Here I had a lot of electronic instruments and preamps (with land) connected to my table (not ground) to connect the stereo while a compressor (not ground) and my Atari Falcon (with ground).
Certain instruments connected to my Falcon did snore with the background noise of 50 Hz and its harmonics. All with very expensive cables. Disconnection of the masses did nothing, even + dangerous disconnect land no effect either.
Discouraged, I order the HD400 in the Behringer brand + is that I can not stand.
Well it cost twenty euros is Made in China, so I'll try.
I suspect that within there is a transformer.
First connection, connection between the table and the Falcon.
Result: more hum!
In + is secure because the land is still connected!
Another instrument with earth, was snoring through the table, one with earth. The HD400 solves the problem.
Design error (Behringer Ha la la!), The jacks are too close together.
In fact it happens that the masses of input and output jack come into contact.
Result, it has more effect! So make sure that by plugging in the masses of input and output jacks are not in touch!
It seems to me that it does not distort sound quality.
Basically, ideally, for all connections between machines with asymmetrical earth would require a transformer of this type. Take several, ca always helps out, and it caused a sensation.
This solution is still unknown, yet it is much the better.
I will still turn to brands more serious as Palmer (ILP-03), or ART Jensen (DTI).