I decided to demystify onboard audio in “gaming” motherboards after realizing people ask about it a lot, and there isn’t a lot of clear information about the topic.
I would like to clarify, I am not an audiophile, I am a gamer in my free time and a geophysicist in my not-free time. I work with seismic signals and I am considered a digital signal processing expert in my area.
The first thing people need to understand is that a DAC reconstructs a digital signal into an analog signal. A DAC that changes the original signal into another signal, it’s just a bad DAC, unless you want to change the signal intentionally for a very specific reason. The same goes the other way around, when you record an analog signal to store it digitally, you need an ADC .You want to preserve the characteristics of the analog signal the best you can.
The AMP shouldn’t change the characteristics of the signal either, it just amplifies the signal, but the signal should remain the same.
So, DAC and AMP reconstruct and amplify a signal, it should not distort/change the signal. But we don’t live in a perfect world, so there is electronic interference, distortions, etc.
There are several measurements to assess how good a DAC is at reconstructing a signal without introducing distortions, noise, interference from the electronics, etc. The same with the AMPs.
When it comes down to onboard audio in modern high-end mobos, the DAC is actually pretty decent. I am not going to comment on every single measurement done to this Gigabyte Z390 Aorus mobo, but I will quote a comment about the DAC linearity: “This is stunningly accurate linearity which even expensive DACs struggle with at times”. Feel free to read all measurements in the link below.
The problem with onboard audio starts to show with the Amp. On a theoretical level, the onboard audio can actually produce more than enough power to drive high impedance headphones. The problem is the output impedance of the onboard audio is terribly high, so there is a lot of power loss. This will change the frequency response of most headphones, particularly those with low impedance (which is funny). And this is totally measurable and audible.
Julian gives a really good explanation about why a low output impedance is important, and how a high output impedance affects the tonality of a given headphone.
The bottom line is your onboard DAC is pretty decent, the amp isn’t. So just get a decent external amp and you can get away with that without the need for an external DAC. Keep in mind that the high output impedance of your mobo will affect more LOW impedance headphones.
That’s my two cents for the community.
A couple of important points from the feedback that I missed in the original post.
Some motherboard manufacturers don’t have a proper implementation of the audio chipset shielding. That means you can get a lot of interference, particularly whilst gaming when your GPU is fully loaded.
The front panel normally has a better shielding and amp solution compared to the back I/O of your motherboard. Connecting your headphone to the front panel is the best course of action if you don’t have a dedicated external DAC/AMP solution.
Additional links with measurements:
Measurements done in three X570 mobos from the well-known igorslab
Measurement on a MSI MPG Z390
PS: Thank you all for your feedback, questions, and insight.