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  1. #1

    Does a ground nut connect to electrical ground?

    Hello all,
    Well, the question is in the title. The reason for asking is that I have a humming REL sub connected to a class d poweramp that I'm trying to find suitable ground for. Connecting the .1 to the preamp works, as per RELs site, but leaves me one pre-connection short. There is electrical ground in the poweramp but no ground bolt/nut on it. My search skills seems to fail me and I cant figure out if amps with a ground nut on the back connects this to the electrical ground or if it is some other sort of ground.

    I'm not planning to open the poweramp but as far as I can tell the electrical ground in it is connected to a screw in the bottom of the chassi and I thought I might try to make connection there if it is a sane option.

    Thanks for your time and take care!

  2. #2
    Senior Member
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    I am not sure where you are located but here in the US, the ground pin on a 3 pin, 120vac/60Hz outlet should connect to the gnd in the breaker panel, then to a ground stake outside. I say should because sometimes this is not the case**

    Your mating ground pin on your AC Chord leading into your amp should tie to the case of the amp. After that "signal ground" could be something different, but often it is the same. You should be able to find the schematics of your amp on the web, but you could try using an ohm meter between the ground pin on your chord and the outer ring of your RCA jacks.

    ** sometimes the ground integrity can be lost in house wiring. Example, daisy chaining outlets and you don't have a great gnd connection (or no connection) on one outlet, so it is lost on all. Hot and Neutral can be switched on install....etc

    Hum can also be caused my ground loops. So, let's say I have a turntable plugged into one outlet, and my amp into another. If there is any impedance/resistance between the grounds of the outlets, tiny current can flow in the ground, causing hum because one device sees a different ground reference than the other device. An example, the outlets are on a different circuit, the panel is a bit of a distance away, the copper wire has some resistance/length x long length causing the two grounds to have an impedance.

    so...

    1) Yes, if you tie a wire to a case screw this should be ground, but can be confirmed with the schematic.

    2) Try all devices on the same outlet or power strip, and maybe move the power strip to different outlets.

    You can also test the integrity of outlets. I have this handy cheap thing: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 Its nice to have for many reasons including testing your GFCI's (which help to keep us safe )

    Jim

  3. #3
    Hello,
    I don't think there is a ground loop as the system is dead silent without the REL. Tried lifting the ground on my DAC, which is where a possible ground loop might be as all audio gear is connected to the same socket but the computers are not, but that made no difference.

    Measuring things sure made it easier The fix proved easier still, kind of. Fixing the RELs ground on an amp chassi screw made the hum go away. Why didn't I do that from the start? Well, I didn't get a connection on the outside of the screw but the inside and the threads connected, no idea why but it seems to work.

    Thanks for the help, take care!

  4. #4
    Senior Member
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    great! maybe the screw's head is plated and you got better contact in a non plated or plated worn off part (threads).

    I had forgotten that you mentioned that the hum is from a sub. Subs are really good at amplifying and reproducing 60Hz (US). That's their job!

    Jim

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