As I am about to embark on making one of these,  on the first diagram on how to make one, it only shows 2 wires. Shouldn't there be an earth wire if working on items that need to be grounded, or is it because with the bulb sucking the load we are only talking low voltage here?

Regards,
Baz.

I have a HH MA150 PA 5 Input Mixer Amp with 2 HH Pro 100 Speakers that I use indoors. It is in near mint condition because it has never been abused.
Just before Christmas I was using it to play some backing tracks, I left it switched on (with nothing playing through it) left the room for 5 minutes when I returned it was making a loud humming noise!  I checked
all the connections etc. and they were all fine. 30 years ago it died and I had it repaired, I was told it was the output resistors. I am more electronic savvy now having done some work on valve amps so I can use a
meter/solder read schematics etc. but not much experience on SS.
I checked the  4 resistors that were replaced last time and 3 were burnt and way out of spec. So I replaced all 4.  The amp switches on, everything lights up, nothing smoking, its cured the humming, but no sound at all?