Shielding NuForce amps?

brj · « **on:** 8 Dec 2005, 02:59 am »

Jason, Casey, et. al.,

When do you plan to offer shielded versions of your amps to address the EMI issues?

I know that this has come up before, but I've never seen a definitive answer.

Thanks!

brj · « **Reply #1 on:** 14 Dec 2005, 07:11 am »

*cough* *cough*

Jason and/or Casey, any chance of an answer? Thanks!

rustydoglim · « **Reply #2 on:** 15 Dec 2005, 07:55 am »

Talk to your dealer about 9.02 and the grounding fix, which addressed a lot of equipment compatibility issues and also reduced RFI.

brj · « **Reply #3 on:** 15 Dec 2005, 12:58 pm »

How can a grounding change alter the EM radiation pattern of switching power supply?

mdconnelly · « **Reply #4 on:** 20 Dec 2005, 02:31 pm »

I'm "borrowing" a pair of Nuforce 9s that the dealer tells me are the latest version. They certainly live up to all the audiophile praise! But... they also seem to render by tuner fairly useless. The tuner is approximately 4 feet above the Nuforce with a simple "T" antenna above that. Since placing the Nuforce in my system, FM reception is now full of static on many channels. Switching back to my regular amp (Levinson 331), restores FM reception to where it should be.

I've seen this problem with the Nuforce posted on the boards before. Has anyone discovered a way to resolve this problem? As much as I like the Nuforce, I'd really rather not run an external antenna to resolve it.

Any help is greatly appreciated...
Mike

brj · « **Reply #5 on:** 20 Dec 2005, 04:22 pm »

To the best of my knowledge, NuForce has only suggested moving gear around to try and put more space between the amps and the other components being interferred with. Personally, I find this to be a completely unacceptable solution. Many people simply don't have the room, and there is also the chance that you would need longer cables, resulting in additional expense.

The complete solution would be to simply shield the amps, but I haven't yet seen a response that indicates that NuForce is implementing such a solution - or even considering it, for that matter. I confess that I find this surprising, as their responsiveness to all other matters and suggested improvements has been nothing short of stunning.

Nick V · « **Reply #6 on:** 20 Dec 2005, 10:57 pm »

Just a thought but has anyone with these issues tried to treat the amps with some ERS Paper?

I'd be curious to see how well the ERS paper would work in an application where the removal of EMI is actually needed rather than being used for a small tweak.

EDIT: Here's a link: ERS Paper

KJ · « **Reply #7 on:** 21 Dec 2005, 06:52 am »

I have a piece of ERS lying around, but I believe the interference bleeds from the binding post connectivity itself. I put in highly shielded speaker cables and tightened my terminal connections with some significant improvement. However, the issue still remains to a degree. Hopefully Jason and Casey will chime in on their plans to resolve these issues.

-KJ

rustydoglim · « **Reply #8 on:** 24 Dec 2005, 07:38 am »

As we have said before, the only solution for now is
1) to use a long shielded antenna cable and place the antenna far away from the amp.
2) check that the latest Ref 9 has extra grounding fix (an extra wire connecting RCA ground to chassis ground through XLR shield pin)
With the above and placement of antenna, you can get most of your channels back (except the very weak one that are below the noise floor).

brj · « **Reply #9 on:** 27 Dec 2005, 04:29 am »

Quote from: nuforce-jason

As we have said before, the only solution for now

So, to be perfectly clear, you have no plans to address EMI output from your amps at the current time? That's fine - I just wanted a clear answer.

Quote from: nuforce-jason

1) to use a long shielded antenna cable and place the antenna far away from the amp.

I'm not worried about FM reception in particular, but RFI and EMI effects on other components in my chain, whether a tuner, TV, pre-amp, unshielded interconnects, or otherwise. A shielded antenna cable will do absolutely nothing for this.

