[nuforce]

I have removed any reference to manufacturer's name and also mask out the photo as we do not want to offend anyone. But we did discover that by making slight change to the preamp grounding, we noticed that THD of the preamp (alone, nothing to do with NuForce) reduced from 0.05 to 0.007% at 10 khz.  If the fact is wrong, then I will be more than happy to correct or remove it.  What else could explain the improvement in the THD as the only thing we did to the preamp is to move the ground.
All measurement were taken with the preamp alone.

Jason

[JoshK]

I think Curt fairly well explained it, and for me at least it suffices that it isn't the preamp at fault here. It is more likely the amp, particularly with a switching PSU which could be contaminating the AC ground like Curt mentioned.

[nuforce]

As I explained, the mod that we did and all the measurement shown has NOTHING to do with NuForce.

[Curt]

I think Curt fairly well explained it, and for me at least it suffices that it isn't the preamp at fault here. It is more likely the amp, particularly with a switching PSU which could be contaminating the AC ground like Curt mentioned.

For anyone interested take a look at this PCB:
http://www.audiocircle.com/index.php?action=gallery;area=browse;album=97

Interesting test result but, I see no difference in the before and after circuit... They are virtually identical. Besides that, this ground connection is really non-critical.

You can see in the upper right hand corner the small earth-ground strip. It touches nothing but the corner mounting screw. It is isolated from the Purist electronics and is used only to ground the chassis for safety and to use the chassis as an shield for the inner electronics.

Top hole in the corner is a plate through where the pcb mounting screw goes and the hole right below it is where we silver-solder the AC filter's center pin earth ground connection. The rest of the holes are not used.

The Purist has no other ground connections, the audio signal is floating and the power supply is floating. It's pretty hard to have a ground loop when you only ground one point.

I find Nuforce's test results a little confusing...

[nuforce]

I talked to Curt and he explained that the AC RFI filter is connected to the PCB ground which is also connected right next to the chasis ground screw and that particular ground trace is not connected anywhere to the PCB.

When we created this thread, our purpose is to generate discussion with preamp grounding or grounding in general and we saw a few good posting. It is not our purpose to pick on any particular manufacturer. NuForce has its fair share of problems in the past too. After checking with Curt (which I apologized to him that we should have checked with him before posting such information), I concluded that the THD measurement improvement was real but can't be explained given what Curt has told me. Further we only have a single unit to do measurement and it is no longer with us.  So we jumped on it too early on this case (previous case was an obvious one).  Shame on us  

I guess Curt is going to do more investigation and we're going to remove our posting on this example.

Jason

[guest1632]

I talked to Curt and he explained that the AC RFI filter is connected to the PCB ground which is also connected right next to the chasis ground screw and that particular ground trace is not connected anywhere to the PCB.

When we created this thread, our purpose is to generate discussion with preamp grounding or grounding in general and we saw a few good posting. It is not our purpose to pick on any particular manufacturer. NuForce has its fair share of problems in the past too. After checking with Curt ( ...

Hi Jason, I don't know the cost to send it to you, but if Nuforce is willing to pay cost both ways, I would be happy to send you my Purist. No mods have been done at all. Now if you find the same problem identically, then there is a problem somewhere, and Curt then has to figure out why. If that problem doesn't occur, then you stumbled on one isolated incident. I suspect that whatever the issue is, that Nuforce take a look at the amp side, and figure out how they can isolate the problem so you guys won't have to be fixing everybody's preamp. I suspect that once again, the problem is small enough that Nuforce can tackle the problem head on. What do you think? Maybe, you and Curt could work on this problem together to fix the amp. Maybe, FedX a copy of the schematic or even an amp to play with. That's between the two of you. I've seen a lot of crap through the years, and looking at Curt's stuff,  he definitely knows his stuff. I don't think Curt took it the wrong way, like you were picking on his equipment, or at least I hope not. So I'll leave it up to you two.   He like me is just puzzled, how moving one wire will solve a noise problem.

Ray

[nuforce]

Ray, we don't have to go around fixing preamp anymore as we have been able to elimiate the noise on NuForce amp in addition to attenuating it. So far, all the pending issues ("Mr. High Fy" in Denmark, 2 in US, 1 in Italy) have been resolved.
The THD improvement on the preamp remains a mystery.

I have no doubt about IRD Audio and Curt's knowledge on grounding. Casey is out of town but when he gets back we'll review his test and decide if we should pursue it.  We learn our lesson and will do it privately. If (a big if) we find out about something, we'll contact Curt and let him decide what to do with the information.  I am glad we clear it up with Curt and he is very gracious and professional in disputing our unsubstantiated claim ( ).

[guest1632]

Ray, we don't have to go around fixing preamp anymore as we have been able to elimiate the noise on NuForce amp in addition to attenuating it. So far, all the pending issues ("Mr. High Fy" in Denmark, 2 in US, 1 in Italy) have been resolved.
The THD improvement on the preamp remains a mystery.

