Unfortunately, the Sonos Amp does not have dual or single RCA output ports that would accept headphones nor headphone amp to send audio. Sonos Amp will only accept a source to output to wired speakers or other Sonos.

You could in theory send music to a Sonos Port and connect headphones  Amp to it. However, the sound would not be muted to other Sonos which defeats the purpose of headphones for private listening. Note: The impedance for headphones used in this manner may not be suitable.

There isn’t a way to connect wired headphones to the Amp even with a separate headphone amp because the Amp doesn’t have audio line-out. You could get a Sonos Port, which has line-out, and connect a headphone amp to the Port.

Thank you both. Unfortunate answers but appreciate clarifying that to me.

Could I connect premium wired headphones ($1K) directly to a Port and stream HiFi to it? I suppose a Port as source for quality headphones would be a better choice than using a mid-range phone or laptop as source. Right?

The RCA line-out on the Port is not designed for a low impedance load so you would still need to use a headphone amp with the Port to connect headphones.

FYI… Sonos is really not known to be a hi-res audio system. The only service that currently offers hi-res audio on Sonos is Qobuz. So if hi-res audio is important to you and you want more hi-res options for your premium headphones, you might consider another option.

Even though I love Sonos and have many Sonos speakers, I personally use a portable DAC (THX Onyx) with my headphones and connect it to my iPhone and iMac to listen to MQA and hi-res audio on TIDAL and Apple Music.

Thank you for your kind help. The THX Onyx looks like exactly what I need. I was afraid you are using audiophile-priced DAC and this is something I can afford.

You have an iPhone and iMac that are both good sources. I have a OnePlus Nord phone (android) and it is classed as upper mid-range (except for my ridiculously large 12GB of ram). If I connect the Onyx to my phone with the USB-c connector and then wired headphones to the Onyx, and using Deezer as source of lossless, can I expect exceptional sound quality? (of course in regards to the setup, not the headphones quality which I will make sure is top notch). Or is my OnePlus an inferior source and will decrease SQ? I also have a laptop I would like to use as source, it is an entry level office-use HP laptop so very low on specs, cards are basic Intel cards. Same question as before - the DAC with the laptop and good quality material - will I utilize my headphones ability? 

Sound quality that is “exceptional” is dependent on the listener and what audio quality they consider to be “exceptional”. But the THX Onyx should help you get the best audio possible from your Android phone and laptop to your headphones.

I noticed that Deezer HiFi only offers 16-bit/44.1kHz audio which is basically CD quality. If you want hi-res audio that is a little higher quality than CD quality, try TIDAL, Apple Music, Amazon Music Unlimited, or Qobuz. I believe the THX Onyx offers a free trial subscription to TIDAL and Qobuz. Of course whether or not you will be able to tell the difference in audio quality is debatable. But your premium headphones might help you tell the difference.

Another popular portable DAC that is highly rated is the AudioQuest DragonFly Red.

Sorry for reviving a concluded discussion...but I just tried my Sony WH-1000XM4 headphones in wired mode for the first time on my HP laptop and the SQ is considerably better than the terrible Bluetooth SQ (all relative of course to expectations). If with my Sony headphones I add the DragonFly or THX, would those even improve the Sony SQ? or would a wired connection maximize the Sony’s ability to the fullest? The Sony are great but not really powerful or high quality audiophile over-ears that only work wired.

Wired headphones will always sound better than wireless headphones over Bluetooth.

The Sony XM4 headphones cannot play hi-res audio on its own. A portable DAC like the THX Onyx or DragonFly will allow you to play hi-res audio files through the headphones. The audio quality is technically better, but whether or not you can tell the difference on the Sony headphones is up to the listener.