What is the difference between the Perfect wave DAC and the Direct Stream DAC?
The PerfectWave DAC was an earlier model that used a Wolfson DAC. The DirectStream is the (for now) current model which uses a programmable FGPA chip to upsample all incoming data to DSD64. I think the DirectStream would be considered the better sounding DAC almost unanimously here. Though the PerfectWave sounds PD Good.
Although a successor is planned for the DirectStream it is still available. The PerfectWave has not been made for a handful of. years.
Agree with @lonson. I bought a used Perfectwave and then upgraded it with PSA’s Directstream kit. The improved sound quality was dramatic and the ability to upgrade FPGA firmware several times for free provided further audible improvements. Go for the Directstream if at all possible. Many used for around $3k.
Edit: And there’s another upgrade that requires some soldering skill. Replace the output transformers with the preferred versions from Edcor. This DS DAC can sound extremely good.