PSAudio Perfectwave DACII


#1

I owned a Perfectwave DAC II which I upgraded to a Directstream. The Directstream has a FPGA chip in it that is programmable. Could somebody please tell what is the equivalent in the Perfectwave DAC II. Is it a Sigma Delta chip? I need to resolve a discussion point with friend.

Thank you
John


#2

The FPGA in the DS is used for many functions, e.g. decoding inputs, measuring sample rates, testing for DSD doing deemphasis, buffering, upsampling and doing a sigma delta modulation to one bit DSD. The DAC part of the DS is on another board and basically comprises a passive low pas filter.

The Perfectwave DAC Mk II, like most DACs these days use a single chip for many of the above functions and most of those chips are based on multibit sigma delta, i.e. they convert PCM to a higher rate but multibit (4, 5, 6, etc.) samples via sigma delta modulation and then use multiple lower precision DACs at random to average out the manufacturing variations in those DACs.

So the functions aren’t really directly comparable, but do have some overlap.


#3

Hi Ted,

Thanks for the quick response. My technical knowledge is minimal. For simplicity can I confirm that what is in the PerfectwaveII is a chip that is termed a Sigma Delta Chip such as a Burr Brown, Sabre or similar? That there is not a FPGA chip so there cannot be a upgrades to the OS for the PerfectwaveII as there is in the Directstream. Or am I approaching the question the wrong way?

Interestingly there is a Sigma Delta modulation aspect to the FPGA that you developed and still program.

Thanks

John

[Edit, Ted - removed extra formatting]


#4

My recollection is that the perfect wave used a PCM1704 which is a sign magnitude DAC, that is, true multi bit, unlike Delta Sigma chips.


#5

The DirectStream DAC is PS Audio’s first DAC that uses an FPGA for the majority of it’s function, and in particular for upsampling and to do sigma delta modulation. There are FPGA’s and/or CPLD’s (a smaller, older FPGA like tech.) in some other PS Audio units that provide customized logic to do various things, but not to implement upsampling or sigma delta modulation and not always user upgradeable.

I can’t speak definitively for PS Audio re non-DirectStream DACs, but I believe the PerfectWave MK II uses a Wolfson WM8741 a sigma delta based DAC. It also supports other digital processing outside the DAC, but done by other single chip solutions.