Re: [gentoo-user] ALSA wizard...

[Mark Knecht <markknecht@gmail.com>]

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<SNIP>
> > >
https://www.amazon.de/dp/B00EK1OTZC/ref=pe_3044161_189395811_TE_SCE_dp_1
> >
> > OK, that device is pretty simple. If you set this device as the default
Alsa device can you get simple audio, from YouTube for example, out through
the headphone jack? We know the mic input works. If both of those work then
what does discord do?
>
> I'm lost here. The headphone jack in the interface is just a monitor.
> I don't think there's any connection with the headphone jack in the
> motherboard? (I can't test it anyway with my headphones---different
> jack sizes)
>

I understand the jack size difference. Your MB jack is 3.5mm, the headphone
jack on the Behringer is 1/4". All the headphones I've purchased for years
came with an adapter to plug into  1/4" jack but if your didn't they can be
purchased at Amazon or general stereo/TV type stores. (Best Buy as an
example in the U.S.) Search for "3.5mm to 1/4 adapter".

I'll explain the headphone monitor function in a moment. You are correct
that the headphone jack on the Behringer has nothing to do with the
headphone jack on the computer. The Behringer is a complete sound card with
2 inputs and 2 output at the end of a USB cable. It has phono jack outputs
on the back which would allow you to hook it to your stereo inputs to hear
computer audio. In that sense it's no different than a CD player or tape
deck. To use the outputs on the back would simply come down to telling
Linux I want to use the Behringer USB device as my sound card and all sound
would be router there. Once the audio is correctly going to your stereo you
should also hear the audio over the headphone jack.

The monitor function associated with the headphones is different on cards
like this. Notice that the switch says "Direct Monitor". Imagine that I am
recording a song. I already have some of it recorded, say drums, bass and
piano. Now I want to record vocals so (wearing headphones so I can hear
what I'm supposed to sing along with) I sing into the microphone but there
is latency in the system. The vocal gets converted to digital by an
internal A/D converter, sent down the USB cable, routed to the recording
application - in Linux lets say that's Ardour. Ardour records it onto disk
but it also sends my vocal back to the Behringer so I hear myself in the
headphones. The probably is that my vocal is delayed by 25mS or more. It
sounds out of time and I'm confused. It sounds like an echo.

Look at the diagram here to see what I'm trying to explain:

https://manual.ardour.org/synchronization/latency-and-latency-compensation/

Direct monitoring changes the signal path in the picture on the Ardour
page. It still sends my vocal down the USB cable and Ardour still records
it but it __ALSO__ sends my vocal __DIRECTLY__ from the mic to the
headphones skipping the whole digital path in the picture. There is no
delay. I hear myself in time with the music. It feels natural and I perform
my part of the song brilliantly and go on to make millions of dollars.
(Well, maybe...)

Direct monitoring probably won't matter i your application because the
real-time nature of what you're speaking won't be effected very much and
probably discord or zoom won't send it back out to the card, but only send
it to the people you are meeting with.

Hope this helps,
Mark

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