Earthing sparks? (ft. Rega Schiit iFi miniDSP & Topping)

[Japt]

First time poster .

I ran into a ground hum problem (very loud) in the following chain:

Rega P1 TT ----> Schiit Mani/iFi Zen Phono (doesn't matter which one) ----> miniDSP 2x4 HD (rca in--rca out) ---->Topping PA 5 x 2* ----> DIY LXmini speakers.

(*The RCA to TRS cables for interfacing the miniDSP and Topping amplifier were made according to the Hypex recommendation. I also tried the Rane configuration but got interference and a different kind of noise.)

The toslink and usb input on the miniDSP are also connected to other sources I have and they are unaffected. The hum ONLY appears when I use the RCA input for the TT. There's also no hum when I run the RCA output from my OPPO 105 to the RCA input of the miniDSP.

After much frustration, I came to the conclusion that the lack of earthing on any of the aforementioned product was probably the culprit. My OPPO does have a 3-pronged power plug and is connected to the miniDSP through toslink (it probably doesn't matter). So I ran a wire from the grounding post in the back of the phono preamp to the chassis of the OPPO and the hum went away completely! I was overjoyed.

BUT, just as I was trying to make the wiring more permanent and elegant, I saw sparks in the copper strands of the wire. (Both the OPPO and the phono preamp were powered off but plugged in when this happened.) Basically as I bring the wire into contact with a chassis screw on the OPPO, I can both see sparks and hear the crackling "electricity sound".

Should I be concerened? Is it safe to "ground" or "earth" my system this way? I have to be extra cautious because I have a 3 year old child.

Thanks in advance for your help!!!

 

[Japt]

Well, instead of connecting the ground on the phono preamp to the chassis of the earthed Oppo 105, I ended up connecting the minidsp 2x4 HD (thru a chassis screw) to the wall outlet directly, with a 1-prong plug (ground prong and wire only). I read a similar solution on the minidsp forum.

 

[antcollinet]

This will come from one of the devices (possibly the device connected to the USB of the DAC) having a high earth leakage current, probably from filter capacitors on it's mains input. It shouldn't be dangerous if the product is compliant with standards, but you can get a "tingle" from it if you touch it. The sparks are caused by the making/breaking of the earth connection as you touch the wire to the chassis screw. (as you can get with a 12V car battery for example)

I have a similar thing with my TV setup where I have many devices with earths all connected together. Then all the earth leakages from all the devices are added together.