|Joined: ||Dec 6th, 2013|
From the video I expect the hum is from unscreened wires feeding hi-Z inputs, both the BF256 FET and the audio amp - but I guess you know that.
Incidentally, I've had problems with FETs which were caused by different pin configurations to those that were published. Sometimes it depends on the manufacturer!
I'm curious to know what's causing the occasional high-pitched interference. Do you have any switched-mode power supplies nearby on standby? Or any data-though-the-mains equipment?
When I've had similar hum problems as a last resort I've switched off the workshop mains!
I like the magnets retained by tape as they try to repel each other - very simple but clever.
Thanks for posting the video.
i shut down the workshop power yesterday (one switch) and the sound was still there.
Only after removing the ground/minus lead of the Fluke multimeter it was gone (or not audible anymore).
As i have just above my head a 6000W (24 panels) solar system i suspect it is comming from there, or at least from the solar inverter and picked up by this minus lead.
Stefan, very nice build, those magnets are going nowhere