|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
74.47.219.118
I had an annoying hum yet not audible when music was playing from ground loops. I bi-amp so there's two different ground paths there and have an AC regenerator for a third. A PS Audio forum post said go ahead and lift it. Wow, not only did the hum go way down (still some from the amps) but it made a great improvement to the sound. Next I lifted the LF amp ground and again things really made a marked improvement. At this point I am really happily stunned at how much better things are. Image, separation, dynamics, clarity and detail have all improved. I reterminated an AC cable I had for the HF amp with a Wattgate 320i and did not connect the ground. I now am ground free and wondering if this last "lift" will make a difference. It helped the HF so much I couldn't believe it! What a huge improvement at each "lift". It sounded like a different amp!
So I am in the process of relistening to favorite recordings, all of which are putting a smile on my face. Hearing details not heard before with an improved soundstage and clarity this system has never delivered. No more than an hour or so into this new level of greatness a cap in my CJ 2500A LF amp, right channel, starts leaking! Doh! This is the third time for leaking cap noise in that channel. The first time they replaced a cap and since I upgraded it from a 2500 to a 2500A at the same time they charged no labor for the repair, just for the part-nice. The second time they kept it for two weeks saying it never made a peep of crackling in the right channel. I don't know what to think here, it was really noisy and actually blew a fuse from a loud crack! I think they did something and didn't tell me-who knows. And now less than a year later the crackle is back for a third time. Oh well...... Something had to spoil the party I guess. Woe is me! What a pain to have to disconnect it, lug it to them and be without it again and now fear the problem will only return again in the future. Does anyone think I deserve something or some consideration for this third failure? And no it's not a speaker problem, DCR is identical on both channels, no shorted speaker wire etc. I never come close to fully driving the amp and its about a 6 ohm load, no problem for this amp. It never even gets very warm to the touch much less hot. Goll dern, witch butt, schmuu ticker........... I just made up schmuu ticker.
ET
Follow Ups:
...and if one has implemented balanced AC power to provide power to their system(s), then lifting the GND can/will result in negating the benefits that balanced power provides although I have found zero drawbacks and only performance benefits from powering "insulated chassis" or 2 prong components from balanced power.
Once you go balanced AC power, all things unbalanced AC power are relegated to the "insignificant" data pool. Unbalanced AC is so fraught with noise problems in that in todays environment, there is a shitload of RF riding on the earth GND line and trying to eliminate that noise, via lifting the GND connection, is not addressing the problem. Try putting a Ferrite bead/filter on just your unbalanced AC earth GND line on the power line feeding your system and have a listen after reconnecting the earth GND connections.
Unbalanced AC is so fraught with noise problems that looking at, and understanding, balanced AC seems like the only logical solution for a noise free AC delivery system.
Cheers,
~kenster
My P-300 outputs balanced power. Lifting its ground reduced about half of the ground loop hum, the two amps the other half.
ET
This sounds like there may be something wrong with your P-300. I have a P-600 and have never experienced any hum problems with the earth GND connected so this is why I am suspecting your P-300.
Are both legs of the balanced outputs on your P-300 putting out identical voltages? If the output voltages are not the same, with one being inverted of course, this may also cause some additional noise.
Check the output voltages of the P-300 and let me know.
Cheers,
~kenster
This sounds like a neat idea. Does it improve sound quality noticeably?
If so, can you describe more closely? I wouldn't know where to get one, and I am not sure what you are telling me to connect it to.
Thanks!
Hukk
Hi Hukk,
"This sounds like a neat idea. Does it improve sound quality noticeably?"
In some cases it can. In my last residence it did make an improvement in noise reduction without hurting dynamics but in my current residence, it made it worse by slightly muting the dynamics.
"If so, can you describe more closely? I wouldn't know where to get one, and I am not sure what you are telling me to connect it to."
Your local Radio Shack carries them, Snap-together ferrite Choke Core | Catalog #: 273-105, and place on the earth GND wire either inside your power conditioner if you use one, or you may have to place it right before the line enters the outlet receptacle that feeds your system. The GND inside your PC will be a Green wire and the GND line at the receptacle with be bare copper in most cases. Be sure to remove power, and verify there is no power via a lamp or a DVM, before popping the hood on your PC or working on the receptacle.
