Power conditioner can improve AC isolation

https://www.amazon.com/Furman-AC-215A-Conditioner-Auto-Reset...

https://surgestop.com/surge-products/m-474.html

Thanks, I'm using two surgex sx 2120-seq power conditioner+sequencers -- one for the desktop devices and one for the stereo. I'm just baffled that even though I'm a completely separate circuit the hairdryer is still able to do something to affect the electricity in my office.

> the hairdryer is still able to do something to affect the electricity in my office.

This may indicate that your neutral line is undersized and/or damaged.

How could I test this?

A first thing to test would be that your voltages are nominal, but the exact details depend on how many phases are coming from the transformer, how they are wired, and whether you are on a TT, TN-C-S or other kind of grounding system, which depends mostly on where you live. Also, you need to take your voltages both at low impedance (simulates a load) and at high impedance (negligible load, "classical" meters are generally high impedance).

Generally, you want to measure the voltage difference between live and neutral depending on the load. However, depending on the tools you have access to, taking this reading properly can be a bit tricky both because simple high-impendance multimeters can easily be tricked by ghost voltages caused by bad connections and inductions from other cables, and also because understanding what to measure requires knowing how is the electrical system wired.

If you know you are in a TT system with 240V between Live/Neutral, I can tell my procedure for inspecting neutrals. In a two-pole TN-C-S system with 120V between L1/Neutral and 240V between L1/L2, I suppose it would be similar, expect that we'd have to do more tests (both L1 and L2 to neutral, and I imagine also L1 to L2).

EDIT: a first simple check to do is to check, using any multimeter, if there is voltage drop in your office when the hairdryer is in use.

Thanks so much for the write-up!

Interestingly, the PCIe 8-pin power cable into a GPU doesn't carry all of the return current. If you put a current clamp meter around the +12V wires and then the ground wires, you'll measure more amps on the +12V wires than the ground wires. This means some of the return current goes through the PCIe slot into motherboard and makes its way back to the PSU. This lets the GPU create audio noise because GPUs draw high current pulses at the frame rate of your monitor, which means the return current through the motherboard has high current pulses, which can create ground bounce on the motherboard where the ground voltage level moves up and down and that can affect other devices in the system.

I don't totally know how that noise would traveling over the ground shield of the HDMI cable into the analog section of the Denon receiver though. Maybe some of that GPU return current is going through the HDMI cable, through the Denon receiver to mains earth, and then through your building wiring back to the ATX PSU? Grounding is freaking weird.

Oh, wow, yeah, that's really interesting. I don't understand electricity or know nearly enough about electrical engineering to be sure I understand the effect or flow you're describing, but if I (dimly) grasp what you're saying, it would explain exactly the behavior I observed.

Grounding really is incredibly weird (and, again, I say this as someone who is shamefully ignorant of electrical principles). It's no surprise that some 'audiophiles' become so superstitious about electricity. Its behavior in a stereo can be mysterious. Just looking at an amp funny seems like enough to cause a ground loop.