[phusis]

Hi

Yesterday I finally decided to have my newly acquired NuForce Stereo 8.5 V3 grounded(via the ground screw on the back), and was thrilled to hear the upgrade this made in sound quality; deeper and tighter bass, (much) more stable sound stage, a better sense of dynamics(contrasts), a more quiet background(lower noise floor), a hightened sense of warmth and clarity in voices, etc.

Sadly I later discovered a little "aber dabei" in the wake of grounding the NuForce: a particular harsh hissing sound(high frequency noise) is now audible when being in close proximity to the tweeters of my Raidho Ayra C-1's. The phenomenon is not completely "static," in that sometimes the hissing sound is higher in volume than other times. When listening closely earlier today, with no music playing, at could hear the hissing from the listening seat - not loudly, but subtly audible. Right now for example, nearing midnight here in Denmark, there's suddenly almost no sound at all when putting my ears right next to the ribbon/planar tweeters of the C-1's(??). And yes, the stereo is on, up and running, the music paused

How can that be - what's provoked the hissing noise, and how come it's sometimes audible while right now there's almost total silence?? Before grounding the NuForce the noise level in the speakers was about equal to what it is right this very moment(that is: almost soundless).

I must add that I use no pre-amp in the usual sense, but outputs from the analogue out of an RME HDSP 9632 soundcard in my mediaserver directly into the 8.5 V3, with great results. The "pre-amp" is instead software-based via a J River 15 playback application, using the internal (24-bit) digital volume control. Maybe I need to ground my mediaserver(PC) as well?

I must reiterate though, that the benefits in sound quality of grounding the NuForce amp has really surprised me. It's a substantial upgrade!!

I'm hoping for some advice or insights in above matter...

Best,
M

[worldcat]

How do you ground your amp?

[phusis]

How do you ground your amp?

Thanks for the quick reply

With a wire from the ground-terminal(socket) in the kitchen - and yes, the ground terminal is indeed grounded. The groundwire(1.5mm2) runs some 30ft.

Edit: perhaps it is better if the amp is grounded via the main socket instead of the ground screw? 

[worldcat]

So you ground it to a wall socket?  To the screw on the back?

[phusis]

So you ground it to a wall socket?  To the screw on the back?

Exactly.

[nuforce-casey]

Since you're getting the source from the RME in a PC, and the ground goes to the kitchen, there may be a ground loop relative to the PC and the REF 8.5.

While there may be no ground plug on Denmark's AC, the Neutral act as a 'virtual ground', so in your house, the connecting point of the neutral may have a substantial impedance difference compare to your water pipe.  IN this case, the PC (grounded via Neutral) and the Ref 8.5 grounded via water pipe has a ground loop.

The best way to solve this problem is to use isolation between the PC and the Audio system.   Nuforce's AID-9 is designed for such needs.   It will improve the sound of your system with the addition of an extra stage due to the isolation it has.  Hard to believe?  I ran it with noisy source such as Squeezebox and it improved the sound.

[Aether Audio]

phusis,

Casey gave good advice.  Best results are likely with the AID-9.  Until you are able to obtain one, there are a couple of other things you can try.

First, it would *probably* be best if you can ground the amp chasis (via the screw on back) directly to the ground pin (NOT NEUTRAL!!!  ) of the same wall outlet that you are plugging the amp into.  A 30 foot run of smaller gauge wire to the kitchen oulet is prone to developing a noise voltage across it as well - not to mention that it probably isn't convenient. 

Second, try running a ground wire from te pc chassis to the ground screw on the NuForce amp as well.  This is because the ground of the sound card (which connects to the ground shield of the RCA cable coming out and going to the amp) may not be very good (higher impedance at RF frequencies than you would tend to think).  The BEST ground you can get on the pc at RF frequencies is the chassis/outer box cover.

The "hiss" you hear may actually be modulated RF coming from inside the computer.  "Draining" it away to earth ground may do wonders. Adding the AID-9 afterwards will most likely give the very best results.

Good luck, 
-Bob

PS.  HF noise/RF can be a real pain to deal with. 

