Headphones in Line_out and Micro in Line_in

Hi,

I have some questions about the Line_in and Line_out connectors.

From what I know, the Headset-connector has a built in pre-amp for Headphones and Microphones. But when I plug my Headphones in to Line_out I can get a clear signal, too. Whats the difference then between this 2 connectors?

I am also able to record through a micro connected to line_in by using the record_from_line_in_micbias.sh script. So whats the difference in the end by using this 2 connections instead of the head-set connector?

I would appreciate any insight.

shabaz over 9 years ago

It will provide audio but it definitely won't be optimal. You'll notice it most on bass (i.e. lack of it) if you have headphones plugged into the line output. Also a slight loss of volume. Also expect the output to be slightly distorted because the line output it is not designed for such a low impedance.

In a similar vein, there may be some additional noise if you use a line in for a microphone connection, since the line input level is designed for a higher amplitude input and you're having to compensate by increased amplitude setting if you use the line input for the microphone.
Note that this information is generic - I've no idea if the Cirrus Logic card can switch between line in and mic functions internally, I've not looked in detail. You could examine the datasheet for the Cirrus part if you are really curious.
However it is generally not a good idea to try to use the line input and output for mic and headphones for the reasons mentioned.
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Former Member over 9 years ago in reply to shabaz

that's helpful, thank you !
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Former Member over 9 years ago in reply to shabaz

would there be a self-built possibility to amplify the line-out for headphones ?
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shabaz over 9 years ago in reply to Former Member

Hi,

You could use any ready-made amplifier. Otherwise, there should be loads of circuits via google for headphone amplifiers with line input.
If you want to create your own, check out manufacturers like TI, NXP, On Semi for appropriate integrated circuits. But, most of them
will be surface mount parts.
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Former Member over 9 years ago in reply to shabaz

Would it be possible to record with the audio-card through the headset-jack and playback to the headphone-jack of the raspberry pi?
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shabaz over 9 years ago in reply to Former Member

I think so, but why would you want to? The RPI built-in analog audio output is very crude in comparison to the audio card you will have attached.
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Former Member over 9 years ago in reply to shabaz

because I need the amplificated headset-jack for a microphone - would the amplification for the micro as high with headphones attached to the headset-jack as for if it is alone jacked-in?

I know, that the quality will not be the best, but that wouldn't be a problem for me.
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shabaz over 9 years ago in reply to Former Member

The microphone circuitry and headphone circuitry is unrelated. They just share a connector. Or use the in-built RPI jack for audio out but the quality is lower.
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Former Member over 9 years ago in reply to shabaz

well, if it is possible to playback to headphones with no loss in microphone-record at the headset-jack, I will prefer that of course
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