I have also found improvements in noise reduction by placing the ferrite beads on household appliance power cords as these are a huge source of RF contamination into your homes power lines. Start with your fridge and then move to the microwave. Place the bead around the whole power cord about a foot down the power cord from where it enters the appliance.
Hope this helps,
~kenster
- http://www.radioshack.com/product/index.jsp?productId=2103222&cp=&sr=1&kw=ferrite&origkw=ferrite&parentPage=search (Open in New Window)
a
I agree in that every system/residence will present it's own unique RF infiltation into the residence power grid and methodical experimentation with the Ferrite snap-on clamps is cheap and an easily removable way to combat RF and the sonic damage it has the ability to impart in our systems.
Cheers,
~kenster
I have had many different ones and cables with different ones. I always breath a sigh of relief when they are gone from my system. I always advise people when they try any tweak to let it breakin and then remove it. In my experience, few survive this test. We all listen for different things, so I am not suggesting that all should avoid ferrite, you may like what it does.
a
The only component that I have that has a 3 prong, grounded cord is the 'table- and thats only to the power supply for the motor (the ground cable from the arm is only attached to the preamp, it doesn't connect in any way to the power supply cable)!
Everything else- amp, preamp, etc, has 2 prong (non grounded) cords.
No idea to compare, but I think my system sounds good...
The Musician has three disciplines: the disciplines of the hands, the head and the heart.
-Robert Fripp
Especially if the component happens to be DIY..... Not all audio equipment has been built to proper safety standards.
If, for example, the safety ground (third pin) is tied to the chassis of a component, its purpose is to provide a robust path to ground for any electrical potential that could hit the chassis in the event of an electrical fault. If this ground is lifted, instead of blowing the line fuse in the component or trip the house breaker, it would subject the user to a "live" chassis, which could be lethal if the user happens to provide a "least resistive" path for that charge to travel through.
?..
Just this past Saturday, someone was modifying an old Music Reference RM9 amplifier, and for a while was dumbfounded over why the unit would play fine for several hours, and then the fuse would blow suddenly. He started disconnecting various stages inside the amp to troubleshoot the cause of the fuse blowing. And in time, after having just about everything disconnected, including the power transformer secondary, it turned out that a winding in the power transformer primary, after heating up, was shorting to the case. And then the path to safety ground took out the fuse.
Now imagine what might have happened had the unit been run with that safety ground lifted.
Shorting to the case made the current flow large enough to blow the fuse. With or w/o that ground it takes a large enough flow to blow a fuse. Why would a human be a ground standing on a wood floor? When I was a kid we had an old two prong electric drill that shorted to the case. If you stood on the cement floor and used it you'd get a shock. So we stood on a 2X6 instead and used the drill fine and never got a shock.
ET
"Shorting to the case made the current flow large enough to blow the fuse."
If the safety ground (third pin) is lifted, the case would become "floating", provided no other current paths exist (not guaranteed one way or the other).
"With or w/o that ground it takes a large enough flow to blow a fuse."
If there is no path to safety ground, the potential on the chassis without a low-resistance path for current flow will not blow the fuse. Even if it's the full potential from the mains "hot" line. The safety ground provides this "low-resistance path" (virtually zero resistance) for the current to blow the fuse.
"Why would a human be a ground standing on a wood floor?"
That's not the issue. (Unless one spills a drink which also contacts a grounded item.) All the user has to do is be unfortunate to come in contact with both a live chassis and a grounded (or non-floating) item. (That item could be another audio component, vacuum cleaner, power drill, soldering iron, cable box, etc.) Or be in the path of least resistance.
"When I was a kid we had an old two prong electric drill that shorted to the case. If you stood on the cement floor and used it you'd get a shock. So we stood on a 2X6 instead and used the drill fine and never got a shock."
All I can say is it's your own risk.....
By the way, many newer homes in California and Arizona do not use wood floors, but tile or carpeting over concrete.
I only mention this because not everybody will be aware of the hazards, as a result of lifting grounds. There is a lot of naivete out there.
Good post, thanks.
