Compact digital converter on Optical - but beware noise source

Have the converter bought to get investment from my digital chinch output of the TV to the digital optical input of my hifi. This works even if wonderful, the basic job done this little device exactly as it should. The power supply also has a sufficiently long cable.
But the problematic part. I have a hi-fi rack, there is the conditioning, CD players, hard disk recorders, and on top of the TV. I use digital cable for the TV. The digital television signal is well on the TV. However, the hard disk recorder uses still the analog signal. And here is the big problem.
The analog signal is extremely disturbed by the power supply of the converter. If the converter is turned on, I need not attempt to record a movie. The picture is very krisselig. If I switch the converter off, the image is good again.

It has helped to change only the antenna cable from the socket in the wall to the recorder. Previously, it was a 0815 cable, unshielded, available at hardware stores. Now I have a 4-fold shielded a well known manufacturer and the picture is good again.

So fundamentally the converter works well, only attention to the shielding of the cable Make when the analog signal is not used. The same applies to all analog signals, like the RCA near (50 cm) are so moved. Because it can be expensive but suddenly, because shielded cables cost, unfortunately, a few euros.