Strange noises in your recordings

Strange noises in your recordings

While we were recording some tests with the ECHO projects microphone arrays, we suddenly heard some short plops in one channel.

The sound was reminiscent of unplugging a connector, but at a significantly quieter volume.
It occurred intermittently and then seemed to disappear. Then, it came back for three or more plops and disappeared again. This ruined some recordings!
I'll give you three guesses as to what caused it.

Okay, it was the power bank. We used a standard power bank that you can buy in almost any store around the world. Since these power banks only provide 5V, and we need 12V for the Zoom F8n and F8n Pro, we used a 5V-to-12V DC-DC power converter with a Hirose connector.
This worked well when we used an F8n or F8n Pro alone. 
However, when we connected them via SMPTE and word-clock, the power demand was slightly too much for this setup. This caused a brief drop in the phantom power of one microphone, resulting in the plop sound.
When we ran the same setup at home with the Zoom PSUs for the recorder, everything was fine for hours on end.
However, as soon as we connected the fully charged power banks with the DC-DC converters, the plops appeared again.

So here is the learning:

Don't use DC-DC converters when you need reliable power for your recorders.
We changed to power-banks that deliver at least 12 V (15 V is better) and make sure, they are completely charged before leaving the house.