It looks like there are a few misconceptions here.

The Amp accepts an analog Line-In. Internally Sonos digitises this at 44.1kHz sampling rate. This is able to encode audio frequencies up to 22.05kHz, i.e. beyond the range of human hearing.

So:

• no, you don’t get a maximum of 96kHz, whether as a sampling rate or a frequency response
• an external iFi DAC on the iMac may well do better quality-wise than the iMac’s headphone outlet in terms of decoding to analog, but this is then digitised at 44.1kHz by the Amp on input as noted above
• as a human this is all you require

Sorry I meant sampling rate of 96khz - im sure i read somewhere that the amp can accept 96khz through its line in? or it may have been a dream..

A pity the iMac doesn’t possess a HDMI arc output.. sigh.

Since the Line-In is analog, it can not accept anything digital at all, regardless of sample rate.  

But it wouldn’t be digital would it if the 3rd party dac has already converted it to analogue ?

As I say, the analog (not digital) Line-In has an effective frequency response up to 22.05klHz, as it is then sampled at 44.1kHz. This is higher than human hearing can go.

Why on earth would anyone be interested in the Amp accepting 96kHz, when only animals such as cats, mice and bats are able to hear it? 

Wow.. I was expecting a response with a cat mouse or a bat but not within the 1st hr...

And rats? Someone may have a requirement for a multi zone ultra sonic rodent repellent that could also be used to play music. 

It also wouldn’t be “higher than 96 kHz” which is what the original question was asking.  

On a side note, if you play so-called “high resolution” audio through the Sonos Line-in, it will sound exactly the same at 96 kHz as it does at 44.1 kHz, as every properly conducted double blind test has shown.  You simply aren’t going to hear anything above a sampling rate of 40 kHz (far less if you are not a teenager).  However, this begs to ask why you wouldn’t bypass all the extra processing by simply down-sampling the “high resolution” audio to strip out the snake oil in the first place? 

And then it appeared, just like that…  snake oil...

Do you have actual objective proof it’s not, or are you just here to lob bombs?  If the latter, I’ll bow out.   I’d rather not deal with the audio equivalent of flat earthers.  

Yes Jog on - I haven’t got 7 years playing internet tennis with you or your chums - im not interested in your thoughts on snake oil ideologies 

KB29R,

You can plug any DAC output into the analog inputs to AMP, even 576kHz if you can find a DAC that supports this bit rate, but it will be difficult to find 576kHz source material at this point in time.

Most flat earthers avoid discussing any concept of a spherical earth too.  Can't say I blame them.

On the flat earth thing - I recently discovered that this is still a fervently held belief in THIS century including explanations/rebuttals for all the reasons supplied to establish that the earth is a not a flat disc. 

576?? Just the odd recordings from quobuz 24/192 would be nice - including Tidals MQA... the dac in question is this:   https://www.whathifi.com/reviews/ifi-zen-dac

I would like to consider another aspect of this question.  Is this method being used to play music files stored on the Mac? If so, why? Rather than set up a Sonos music library?

SONOS is a music playing system, not a music storage system. SONOS will play music stored on a PC, Mac, an external hard drive, dozens of online music services, Airplay 2, and music stored on an Android. For music files stored on a PC, Mac, or external hard drive (Known as a NAS Network Attached Storage]) SONOS builds a music library index that is stored on the SONOS players. Storing the index on SONOS players improves system features and response time as the system operator requests play.

Of course, if files are stored on a PC or Mac, one is limited to the bit rates supported by the SONOS hardware. Similar for the online music services. If you believe that bit rates higher than 44.1Kbps are better, then storing the high bit rate file on the PC or Mac and using an external DAC is a better approach.

By the way, 576 is used in some studios for their recordings. The really, really serious Purist should seek these, but I have not seen any of these files in commercial distribution.

Much like wine testing events, the elite are not willing to accept the outcome when the boxed wine in a fancy glass wins the contest, the audio elite will always consider 44.1 less than worthy, even when they cannot figure out which glass has 192 or which glass has 44.1 simply by listening.

I have Hi Res files stored on my Mac and Subscribe to Qobuz hence the external Dac question

Bizarrely Sonos have responded to me refusing to specify what the line in’s maximum sample rate is...

Perhaps that’s because, as we’ve been reiterating, the Line-In interface doesn’t have a sample rate. It’s analog.

Once again, internally Sonos digitises Line-In into 16/44 WAV (for Uncompressed Line-In operation). Some newer devices may use 16/48 WAV instead, but in any event the ADC sample rate won’t exceed 48kHz.

https://support.sonos.com/s/article/79

https://support.sonos.com/s/article/4839

Those links are not specific in regards to the Line Ins and if the line in didn’t have a sample rate then why would Sonos say that they are unwilling to provide that information to the public?

The really bizarre thing is that you think that is a meaningful question.

Almost as bizarre as using your computer's DAC to convert your files to analog then send the music out through the headphone socket. 

Stock response, possibly from a junior support staff member

IT IS ANALOG.

I’m sorry but this is a senseless debate. There appears to be a lack of understanding of how digital audio works, or of why chewing up precious network bandwidth to ship around inaudible ultrasonics makes no sense whatsoever, or maybe of both.

Hence the Dac question…

Nope it was escalated to a senior apparantly

KB29R,

As ratty noted, the internal and network traffic is at 44.1 or 48. It makes little sense to use an ADC that runs at a higher rate, only to down convert the sample rate a fraction of an inch away on the printed circuit board. By the way, the internal DAC has been 24 bit since the initial product in 2005.

There is no “sample rate” or “bit rate” associated with an analog signal. For your own understanding, if you need to assign a bit rate to an analog signal or live performance, use infinity. (a person steeped in quantum mechanics might argue with that point, but we don’t need to get into that here) “Sample Rate” and “Width” enter the discussion as we convert between analog and digital or process in the digital domain.