'Back in the '60s when people were putting their classy Hi-Fi seperate systems together (and yes - for about a decade people really did strive for Hi-Fi and did actually listen to real music.. ) the stuff I have posted would be deemed elementary.. But these days even fitting a simple adaptor, and the possible problems these could create, is beyond the understanding of most'-Fred
Well I was one of those folks in the 70’s and 80’s who had good (well, as good as I could afford) Hi-Fi separates and as you rightly say, the way to interconnect the individual units was well understood and at the first signs of any mains hum, the earthing path was always the first thing to be examined.
I think the decline started when ‘mini’ systems started to appear so that not only was the interconnection of separate units not necessary but due to the design of the mini unit, was almost impossible. No longer could you easily add a tuner to your amp because the amp which was part of the mini unit didn’t have any suitable inputs.
Then for some reason double insulation of electrical units means that there is no need for an earth since none of the external parts are exposed to the live and as you again point out, these days it is more common than not to buy a power adaptor which has no earth but instead has a dummy earth pin just to enable the entry of the plug into the socket.
My theremin never had an earthing point in the design but to me it made sense if I was going to use it with the battery operated amp.
I’ve made a lead consisting of a length of bell wire connected to the earth pin in a mains plug and at the other end to a banana plug which goes into the theremin.
The full importance of having a good earth on the theremin was unknown to me until it wasn’t there…
Roy
PS-I still have my Hi-Fi separates and wouldn’t get rid of them for the world!