ET
?
if the equipment has a metal case it is tough to double insulate per the requirements of the safety standards. If the equipment has a plastic case it can be difficult to meet EMC requirements. If metal enclosed double insulated equipment is in contact with other grounded metal then the case of the DI equipment can still be a conductor in the return path for the other equipment's fault current.
> > if the equipment has a metal case it is tough to double insulate per the requirements of the safety standards. < <
> > > > > > > > > > > > > > > > > > > > > > >
Not really..... The power transformer as well as circuit boards and any associated metal parts are insulated from the equipment case.
Good example CD and DVD players as well of a lot of the newer A/V receivers on the market today. Most if not all have metal cases to reject RFI.
Do a search in the archives under my name and posts with the word "ground". There is a very minimal safety risk involved, so be sure to read my posts completely to understand what the risk is. Then you can make up your own mind about lifting all the grounds from your system.
Me -- I will never listen to a grounded system again.
Bummer about your amp -- sounds like an under-specified part or something. Three times in a row is too much. That's not what CJ normally does. If you read the forums, there are virtually no complaints about their gear. Good luck getting a permanent fix.
?
appliances, hand power tools, etc. to use a two-prong power cord, there may well be a cost issue involved, but there may also be other considerations. From what little I know of the subject (mainly observation) these devices often use a non-metallic (nylon, plastic, etc.) case as part of the 'double insulation' process, so perhaps increased RFI would be a potential drawback for audio playback electronics. Though I suppose a work-around could be found...
Anyway, good question.
"Dammit..."
> > If you're referring to the 'double insulated' designation that allows manufacturers of small appliances, hand power tools, etc. to use a two-prong power cord, there may well be a cost issue involved, but there may also be other considerations. From what little I know of the subject (mainly observation) these devices often use a non-metallic (nylon, plastic, etc.) case as part of the 'double insulation' process, so perhaps increased RFI would be a potential drawback for audio playback electronics. Though I suppose a work-around could be found... < <
> > > > > > > > > > > > > > > > > > > > > >Actually most Cd and DVD players do not use the safety equipment ground. The AC power wiring is double insulated. The case is floating.... And the case is made of a conductive metal material to reject RFI.
A Faraday cage does not need to be grounded to reject RFI.
Also more and more manufactures of A/V equipment are going to the two wire power cord. Less ground loop hum problems and complaints.
Marantz is a good example of one.
< < The AC power wiring is double insulated. The case is floating.... > >
Actually the case is connected to the signal ground of the internal circuitry.
I think the main reason that most manufacturers use 3 wire power cords with a safety ground is ignorance. It's the easiest way to ensure safety, and it's also the method most commonly espoused in textbooks.
Kind of like FETs versus bipolar transistors. All the textbooks focus on bipolars. Not much is generally known about FETs. So designers follow the path of least resistance. It's too much work to dig up all the stuff to learn about some other technology like FETs or double insulation.
I have had a custom amp and preamp made for me in which the designer does not connect the ground to the either components IEC. Just the hot and neutral. He says it's a source of noise. In essence is this similar or the same as a "floating" ground?
< < the designer does not connect the ground to the either components IEC > >
I assume you mean he does not connect the chassis (normally tied to signal ground if the designer knows anything at all about grounding) to the ground pin of the IEC inlet, which would in turn be connected to the AC safety ground of your house.
In this case, the AC safety ground only connects to the IEC connector and not the circuitry nor the case. This achieves the same effect as "floating" the component with a "cheater" plug, but without the extra contact resistance of the "cheater" plug.
This does avoid the introduction of RFI noise that is present on the AC safety ground. But it also requires that the unit be "double insulated" to provide safety to the end user. If he doesn't use "double insulation" the risks are minimal (as long as he uses good construction techniques). But if he starts selling them this way, he should use double insulation so that he doesn't get sued on the off chance that somebody *does* get hurt.
Thanks for the response.
Your first paragraph is correct.
However, I'm a little confused about your second paragraph. If I look inside the chassis at the IEC inlet, nothing is connected to the ground pin. Does this affect your response?
Using a three-blade IEC connector and not connecting the safety-earth pin inside is the low frequency equivalent of lifting the ground at the AC plug with a cheater.
