Electronic – Multiple grounds from diode bridge? Safe or really stupid/dangerous

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I am making a hybrid tube preamplifier (one vacuum tube and one op-amp). Both use very different voltages – the tube is getting somewhere about ~150V DC and the op-amp gets ~6V DC. The differences are huge.

Can I connect the ground from 150v DC to the ground of 6V DC? Both are 'made' from a transformer and a diode bridge, filtered with capacitors. I assume they both should be at 0V. Based on that it seems to me that it should be somewhat safe.

Am I wrong? Can it be done? And can it be safe? Or is it really stupid and should never be even considered? I am just wondering, didn't actually try it – now I am asking.

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*First stage of the preamplifier: (~ 150V DC)
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Second stage of the preamplifier: (6v DC)

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Best Answer

Yes, you can do that, even need to do that if each of the AC feeds in your schematic come from separate transformer windings. Put another way, the two AC feeds must be floating with respect to each other.

With the AC feeds floating, the DC voltages derived from them will also float. If you want the circuitry powered by one to drive a signal to the other, you also need to connect one other point between the two sections that will be the reference voltage for this signal. The negative of the DC supply is a obvious choice, and it simplifies thinking about the circuit if you consider that to be the ground for both sections.