Hi all.
I understand people who have or may have noise problems and I feel sorry for them, but I think that it is impossible to design a specific equipment such as the A90 or another, I do not care about the brand and model, which can satisfy the Once, all the needs in terms of each person's personal design tastes and component installations so varied in our homes.
Leakage currents are common in all grounded equipment whether or not they are audio and generally PCs are literally huge generators in this case.
Especially when we work with analog signals produced by the same PC. It is inevitable that the ground / earth signal can be contaminated with the leakage currents created by the same PC depending on the installation. And that can happen with the A90 or with any other amplifier.
Luckily, I have no problems in this regard using or not using RCA connections, both through headphones and with Edifier active speakers.
I know that it should not be necessary to buy anything, but this would be a reasonable price option to solve or at least minimize the problems if we use a PC and the problem that we detect is the one that appears in the video.
For the record, I have nothing to do with iFi audio, I have simply been experimenting with USB audio for several years and tried many devices with more or less fortune in my previous systems, this included.