Quote from: nuforce-jason

2) check that the latest Ref 9 has extra grounding fix (an extra wire connecting RCA ground to chassis ground through XLR shield pin)
With the above and placement of antenna, you can get most of your channels back (except the very weak one that are below the noise floor).

And again, I ask... what does grounding have to do with switch mode power supply induced EMI?

I'm not trying to harp on the issue, but you seem to be answering questions other than the ones I'm asking. Heck, I'm listening to some Ref 9.0s right now and enjoying the system quite a bit. I think you have a great core technology and the system I'm listening to sounds fantastic, but I'm concerned about some of the implementation details that don't directly affect the sound (EMI, no-load behavior, etc.). I'm simply trying to get more info to help me evaluate those details.

timothyharnett · « **Reply #10 on:** 27 Dec 2005, 06:23 am »

Quote from: brj

And again, I ask... what does grounding have to do with switch mode power supply induced EMI?

I'm not trying to harp on the issue, but you seem to be answering questions other than the ones I'm asking. Heck, I'm listening to some Ref 9.0s right now and enjoying the system quite a bit. I think you have a great core technology and the system I'm listening to sounds fantastic, but I'm concerned about some of the implementation details that don't directly affect the sound (EMI, no-load behavior, etc.). I'm simply trying to get more info to help me evaluate those details.

I agree with BRJ. I absolutely support you in the development of your product (which I too enjoy) but The EMI/RFI issue is the most serious problem with the unit. It's quite significant. It does make you wonder what the system would sound like with the EMI/RFI factored out.

The other issue is that, although I like the amps, I would be nervous of adding any more products to the stack because I would be afraid of the cumulative affect of more pollution so that would rule out biamping and preamps for me.

Mr. High Fy · « **Reply #11 on:** 28 Dec 2005, 05:01 am »

Maybe its not possible to get rid of the noise? If it was that easy, don´t you think they had fixed it by now? I don´t have the answer

Adamay · « **Reply #12 on:** 5 Jan 2006, 08:53 pm »

Has anybody tried ERS sheets or Mu Metal around the amps? Please report your experience if you have. The RFI with my tuner is bugging me a bit, but I have absolutely no time, unfortunately, for experimentation with solutions. (The amps sound fantastic, however, so I'm putting up with the RFI for the time being.)

Russell Dawkins · « **Reply #13 on:** 6 Jan 2006, 01:38 am »

I'd be interested if RFI was still a problem with shielded power cords, shielded speaker cables and balanced inputs. Has anyone done this and still had reception problems?

Seems to me the most effective antennas for the transmission of RFI would be the various wires coming out, since the case is solid aluminum. Maybe someone can correct me; RFI is a pretty arcane subject to me.

NealH · « **Reply #14 on:** 6 Jan 2006, 02:14 am »

One of the issues with conducted RFI is that it propogates through the power cord and on into the house wiring. Shielding the power cord will help mitigate the radiation from the power cord however, there is still house wiring to be concerned with. It makes an excellent antenna too.

It's probably better to install at minimum a two stage RFI filter in the line feeding the amplifier. These are relatively inexpensive today and, are often found in typical power conditioners such as the Monster boxes. Corcom makes many models. Some are better than others but, any are better than none. There have been comments in the past that these increase system impedance which is what you don't want on the power feed to an amplifier. However, being a digital amplifier and very efficient, I have no concern at all about raising the line impedance a bit. A digital amplifier doesn't consume the large surges associated with the rectifier current in a linear amplifier.

There will likely be radiation from the enclosure if grounding is not very good and, from any seams or openings regardless of grounding. It's best to address this in the design stage with multi-layer boards (never, ever use a 2-layer) and, smart component selection and trace layout. It's mandatory to do this if the product is expected to meet the FCC class B requirements (equipment for use in residential environments).

For enclosure grounding, I would recommend a relatively heavy (6 or 8 AWG equivalent) braided shield construction (litz wire will work fine) ground wire run from the enclosure ground screw all the way to your feeder service ground. The problem with just running the litz ground wire to the local outlet is that the solid ground wire from the outlet to the service panel is probably of significant length thus producing more ground impedance in the path than desired. You want a low, low ground impedance at high frequency to help shunt off this energy.

