PS Audio Direct Stream

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 what’s 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

Sarcher30. Any update from the Meeting?
I have now heard opinions good and bad on this unit.
What I am hoping for is that this unit can replace my preamp.

Hi Ozzy, Not sure if it can replace your preamp. We played it through our clubs Genesis I-60 integrated amp, into Genesis G7.1f loudspeakers. It seemed to have less gain than the clubs Oppo-95. Depends on how much gain your amp has, input impedance, length of cables, speaker sensitivity, etc.

A lot of the members really liked it. It does depth really well. I thought it was a tad soft sounding, and could be a bit more extended in the treble region. It was really easy to listen to. Very smooth with no nasties at all.

As with anything I would try to demo it in your own system first, if possible.

Sarcher30, Thank you for your comments.
I see others have also commented that it was a bit laid back in the treble. PS Audio claims that you need to retune your system to account for the different equipment.
Perhaps toeing the speakers in a little more.
I sure wish I could try before I buy, but right now if you want one you've got to pay in advance just to get on the waiting list.
Perhaps PS Audio has a 30 day refund policy, that would be nice.

Sarcher30, This is what PS Audio posted on their forum from Ted on your posting.

"Yeh the club's speakers weren't up for the bass. They didn't want to run the integrated amp more than 3/4 of the way up and they used an unbalanced connection. The DS volume was being controlled by a fellow in the first row. I don't know how often it was at 100 or not. For some I was turning the volume down on the laptop when people indicated to or seemed to be in distress.

On a few tracks there was a difference in opinion with the people who were sitting nearer the front that those standing in the rear. Some members tried lots of places in the room, some didn't. The biggest difference to my mind was that in the room the front could be too loud at the same time that the rear was, perhaps, too quiet.

The designer of the speakers didn't like the setup and moved them at the break, unfortunately I don't have any idea what he didn't like or how the change affected the sound.

As to soft, after most had left the head bangers thought Alice in Chains and Porcupine Tree sounded great :)"