I'm looking for the "best practices" of using headphones and speakers interchangeably on the PC.
If you are using on-board sound you can simply connect your speakers right to the motherboard audio output and plug-in your speakers to the phones output somewhere on top of your PC case when needed. But it has two obvious cons: sound quality of the on-board audio far from being perfect and the phones output on the case is also quite bad quality and has noises too. The solution is to use a sound card, either external or internal.
External cards are quite massive and have a lot of options like XLR mic inputs, MIDI, fantom power etc but the allow you to connect both speakers and headphones (to the front panel). But it's quite silly to overpay for the card if you don't need most of the options.
When it comes to internal sound card, I see couple problems over there. First of all, seems like the market of internal sound cards is quite dead. Plus I need a card that works perfectly find with Linux Debian (means Creative cards aren't my choice). The next popular cards you can most likely meet are Asus Xonor cards. Let's take a look into the manual for Asus Xonar XS.
Here is how they suggest me to connect my headphones:
And here is how I should connect my 2.1 stereo speakers:
Same output! Beside that I will have to literally get under my table each time I would like to wear my headphones. This is extremely uncomfortable. At the same time if I use a "splitter" this will make my headphones work all the time, even when I do not really need them.
Am I getting anything wrong or you guys have some magical trick that let you turn off speaker and switch to your headphones and vice versa smoothly? The Asus Xonor card is over $70 already and looks quite useless for me, but external cards are getting easily over $200. Does it really the price for the solution I'm looking for?
You haven't rejected yet another piece of hardware, so allow me to make that suggestion. Headphone/speaker switches have been around since the days of Radio Shack and are a convenient, sometimes pricey option.
Many features abound, including amplification and volume control, but the simplest version will be a pair of cables and a button.
One lead from the switch connects to the speaker output on the computer. There may be a microphone connection option as well, as many people have headphones with microphone capability. If unused, there are no complications.
The switch will usually have two jacks, one into which you plug your speakers, the other accepts the headphone. If a microphone is involved, a microphone jack will be indicated.
Push the button, headphones are live. Push it again, speakers are live.
Use caution when selecting the product online. My first search for a not-overpriced unit presented one with a 3mm mini-plug where one would expect to find a jack.
Use your favorite search resource for "computer headphone switch" and watch out for transcription or telephone related results, as they may not be compatible.
You didn't say which Asus Xonar you want, so I quickly googled and downloaded the first manual I found (Xonar DX). It has the same outputs as in your picture, with
1 being Front Out, followed by Side Surround Out below, then Center/Subwoofer, then Back Surround Out.
That basically means you have 8 channels, in the form of 4 stereo-pairs. Both in Pulseaudio and ALSA, you can redefine channel assignments, and split off channels. So with a bit of custom configuration (google), nothing prevents from plugging in headphones in
1, speakers below, and two other stereo devices further below. You can use them individually, or playback the same stereo sound source to all four. Etc., etc.
I suppose it will work similarly for other Asus Xonar cards.