Instruction manual

DAC1 PRE Instruction Manual Rev I Page 6
Any signal that can be decoded by the USB or
AES/EBU receivers will be reproduced without
the addition of any measurable jitter artifacts.
The AES/EBU receiver IC has been selected
for its ability to accurately recover data in the
presence of very high jitter levels.
HPA2™ Headphone Amplifier
Two ¼” headphone jacks are driven by the
HPA2™ - Benchmark’s signature high-
current, 0-Ohm headphone amplifier. The
HPA2™ is capable of delivering the full
performance of the DAC1 PRE into the
difficult loading presented by headphones.
The HPA2™ maintains less than 0.0003%
THD+N under full load.
High-Current Output Drivers
The DAC1 PRE features new high-current
output drivers that are capable of driving
300-Ohm loads without an increase in
distortion. They are also well suited for
driving long cables or high-capacitance loads.
‘Audio-Always’ Design
Philosophy
The DAC1 PRE is designed to perform
gracefully in the presence of errors and
interruptions at the digital audio inputs. A
soft mute circuit eliminates pops when a
digital signal is applied. Power management
circuitry controls the muting and resetting of
all digital circuits upon removal and
application of power. Audio is present at the
outputs only 60 ms after applying, selecting,
or restoring a digital input signal and only 500
ms after applying power to the unit.
The DAC1 PRE is designed to avoid all
unnecessary mute scenarios. Muting is only
enabled upon loss of power, or when digital
transmission errors occur. The DAC1 PRE
does not mute when the AES or S/PDIF input
data is all zeros. Consequently, no audio is
lost when an audio transient follows full
silence. Furthermore, the DAC1 PRE signal-
to-noise specifications represent the true
system performance, not just the
performance of an output mute circuit.
The DAC1 PRE will operate even when
sample rate status bits are set incorrectly.
Sample rate is determined by measuring the
incoming signal. Lack of sample rate status
bits or incorrectly set status bits will not
cause loss of audio.
The DAC1 PRE includes non-volatile memory
that saves the state of control settings when
AC power is removed for a period of up to
several hours. The unit will resume normal
operation after interruptions in AC power.
Low-Noise Internal Power
Supply
The internal power supply supports all
international voltages with generous margins
for over and under voltage conditions. It has
excellent immunity to noise on the AC line
and no external AC filtering is required.
Phase-Accurate Multi-Track and
5.1
The DAC1 is phase-accurate between
channels at all sample rates, and is phase
accurate between any combination of DAC1,
DAC1 USB, and DAC1 PRE converters at
sample rates up to 96 kHz. Phase-accurate
multi-track and 5.1 surround systems are
easily constructed using any combination of
DAC1 series converters.
Automatic Digital De-Emphasis
Pre-emphasis was used on many early CD
recordings. It is rarely used on newer
recordings and consequently some D/A
converters omit de-emphasis. The DAC1
PRE will correctly apply precise digital de-
emphasis when and if it is needed. The de-
emphasis circuit supports 44.1, 48, 88.2 and
96-kHz sample rates and is automatically
enabled in response to the pre-emphasis
status bits in consumer format digital signals.