Hi everyone!
I'm a relatively new owner, having joined the PM-1 party less than a year ago. I had been using a PM-3 (alongside an AirPods Max) as my go-to headphone ever since I bought it when Oppo was shutting down. Like many PM-3 owners, I had wondered about its older and more capable sibling and when the chance arose to pick up a mint, largely unused copy locally, I jumped at it!
What a wonderful piece of equipment. The love that went into its design is readily apparent and I completely perceive the difference between the PM-1 and PM-2; the latter is a capable headphone whereas the former is a luxury
experience. Just opening the box for the first time was an event. Since then I've been enjoying it but also learning to get the most use out of what I suspect will be a pair of headphones I hold on to for a long time to come.
I have all four ear pads and find a combination of the velour and "alternate" lambskin ear pads to be my preferred choices... mostly about comfort. Lambskin feels more comfortable at the beginning of a listening session, velour more comfortable at the end

The ear pad interchangeability system is excellent and a joy to be able to use on a headphone of its era, although I tend to be nervous about wear and tear and would have loved to see a more sophisticated mechanism like the AirPod Max's magnetic clasps.
I have a couple of opens that I am entertaining and would love advice.
1.
Balanced audio, pros and cons. Right now I mainly use two sources. One is the UDP-205 I was fortunate to pick up directly from Oppo (office was ~10 miles away from home) as things were starting to wrap up. I use it interchangeably as a source (movies, CD and SACD) as well as a USB DAC connected to my desktop PC. It's an inelegant behemoth, but the sound quality with the PM-1 feels outstanding to me via the 1/4". The other source is my 16" MacBook Pro which has a capable DAC and amp but only switches to 3V output at 150 Ohms; I've ordered an impedance dongle to add in some impedance and hopefully work around this limitation. Without it, the PM-1 sounds good and gets loud, but doesn't feel nearly as well driven as it does on the UDP-205. (Whereas I have a Senn 650 that is capably driven by the laptop as easily as the Oppo player.)
I'm thinking about whether I should explore balanced audio. This would be more of a learning experience for me than a specific goal, but it would appear to come at a price tag. I'd need a balanced cable for the PM-1 (Moon Audio seems to be the main option at $200+) and then I would also need a balanced headphone amp. Presumably, the UDP-205 could remain a perfectly serviceable DAC into that setup since it has balanced stereo output? I have an idea as to the price point of the cable but not as good a sense for the amp. I'd love to hear any input anyone has to share; my gut says "don't worry about this, there are other hobbies to tick off."
2.
PM-3, does it have any role in a Oppo-Nostalgic PM-1 household in 2023+? I've loved it but whereas the PM-1 feels truly special, the PM-3 as a portable, travel & work headphone doesn't feel nearly as compelling. I have to admit the AirPod Max set feels just as capable musically, with far, far super convenience features including outstanding ANC, insane portability and world-class microphones. This is a PM-1 thread, not a PM-3 set, but I'd be interested to know if anybody else has both and is able to rationalize keeping ach.
Anyhow, I love this set and hope to keep it for a long time to come. I even bought a pair of replacement grills from Oppo since they're still available ("just in case").