speaker connection to ground

[Marc]

I have seen some old schematics (like Valco) that do not show a ground connection to the speaker and it got me to thinking that I can't for the life of me remember if I've ever seen a speaker that was not connected to ground. Is is possible to not have the speaker connected to ground and have the same function from the amp? Is this a full moon question?

[Diablo]

Yes, the speaker has to connect to the ground side of the output transformer some how to make a complete circuit. Maybe the speaker jacks are metal and ground to the chassis when mounted?

[Enzo]

If you use any NFB - and many of our amps do of course - it is a signal that has to be referenced to ground because all the rest of the circuits are referenced to ground. SO then you have to ground one side.

Without NFB you can go groundless. To do that you either run wires directly from the circuit to the speaker or you insulate the jack from the chassis. In that latter case, why bother?

[Marc]

Thanks Enzo!
That makes perfect sense now.

Marc