However, it does connect the safety-earth wire inside the power cord to the house AC safety-earth wiring. This allows the power cord safety-earth wire to resonate and receive noise, and convey the noise to the house AC safety-earth wiring network. It also allows this wire to convey noise already on the house AC safety-earth wiring network to the hot and neutral wires in the power cord.
This is a compromise. A better approach would be to use a two-wire power cord.
If you disconnect a guitar string at one end it will not resonate. If you strike the string vibrations will travel down it and dissipate quickly but it will not resonate.
Are there different mechanisms in play with RF and wire?
The electrical wave comprises electric and magnetic fields. An unterminated conductor supports a series of standing waves, where the boundary condition is that the current be zero at the unconnected end. The electric field components of the standing waves will be maximum at the unterminated end, and the magnetic field components will be null (because the current is zero).
The fundamental frequency is the mode where the unterminated wire is half the wavelength of the electrical wave. The harmonics are related by integer multiples of the fundamental. Thus, the first harmonic (the second mode) has the full sine wave contained on the unterminated conductor, the second harmonic (the third mode) has 3/2 of the sine wave contained on the unterminated conductor, etc.
This oversimplifies what happens in a power cord, because there are also modes to do with waves between pairs of the conductors, and the velocity of propagation may not be constant for all important modes.
I would also need to float the grounds on my power cords. If I recall correctly Charles also mentioned something about lifting the ground on the outlet the system is plugged into as well (I'm assuming this would also be true for a power strip I'm using).
Of course this is all at my discretion and risk.
Many systems are plugged into a power strip, which is plugged into an outlet. If you plug some three-wire audio components into a power strip, then float the power strip by using a cheater plug at the wall outlet, you will still have ground loops in your system. The individual power cords will have their safety-earth conductors connected together in the power strip. You may experience a reduction in noise (see my essay "Noise and distortion" in a thread above), from disconnecting the system from the house wiring AC safety-earth, but this arrangement will still pick up local noise.
To fully experiment with "floating the grounds," you need to make sure the individual component safety-earth wires are all disconnected, from each other as well as the house AC wiring. This is at your own risk.
Please explain why the signal ground is connected to the case.
With the case connected to the signal ground it puts the case at signal ground potential, correct?
Would the case otherwise act as an antenna or something?
Thanks.
The only way that the case can provide any shielding for the audio circuitry is if it is connected to the signal ground. In addition, if it is left unconnected from the signal ground, then it will create unwanted capacitive feedback loops (both positive and negative) between various parts of the circuitry. Refer to Morrison's books for additional details.
In my last house the internal house ground was not even grounded to earth thanks to the contractor. But I assume the cases were grounded to the non ground throughout my system to what effect, I know not.
Greetings from the sunny Brønshøj riveria on the banks of the lovely Utterslev Mose
> > In my last house the internal house ground was not even grounded to earth thanks to the contractor. < <
> > > > > > > > > > > > > > > > > > > > > > > > > > >In my area the power company will not do a hook-up if the main entrance neutral is not connected to earth ground properly.
But before the Power company will even come out for an inspection a release must first be given by the city inspection department.
==================> > But I assume the cases were grounded to the non ground throughout my system to what effect, I know not. < <
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >That means the equipment grounding conductor was connected to the neutral conductor at the main electrical service panel.
In the event of a leakage or short from the hot conductor to the case of a piece of equipment, with an equipment grounding conductor connected to a branch circuit with an equipment grounding conductor, then the equipment ground would have carried any ground fault current back to the source. If only a small ground fault leakage the current returning to the source would just become part of the circuit and be dissipated in the form of heat at the utility transformer.
If the ground fault from the Hot conductor to the case of the piece of equipment, resistance low, then the ground fault current will be high and cause an overload on the branch circuit breaker causing the breaker to trip open, thus doing its designed job.....
============Now back to why the main service entrance neutral is connected to earth.
The main purpose is for lightning protection. Another reason is for a common ground plane through out your home as well as the surrounding area outside your home where you might use power. There in main incoming metallic water, gas piping, or what ever else might be at earth ground potential......Though they will not admit it, connecting the entrance neutral to earth at every electrical service gives the utility company a somewhat added protection if for some reason their neutral conductor from their transformer becomes broken, for what ever reason, from the transformer to the house.
Also for lightning protection the neutral is connected to ground at every utility transformer...... Connecting to earth of the neutral up the ying yang for lightning protection.