Putting the amplifier in yet another well grounded enclosure will also mitigate some of the radiated RFI. But again, a good low Z ground connection is key.

I had these same radiation issues with the first Bel Canto amplifier (evo 200.2). The later models (evo2 and 4) were far better regarding RFI. I currently have the evo4 and it does not bother my FM reception at all. Very well behaved. But, the first one wasn't.

rustydoglim · « **Reply #15 on:** 6 Jan 2006, 10:44 am »

Hey guys, I don't need to repeat this so many times.
NuForce amps passed FCC and CE but that doen't mean it won't have RFI for FM. It depends on your tuner, location of antenna (and wiring), and the strength of your FM signal. Few customers listen to FM so it is not a high priority for us (but we intend to fix it eventually). Some customers are able to get good FM reception by using long (>5M) FM antenna wire with good antenna.

The bottom line is this, NuForce amp is one of the best sounding amp on the market regardless of price (check us out at CES 2006 and tell us if there's any other rooms that sounded better). We continue to be amazed that NuForce Ref 9 revealed problems that are in some seemingly good system. This amp is incredibly good but it is not for everyone!
If you still have concern about EMI/RFI or whatever, even if you're not a serious FM listener, then go buy some other amps. There are many other good amps out there.
May be we'll eventually come out with another series of amps that have zero RFI on FM but not sounding as good, or they may sound better. Who knows.

My point is that you should stop pestering us to fix the RFI FM problem for you now. We'll have to do it at our own pace as we have many projects with various priorities. As we have said, NuForce Ref series amps are upgradable and if you are not a serious FM listener, you can buy it now and upgrade the board later. Or go with another amp if you can't wait

rustydoglim · « **Reply #16 on:** 6 Jan 2006, 10:57 am »

By the way, we are showing a very simple system at CES:

Marantz SA-11S1 SACD
NuForce P-8
Ref 9 bi-amping with Usher Audio Dancer series CP-8571 speaker

Even on the first day of CES, our 2 channel room is full of people all day.

Oh, never connect NuForce amps or preamp P-8 inito any power conditioner that does voltage or current regulation. We recommend plugging them into simple power socket with filters such as Brick Wall.
But we do recommend that you connect the source component to a power conditioner.
We tried it at our demo room in CES and we got the best sound with the above setup. The combination of P-8 and Ref9 is just amazing.

Adamay · « **Reply #17 on:** 6 Jan 2006, 05:12 pm »

The comments above about cabling, etc., may be right on. I recently switched my speaker cables from a complex braid of tefloned copper to a very simple run of magnet wire, and the RFI interference on my tuner went up dramatically. I suspect the braid was performing a shielding function. Although the magnet wire sounds better, I may go back to the braid because I'd very much like to hear stations that I can't anymore due to the interference.

beachbum · « **Reply #18 on:** 6 Jan 2006, 10:32 pm »

jason i am using a bpt 2 with my p-8 and ref-9s with no problems at all, and with no input there is absolutely no hissing or anything comming out of my tylers, and one thing is for sure the p-8 ref-9 combo is fantastic, if you want to hear piped in music get a cable box and tune into the music channels, no commercials and good sound,

rustydoglim · « **Reply #19 on:** 7 Jan 2006, 06:53 am »

Quote

jason i am using a bpt 2 with my p-8 and ref-9s with no problems at all, and with no input there is absolutely no hissing or anything comming out of my tylers, and one thing is for sure the p-8 ref-9 combo is fantastic, if you want to hear piped in music get a cable box and tune into the music channels, no commercials and good sound

Satelite or cable music will do great

.
You're right about the P-8 and Ref-9 combo, we've been saying that we over designed P-8 and the performance is "too good" for the price. I am sure future reviews will validate that.