Some noise does pass between the primary/secondary of a balaced isolation transformer, especially toroid, which just about all the popular units employ. IMO, its more effective to place the other device before the balanced power unit, to act as a pre-filter.
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I have two Furman balanced power conditioner-15 amp and 20 amp.
I have had no problems running Shunyata Hydra 2 and Hydra 8 after the Furman.
I had inquired of Shunyata about any harm that would happen if I ran two Hydras together -daisey chained-as Blue Circle used to do.
They said not to do it.
A year later they come out with a daisey chained power conditioner.
I was never curious enough to try the Hydra before the Furman.
Somehow it just didn't seem right.
The Furmans have a large transormer and to rob it of any juice, filtered or not, it just seemed wrong to power it thru a Hydra 2.
In my mind I felt delivering 20 amp dedicated line to the Furman was a good thing to do.Then when the power is balanced, filter the balanced power.
It would be informational to know if anyone has done as Elizabeth has suggested and what the outcome was.
All I can say is that no harm was done to any components doing it my way.
I used to run a Burmester 948 conditioner. Then moved to a 4kVA balanced transformer, improvements across the board. But on putting the Burmester back in the chain after the transformer was an unmitigated disaster.
So, if choose to go down the balanced route, pass on the conditioner. I've now installed an Entreq Silver Tellus passive grounding device which has enhanced the quietness of my balanced powered system.
Ptss, you have it right. In my DIY balanced power supply, I put a big EMI/RFI block filter with good differential noise reduction figure ahead of the transformers.
Plitron has a balanced isolation transformer, Part #8575-X0-02, that is available for sale to DIYers. Equi=Tech has factory B stock and "blems" available for sale direct from the factory from time to time. Toroid Corporation of Maryland also sells balanced isolation transformers. Factory quoted lead time is 2 weeks, but in my experience was more like 3 business days. The transformers in my unit pictured are from Toroid Corp. Schurter, Corcom and Qualtek make EMI/RFI filters that are suitable as pre-filters ahead of an isolation transformer. PM me at firstname.lastname@example.org if you need more specific details.
You're welcome. I have used a daisy-chained front end for years -- iso transformer > power conditioner > power regenerator. I have tried all configurations and this is the optimum configuration in my system. I read a thread on another forum years ago -- I lost it, unfortunately -- where 2 other fellows discovered the exact same configuration for daisy-chaining their front end.
I have no idea how my medical grade iso transformer would compare with Equitech. All I know is that mine is from Block in Germany and is a very high quality unit -- rated at 1380VA which gives me plenty of overhead -- about 50%. It cost me only $300 and it does a wonderful job on SQ. It is an enclosed unit, by the way. I could not find it on the Block site or anywhere else.
Hello Sabai. "Block" is an interesting company. I think of quality when I think German made and they reinforce quality in their literature. Just reviewed one of your posts and agree with you entirely "not everything that can be measured matters and not everything that matters can be measured" but I also think science is moving fast in learning to measure more and more phenomena.
I agree, but I might suggest add "knows now". Although not at all scientifically inclined I believe eventually there is a "scientific" answer; even if it's not known for a few centuries. The explosion of knowledge in the past 25 years seems to lead to an increasing learning curve that I don't see abating. Hopefully giving us enhanced listening at home :-).
The learning curve does not affect what my ears hear. For me, important as science is in high end audio, this is just an intellectual thing. If one day a testing machine can tell the difference between Roberta Flack's voice and Dionne Warwick's voice that will not affect my appreciation of their music. If testing helps indicate certain things about equipment, that may or may not help in decision making. IMO, the ultimate arbiters are the ears. I hope there will never be a scientific answer for everything in audio -- or in life. That would turn everything over to the left-brain, reducing the spiritual plane to the physical plane.
I've always been curious about the idea of balanced power. Funny thing is though, the balanced transformer systems I have seen use a center tap which goes to ground.
Its very well known that this will degrade its noise performance. If there is noise common to either side of the AC line it will get though easier if there is a grounded center tap.
This is because no center tap is truly a center tap- they are always off by just a tiny amount. This is why in most balanced systems no center tap is used.
I have read the PDF from the Furman site; it appears that there is likely a better way to do this than use a center tap. It could yield another 20 db lower noise...
Grounding of the center tap in balanced power systems is to keep voltage stable, and for quick clearing of ground faults in equipment operated on such systems. It is an NEC requirement. The same applies to a household supply. The incoming neutral (power company transformer center tap) is grounded at the service panel for the same purpose, to keep line voltage stable, and for fast clearing of ground faults in branch circuits. Any equipment being operated on balanced power needs to have the same quick clearing of ground fault current. I have used balanced power for more than 10 years, and find the benefits to be significant.
