Owner’s Reference
DirectStream DAC
©2014 PS Audio Inc. All rights reserved.
Introduction
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Introduction
shaping fi lters in the sigma-delta modulators in particular, offer
many degrees of freedom for a fi lter designer. There isn’t a
mathematically perfect fi lter to use (they all have tradeoffs), so
we’ve chosen the fi lters 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 fi lters. 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 fi lter. Our instrument still runs the noise
shaping fi lter 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) fi lters with wide coeffi cients and 144dB S/N
are employed along with many guard bits in the IIR fi lters 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 signifi cant 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 fi ltering
In Conclusion
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