Instruction Manual for HPA4 with 1.0.X Firmware – REV B Page 24
HPA4 System Overview
The Ultimate Headphone Amplifier
Benchmark Media Systems, Inc. and THX,
Ltd. have partnered to introduce the
Benchmark HPA4 headphone/line amplifier
featuring THX Achromatic Audio Amplifier
(AAA™) technology.
THX AAA™ reduces harmonic,
intermodulation, and crossover distortion by
20 to 40 dB to guarantee a realistic and
fatigue-free listening experience. It
accomplishes this using a patented feed-
forward topology to null conventional
distortion and noise mechanisms, resulting in
the world's most linear amplifier. THX
AAA™ allows the amplifier to reach its
maximum output power and sound pressure
level (SPL) without producing the distortion
that normally accompanies increased output
levels in traditional amplifiers.
Featuring the flagship THX-888 amplifier
design, the revolutionary HPA4 headphone
amplifier incorporates the same THX
AAA™ technology that Benchmark uses in the
AHB2 power amplifier. The HPA4 delivers
sonic perfection. Hear the music without any
contamination from electronic noise or
distortion. The HPA4 delivers power, audio
fidelity, speed and accuracy over an utterly
silent background.
The Ultimate Line Amplifier
The THX-888 amplifier is driven by a
Benchmark line amplifier that features relay
gain control, relay input selection, and relay
muting. It is designed to deliver the lowest
possible distortion and noise over a wide
range of volume settings. We believe that the
HPA4 line amplifier is the finest available at
any price.
Relay-Controlled Gain Stages
The relay-controlled gain stages provide 256
volume steps in precise 0.5 dB increments.
These gain stages feature the finest gold-
contact relays available.
Relay closures are precisely timed to deliver
silky-smooth volume changes. No other relay-
controlled gain stage offers this level of
precision or performance.
The HPA4 includes 4 independent fully-
balanced 256-step volume controls: two for
the L&R headphone outputs, and two for the
L&R line outputs. To make this all happen, the
HPA4 includes a total of 64 precision relays.
Balance Controls
The line and headphone outputs feature
independent balance controls that are
adjustable in 0.5 dB steps.
100% Analog Signal Path
The HPA4 is 100% analog. It is designed to
be driven from an external D/A converter or
an external analog source. The HPA4 is
designed to provide the ultimate analog signal
path between inputs and outputs. The HPA4
eclipses the performance of typical high-end
preamplifiers by achieving much lower noise
and distortion.
Fully-Balanced Signal Paths
The internal signal paths are fully balanced.
The inputs are routed to a balanced pair of
precision differential amplifiers. These drive
two sets of fully-balanced 256-step volume
controls. The balanced outputs from the
volume controls drive the headphone
amplifier and line output drivers.
Differential Amplifiers
The HPA4 features precision differential
amplifiers on all inputs. These reject
common-mode noise, common-mode
distortion and common-mode interference.
This feature is especially important when
using D/A converters that lack their own
differential amplifiers.
Benchmark D/A converters include differential
amplifiers, but many competing converters
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