WH-1000xm3 sound much worse when wired. They are made to use internal DAC.

You can turn them on, and they will use the wired input but pass it through the nice internal DAC.

But the jack output isn't digital. Are you thinking about it's amp?

That just means your phone's or PC's DAC is crappy compared to the internal one, and any other headphones would sound just as bad.

I have an older pair of JBL E55, which are about 50% cheaper than yours, and on a modern phone they sound slightly better on wire than on wireless, presumably because their internal DAC is mediocre.

In theory they could use an ADC to convert the analog input to digital then run through the same DAC as bluetooth goes

If the original device's DAC has produced a shitty analog signal, the best ADC in the world will only be able to turn it into a shitty digital signal.

The strength of a chain is that of its weakest link.

I have new MBP 14', and even external fiio E10k headphone amp. They work great with my Sennheisers HD 650, but suck with WH-1000mx3 compared to internal AMP.

I use my xm3 daily and don't notice a difference. I use both methods of connection because sometimes it's quicker to just plug in on some devices, and others it pairs right away. Love these headphones.

Wouldn't wired use the DAC on the device rather than the headphones? I thought the 3.5mm jack carried an analog signal.

Those Sony headphones do processing to the signal regardless of whether you're using wireless or a 3.5mm. They can still make sound with no power but it feels more like a backup in case the battery is dead. It seems like a sensible design decision given that most users will want them turned on for noise canceling even if they're wired.

That's his point. They're using the device's DAC when wired which is why it doesn't sound as good as when using Bluetooth through the headphones' DAC.

Sure but that's an issue with wired headphones in general, not specific to these.

I mean, I'm pretty sure that DAC on my MBP is better, but it does not fit those headphones well.