Absence of digital filter yields accurate impulse response.
of brickwall filter yields phase accuracy across the band.
of extraneous components yields purity of signal.
Absence of complexity
yields purity of tone.
Conceptualized by Ryohei Kusunoki and made popular
by Audio Note and Sakura Systems, the original dAck! idea was brought
about on the Gainclone discussion boards. We were not happy with
the conventional CS8412->TDA1543 DAC design at many levels. The
passive I/V conversion used in that design had three major faults
– the output impedance was too high, the signal was degraded
while passing through low-quality electrolytic capacitors, and the
output utterly anemic. Sonically, we felt the resulting sound was
unfocused, grainy, and undynamic. Furthermore, the character of
the conventional Kusunoki design is completely unpredictable from
system to system.
The battery-based power supply provides the foundation
for dAck!'s unique sound. The transformer, rectifier, and filtering
circuits present in most digital to analog converters contribute
to a gritty, shrill, and unrestrained sound – something digital
sources cannot afford if the end goal is to convey music. Three
Linear Technologies precision regulators are used to further eradicate
noise in already ultra-quiet battery supplies. Oversized supply
capacitors are highly regarded Panasonic FC series incorporating
ample bypassing by high quality film parts. Proper grounding –
extremely important for any digital system – is accomplished
on the high quality PCB with oversized traces routed for noise prevention
and isolation from stray currents.
The dAck! is designed to provide tonal purity, extraordinary
soundstage coherence, and timbral accuracy, but not at the expense
of dynamics. Its sound is never fatiguing. A Philips TDA1545A multi-bit
chip – the simplest of converters – is the heart of
the conversion system. It accepts signals provided by the Cirrus
Logic digital receiver, which decodes 16-bit stereo datastreams up
to 96KHz provided through a high-bandwidth 75Ω BNC digital input. The
D-to-A chip's output is converted into voltage waveforms using high
input-impedance FET-input amplifiers from Analog Devices that are
biased into high class A using cascode FET current sources. The
analog signal travels through only one ultra-precision resistor
and one reference-grade film capacitor before reaching the preamplifier.
The resulting sound can only be characterized as clear and coherent
throughout the midband with delicate upper mids and highs.
Its small size makes it easy to fit into any installation.
Faceplates are carefully machined from 1/4" aluminum plate,
and fitted onto a distinctive steel enclosure. Each unit is meticulously
hand-built, and tested in a real system for several hours before
deployment. By selling factory direct, the dAck! provides the same
caliber of performance as vastly expensive converters costing thousands
of dollars at a small fraction of the cost.