Pacific Northwest Audio Society meeting tonight.
Ted Smith presents discrete DSD DAC to PNWAS
Ted Smith is a longtime friend of PNWAS and was the lead designer of the new PS Audio DirectStream DAC.
Over three years ago, Ted presented an early prototype of this DAC. I remembered liking it a LOT, and members asked if it would ever get into production. It is a discrete DSD-based DAC. All of the input processing, upsampling, DSP and DSD conversion is done in field-programmable gate arrays (FPGA; a type of software configurable hardware). The analog output is a purely passive filter based on transformers. In the PS Audio unit, the digital and analog boards Ted designed are direct replacements for the boards in a current PS Audio Perfect Wave DAC or Perfect Wave DAC Mark II, enabling a field upgrade for owners of these units, to a DirectStream DAC.
One feature of the FPGA input processing is that there are no PLLs (phase loop locks): the bits are pattern matched to figure out whatÂs coming in and then they are placed into a buffer. In a sense, all inputs are locked at all times. You can go from input to input seamlessly and you can change sample rates of incoming material seamlessly. Most importantly, you can go from PCM to DSD seamlessly. This architecture also leads to a very low susceptibility to incoming jitter. I2S, AES/EBU, S/PDIF and TOSLink within their bandwidths all sound the same. For 96k and below, optical TOSLink can sound better since it can eliminate ground loops.
All digital inputs are upsampled to wide words at 28.224 MHz (10 x the DSD rate!). Then that signal is sigma delta modulated to double rate DSD and then lowpass filtered.
The upsampling filters are chosen to keep as much detail as possible not for computing convenience: they use a lot of CPU power, but the FPGA has the resources to do a great job. The result is that the FPGA digital processing looses less audio information than most other designs.
Ted will be present to talk and answer questions about the DAC.
A couple of Executive Committee members have already heard this DAC and they have reported that it sounds really great. Everything in the DAC was designed to get your toes tapping, to allow you to enjoy all the music you already have. The DirectStream DAC uncovers more music than we knew was present in any of our sources, from Redbook to hi-rez PCM, to DSD.
As usual - visitors and guests welcome.
Thursday, May 8th. 7:30pm
Mercer Island Congregational Church (basement)
4545 Island Crest Way
Mercer Island, WA 98040
