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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
whiterockman OP
21 posts
 

Thx!

erik_squires
16,121 posts
 

If you hear a buzz instead of a hum the problem may be induced noise instead of a ground loop. Try turning all the other circuits in your home off as a quick experiment.  It could also be a result of the amplifier transformers being too close to your other gear.

You don’t want to ground 2 prong devices. The lack of grounding is keeping them from being part of the problem, nor do you want to use a cheater plut.

First issue is to narrow down your problem. Disconnect all inputs from your processor, and put it and all your amps on the same Furman conditioner. See if the hum still occurs. Then start turning amps off.

Despite the fire department recommendation, you CAN extend a Furman conditioner with a pure power strip that has a built in breaker, like the one below. The reason fire safety people are concerned about daisy chaining power strips is that many strips and power cords are not fused and easily overloaded. The unit I show you below is 100% safe to extend a Furman power conditioner. Just don’t use a cheap, unfused/unprotected power cable in the middle.

 

https://amzn.to/3K0gZOW

whiterockman OP
21 posts
 

Thanks. I haven’t tried turning off power to everything in the house - except that circuit - but did have an electrician out to look everything over. And to clarify, it does sound more like a 60 cycle “hum” than a “buzz”. I appreciate the info! As far as amplifier placement, I’m kind of limited there, though I did consider - thinking it could have been an issue - getting some EMI/RF blocking fabric to put on the shelves that the amps sit on… it’s on Amazon for $70. Block EMF RFID EMI RF Shielding Conductive Copper Nickel Fabric for Smart Meter RF Blocking Plaid Ripstop Type Military Grade 197"x43" inch https://a.co/d/0avEBWV

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williewonka
3,075 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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