"Balanced Power" (Equitech) Have we discussed this

Equitech (www.equitech.com) has been around for a few years touting the benefits of balanced power. I'm curious, beyond the market-speak, what benefit there might be.

Here's a quick link to their white-paper: http://www.equitech.com/articles/widescreen.html

Is it really just as simple as 'figure 4'? Just a big custom transformer with the center tap grounded? Their boxes are pretty expensive. Thoughts?

> Is it really just as simple as 'figure 4'? Just a big custom transformer with the center tap grounded?

"...patented "bifilar" AC power transformer winding method which very cleverly balances it's two output coils like identical twins."

You can buy center-tapped transformers (though 120VAC will be a special). They will balance 60Hz, but not 6KHz... they are POWER transformers and power-tranny guys don't think about the high end. Yet rectifiers spew tons of HF crap onto the line.

Yes, a plain 120VAC CT winding will help some, but Equitech follows-through up the audio band. Whether tis worth the price or not, I don't know.

Do note that a few odd bits of gear can be very upset by balanced 120VAC.

And you may have to educate your local Electrical Inspector (I suppose some of that is included in Equitech's price).

I believe the guys who started Equitech actually were electricians, interestingly.

When there are installations with a lot of unbalanced stuff, and where the balanced equipment is not well-designed, the balanced power can help. Whitlock (who was rather critical at the outset of Equitech) was saying that Jensen is selling a lot of video isolation trafos to video duplication facilities and even home theater installers. He acknowledged that balanced power would also make some sense in these cases.

I told a war story a while back about a Harman product with a manufacturing defect being tested by Keith Johnson. It somehow managed to have a short between the a.c. neutral and the signal common, and promptly blew up the D/A in Johnson's setup before blowing the breakers. Keith was using balanced power....

Any equipment that is manufactured to meet European (or US) safety standards will not and cannot benefit from so called 'balanced power'. The thing is a piece of HiFi flummery of the worst kind; and could conceivably be dangerous in some unusual circumstances as bcarso says.
It is in the same league as 'unidirectional cables' and 'gold plated mains plugs'; just complete and utter nonsense.

> meet European (or US) safety standards will not and cannot benefit from so called 'balanced power'
> just complete and utter nonsense.

Disagree. Safety standards do not assume that either side of the line is grounded. Signal designers should not assume so either, but do.

Personally, I think the boxes should be built right, quarantining and blocking wall-power influence. But I think small. Bcarso points out that quite huge systems are sometimes assembled of imperfect boxes. Then a line mod may be simpler/cheaper than modding or isoing everything individually. (Video has the special problem that it is always distributed unbalanced low-Z common solid ground. Ground crap goes right into the picture.)

It is no different than insisting on balanced audio outputs. Why do we balance outputs? It does not improve signal quality on that line: that's set by the next input's CMRR. But when we bundle a lot of lines together, balanced sources greatly reduce the coupling from one line to another. When MegaMetal plays in studio A and the Kindergarten Choir plays in studio B through the same bunch of cables, MM is putting 10V signals on their line which couple into the 10mV signals from KC. While MM's 10V signal fades quickly with distance, cables in a bunch may be very close. If MM's line is balanced, the external field starts from (+5V)-(-5V)= zero volts and coupling is zero, or at least much less.

Same for power. Conventional 120V/0V power radiates from a 60V average. While we should not bunch power with audio, there are a lot of small power/audio couplings in a large system. Balanced power radiates from a zero V average. In theory coupling is zero; in practice it may be much less than conventional power.

There is an additional advantage they don't claim. It is darn hard to get killed by 60V power. Apparently England now uses 60V tools on construction sites for this reason.

While the safety may seem good if you are plagued with electrocuted singing guitarists, balanced power will increase[/b] the buzz of the older US 2-pin guitar amps compared to the trick of flipping the plug until buzz is minimum.

That does it, I'm calling my next band "MegaMetal."

:razz:

IMO band name should be MegaMetal and the Kindergarten Choir... :green:

Not sure what you are saying PRR.... Do you agree that balanced power is a hype or not?
Properly built 'boxes' will work perfectly with 'unbalanced' power, so should we endorse balanced power as a way to fix the inadequacies of poor design? No, I stand by what I said. And it's certainly not the same as insisting on balanced audio! (I think you are just winding me up!! :? )
Your arguments about MegaMetal etc. are fun, but not very persuasive.

Alright, I will concede that the actual radiation from an accurately balanced mains cable will be less than from the normal 'neutral is ground somewhere back along the line'. But while theoretically the video boys might find that to be a serious problem, I don't find it so, and I certainly don't believe that nonsense about dramatic improvements in signal/noise.

If the gear is designed right, it will work fine either way; if it's designed wrong so that an offset in the mains gives noise problems, then it's most likely that there will other problems too.

I work in television and FWIW, most of the better "pro" video equipment, distribution amps and other terminal equipment, has differential bridging inputs even though the lines are unbalanced. With these, we don't see problems with equipment connected to different power circuits, even when located in different buildings altogether.

