Am considering buying a DirectStream from a private seller with the Bridge II upgrade. He claims the device is around 5 1/2 years old. Have there been any hardware updates in these from back then to now or are they essentially the same product? Should I stay away from one this old? Opinions welcomed
Josh
I don’t believe there are any hardware differences, only the multiple firmware upgrades. I personally think you’re safe purchasing a used DS. Plus it’s already broken in. If the price is right and you trust the seller, I’d go for it. Mine is that old and I have had no issues. Additionally, I’ll add that the DS is the heart of my system. It was more money than I’d ever spent on a DAC, but I have never regretted the purchase.
Many DS’s started life as a PerfectWave DAC or a PerfectWave DAC Mk II. As brumtech said: The hardware hasn’t changed since the initial release. Mine are certainly that old 
I bought a PerfectWave DAC MkII about mid life span for that device. Shortly after the PWD was announced, I had PSA update it. It has worked perfectly it’s entire life. Best money I’ve ever spent on this hobby (and like many on this site, I’ve spent some money).
The first samples of the PerfectWave DirectStream DAC shipped at the end of April 2014
Read more at https://www.stereophile.com/content/ps-audio-perfectwave-directstream-da-processor#DMemCV3JWdmA1Epm.99