Confused with audio in and audio out

[gigatoaster]

Hello there

On a Mac mini 2014, I connected my amplifier (Rotel RA-12)

When I plug it to audio line in, there is no sound but when I plug it to the headphone, I have sound!

I use Roon and I chose to upsample to 192k. The amp shows 192k.

Could someone help me understand what is the difference between audio line in mini jack and audio out (optical/analog)?

 

[cbautis2]

If you use Audio Out (mini toslink) you should get digital audio out of the mac to your Rotel.

Audio line in is for a mic input of a headset

 

[MajorFubar]

In = recording to your Mac, line or mic level
Headphone = analog out via the Mac Mini's DAC, and toslink to an external DAC.

There's a big clue in the socket names. I'm trying to understand why you thought the input socket would send audio to your amp. I notice you're from France so perhaps it's just a 'language-barrier' thing.

 

[gigatoaster]

Thanks for your explanation. It’s me, I never understood audio out & audio in. It’s like pre out, I never knew what it is for.

 

[MajorFubar]

Thanks for your explanation. It’s me, I never understood audio out & audio in. It’s like pre out, I never knew what it is for.

No problem. Pre-out on an amplifier sends a line-level output to a separate power amplifier, attenuated by the volume control. It differs from an amp's line-out in so far as line-out is not attenuated by the volume control, so if you plug an amp's line-out into a power amp with no volume control, you'll deafen yourself when you play something.

The output on a computer is different: it's kind of equivalent to a pre-out because it too is attenuated by the (software driven) volume control.

When you plug your computer's headphone output into the input of a pre-amp or integrated amp, it's usually wise to turn the computer's headphone volume to maximum, to maximise the signal to noise ratio going into the amp.