deuce42
Well-known member
Dear all - I have done extensive searches here but am getting slightly confused with the reason for ground loops in a microphone project I am building. I have gutted a chinese tube mic and power supply and am doing the following:
1) The circuit I am building uses a Telefunken EF12 tube, of which the components requiring ground connection have been soldered to the pin on the tube socket that relates to the tube's heater's ground pin.
2) This heater gorund pin is connected to the 0v wire which in the 7pin mic cable is pin 5. At the mic's cable socket, Pin 5 (0v Cable), pin 7 and the socket shell (flat pin "8" if you like) have been internally connected. The mics body also appears conduct with these pins so must be connected by touching the socket shell.
3) At the power supply, the mic cable socket has 0v cable connected connected to pin 5 and just like the mic socket end, pin 7 and shell have also been connected internally. The shell of the seven pin mic cable socket is wired to the shell of the 3pin mic cable socket and the shell of the 3 pin socket is wired to pin 1 (shield) of the 3 pin socket of the other cable that goes to the preamp etc.
I simply cannot find where the ground loop is occruing and creating the aweful hum
Any assistance would be greatly apprecaited.
thanks
1) The circuit I am building uses a Telefunken EF12 tube, of which the components requiring ground connection have been soldered to the pin on the tube socket that relates to the tube's heater's ground pin.
2) This heater gorund pin is connected to the 0v wire which in the 7pin mic cable is pin 5. At the mic's cable socket, Pin 5 (0v Cable), pin 7 and the socket shell (flat pin "8" if you like) have been internally connected. The mics body also appears conduct with these pins so must be connected by touching the socket shell.
3) At the power supply, the mic cable socket has 0v cable connected connected to pin 5 and just like the mic socket end, pin 7 and shell have also been connected internally. The shell of the seven pin mic cable socket is wired to the shell of the 3pin mic cable socket and the shell of the 3 pin socket is wired to pin 1 (shield) of the 3 pin socket of the other cable that goes to the preamp etc.
I simply cannot find where the ground loop is occruing and creating the aweful hum
Any assistance would be greatly apprecaited.
thanks