My brother is fairly new to guitar playing (I am not), and last week got a nice new CIJ Hybrid Strat, which is his first electric guitar with single coil pickups. Last night I got a worried text from him that he'd changed strings and now there was terrible noise when he took his hands off the strings (sound familiar?).
My brother is an industrial electrical engineer (designs electrical systems for chemical refineries and power stations!), so whilst he knew fairly little about how electric guitars might behave, he understands far better than me electrics and electronics.
I explained that almost certainly the string change was a coincidence, and what he was hearing was EM interference picked up by his body being "heard" by the single coils, and gave him the list of usual suspects. Five minutes later he texted back that he had tracked the noise down to one of the dimmer switches in his house, the other one apparently having little effect.
He went away and did more research and this morning he texted me with the info below - might be of interest, and might help some of us with dimmers reduce the problem....
I’ve read up on dimmer switches, they work by the pot giving a control level to a triac which then turns the wave form on and off, so it’s not a reduction in voltage or current, it’s on and off very quickly the amount of time between the on and off giving the different lighting levels. So no wonder they chuck out so much crap, it’s a very crude rectifier.
Industrial equivalents were outlawed by EU directives about 20-30 Yrs ago due to EMC problems. Which is why I’d not really seen this problem elsewhere.
Seems that the reason that one dimmer circuit is ok and the other not in our dining room is because one is on the overhead led’s and the other is on filament bulbs on the wall lights... the LEDs aren’t a problem as lower current so less interference.
Solution is to replace the old bulbs with leds.
The better technical solution is to use dimmers based on autotransformers instead of triacs, but they’ll be bloody expensive. So aiming for lower current options is most practical, as the varying magnetic fields, which are causing the pickups to buzz, are proportional to the current flowing. So this doesn’t get rid of the problem, but does reduce it such as much less noticeable