Just want to share my personal experience:
I’m running a SCPH-1001 with the dogbreath mod to the output stage with electrolytic DC blocking caps, upgraded RCA cables and a tube preamp buffer. For the power supply, I’ve replaced the stock unit with a good quality linear power supply. If I had to summarize the sound with one word, it would be “ridiculous.” This setup is better than my CD transport and DAC which if you include the upgraded power cables, coax cable, etc. rings up to around $1,100. That’s right, the 1st generation PS1 is besting an $1,100 transport/DAC setup at somewhere around a quarter the price including mods and the power supply.
Now it doesn’t do everything better. The bass isn’t as crisp and the highs don’t have as much “sparkle.” Whereas the transport/DAC is capable of delivering a forceful punch in the bass department, the PS1 is more akin to a quick shove, but still impressive. What the PS1 does right is completely worth the slight trade offs. The mids are ever so impressive. Stringed instruments have a realism that I’ve not heard before. Horns sounds right. I think where the PS1 really shines is that instruments just sound realistic. It doesn’t have that hyper-realistic sound in the highs that so many digital setups try to reproduce but usually fail at miserably which causes listener fatigue and while it’s impressive for a short while, it leaves you thinking, “this isn’t what instruments actually sound like.” The PS1, especially with the mods and upgraded power supply, has the most analog sound I’ve ever heard out of a digital system.