Setup considerations for a great audio recording experience on a MacBook Pro 16'' with AKG C 520 + Rode AI-1
I "only" wanted to record some podcast and online courses - and thus bought a AKG C 520 Vocal Microphone and Rode AI-1 Audiointerface, connected them to my MacBook Pro 16'' (2020) and installed OBS to record my screen and voice...
But - as always - it wasn't that easy. I got a chirp on the recordings, which was quite nasty since my voice - together with my screencast - is the only thing people get when the listen to my recordings.
As a long year reader of the great c't Magazin I removed the power supply of my mac to see what happens. I didn't use the standard power supply, but in my setup I used the 349€ Belkin Thunderbold 3 Pro dock, which I really loved since the old dream of using only one cable to connect my laptop to any device (USBs, Ethernet, power supply, external displays...) came true with it.
Now having disconnected the Belkin doc, my recording got rid of the chirping - but now there was a humming. After googling around I soon found a seamingly well known issue: the magic hand issue. Because simply touching my MacBook the humming was gone. I could "see" that in OBS:
and touching my MacBook:
This leads us to the root cause of the humming: no proper grounding! After a while of googling and thinkering it became clear to me. Current MacBooks don't ship with a grounded! TODAY! Having a look at the power supply this becomes obvious:
In the detail view you see the 2 power supply conductors. And the bigger round grounding plug:
But looking a the plug there's only plastic inside!!
So our MacBook Pro does not get grounded with the 2020/21 power supply setup.
But there's help! Many people suggest to build your own cable which is definitely possible, but not without risks for the non-electrically trained (like me). But I'm working with MacBooks since 2015 and luckily I have every cable right in my cellar - even the old extension cable from my MacBook Pro 2015! Let's have a detailled look onto it:
and especially the plugs:
There's metal inside the power supply plug - and it's grounded into the socket! Using this cable together with my MacBook Pro 16'' power supply I got rid of the humming!
After getting rid of the chirping and humming I started to get my first usable audio recordings. But there was a subtle humming left - not noticable on screen looking at OBS, but I heard it when using headphones and turining up the volume a bit more. But I also got rid of this last audio recording issue: I simply used OBS' noice suppression option. Therefore right click onto your microphone in OBS and click on Filter. There create a new filter from the + menu using noise suppression (or Rauschunterdrückung in german).