The crackling is annoying but I don't know how to fix. Two, Microphone doesn't work unless you turn levels to 100. But this works all good for one year. Then two things break. It works fine for my headphones, my speaker output is disabled because I have other USB speakers. I have normal Xonar U7 since January last year. I wonder if someone can please help me, i'm going crazy.

If you want to record the sound that you hear through your speakers, you'll need to utilize 3rd party software such as Voicemeeter (it's free). Finally, unlike Asus' internal Xonar soundcards such as the Xonar DSX, the Xonar U7 does not have built-in 'Stereo Mix' hardware capability, meaning that you cannot record everything you hear from your PC even though basic Realtek onboard audio has that capability. This means that your headphones/earphones with inline-mics will be prone to disconnecting from the jack with small tugs, but this can be remedied if you connect your headphones to the jack with any cheap 3.5 mm 4 pole to 3 pole adapter. To fix this, you'll have to not fully insert the jack in (maybe 90%) until you get full range sound. The way the U7's headphone jack has been designed, means that any headphones/earphones you plug in that has an inline-microphone will sound distorted with missing frequencies. The U7 has a relatively weak built-in headphone amplifier pushing only 1.3 Vrms at an unknown amount of load, which means that headphones rated at 250 ohms of impedance and above might not get as loud as you want them to, in which you'd need to run it through another amplifier. This higher output impedance can be negated if you are using a good amplifier with the U7.

Most Dynamic Driver headphones/earphones should be fine and should sound great. The U7 has about 17-21 ohms of output impedance meaning that it's not suitable for use with low or medium impedance Balanced Armature Driver earphones if you have any. For people potentially looking to buy the U7, my review is that it's excellent sound quality for the dollar, but there are 4 main weaknesses you might want to consider:

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