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SondreParticipant
Hi, finally got to test the gu50 with No earthing, and as suspected there were No music, just a very loud 50hz hum. So I will go ahead and put in the signal path earthing just like I did on my second amp. This one played music and behaved normal.
SondreParticipantOk, signal wire is connected as pr instructions in video, so no ground connection in signal path. I will test this and see what happens. If it doesnt work I’ll add a wire straight from the RCA to the star ground point as would be the closest match to using the mains ground. Btw, one of my preamps have dual isolated configuration, so even with household mains ground this one would not complete the ground circuit as is your intention.
SondreParticipantSorry, I missed that there was two posts from you. Yes, I see the risk of having a ground loop, but in my house there is No eart in my mains, old house, so the preamp and the amp does not see a common earth, so I need some way of getting that negative part of the signal to the gu50 amp?
SondreParticipantGood morning Charles.
That was a clarifycation. Thank you. But please try to understand me now. According build video for mounting small parts we install phono socket with the small plastic shims that isolate the phono socket mass from chassis effectivly isolating phono signal ground from chassis ground. Then we prepare signal wire in a following video, both to the gu50 from driver board, and to the phono socket. BOTH wires we are instructed to cut shield/ground in one end. This is ok for the gu50 side as the tube has ground through pin 7. But the wire between phono socket and driver board need to carry both negative and positive signal, and this is not possible per instructions when we cut shield/ground on one end? How does the prototype get signal ground? Have you removed the spacer that isolate the phono socket mass? Or as I said in my initial post, if I am getting ahead of myself, and you have planned to put in a separate wire to carry signal ground from phono socket to chassis?
Regards
Sondre BarstadSondreParticipantThis is ok, the tube is grounded-pin7. But now, if i use my multimeter in “beep” mode,(cannot remember what it is in english) and check between phono socket ground, the outer part/ negative, there is No continuity to amp ground/chassis plate. So the incoming ground/negative signal from my preamp is not connected as per following build istructions. The schematic clearly States that the phono negative in the socket must be connected to ground. And this has been the case with every other amp i have built and repaired. So using the signal wire that was prepared in the video that only has the positive White lead connected to the driver board is confusing for me at the moment.
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