Detect number of channels of soundcard device?

I feel like I’m missing something very basic here, I want to get the number of (hardware) channels available from my soundcard, before booting the server.

ServerOptions.outDevices[0];
returns:
Built-in Output

and

ServerOptions.outDevices[0].numChannels;
returns:
1
When it should return 2, or am I mistaken?

Booting the server posts this:

"Built-in Output" Output Device
   Streams: 1
      0  channels 2

So the correct number of channels (2) is stored somewhere but where can I access this?