I have no doubt about IRD Audio and Curt's knowledge on grounding. Casey is out of town but when he gets back we'll review his test and decide if we should pursue it.  We learn our lesson and will do it privately. ...

Hi Jason, Well, my offer still stands. By the way, did moving that wire when hooking up the Nuforce amp, also resolve the noise problem? Well, let me know what you guys decide. this can be done privately. Thanks.

Ray

[nuforce]

I will work it out with Ray privately. But in response to what happen to the noise problem, the customer reported that it went away. We can't confirm whether it is the moving of the ground wire on the preamp (that should not have any effect) or the upgrade we did on Ref 8.  As I have mentioned earlier, based on similar successes from several outstanding cases (4) with noise issue, all customers have reported that the problem went away after the upgrade.

Jason

[igroucho]

The Q remains: what has Curt to add more to his comment to one user, that they had had noise problems w the combo Purist/NuForce?

[guest1632]

The Q remains: what has Curt to add more to his comment to one user, that they had had noise problems w the combo Purist/NuForce?

There wasn't much that Curt could say, moving a ground waire that is attached to a trace on a circuit board which went to a screw, part of a standoff attaching ithat standoff to the same board the trace was on. Taking that wire and just hooking it directly up to the screw, about a quarter of an inch away. No difference in the ground. Curt was not able to reproduce the situation. Nuforce was however able to fix the noise issue on the amp's end, and that is what counts.

The Purist is  by design a very quiet preamp.

Ray

[igroucho]

I think anyone who reads these posts, esp the ones concerning the Purist vs NuForce gotta come to either conclusion:
1) Curt is just one of those in the biz who when confronted w problems w his own product always blame either a third party OR the user/customer. Never it could be something wrong on his own side. It's not only sad but it's counterproductive & self-conceited. And w size ego grows too. He's clearly stated that NuForce pollutes the signal and there's been problems w this combo (which in itself contradicts the following possibility)
2) something's wrong w this specific sample
 which in turn could indicate
3) poor Q-control on the Purist side which gotta be unthinkable w an expensive self-appointed hi-end product.

Jason in a very polite manner laid down on his back, more than I think he should have, but it's nevertheless to his/NuForce credit!

[Curt]

There wasn't much that Curt could say, moving a ground waire that is attached to a trace on a circuit board which went to a screw, part of a standoff attaching ithat standoff to the same board the trace was on. Taking that wire and just hooking it directly up to the screw, about a quarter of an inch away. No difference in the ground. Curt was not able to reproduce the situation. Nuforce was however able to fix the noise issue on the amp's end, and that is what counts.

The Purist is  by design a very quiet preamp.

Ray

Ray,

"igroucho" is a troll, don't let him bait you. He signed up at AC yesterday to make these posts.

Look at the name... igroucho... obvious or what?

This is a pretty clear attack, troll style, you should ignore his posts.

Anyone that knows me or has done business with IRD knows his statments are way off. Enough said.

[DVV]

Anyone who has ever designed and personally made any electronics at all will know that grounding is THE problem to solve. You don't need to have a hum loop or anything as obvious as that, you can have a different grounding scheme and watch your distortion figures slide off the screen.

In theory, ground is ground is ground, but in real life, it's anything but that. The problem, in very simplified terms, is ground potential; not all grounds have the same potential.

I've never even seen Kurt's products, so please understand this post is not in defence of Kurt or anyone else, it's a reflection of my own experience. Getting the grounding right is easily the worst problem one ever has in designing anything, followed by component placement and orientation. Ghosts, both of them, you could spend months trying and not get it just right.

From a manufacturer's point of view, the number of variables he has to deal with is extremely large. Should he rely on socket grounding or not? What will the input signal be like? What will the workload be like? I could go on and on, it's quite a list.

And the worst of it that grounding influences the sound we hear, and then some. So, go easy on all designers and/or manufacturers, believe me, they have their work cut out for them.

Cheers,
DVV

P.S. Just ask Dan Banquer what he had to deal with, and what he achieved by reworking the legendary Yamaha tuner he has. And I fared just as well by completely redoing Harman/Kardon's grounding in their 680 integrated amp (1999).

[igroucho]

Ray,

"igroucho" is a troll, don't let him bait you. He signed up at AC yesterday to make these posts.

Look at the name... igroucho... obvious or what?

This is a pretty clear attack, troll style, you should ignore his posts.

Anyone that knows me or has done business with IRD knows his statments are way off. Enough said.

It's YOU, Curt, who is the producer, ME I'm only the common user/customer. The burden of evidence is on YOU! If you think for one minute that your reputation and credibility is going to last among the readers of these posts by disposing of my questions calling me a troll, THEN you're dead wrong. Sometime is going to be the first in a forum, and furthermore, to your satisfaction I might speculate, I keep my mouth shut and my keyboard at rest, til enough is enough!!! In my line of work I'm also acustomed to keep a low profile in matters I don't know, electronics is NOT one of them.
You could lay this discussion to rest by SIMPLY answering my Q or contradict my opinions, but NO, YOU are the BIG producer which can do or say nothing wrong. Is that pompeous??
Ray seems to be a modest and fine person and I have no grudges to him.
And may I finish by saying that it may well be so that your track record in quality and customer care is impeccable, I just don't know, I once heard a restaurant owner say that you can work hard for 10 years to make your restaurant a fine and upheld institution and just one sloppy night to ruin everything!