Here are the NEC requirements. You're not running balanced power everywhere, just the audio system, right? At any rate you might want to read all the way through:
NEC 647, which defines the requirements for balanced power systems, places some important restrictions on both their installation and use.
1. Conductors must be sized so that the IR drop does not exceed 1% of the line voltage under a load equal to 50% of the branch circuit current rating, and so that the
combined IR drop of the feeders and the branch circuit wiring does not exceed 2%.
2. A dedicated Equipment Ground conductor must be run to all equipment and each receptacle.
3. All receptacles must be protected by a GFCI.
4. The neutral must be bonded per NEC 250, and must also be connected to the grounded conductor of the circuit that feeds the system.
5. Balanced power systems are restricted to industrial and commercial occupancies.
6. All outlets shall have a unique configuration and must be identified using specific language called out in NEC 647.7.
7. There must be a receptacle having a grounded circuit conductor (i.e., conventional unbalanced power) within 6 ft of each receptacle for the balanced power system.
8. All lighting fixtures connected to balanced power must be specifically rated for 60/120 VAC balanced power, must have a disconnecting means that interrupts all
ungrounded conductors, and must be permanently installed.
9. Isolated ground receptacles are permitted. Balanced power systems are expensive, and their noise reduction capability is limited to about 10 dB. Isolated ground systems are generally a far more effective and less costly solution.
This might be old hat for you, but that final point is where I was going...
The final point is interesting.. but misleading -if I understand it to mean the maximum noise attenuation that can be provided by a balanced power system 10db. Can we agree that due to the physics of balanced power there is the potential for a range of "quality" for noise reduction achievable by balanced transformers? I'm surprised the NEC would make a 'blanket' assessment that "noise reduction capability is limited to about 10db". They're not identifying if they're talking about differential or common mode noise; nor specifying any frequency range(s)--both of which are necessary to make a meaningful statement. Don't you agree?
No, although more detail would be helpful.
The comments do support my view that individual grounding is cheaper and more effective. It would be nice to see exactly how though, as my opinion is based strictly on the observation I made earlier about center taps and these guidelines don't provide any supporting data.
The only reason you don't agree is your present lack of specialized knowledge about "Balanced Power". The statement that individual grounding is more effective is utterly untrue (and I wouldn't want to misinform through my thread). The EQUITECH website has technical articles that would help you understand more than you can discover by simply reading/paraphrasing parts of the NEC. I believe you would find it enlightening. It's also worth reviewing their list of clients, including NASA, CAL TECH, Gemini Observatory, Oakridge Lab, NSF, FAA and the US NAVY, UCLA, Princeton, NPR, and many more. A rather nice list of customers, wouldn't you agree?
It is a nice list of customers, but I think there is more to it than that.
I've read stuff off of their website but I see troubling comments. Here is one:
Can the problem of AC noise common in Class-A tube amps be addressed? How about noisy guitar amps?
The answer is of course 'yes' (BTW this is in the article 'lifting the ground', http://www.equitech.com/articles/enigma.html).
Fixing the problems in the quote is easy through proper grounding, and its not rocket science. I have found that a lot depends simply on whether the designer knows what he is doing or not- and has nothing to do with the AC power (and apparently, nothing to do with whether the designer is an engineer for a pro audio company or high end audio). A lot of noisy guitar amps are simply that way because they don't ground the circuit and the chassis properly. Class A amplifiers, FWIW are no more prone to noise problems than any other amplifier as the quote suggests. When I see stuff like this it makes me suspicious.
Indeed, further down we have this comment:
The power resembles a balanced audio circuit or an XLR input from an unbalanced to balanced audio transformer.
This is not true. If you want to do balanced, the thing you **don't** do is use a center tap! The reason is as I mentioned earlier- you reduce the CMRR figure significantly simply due to the fact that the center tap is not in fact at true center.
So when I see stuff like this I begin to wonder- does this guy know what he's talking about? Apparently he knows power but not balanced line operation...
What I am seeing here seems to boil down to this: If the equipment has design bugs in its grounding scheme, the balanced power will help. If the equipment has no grounding bugs, there will be no improvement.
This has everything to do with the fact that if the audio equipment is grounded correctly, there will be no current in the ground connection. IOW if there is current in the ground connection, you have a problem!
