@newbpd

I‘m very quite sure that won’t work at all. 
Even if the hardware would fit, the OS on your Apple device has to recognice and support the hardware. Also software on your Apple device would have to support usb c digital audio in. 
 

The HW does fit, since it’s just USB-C.

There is a standard way to enumerate as an audio interface without having to install custom drivers in macOS/iOS.

The question is if Sonos adapter is a standard audio interface if they’re doing something proprietary?

Does anyone have a line-in adapter that they can try with their iPhone or MacBook? On the iPhone it should allow you to use to the voice memo app and record the 3.5mm, if it works.

I would tend to agree this likely doesn’t since more people would have already confirmed this, but I haven’t seen anyone definitively confirm either way.

@newbpd 

Ok, I haven’t excepted that to work. But it does… though there definitely is something „special“ like a chip recognition on the Sonos adapter, because for the compatible Sonos devices with usb c line in only the original Sonos adapter will work. 
But now after running a test I can confirm that the other way it works. I tested the Sonos adapter on my iPad 10 with usb c port. Put a bt receiver to the adapter and played some music via bt from my iphone. 
Apple voice recorder app was working this way. 
So indeed iOS / iPadOS recognize the adapter and there probably will be some more apps that support usb c audio input like voice recorder app does.

So you can give it a go and spend the bucks on an adapter. 
 

That’s perfect!

Thank you so much for checking!

I’ll order one right away.

So essentially you’ve found that the Sonos adapter also works “the wrong way round”? Because you are using USB-C as en “out” now, not as an “in” like the speakers do? That’s interesting.

It works the in the same direction as Sonos’ intended function.

Sonos advertises their dongle usage as taking audio from a turn-table output into an Era 100 input.

Ralf showed that it works in the same direction from a BT Reciever output to the iPhone’s Voice Memo input.

The Sonos’ Line In adapter is the reverse of Apple’s “USB-C to 3.5 mm Headphone Jack Adapter”, but that’s exactly what I was looking for.

No, it’s the same way… and I wouldn’t have expected that to work because in my mind probably there’s something different to other adapters why they (also they are didirectional) don’t work on Sonos devices. 
But if there’s a kind of „chip protection“ on the Sonos adaper, it obviously is a one way security.

And just to add… the Sonos adapter isn‘t a bidirectional one. It doesn’t output audio from my iPad like the apple usb c to audio adapter will do. 

So the Apple usb c to audio adapters are bidirectional with Apple products?  It’s more out of curiosity than any need, but that would mean that an Apple adapter could be used for the same experiment you performed above.   The adapters I see on Amazon all appear to be one-way.

Did you test to see if the Sonos adapter could be used to output from the iPad or are we assuming that it won’t?  If these digital/analog adapters are bidirectional, it seems like the easy ‘solution’ for Sonos would be to use a standard adapter with some sort of Sonos signature on the chip so that the Sonos speaker won’t accept a digital signal from any other adapter. Other output devices, like the iPad in your example, would simply ignore the signature as they are not looking for it.  The adapter would not need anything to stop output to analog since the speaker itself would never send anything.

I see now I misunderstood your set up. The bluetooth receiver is used to play music on the iPad.

I do think, though, that other non-Sonos adapters are different from Sonos because they are used to get sound from USB-C to analogue and do not work from analogue to USB-C as Sonos needs it to be.

So the Apple usb c to audio adapters are bidirectional with Apple products?

No the Apple USB-C dongle (and pretty much all other vendors) are uni-directional output.

The Sonos USB-C dongle is uni-directional input.

The only bi-directional cable is Apple’s Lighting to 3.5mm.

That cable can be used to output audio from your iPhone w/ Lightning to speakers and also input audio to AirPods Max. I’m guessing that specific cable is smart enough to recognize AirPods Max and knows to switch the direction to input.

But if there’s a kind of „chip protection“ on the Sonos adaper, it obviously is a one way security

I wonder if Sonos is actually doing any protection at all.

As far as I know only Sonos makes a USB-C input dongle, every other dongle is USB-C output which is probably why it might seem like there’s chip protection.

@melvimbe 

No, the Apple adapter is a one way usb c to 3,5mm audio adapter as @newbpd also said. I just wanted to point out that the Sonos adapter doesn’t work bidirectional. 
 

@106rallye

@newbpd

I‘m not sure if there is any communication between the Sonos adapter and Sonos devicees that could be the reason why other adapters don’t work. I supposed so because some people told they tried a different way adapter (microphone to usb c) or a bidirectional adapter that should work both ways and it didn’t work. 
I know most adapters are one way usb c to 3,5mm audio out just to connect headphones to usb c. 
But there are a few others and if they would work the same way like the Sonos one, why  won’t they just work. Strange…

Imo then for example the following two should work…

These are both microphone inputs and not line-in inputs.

As I understand it if you try to use line-in levels with a microphone input you get distortion/clipping.

Another difference is that Microphones are mono and Line-in is stereo.

I’m just speculating here, but maybe Sonos requires a stereo input?

@newbpd

Of course you’re right about the difference between line in and microphone and the effect on using a microphone in. But the signal direction is the same so I thought it could help to figure out if there will come in a signal at all. 
I willl hold on to find that 3rd party usb c line in adapter.