classic vacuum tube designs, the D908 boasts a
high energy, ultra-stiff power supply. A regulation stage
containing proprietary error correction circuitry
minimizes distortion and provides a more accurate
interface with low level stages and driver circuits. These
power supplies have been combined with cross-coupled
and fully balanced output circuitry to create a highly
stable amplifier capable of providing its intrinsic
performance into even the most difficult speaker loads.

Contemporary design features include servo coupling
of the direct coupled stages so that once set, drift and
consequent distortion are eliminated. An automatic self-
compensating, floating bias keeps bias settings correct at
the output stages, assuring smooth, non-distorted
response regardless of fluctuations in line voltage.
Extensive research into transformer technology has lead
to the creation of more efficient output transformers
offering increased detail, wider bandwidth and more
accurate staging of voices and instruments.

Consistent with Audio Research methodology, the
0908 uses only the finest materials in its construction.
Included are special wiring; a single, military quality,
double sided circuit board with enlarged foil paths for
Optimum signal transfer, and premium grade vacuum

tubes rated for industrial service. Premium grade
components are critically evaluated for their sonic
qualities and carefully selected for incorporation in signal
carrying paths. A heavy, anodized aluminum front panel
and chassis are designed for function and add to the
overall ruggedness of the amplifier. This emphasis on
unencumbered simplicity makes the D908 an
outstanding value to the listener who insists on sonic
accuracy and quality craftsmanship.

Ultra-stiff power supplies with innovative error
correction circuits, premium grade componentry, cross-
coupled and accurately balanced circuitry with self-
adjusting bias contribute to a power amplifier of utmost
musicality. Extensive research and proper execution of
all four primary design criteria have created an amplifier
that displays all of the hallmarks intrinsic to the finest
Audio Research designs; clarity, High DefinitionE,
harmonic integrity and a musically accurate dynamic
range.

The D908 is designed to meet the needs of a wide
variety of audio systems, offering peak performance at
all times. Because it is a highly accurate music
reproducer, it is suggested that it be used with
components of commensurate quality in order to
achieve best results. To fully appreciate the D908,
please contact your local authorized dealer for a
demonstration.

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FEATURES

Direct coupled push-pull input driver circuitry is servo
coupled with IC error correction for long term stability
and minimum dynamic distortion.

Individual bias adjustments for all output tubes.

Low-surge start relay circuit to protect internal
componentry from turn-on transients.

Input level controls located on rear chassis for level
matching.

SPECIFICATIONS

Power Output:

80 watts per Channel minimum continuous (both
. channels operating) at 16 ohms from 25Hz to 20kHz
with less than 0. 92. total harmonic distortion

Typically below 005% at 1 watt

Approximate actual power available per
channel at clipping (both CH. OP, 1kHz): 90 Watts

Power Bandwidth:
(-3dB Points) 12Hz to SOkHz

Intermodulation Distortion:
Less than 3% at ldB below rated output (100V p to p,
16 ohms)
(SMPTE method)

Input Sensitivity:
1.2V RMS lor rated output (adjustable)

Input Impedance:
75K ohms. nominal at maximum gain

Output Regulation:
Approximately .3dB, 16 ohm load to open circuit
(Damping factor approximately 25)

Negative Feedback:
21.5dB

Slew Rate:
15 volts/microsecond

audio research nurnnratsiiin

6801 Shingle Creek Parkway
Minneapolis, Minnesota 55430
Area Code 612 566-7570

Sonically-selected components sExtensive use of
selected low noise premium grade vacuum tubes, special
resistors and capacitors and special wiring contribute to
optimum sonic accuracy.

Other features include a military grade, double sided,
plated through-hole circuit board and industrial grade
components for long service life under continuous use.
Front panel is two color anodized aluminum for
permanent finish and lettering.

Rise Time:
5 microseconds

Hum & Noise:
Better than 90dB below rated output 20kHz
bandwidth unweighted

Power Supply Energy Storage:
200 joules

Power Requirements:
105-125VAC 60Hz (210-250VAC SOHz) 800 watts
maximum
400 watts at idle"
500 watts at rated power

Dimensions:
19" (49 cm) W (standard rack panel) x 7 (18 cm) H x
16.5" (42 cm) D (front panel back). Handles extend 1535-.
(4.1 cm) forward of the front panel.

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Weight:
64 lbs. (29 kg) Net; 80 lbs. (36.3 kg) Shipping

Authorized Dealer

D