FWIW I have followed some threads on some of the grounding products like the Entreq Tellus. I did a survey of owners, who I asked to do some measurements for me. What I found was that in 100% of the cases where the owner reported an improvement through the grounding system, the audio equipment associated had a grounding problem somewhere in the system. I may be jumping to conclusions here but I am thinking the same thing is going on with balanced power. Its there to fix bugs in the grounding design of the associated audio gear.
IMO if there are such bugs in the audio gear, it should be fixed (whether the designer knows how to do that is another matter altogether). This will solve more than just AC power issues- it will also solve ground loop issues.
Atma, instead of being troubled or suspicious, neither of which sounds like fun; why not turn your 'concerns' into profit?
It sounds like you have a solution for which the need is there. People are obviously spending (wasting?) money on relatively expensive Equitech products to cure the problem-as you describe it. Why not earn good money by tutoring all the designers (you infer there are many) in what you have said is the relatively simple art of proper internal grounding? Or, offer a custom service of rectifying inadaquate/faulty grounding schemes in noisy amps? Since one can easily spend $3000+ for one of Equitech's balanced power products I'm confident many owners would prefer to pay you to fix the problem at the source.
Again, if you don't know how Equitech ( the only one I'm familiar with) balanced power solutions for AC current effect a very significant reduction in line borne power distortions-which benefits the power supplies of ALL audio gear transistor or tube- you may find reading the Equitech technical information to be enlightening. It's interesting you find the problem of AC line borne pollution/noise so simple. I quote ANGELO BAGGINI'S book-HANDBOOK OF POWER QUALITY- "power quality is apt to waiver". Seems to be a huge problem for many. Also, if MARTIN GLASBAND doesn't know about balanced power-I'd like to know who does.
Atma, as a follow up, in Baggini's book there is a section titled
MONITORING POWER QUALITY. In it Andreas Sumper & Samuel Galceran-Arellano open by stating "power quality phenomenon are physical phenomenon that, in many cases, are APPEARING AND DISAPPEARING ARBITRARILY (not based on reason or evidence)." This arbitrariness is something that definitely bothers lesser designers than yourself; so it looks like there is a profitable business opportunity; perhaps a global one. Best regards, Peter.
I have found that designers in this industry often do not like being told that they have introduced a bug in their product.
The way you ground audio equipment BTW is simple: the circuit ground in the gear is kept isolated and insulated from the chassis. This includes the input and output connections. The chassis is directly grounded to ground through the AC cord. The audio ground is then referenced to the chassis through a resistance, one that is large enough to prevent any significant ground currents. In this way the equipment will not put any current though the ground and will be immune to ground loops.
Its simple- not rocket science, but you would be amazed at how many designers have not sorted this out. As a result there is a lot of snake oil out there dealing with the aftermath of poor grounding, and its not limited to high end audio.
^^ thanks for that, I did not find that in my search. Someone asked about balanced power on the OTL Asylum over on audioasylum.com, to which I responded:
The part about there not being a second fuse is pretty important. In nearly all equipment made, there is an assumption that the 'neutral' side of the line as at ground. So if it is shorted to the chassis not much can happen- thus no fuse for that side of the line.
Balanced or more correctly, symmetrical power, is not anticipated by any equipment manufacturer or designer I know of. What this means is that if the chassis is shorted to the other side of the line from the fuse, 60 volts RMS (84 volts peak) will be exposed to the operator. If this occurs in the wrong environment and conditions, it could mean instant death.
Now you could have a fuse in the power circuit and that would be a good idea because if it is not there, the transformer supplying the balanced power will be damaged if there is such a short. But you would want to have separate fused outlets for each unit in use so that anything running on the balanced power would have protection for the user.
I've looked at several balanced power products and not been able to see any such fuses (which would have to be selected by the user) which suggests to me that they could be dangerous to use.
Jea, technical verbage discrediting medical grade transformers is trivial here. When you're in hospital next then you can worry about them. :-) . Maybe invite Bill in to discuss the topic with you as well as he too obviously knows absolutely nothing about EQUITECH'S patents and products. "Shocking! ;-) ...(all tongue in cheek :-) But, I can't imagine what got into you and Atma; hope it passes.
Actually, if a GFCI is installed, it does not need the ground circuit to operate correctly. So what is needed is exactly as the NEC requires: each outlet must be of the GFCI type.
If the installation does not have GFCI outlets for every component used, then there is a danger. But otherwise its OK as far as the user is concerned.
If there is a short in the equipment as I had proposed in my prior post, the GFCI outlet will still trip. So my safety concerns were the result of over-thinking this...