Benchmark Media Systems, Inc.
Page 4 of 39
SYSTEM OVERVIEW:
The DAC1 is a reference-quality, 2-channel 192-kHz 24-bit audio digital-to-analog converter featuring
Benchmark’s
UltraLock™
technology. The DAC1 is designed for maximum transparency and is well suited for
critical playback in studio control rooms and in mastering rooms. A compact and rugged enclosure makes the
DAC1 an excellent choice for location recording, broadcast facilities, and mobile trucks. The internal power
supply supports all international voltages and has generous margins for over and under voltage conditions.
Two ¼” headphone jacks are driven with Benchmark’s new
HPA2™
headphone amplifier. The
HPA2™
is a high-
current amplifier that is capable of driving a wide variety of headphone loads while achieving less than 0.0003%
distortion under load.
The gain control sets the output level of the headphone jacks. It can also be used to control the output level of the
balanced XLR and unbalanced RCA analog outputs. A rear-panel switch selects
Variable
or
Calibrated
output
levels.
The DAC1 is designed to interface directly to power amps and powered studio monitors in order to provide the
cleanest and shortest path from digital to monitor output. 10, 20, and 30 dB pads are provided for interfacing to
studio monitors having high input sensitivity.
Three digital inputs (balanced XLR, coaxial, and optical) are provided and are selected from the front panel. All
inputs accept either professional or consumer formats.
The Benchmark
UltraLock™
system is 100% jitter immune. The D/A conversion clock is totally isolated from the
AES/EBU digital audio clocks in a topology that outperforms two-stage PLL designs. In fact, no jitter-induced
artifacts can be detected using an Audio Precision System 2 Cascade test set. Measurement limits include
detection of artifacts as low as -140 dBFS, application of jitter amplitudes as high as 12.75 unit intervals (UI) and
application of jitter over a frequency range of 2 Hz to 200 kHz. Any AES/EBU signal that can be decoded by the
AES/EBU receiver will be reproduced without the addition of any measurable jitter artifacts. In addition, the
receiver IC has been selected for its ability to decode AES/EBU signals in the presence of very high levels of
jitter.
The DAC1 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 a digital input signal and only 500 ms after applying power to the unit.
The DAC1 is designed to avoid all unnecessary mute scenarios. Muting is only enabled upon loss of power, or
when digital transmission errors occur. The DAC1 does not mute when the input data is all zeros. Consequently,
no audio is lost when an audio transient follows full silence. Furthermore, the DAC1 SNR specifications represent
the true system performance, not just the performance of an output mute circuit.
The DAC1 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 is phase accurate between channels at all sample rates, and is phase accurate between other DAC1
boxes at sample rates up to 110 kHz.
A fully digital 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 of consumer format digital signals.
