Owner’s Reference
DirectStream DAC
4826 Sterling Drive, Boulder, CO 80301
PH: 720.406.8946 [email protected] www.psaudio.com
Introduction viii
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©2014 PS Audio Inc. All rights reserved.
Introduction
14. Digital filtering in general, and the upsampling and noise
shaping filters in the sigma-delta modulators in particular,
offer many of degrees of freedom for a filter designer. There
isn’t a mathematically perfect filter to use (they all have
tradeoffs), so we’ve chosen the filters that sound best in our
experience and in addition to that we run everything with as
wide of an audio bandwidth as possible.
15. Although design choices might have been made to run
everything at single rate DSD (64 * 44100Hz), it was decided
instead to run at double rate DSD to have a wider audio
band below the upsampling and noise shaping filters. Noise
shaping is how a high rate sampled signal can have more
accuracy in part of the spectrum than the 6dB / bit rule and it
is understood that the quantizer in a sigma-delta modulator
can hide a multitude of sins in the noise shaping filter. Our
instrument still runs the noise shaping filter at full precision to
get the cleanest DSD signal possible.
16. No shortcuts are ever taken in the Digital Signal Processing
(DSP) section of the FPGA. Despite the fact that DSD is only
nominally 20bit S/N, the design uses a minimum width of 24
bits throughout the device. Where needed, very expensive
(in terms of math operations) filters with wide coefficients and
144dB S/N are employed along with many guard bits in the
IIR filters and the sigma-delta modulator.
17. Every trace on the PC board is hand routed: even for the
digital sections. No autorouting is employed so that each
trace, each critical path is calculated and designed for lowest
noise, jitter and isolation.
The PerfectWave DirectStream DAC represents a significant departure in the design and
execution of PS Audio’s products. We believe this new instrument will help further our
industry, music and the faithful reproduction of music around the world.
Double rate
DSD
Digital filtering
In conclusion
