The Ultimate Line Amplifier
The LA4 is identical to the HPA4 except that it eliminates the
headphone outputs. The LA4 is well-suited to customers who do not need
the headphone amplifier.
The LA4 is a line-level preamplifier that is designed to sit between a
reference-quality D/A converter and a reference-quality power
amplifier. This is not an easy task. Most hi-fi preamplifiers introduce
significant noise and distortion due to the necessity to provide volume
control and input switching. To solve this problem, the LA4 is
completely relay controlled and features analog amplifiers with
vanishingly low distortion. It features relay gain control, relay input
selection, and relay muting. The entire system incorporates the finest
gold-contact relays available. The gain control has 256 steps in 0.5 dB
increments. It also features a relay-controlled balance adjustment.
Relay closures are precisely timed to deliver silky-smooth volume
changes. No other relay gain control offers this level of precision or
performance. The LA4 includes 2 independent 256-step attenuators: one
for the left channel and one for the right channel. To make this all
happen, the LA4 includes a total of 40 precision relays that switch
high-precision metal-film resistors.
100% Analog Signal Path
The LA4 is 100% analog. It is designed to be driven from external D/A
converters and external line-level analog sources. The LA4 is designed
to drive any professional or hi-fi power amplifier. The LA4 provides the
ultimate analog signal path between inputs and outputs. The LA4
eclipses the performance of typical high-end hi-fi preamplifiers by
achieving much lower noise and distortion.
At any volume setting, the relay-controlled gain stage provides an
optimized attenuator to match the upstream analog source to the
downstream power amplifier. This optimization of the gain staging
delivers the best possible system SNR for each volume setting. The LA4
will match high-output D/A converters to low-input power amplifiers and
vice-versa. It will also provide an optimized interface to and from
balanced and unbalanced devices. In addition, it will match high-level
professional balanced interfaces to low-level hi-fi balanced
interfaces (in either direction).
Speed and Precision
The bandwidth of the LA4 extends from 0.01 Hz to over 500 kHz. This
means that the LA4 delivers very precise amplitude and phase accuracy
over the entire audio bandwidth. Wave shapes are accurately reproduced,
and the entire spectrum is delivered with precise timing. The LA4 will
deliver musical overtones with life-like accuracy. This means that
musical instruments are rendered without changing their sonic character.
Balanced and Unbalanced I/O
The LA4 features two balanced stereo inputs and two unbalanced stereo
inputs. The line amplifier provides one balanced stereo output, one
balanced mono sum, and one unbalanced stereo output.
The LA4 includes IR remote control and can be operated using the
optional Benchmark remote. The LA4 is designed to work with the
Benchmark DAC2 and DAC3
converters but may be driven from any high-end D/A converter. When
paired with a Benchmark DAC, a single remote control will operate both
The LA4 (line amplifier) or HPA4 (line amplifier + headphone amplifier) are the perfect complement to the Benchmark AHB2. These
may be the only preamplifiers or line amplifiers that exceeds the
signal to noise ratio of the ultra-quiet AHB2. This means that the LA4
will extract the full performance of the AHB2. In contrast, other preamplifiers limit the system noise performance because they cannot match the SNR performance of the AHB2. The LA4 and HPA4 are the only line amplifier/preamplifiers that we recommend inserting between a DAC and the AHB2. The LA4 or HPA4 can be inserted between a Benchmark DAC3 and AHB2
without degrading the system noise performance. With the LA4 or HPA4
inserted, the DAC3's 32-bit digital gain control is replaced by a
more-resolving fully-analog relay gain control.
12V trigger ports can be used to link the LA4 with external D/A
converters and power amplifiers. The trigger signal controls the
power-up and power-down sequencing of the entire audio system. The
trigger ports are compatible with most industry-standard trigger input
or output ports, but can communicate bidirectionally with other
The touch screen provides easy access to advanced features such as
balance control, input level offsets, input names, screen dimming,
remote control, and function locking. Help screens explain the special
The volume control knob features a high-quality optical encoder that
is rated for heavy use. An acceleration feature makes it easy to move
through the 256 volume steps while maintaining 0.5 dB/step resolution. A
press of the control knob will wake turn on or brighten the screen if
you are using the screen sleep or auto-dim functions.
The LA4 includes an on-screen mute button for the line outputs.
Outputs can also be muted with the volume knob or with the optional
The LA4 includes an on-screen -20 dB "audio dim"
button that instantly reduces the level by 20 dB. This function provides
a temporary volume reduction and makes it easy return to the previous
listening level. This control makes it easy to transition between a
normal listening level and a background level. The -20 dB "dim" function
is also accessible from the optional remote control.
Inputs may be renamed and unused inputs may be disabled. Input levels can be trimmed to provide input-to-input level matching.
brightness is adjustable and timers can be set to dim or shut off the
display. The screen can be locked to prevent access to advanced
The LA4 is available with a black or silver faceplate and is designed to match the Benchmark AHB2 power amplifier. It occupies the same footprint as the Benchmark DAC1, DAC2 and DAC3
converters. The case features a milled faceplate and milled sides. Top,
bottom, and rear panels are made from thick aluminum and feature a
brushed texture. The LA4 is built to last and will be a fine addition to
your listening space.