Thanks for your post Charles. I know CJ will take care of things for me, it's just kind of drag to be w/o my system for a week or two especially now that it sounds so good! The ground lifting provided an amazing improvement, I thought it would just quiet the annoying hum audible only when the system was idle. Wrong! It's one of those "time to listen to everything again" upgrades.
ET
nt
Probably. I never tried it. However, I did have a system that was completely floating and grounded it to an incoming copper cold water pipe that was only about 2 feet away from my preamp. The system sounded *very* slightly better with that ultra-clean ground. The ground on a dedicated circuit cannot be as clean as the ground I tried, so I still would recommend floating the system for best sonics.
Do this at your own risk. The danger is miniscule but real. You are a grown up. Decide for yourself if it is worth the risk. (Every house in this country built prior to 1960 had ungrounded outlets. It was only two years ago that I moved into a house with grounded outlets. Somehow I lived through it.)
nt
a
Beats me.
I would guess that the "ground" is actually acting as a big antenna, dumping a bunch of RFI into your system. But I don't actually know that for a fact.
Based on my experiments I can say with confidence that the AC safety-earth wiring in my house does carry enough RF noise to affect my audio system. Any non-audio appliances that contain switching power supplies will have a Y-rated capacitor connecting the output of the supply to safety-earth, by law. These appliances may well be built to double-insulated standards, but still must have the safety-earth connection because of the switching power supplies.
Even though the safety-earth wiring is connected to earth at the breaker panel, the lengths of the wires from most outlets to the panel prevents them from effectively attenuating the RF noise presented to them.
The best approach is the one you champion: eliminate the AC safety-earth connection by design.
I bought the Morrison new edition.
Good luck. It's a great source of information, but also one of the most difficult reads I have ever encountered. He pares everything down to the bare minimum. In the older editions he would highlight a handful of concepts as "rules that cannot be ignored". I had to spend hours thinking about one single sentence. Dense, dense, dense writing.
If nothing else, it's great reading for those nights when you are having trouble falling asleep!
a
a
much misunderstood term.
AFAIAC, the following methodology will fulfill electrical safety in any country and doesn't give you any ground loops, hum etc. in your system:
* use 3-core in-wall wiring which is active + neutral + earth.
* by all means use multiple spurs to power your total system but make sure the in-wall wires are all the same length (or you will get different earth potential at each component ... which can lead to hum).
* wall sockets have an earth hole/slit which is connected to the central household earth. In Oz that's back at the Consumer Unit ... and an earth wire goes out to a copper bar sunk into the ground.
* use 3-core mains cable to each component.
* inside each component, the earth wire in a captive mains cable (or the earth pin of the IEC socket) is bolted to the bare metal case - "safety earth".
* all RCA sockets & speaker BPs are insulated from the component case.
* PSes in each component have a star ground - but this is not connected to the case (and, hence, mains earth).
* the "system" ground is passed from one component to the next via the IC ground wire but it "floats" relative to the chassis.
All I can say is ... this works in my system.
Regards,
Andy
< < PSes in each component have a star ground - but this is not connected to the case > >
Unless the signal ground is connected to the case, the case cannot provide any shielding. Furthermore, the case can create capacitive coupling between different parts of the circuit that can introduce unwanted feedback (both positive and negative).
Much of the rest of your post is equally misleading. Go read Ralph Morrison's "Grounding and Shielding in Instrumentation" for some real information.
you would have seen that I said the earth pin of the IEC socket should be bolted to bare metal of the case. This "grounds" the case - thus providing shielding to the internals.
IMO signal ground should not be connected to case (which in my scheme of things is mains earth) and preferably, signal ground should be lifted from PS ground (also not connected to the case) by a 10ohm res, so signal and PS grounds do not interfere with each other.
Thanks for the Ralph Morrison reference - I shall see if I can get hold of it.
Regards,
Andy
< < Thanks for the Ralph Morrison reference - I shall see if I can get hold of it. > >
It's a slim volume because it's very dense reading. I had to read it at least twice to follow what he was saying. The latest version of the book is relatively expensive:
http://www.amazon.com/Grounding-Shielding-Circuits-Interference-Techniques/dp/0470097728
But used recent editions can be had for a reasonable price. (See link.) If you read the book, you will change your views on configuring your system. Connecting the chassis cases to earth ground is not a good solution.