[phusis]

Hi Casey and Bob

Thanks very much for your replies - I appreciate them And sorry for my late respons, but I've only just gotten around to follow up on this thread, and finally try out finding a possible solution to the problem with the hissing sound, based on your recommendations.

The thing is, there's no groundwire in the wall outlets in my apartment, apart from the kitchen - which is then the only option of mine. But before going the possible AID-9 route I wanted to try out what was at hand, so to speak, so I followed your advice, Bob, cutting out a piece of solid core wire(the same wire used from the kitchen), tightened it to a screw on the PC chassis and the back screw on the NuForce amp, and... IT WORKED!! 

There's now practically dead silence in the tweeters when pausing the music, and no humming in the woofers as well(not a problem before either), so that's just wonderful Prior to the initiative(connecting the the PC and amp with a groundwire) I'd noticed the hissing sound to be pronounced from morning till early in the evening. Later in the evening the hissing almost all but vanished, though not going as silent as it is now. Anyway, when I connected the PC and amp with the groundwire today around noon(when the hissing sound seems to peak), it was certainly a relief hearing the problem disappear for good.

Thanks again for your replies and the advice that helped my problem! I'll think about the AID-9, and see what comes of it

Best,
M

[phusis]

phusis,

Casey gave good advice.  Best results are likely with the AID-9.  Until you are able to obtain one, there are a couple of other things you can try.

First, it would *probably* be best if you can ground the amp chasis (via the screw on back) directly to the ground pin (NOT NEUTRAL!!!  ) of the same wall outlet that you are plugging the amp into.  A 30 foot run of smaller gauge wire to the kitchen oulet is prone to developing a noise voltage across it as well - not to mention that it probably isn't convenient. 

Second, try running a ground wire from te pc chassis to the ground screw on the NuForce amp as well.  This is because the ground of the sound card (which connects to the ground shield of the RCA cable coming out and going to the amp) may not be very good (higher impedance at RF frequencies than you would tend to think).  The BEST ground you can get on the pc at RF frequencies is the chassis/outer box cover.

The "hiss" you hear may actually be modulated RF coming from inside the computer.  "Draining" it away to earth ground may do wonders. Adding the AID-9 afterwards will most likely give the very best results.

Good luck, 
-Bob

PS.  HF noise/RF can be a real pain to deal with. 

Bob - 

Maybe I should add, that in my setup the groundwire from the kitchen runs to the amp first, and then with the additional groundwire connected from the back screw(on the amp) to the PC chassis. Does it make any difference if the groundwire from the kitchen runs to the amp's back screw or the PC chassis screw first(and then, respectively, being connected to the other component)?

As of now(with groundwire from kitchen to amp, and then to PC chassis), I've got no problems with hissing sound or hum at all, but is that necessarily any indication of whether it's the best way to ground my setup?

Best,
M

[Aether Audio]

phusis,

But before going the possible AID-9 route I wanted to try out what was at hand, so to speak, so I followed your advice, Bob, cutting out a piece of solid core wire(the same wire used from the kitchen), tightened it to a screw on the PC chassis and the back screw on the NuForce amp, and... IT WORKED!! 

Cool!!!    I had a feeling that might do the trick.  Signal grounds are *supposed* to be tied to chassis ground and in most standard analog equipment they are.  What some "bit queen" computer design geek thinks is ground can be another story though.  "If it works... it's good enough" is their typical motto.

As of now(with groundwire from kitchen to amp, and then to PC chassis), I've got no problems with hissing sound or hum at all, but is that necessarily any indication of whether it's the best way to ground my setup?

Well, if you wanna get "picky," from a technical standpooint true "STAR" grounding is the best.  That would require you to take two equal lengths of wire and connect one end of each to the amp and pc.  Then connect the loose ends together and from that point connect a third wire that goes to your kitchen ground point.  But hey... if it ain't broke - don't fix it

I'm glad things worked out for ya!

Have fun 
-Bob

[Speedskater]

When grounding audio (or A/V, PC) equipment. The Hot, Neutral & Safety Ground wires should have one to one to one relationship, all in close proximity to each other all the way from the circuit breaker box to the outlet.  Sharing only 1 or 2 of the wires with an other circuits or separating the Safety Ground wire from the others will increase noise pick-up.