• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

hifi 6j4- 6p6p tube preamp

I have put together this preamplifier kit ,

I have a few questions on the grounding that is troubling me ..

The negative rail of the circuit is connected to the chassis that also acts as a ground for the transformer and the rca connection . basically they all share a ground that is connected to the chassis .

as far as I'm aware that is not a great idea and in my mind can't be that safe ? can someone please advice me on this matter

also one more point is that the earth in the iec ( 230 ac input is not connected in the schematic , I guess if that is connected to the chassis as well that will produce noise into the circuit )

Hopefully someone will be able to put my mind at rest


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For safety reasons when having a metal chassis - the IEC safety ground must be directly connected to the metal chassis!! Never leave it unconnected!! A floating metal chassis can be lethal if there is a short from a high voltage node to the sheet metal.
"Are you running the inputs over unshielded wire (red/black at the left) to the input selector? Not a good idea." Spotted that to, better to use screened cable. The RCA wiring is sitting right next to the heater wiring, the signal wiring would be better lifted up out of the way and secured to the wood side.

Lastly all grounds should go to one point on or near to the main negative of the PSU. If using a bus, small signal grounds should go first, then higher current grounds. A 10r resistor from the main ground to chassis can help, it can also be done with diodes.

thank you for everyones reply's .

I am waiting on some parts to arrive . I am redirecting the on how the ground is ran and I'm using a busbar - not tied to chassis and I'm connecting the earth to the chassis right next the main input .

as for the unshielded rca wires - I'm not sure on this matter I have wound the wires together . if I find it to be a problem I will change them to shielded wires, I would like to point out that I'm still in learning and I thank everybody for there help