I’m currently building a K8084 “VOLUME AND TONE CONTROL - PREAMPLIFIER” and have a couple of questions about grounding the case and earthing the whole circuit. I’m finding the manual a little confusing in this regard.
I plan to build a wooden enclosure with a copper lining and then connect the lining to the marked ground terminal on the bottom right hand corner of the PCB. However, I’m not really sure how to go about safety earthing the enclosure and the circuit itself. I assume that if I simply connect the earth wire from the wall plug to the copper lining I could set up a ground loop and end up with humming. Do I need to use a loop breaker circuit? The manual itself makes no reference to safety earthing the circuit.
This circuit does not really need grounding. All levels are line-levels and all drivers are low-impedance.
If it would have been a phono amp and/or a tube circuit it would have needed grounding.
If you decide to ground it anyway, experiment for best result and (as you state) make sure to avoid ground loops.
Connecting all grounds to a star point, e.g. the transformer ‘0’ on the PCB is a good starting point.
Thanks for the reply. That means that I can probably get away without grounding the copper lining. I’m still a bit concerned about safety earthing of the circuit and enclosure. Do I not need to connect the circuit and enclosure to the earth wire to protect against electrocution?
I’m planning to use a wooden case but I’m concerned about the input and output RCA connectors accidentally becoming live in case of a fault. I was mainly wondering how I would go about preventing this.
This is impossible.
The unit is run from a transformer, so it is always isolated from the mains (if the unit has been assembled and wired correctly of course).