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In the Forum: Audio Discussions
In the Thread: It’s mad, mad, mad... electricity.
Post Subject: Victory over GNDPosted by N-set on: 12/8/2020
1) GND NOISE
After more experiments, I can proclaim a victory over the 100Hz noise on my End of life phono. For whatever reason the GND connection does not want to run in a close physical proximity of the line and neutral and demands a separate cable. So this was not a faulty PP. Where I terminate this cable: at the PP output sockets or at the wall it does not matter - the audible noise is gone, only my FFT shows a pronounced 20Khz peak but more on that later. The PP is 2m away from the rack, the power is connected via a normal household strip for a moment, the separate GND wire is 5mm, 13ga cable connected to the phono input ground terminal.
Proximity effects: If I disconnect the GND wire from the ground and start moving it around, the closer it is to the PP output cable (the power strip cable) the more noise is picked and present at the phono output. So there is some coupling, which lead to the noise. I examined the field around the power cables - connected a small 47mH RF choke to one input of the sound card and a pair of loose cables to the other to catch both B and E fields on my laptop scope. Indeed there is quite some trash around the power cables: The closer to the phono power supply the more of it and more spread in the air (phono cable has a gnd drain cable connected to PP gnd on one side only), while the closer to the PP output socket the quieter and more concentrated around the cable. 20kHz is all over in the air, in the radius of 2m around the equipment and is happily picked by my cartridges (esp. the Decca). I speculate most of this noise is electric field and open loop antenna picked much more than a coil.
Given that, PP users, do you use shielded power cables around your PP's to constrain the emission?
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