Double grounded 5si hums and bites with static electricity

When listening to the 5si amplifier double grounded using a separate cable, a hum appears after a while, say, from minutes to half an hour. If at this moment you touch the amplifier, a spark of static electricity jumps.
What might be the cause of this bite?

There should only be one grounding point at the mains earth connection. How have you double grounded it?

The other ground is on the streamer side. 5si is recommended to be double grounded

Can you add a photo showing all the connections, in particular, the double grounding.


Who recommends this?

What do you mean by double grounding?

The NAIT 5SI should be earthed via the mains. How is the source earthed? Your profile say it’s an ND5XS2?

Please remove any cables from your system apart from the supplied mains cables, interconnects, and speaker cables.

I’m trying to help to setup my former 5si which I had to sell to pay the loan. By double grounding I mean the source is grounded the same way.
If the source is not grounded, I hear the hum immediately. However, if I use the properly grounded source, the hum slowly grows with time and the static electricity hits when you touch the volume control.
To me, this looks like the grounding is broken somewhere behind the wall socket.

Done. That is why I started the thread.

Please, look at the advice by the link Massive sudden hum - frightening! - #15 by james_n
At my home the issue with hum was solved using this cable, when connected to the source. I used it before I bought nd5xs2, with wxad-10
At the buyer’s home it helps partially, the hum goes away, then slowly returns and grows. At some moment the device starts hitting with static electricity

I’m still slightly foggy as to what you have done. Is the following understanding of your current setup accurate?

  • The amplifier is plugged in to a standard 3 pin earthed mains socket.
  • Nothing is connected to the signal ground screw on the back of the amp.
  • The source is plugged in to a standard 3 pin earthed mains socket.
    The source’s earth switch is set to “chassis”.
  • The source is connected via a standard Naim 5 pin DIN interconnect to the amp.
  • Only one source is connected to the amp.

Just to avoid misunderstand can you correct any of the above that do not match your set up?

  1. Correct
  2. There is no such thing in the 5si as the signal ground screw
  3. The source uses 2 pin + I added an additional ground cable, and there is no switch ‘chassis’.
  4. RCA
  5. Correct

Two questions;

  • why not use the DIN lead
  • what is the additional ground lead you added. Please include a photo of the lead and how it is connected at both ends.


The ND5XS does have a ground switch on the back with options for “floating” and “chassis”. And the device must be plugged in to an earthed 3 pole mains socket. It should be set to “chassis” and the supplied 5 pin DIN that came in the box has a dedicated single signal ground pin. As such I agreed with @DiggyGun that as a starting point, the supplied DIN cable should be used - at least until the problem is root caused.

If the problem is only at the buyers home, and you never experienced it at your home, there could be a problem in the power system in the buyers home and a qualified electrician should check it out. Maybe the mains power system in the buyers house isn’t earthed properly or some other issue.

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As I said I’m helping to setup my former 5si which I had to sell. The source is Yamaha-303, it has 2 pin mains.
The ground cable is connected somehow to yamaha, using the cable like this Massive sudden hum - frightening! - #15 by james_n

I got your point, thanks!

We’re getting confused here.

You state that the Yamaha 303 is connected by two pin. Yet use a three pin plug for a separate earth.

Please include photos of all the connections and plug sockets, it will really help for us to understand what is going on.


It is a bit difficult to make photos, by some reasons, I’m just helping the buyer as I like this amp very much.
Yamaha uses two pin socket and the ground is made the same way as here Massive sudden hum - frightening! - #15 by james_n
Actually, it was working for me, when I was using another Yamaha. But now it works strange when setup in another home.
No difference, if this ground cable is connected either to yamaha or to 5si - the hum disappears and then slowly returns and grows.

Have you checked your mains earthing (ground potential) at the sockets?

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