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Another buzz issue

Hi All, I recently updated my preamp to a Marantz AV7706. The Marantz has a 2 prong plug and after extensive trial and error have determined the hum must be a grounding issue. I have separate amps on all channels (a total of 4 amps with 3-prong plugs and a Marantz, 6 channel amp powering 3 pair of overhead fronts, sides and overhead rears for (ATMOS) configuration that, like the preamp, has a 2 prong plug. I don’t want to put cheater plugs on ALL of my 3 prong plugs so was wondering if/how it’s possible to “ground” - or convert - the 2 prong plugs to 3 prong? FWIW - I have a dedicated circuit for the HT/sound system, almost everything is plugged into a Furman AC “conditioner” and all plugged into the same circuit. There are NO coax runs. I’m sure there is another thread on this topic somewhere but am looking for guidance. Also, all the interconnects are in shielded, RCA (my 4 old Hafler 9300’s don’t take XLR). To rule out the cables I put in some old AQ shielded cables with no luck. I will also mention that there are a few auxiliary components (subwoofer, Amazon cube and and Apple TV that are plugged into a Panamax which is plugged into the same outlet/circuit - I just don’t have any more outlets available on the Furman. I have tried to troubleshoot this for over a year and have had 2 installers come out with no luck. At first I thought there was a problem with the Marantz but swapped it out for a new one (same model) so doubt that’s the issue.

whiterockman

Showing 1 response by williewonka

williewonka
3,067 posts
 

@whiterockman - The problem may be due to mixing isolated components and grounded components.

For example...

  • I have a grounded Bryston amp
  • a Bluesound isolated (two pin) streamer
  • I get a hum when the two are connected and running in my system
  • But- if I connect my grounded Simaudio Moon phono stage the hum goes away

So you might want to try this little experiment

  • take an old piece of wire 4-5 ft long and strip both ends
  • attach one end to a mains ground point
    • I use an old plug, with the wire attached to only the ground pin and plug it in an outlet
  • touch the other end to the NEUTRAL on any unused RCA socket on the pre-amp
  • If the hum gose away, then make this temporary grounding lead more permanent by attaching the bare end of the wire to the neutral side of an RCA plug and insert it into any unused socket.

 

Like you I spent a long time trying to resolve this problem until I read about NAIM products

  • turns out most NAIM sources are all grounded, but using an ungrounded source with a Naim amp will result in a hum.

Hope you find a solution

Regards - Steve

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