BENCHMARK
DAC1 PRE Stereo Pre-Amplifier / DAC / Headphone Amp

Features

• Six Stereo Inputs: Analog RCA, USB,
TOSLINK optical, and three digital coaxial

• Utilizes 24-bit, 192-kHz DAC1 D/A
conversion system

• Benchmark’s phase-accurate UltraLock™
technology provides total jitter immunity

• AdvancedUSB™ computer audio interface
for native 96-kHz / 24-bit USB audio

• Compatible with Windows Vista/XP/2000
and Mac OS X without driver installation

• State-of-the-art LM4562 high-current, low-
distortion opamps in critical analog circuits

• Four stereo outputs: XLR balanced,
RCA unbalanced, and two headphone jacks

• True-analog volume control on front panel

• Built-in HPA2™ headphone amplifier -
0-Ohm, high-output, two output jacks

• Selectable gain-range for headphone
amplifi er to match headphone sensitivity

• Left-most headphone jack mutes XLR and
RCA outputs (this feature is defeatable)

• Power button and rotary source selector

• “Calibrated/Variable” switch determines
gain control for main analog outputs

• Front-panel gain control of all analog
outputs (in “Variable” mode)

• Front-panel gain control of headphone
outputs only (in “Calibrated” mode)

• Rear-panel trim-pots control gain of XLR
and RCA outputs (in “Calibrated” mode)

• Selectable, low-impedance attenuators
(0, 10, 20, or 30 db) on XLR outputs

• Status LED’s - display input selection and
error conditions

• Low radiation toroidal power transformer
significantly reduces hum and line-related
interference


The DAC1 PRE is a reference-quality stereo pre-amplifier, headphone amplifier, and
computer audio playback device, incorporating the 24-bit, 192-kHz DAC1 digital-to-
analog conversion system. With the DAC1 PRE, the music engages the listener with a
stunning delivery and breath-taking realism.
The DAC1 PRE is the culmination of years of high-precision analog and digital audio
circuit design. Benchmark has achieved unprecedented sonic purity in their audio
systems through an intelligent engineering philosophy–establish a pristine analog
delivery path and eliminate digital distortion artifacts. The DAC1 PRE continues this
tradition of excellence.
With six stereo inputs and four stereo analog outputs, the DAC1 PRE anchors
expansive media systems and provides a pristine audio path from source to amplifier.
The six stereo inputs include an analog input, a USB computer input, an optical input,
and three coaxial digital inputs. The output section includes stereo XLR balanced,
RCA unbalanced, and two headphone jacks driven by Benchmark’s HPA2TM 0-ohm
headphone amplifi er.
All digital inputs of the DAC1 PRE (including USB) feature Benchmark’s jitter-immune
UltraLock™ clock system. The USB input operates with Benchmark’s AdvancedUSB™
native 24-bit, 96-kHz USB technology. Other features that make the DAC1 PRE special
include a high-current output stage designed to drive even the most difficult loads,
selectable headphone gain ranges, and a rotary source selector with power switch.

The Acclaimed DAC1 D-to-A Conversion System
Engineers and audiophiles have grown to rely on Benchmark for critical digital audio
conversion for more than 10 years. They are consistently finding themselves engaged in
the music when using Benchmark converters–engaged in a way that is rarely achieved
with digital converters.
The superior performance of the award-winning DAC1 has made it the ‘Benchmark’ of
D-to-A converters. The DAC1 PRE gracefully merges the DAC1 conversion system with
elegant analog circuitry, Benchmark’s HPA2™ 0-ohm headphone amplifi er, and essential
features and functions.

Jitter-Immune UltraLock™ Clock System
Benchmark’s proprietary UltraLock™ clock system achieves an unprecedented immunity
to jitter. Many modern (and expensive) converters suffer from significant jitter-induced
distortion. If jitter is not effectively addressed, a converter will generate non-musical
sideband tones and digital distortion. Benchmark’s highly-regarded UltraLock™ clock
system ensures that jitter is never a problem, even under extreme conditions.
Even in the presence of extremely high input jitter, no jitter-induced artifacts can be
detected on the outputs of the DAC1 PRE (using state-of-the-art testing equipment by
Audio Precision). UltraLock™ will block more than 12.5 UI of jitter (@ 1 kHz).
With the UltraLock™ clock system, the D/A conversion-clock in the DAC1 PRE is totally
isolated from the clock of the digital audio source. The UltraLock™ clock system easily
outperforms most well-designed two-stage PLL designs.
The bottom line is this: Benchmark converters will consistently and faithfully deliver
truthful audio without jitter-induced artifacts, no matter what variables are present.

AdvancedUSB™ Audio Technology
The USB interface of the DAC1 PRE operates with Benchmark’s unique AdvancedUSB™
technology. Unlike many USB equipped D/A converters, Benchmark’s Advanced-USB™
technology supports 24-bit audio at sample rates up to 96 kHz without the installation of
any drivers or other special software. Benchmark’s UltraLock™ clock system isolates the
converter from the high levels of jitter that are found on USB interfaces. AdvancedUSB™
responds automatically to sample-rate changes to bypass the operating system’s
sample-rate conversion. The DAC1 PRE achieves transparent, audiophile-quality
playback through a true plug-and-play solution.
It is very important to have a 24-bit USB path, even for 16-bit playback, because digital
volume controls and other DSP functions can increase 16-bit audio to 24 bits. If a 16-bit
USB interface is used, up to 8 bits of each digital audio sample will be truncated resulting
in significant, non-musical digital distortion at audible levels.
Audio streamed via USB is subject to significant amounts of jitter. The AdvancedUSB™
interface utilizes the UltraLock™ clock system. Consequently, the performance of the
USB input is equal to the performance of the other inputs, regardless of the jitter present.
The DAC1 PRE is natively compatible with Windows Vista/XP/2000 and Mac OS X. As a
native device, there are no drivers or other software required to install or configure.

HPA2™ Headphone Amplifier
The DAC1 PRE includes the HPA2™–Benchmark’s signature high-current, 0-Ohm
headphone amplifier. The HPA2™ is arguably the ultimate reference headphone amplifier.
It will deliver the full rated performance of the DAC1 to the headphones. The HPA2™
maintains less than 0.0003% THD+N under a full load from two sets of headphones. The
DAC1 PRE has two 1/4” headphone jacks on the front panel.

A rear view

SPECIFICATIONS

• Digital Input Sample Rate Range:
28 to 195 kHz

• THD+N: -107 dB, 0.00045%
(w/ -3 dBFS input)

• SNR–A-weighted: 116 dB
(w/ 0 dBFS = +20 to +29 dBu)

• Maximum Amplitude of Jitter-Induced
Sidebands (10 kHz- 0 dBFS
test tone, 12.75 UI sinusoidal jitter at
1 kHz): < -141 dB

• Maximum Amplitude of AC line-related
Hum & Noise: < -126 dB

• Headphone amp output impedance:
0.01 ohm

• Headphone amp output-level range
(@ 0 dBFS into 60 ohm load):
Off-to+21 dBu

• Headphone amp THD+N:
-107 dB, 0.00045% (w/ -3 dBFS input)

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© 2008 Posthorn Recordings