@ Richard.Dane, any help is very welcome and I appreciate that very much. I also understand what you mean. I know it’s often difficult to help when the situation is only described and not experienced on-site.
The German distrubutor has a helpline to which I have turned several times. The result was a burndy cable as an exchange. The dealer says with every call, the problem is solved, but nothing happens. Now I have to admit, it’s not the typical Naim dealer,but a big Linn dealer who also sells Naim. Maybe he does not have the best connection to the distributor. Unfortunately I have to fix an appointment, where the problem is solved. If it has not been solved by then, I’ll probably have to reverse the entire purchase and seek alternatives.
OTOH I’m very familiar with Naim, as I use it more the 40 years in very different setups.
However, I think those who are trying to help continue to inform what happened. However, if this is not desired in the way I do no problem. Please let me know.
I have kept the SL as far away from power supplies as possible, but nothing has changed . If it were just the humming, I could understand that this is an interference caused by the grid frequency. But it’s more than that. And only with the Burndy and not with the 5 pin SNAIC. With SNAIC its dead quiet. If it were interference, it would have to happen for my understanding with the SNAIC too but it does not.
As I wrote, it sounds like capacitors discharging. Unfortunately, I can not upload an audio file that shows it very well. The recording was made when the SL was as far away as the Burndy allowed. 552PS and 555PS are even further away, as can not sprinkle.
@Yeti, It may have been a bit vague, sorry for that. I have exchanged everything that is movable, power cord, other circuit used, even other sockets, burndy, plugs for the Kandid.
The next logical step would be to swap the supercap.