.
.
a
It is hard to make a great analysis here because what you describe as a crackle I may take to mean something else, but I don't associate that sound with leaking caps. That sounds more like the sound a transistor makes when breaking down. I don't think the film caps they use are likely to leak so that leaves electrolytics in the power supply and those would more likely cause a hum rather than a crackle.
In any case I agree that CJ really has nothing to gain by lying to you about a repair. I always received world class service from them. Take it in and let them look at it. I would be curious to hear what they find.
Why do you think you deserve some consideration? They already did some work for you at a discounted price. The first of these would be 10 years old so not unusual they would break.
I also don't buy into that whole "lemon" idea. Electro/mechanical devices fail everyday and some percentage of of CJ 2500's fail at some interval. That doesn't mean yours fails this time so somebody else's has to fail the next time. It could be yours that fails twice in a row. That doesn't make it a lemon. That's just bad luck.
(iTunes) or (Wilson Benesch ACT2/analog cart - M-Audio Fastrack pro 24/96) - iMac core audio 24/96 -- Toslink - Monarchy DIP - modified Behringer DCX2496 - MSB multichannel volume control - SET triamp Avantgarde Duo Omegas with DIY bass horn
I'm not saying its a lemon, I was a dealer, I know their reliability. But all three times the problem has been crackling in the right channel. The first repair was a leaking cap replaced. It was a B stock which with CJ has the same warranty as a new unit. <3 yrs.> The first failure was 8 months after the warranty ran out and it's less than 6 years old now. Even though I'm pretty broke now the money for the repair doesn't bother me, its the hassle factor - stuff happens...........
ET
Crackling doesn't always mean a leaky cap... Have you actually observed goo coming out? A failing cap may either fail to pass signal or short and cause very visible destruction inside the amplifier. Post more details...
There may be a problem with the design, or the present supply of that type of capacitor may be compromised.
Not sure Al. I think it was a polyprop on the driver board. As a dealer I never repaired any of the 2500's we sold including other B-stock units which carry CJ's same as new 3 year warranty. After the repair I will post the results.
ET
A couple of thoughts:
1) Your post is extremely hard to read, so I had difficulty understanding what you were describing. Paragraphs?
2) Conrad-Johnson has a great reputation, well deserved, I think, for reliability and excellent service. I find it hard to understand why anyone would blame them in this situation when you have been making changes that may not be in the best interests of your system. (I think that's what I understand.)
Is it possible the culprit is elsewhere, but manifests itself in amp problems?
""Is it possible the culprit is elsewhere, but manifests itself in amp problems?""No
""I find it hard to understand why anyone would blame themin this situation when you have been making changes that may not be in the best interests of your system."" First I don't blame them. I just wonder what others think about taking a unit in for the same issue three times. Lifting ground which was only done this week has nothing to do with this and was not done the first two times the problems happened. I love CJ and was a dealer.
My reference to blame wasn't so much directed at you, but at some of the comments by others, although I suppose that even C-J can occasionally produce a lemon. Sorry, even though I think I now understand the purpose of your post, I don't really have any suggestions.
Thanks-no problem, it was late and I wanted to post it quickly thus the lack of proper structure.
ET
You should have sold it after it was repaired the second time. Sorry to be so unhelpful. This is my own experience with lemons, from cars to TVs. Unless you can convince the dealer to replace the unit, the story always gotten more and more painful and expensive, round after round, in my case. I think, either dealers go to school to learn about how to deal with this, o else the mfr. puts so many lemons on the market that the dealers quickly learn what to do when the mfr will not back them up.
I would "abandon hope" and take it to an independent repair place, if you haven't already.
Greetings from the sunny Brønshøj riveria on the banks of the lovely Utterslev Mose
Actually I was a dealer when I bought it and will be taking it back to CJ, the manufacturer, myself not a dealer or repair shop. I have a sort of relationship with some of them and will plead my case. The amp itself has been around a while ands has a great rep- of course mine could be cursed.
ET
NT
Greetings from the sunny Brønshøj riveria on the banks of the lovely Utterslev Mose
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: