Be careful which settings or effects you enable.

If you are using speakers and want to reduce speaker output from being picked up by the microphone then enable Acoustic Echo Cancellation option that's under Microphone Effects.

Having the bit-depth set to 24 bit will slightly improve the recording audio quality. The 44.1 kHz (44100 Hz) sample rate is the one used by most media (games, movies, music), while video DVDs use 48 kHz.

Set Microphone and/or Line In Default Format to 24Bits, 44100 Hz.

Do not set the impedance much higher as it may damage the headphones.

If your Realtek Audio solution has a dedicated headphone amplifier, set the soundcards output impedance/gain ( Ω = ohm) to a value close to the headphones input impedance.

You can find detailed information on audio bit-depth here. Having the bit-depth set to 24 bit will slightly improve audio quality.

Increasing Sample Rate without having a source that’s sampled at a higher rate won’t improve sound quality, in fact, it might degrade it. Set playback Default Format to 24Bits, 48000 Hz this is generally good for most media (games, movies, music) which is sampled at 44.1 kHz, while video DVDs use 48 kHz.Selecting more channels than the number of speakers you have connected won’t enable you to hear more sounds or hear the footsteps and positioning of enemies better in games. For a 5.1 audio system select 5.1 Speaker. Under Speaker Configuration select the number of speakers that you have.In sound card application settings (Realtek HD Audio Manager, Realtek Audio Console):

Realtek hd audio manager headset setup