[JoshK]

The Q remains: what has Curt to add more to his comment to one user, that they had had noise problems w the combo Purist/NuForce?

You, who by your own admission know nothing about electronics, are assuming the problem is with the Purist.  There are many Purist owners (including once myself but no longer) that have used the Purist with numerous amps with no such noise problems.  Then along comes Nuforce, a noise problems occurs and you assume its the Purist at fault.  

Nuforce originally implied blaim on the IRD implementation of ground. They however proved that they either didn't understand its scheme or they just threw shit against the wall to see what would stick.  They also did something to their own amp (changed the grounding scheme?) and viola the noise was gone.  Now when we examined what was done there was no explanation for why the Nuforce change could have fixed the problem offered by Nuforce, in fact they retracted their implication.  Curt went a step further to explain what was going on and how it wasn't possible that anything was being done in the change.

The jury is still out, but the burden of proof still quite logically falls on Nuforce.  What DVV said is right that grounding schemes are the thorn of audio designs, and one cannot account for every potential implementation out there.  Clearly though with the Purist's scheme working well for years now with numerous amps its scheme has shown evidence to play nicely with the vast majority of amps out there and that is what the goal of any designer can be.  Along comes something different, a problem arises and it is now Curt's fault?  

Do a little reading on this forum and you will quite easily find Nuforce's grounding schemes being called into question for both safety and practicality by knowledgeable people aside from any IRD vs. Nuforce incident.  The guys at Nuforce may very well be nice guys who offer a great product, but the overwhelming evidence is against Nuforce in this case and I see no other logical explanation.  

Curt is not stressed about what people will read in this thread as you threaten because the truth is quite plain even if you fail to see it.  I don't know what issues you have with him but your mud slinging without evidence or by your own admission any technical understanding of the problem suggests that you are indeed a troll.  

Note:
I write this not because I am a schleper of IRD products.  I currently don't own any IRD products, however I have owned the Purist in the past.  It is a wonderful product at a very competitive price. Curt through the years on this forum and in customer service has proven that he is a wonderful guy, very knowledgeable and courteous.  Someone with less understanding of the events here or less technical understanding my fall victim to igroucho's trolling.  I hope to shed more light with my post.

[DVV]

Josh makes some good points there. Let me try to clarify the matter for most intersetd readers.

As most (should) know, I make and sell power line filters named DeZorel. At one point, we made what we felt was aground breaking product, a power line filter which actually filtered the ground. We assumed (my associates and I) that this would really do wonderful things to gear capable of wonders once freed from many uncertainties.

We were dead right - about 50% of the time. Product using star grounding, as Dan banquer and I, to name but two, propose as the best overall solution, improved anything from good to very, very good. That's the good 50%, and fortunately, the vast majority of tube gear tended to come on song.

But there was also the other 50%, which was anything from very little improvement to outright deterioration of the sound. Nightmare stuff, not only zero improvement, but it got worse - and that was no Joe's Garage slap together stuff, that was Jadis.

We started investigating and soon enough found things from floating grounds to incredible schemes which I have no idea to this day how they work at all. With folating ground, the case is clear enough, there can be no improvement, so we added that comment in our advertyising literature, warning people to read their manuals first. As for Jadis, well, they pulled a dirty trick and let's leave it at that, but from then onwards, we warned people who own Jadis equipment NOT to buy our filters.

So, if we got anything from zero to hero all related with the grounding, it stands to reason that each and every other audio gear manufacturer will face exactly the same problems. Hence, Kurt here is not, and cannot be, any exception, so it's just a matter of time before his products, like everybody else's, run into a mismatch problem with potentially disasterous results for the sound.

If everything was level, we wouldn't have half the problems we have in mixing and matching, would we?

Cheers,
DVV

[Dan Banquer]

"If everything was level, we wouldn't have half the problems we have in mixing and matching, would we? "
I estimate that at least 50% of the problems that audiophiles have that they claim is synergy are really grounding issues. You can bring that to 70% if you are dealing with solid state only. As I have said in the past and I'll say it again: When there are no standards there is chaos.
                 d.b.

[TheChairGuy]

ahhh, igroucho, you have made quite an inauspicious start for your first three posts here at AudioCircle. All three are quite strong attacks on Curt and IRD.

I think anyone who has dealt with Curt has found him to be quite a gentlemen and rather open to talk about anything, civilly.  We really don't condone your kind of behavior at Audio Circle and certainly don't want to encourage it. So, this topic is locked pending further review of things.

If you can't play nice-nice in the sandbox, little 'igroucho' must leave

TheChairGuy
Moderator - Audio Central.