[BossaNova31]

Hi everyone,

There is some kind of electrical gremlin in my system that I just can't seem to fix. I have a pretty basic 2 channel stereo - CDP, tube preamp and monblock tube amps. No TV or cable box in the room. The interconnects running between the CDP and the preamp are Acoustic Zen Silver Ref and the interconnects between the pre and the monoblocks are the Acoustic Zen Matrix Reference. Both sets of interconnects are RCAs because Manley gear isnt set up for balanced connects. Both the CDP and the pre are plugged into an Ultimate Outlet, which plugs into the wall outlet via a 3 prong plug. The monoblocks are both plugged directly into the wall, and each have 3 prong plugs. I do not have dedicated AC lines because I live in an apartment.

The sound I am hearing is a high pitched ring coming out of both speakers (my hearing is great so its not me) that I can hear faintly with no music playing from my listening position and is pretty obvious when I put my ear a foot away from the speaker. It isnt the typical 60hz ground loop sound that would be more of a lower rumble. This sound is more like several thousand hz.

So if I put cheater plugs on both monoblock plugs the system becomes dead quiet. Perfect. So thinking it was some kind of group loop issue, I ordered up a Granite Audio Ground Zero unit (because I definitely dont want to use cheater plugs indefinitely). The Ground Zero is supposed to cure ground loops thru star grounding and eliminate the need for cheater plugs.

Unfortunately, upon experimenting with the Ground Zero unit (making sure that all of the wire leads were well grounded to each of my system components), I found that it does nothing to solve the noise issue (with the cheater plugs removed). I'm a bit confused now and don't know what to try next. The Manley tech person says that using cheater plugs is perfectly fine (they actually recommend using them in the owners manual for ground loops), but I eventually want to upgrade the monoblock PCs and it doesnt make sense to me plugging a few hundred dollar PC into the wall with a $2 cheater plug in between....

If the noise Im hearing is in fact RFI noise, why do the cheater plugs eliminate it while the Ground Zero does not? Are there any additional shielding jackets I can buy to further shield my ICs (the AZ are relatively expensive and I really like how they sound so I dont want to get rid of them).

Thanks     

[ooheadsoo]

Find a diy'er to build you a $500 cheater plug 
Sorry, couldn't resist...I'll delete this post at your request.

[satfrat]

Being a rented apartment, I'm wondering how grounded your 3 prong outlets really are? Sounds simple, you take the ground out and the noise goes away. Being a rented apartment, there's probably very little you're going to do about bad wiring. If you can't live with a cheater plug, maybe a custom power cord w/o a connected ground?

Simply an uneducated opinion here, hopefully someone can present a solution to address  a specific unknown noise source but w/o a solid ground connection, I'm not sure what it could be. In my situation, I ran a gound to a foundation water pipe when i installed a 3 prong outlet just so I could properly setup my BPT power conditioner.

Hopefully, you'll follow thru with an undate if indeed you are able to fix this,,,, just so it may help someone else down the road.  

Cheers,
Robin

[BossaNova31]

Yes, well PS Audio power cords do have a removable ground pin, but I had my heart set on some Black Sand PCs for my monoblocks 

In any case, you are still effectively lifting the ground.

Still, with the preamp and the CDP grounded, are the monoblocks also effectively grounded to those components via the interconnects?

Still havent ruled out some kind of RFI issue with the interconnects. Are there any additional shielding options (Im hoping like an additional shielding sleeve I can slip over my ICs)?

[S Clark]

So if I put cheater plugs on both monoblock plugs the system becomes dead quiet. Perfect.

Am I missing something?

[BossaNova31]

Yes I know the cheater plugs work but its not the proper way to fix the problem. 

[*Scotty*]

It's kind of hard to have an RFI problem that disappears when your grounds are lifted. If your problem disappeared when an inexpensive set of fully shielded ICs were put in between the pre and the power amp I would say RFI might be the culprit. The high frequency sound you are hearing from the system sounds like a ground problem in the power amp that is causing it to oscillate. If you put a set of shorting plugs in the inputs of your amps and still have the high frequency ringing and can make it disappear by using cheater plugs I would contact the amp manufacturer about your problem. This would indicate a potential design problem affecting the stability of the amp.
Scotty

[NewBuyer]

You might consider trying the EBTech Hum X in this situation, instead of using cheater plugs...

[DaveC113]

Try plugging the amps into a different circuit...

[dhrab]

Components designed with 3 prong power cords need to be mated with modern duplexes that use a 3 wire set up ... the 3rd wire is the safety ... we all know this

Components designed with 2 prong power cords are designed with double insulated power supplies that are designed to contain any short within the power supply, and do not allow the (possible lethal) current to be passed to the chassis where you may come into contact with it ... Do we all know this ??

I'm with you in not using a cheater plug ... lets fix the problem not just put a bandaid on it ... and I think I have a idea where your ground loop is emanating from.

When a house/apartment/condo main panel is wired ... the electrician is concerned with balancing out both phases equally ... this is important and we would need an electrician or an EE to explain why ... but lets accept it as fact for now.

In an effort to keep the main panel balanced ... it's not uncommon to see half the room's duplexes on one phase, and the other half of the room's duplexes on the other phase ... so if you were unfortunate enough to plug your equipment into 2 separate duplexes, in the same room on different phases of the main panel ... you have instant ground loop. "HAPPY BIRTHDAY"

Clear as Vodka ... I hope

This is easy enough to test ... just get a extension strip box and plug all you equipment into the extension box ( basically they are all on the same phase  now) ... then plug the extension box into any duplex .... now all your components are on the same phase and the ground loop should go away.

When you have equipment plugged into both phases (OPPOSITE SIDES) of the main panel box, a slight difference in ground potential causes oscillation between the two different ground potential which we perceive as a hum or ground loop.

Put everything on the same phase and there is no ground potential difference ... no ground loop and no hum.

This has happened to me  in 2 different rooms in my house and it wasn't until I really dug into the problem in the second room that I realized what the fix was.

If the extension box eliminates the hum ... it may be just a matter of locating 2 duplexes in that room that are on the same phase on the main panel box ...

If my guess is correct, divide the room in half down the middle along the long dimension and I'll bet the outlets on the left side of the room are on one phase and the  outlets on the right side of the room are on the other phase  (electrician balancing act) ... so if your plugged into the outlets behind your speakers ...  your probably plugged into duplexes on the back wall and I don't think the left and right duplexes are on the same phase

Try the extension box trick and let us know how you make out

ATB, Dave

[Thebiker]

The high pitched ringing is something I have run into before.....and in my case it was a microphonic
tube(s). 

Before you make yourself crazy (in my case it would be crazier), give Paul at Manley tech support a call:
909-627-4256 xt 325.  Paul is a great guy, extremely knowledgeable and has solved a the couple of issues I had with a phone call, which beat the hell out of shipping my tube gear across the country.

Good Luck!

Walt

[BossaNova31]

Thanks for the ideas everyone. In reponse to the last few suggestions, I think I might try a power strip test just to check the phasing as Dave suggested. Plugging all of the components into one outlet could be the fix. I dont think the issue is a microphonic tube as the same high pitched frequency is coming out of both speakers.