We have a couple of pieces which do not have diff inputs... and for those which are connected to lines originating outside the room, we have to use video isolation transformers. We bought a new Leitch proc amp a while back and neglected to order the diff input option. We hooked it up to a line emanating from another building and got instant "hum bars." Adding the transformer got rid of the problem.

Gerald Stanley (the amplifier guru at Crown) has remarked that it's almost always better to do things at the small signal level than at high power, if you can. The Equitech boys have taken a brute-force approach to fixing things at the power level, and it works, sort of. The improvements are enough to make some marginally unworkable systems work, although as Ted says if they are that susceptible to begin with there will probably be other problems.

The video/audio duplication plant system is a case in point. You can put galvanic isolation in the video lines with a bunch of good transformers and break up ground currents, for cost x. Or you can have a whole tearup of your power system with monster Equitech trafos for cost y and substantial downtime z and see how well that works (I've heard figures of 10 dB or thereabouts thrown around).

Note as well that the balanced power approach is susceptible to getting unbalanced by the loads, if there isn't equal impedance to safety ground.

As PRR points out some unbalanced equipment will work worse without the option of hot-neutral swapping when electric field pickup dominates. Some will work a lot better, such as the situation with two-conductor mains input and equal primary-secondary interwinding capacitance with a mains freq power transformer or off line switcher supply, which normally imposes a cap-coupled current from what looks like half the primary voltage. If the high-Z circuitry thus powered looks out at a section of the rest of the world that's at safety ground potential, you get hum and other mains noise coupled in. With balanced power you get about nothing to the extent that the interwinding capacitance couples equally to hot and neutral. Since the coupling is rarely exactly equal your mileage may vary, but there will still be an improvement.

But this is an example of a "bad" piece of equipment---it should have had a shield internally for those high-Z sections, referenced to its local common, so as to make it immune not only to seeing ground but to other external electric fields as well.

> Note as well that the balanced power approach is susceptible to getting unbalanced by the loads, if there isn't equal impedance to safety ground.

It should not be significantly unbalanced by load. In fact it would be illegal if that happened (though such things happen).

Their transformer MUST be center-tapped to building ground bus. Only rare exceptions allow a fully floating power feeder, and I doubt a whole studio could be treated that way. The legal and common option is to ground one end of the 120V feed, but that causes the problem they are addressing.

The loads must NOT conduct significant current to ground (green-wire or dirt). Ground leakage should be few-mA at most. This is confirmed by the fact that GFIs generally will not trip on any good appliance.

In the illegal case that there is more current in one side of the CT winding than the other, how much is the drop? 2% at full load. Unless you deliberately load to ground (instead of the other hot pole), you should not be near this; even if you did, the unbalance between 58.8V and 60V is 0.6V, very much less than between 120V and 0V or 60V unbalance.

> a whole tearup of your power system

It may not be necessary to change the power lines in the room. Ensure that there is no short to ground, and then switch the black and white wires onto the two hot terminals of the CT winding. Downtime could be 10 minutes, unless bad-design signal boxes smoke at switch-on.

> almost always better to do things at the small signal level than at high power

Sure, as you and he and TedF say: we should not have crappy inputs or leaky boxes. But in some Real Worlds, we do, and replacing them may be a monster undertaking. Reducing the AC field in the room is an alternative, not morally sinful idea, and in some cases may be cheaper than replacing a room full of leaky crappy boxes that hum but are otherwise satisfactory.

[quote author="PRR"]..snip..The loads must NOT conduct significant current to ground (green-wire or dirt). Ground leakage should be few-mA at most. This is confirmed by the fact that GFIs generally will not trip on any good appliance.

In the illegal case that there is more current in one side of the CT winding than the other, how much is the drop? 2% at full load. Unless you deliberately load to ground (instead of the other hot pole), you should not be near this; even if you did, the unbalance between 58.8V and 60V is 0.6V, very much less than between 120V and 0V or 60V unbalance. ...snip...

> a whole tearup of your power system

It may not be necessary to change the power lines in the room. Ensure that there is no short to ground, and then switch the black and white wires onto the two hot terminals of the CT winding. Downtime could be 10 minutes, unless bad-design signal boxes smoke at switch-on. ...snip...

[/quote]

I was thinking, regarding the imbalance, both low and high frequency stuff, and things like line filters with 100nF caps from each side to safety ground. Not that the balanced power makes it worse than the alternative, but just that these sorts of issues limit the extent of the improvement, compared to doing things right at the equipment design level. For example a really terrible piece of equipment in terms of susceptibility might work deceptively well when the balance was nearly perfect, and then deteriorate mysteriously as other loads were put on line.

As far as the tearup: in an ideal world the electricians could work with little disturbance, and then make that changeover as you describe in little time indeed. I suspect though that most of the time, mismanaged as such projects tend to be, it would be significant downtime.

I actually think the whole thing is a pretty good idea, especially if it could be part of installations from the outset, and taken into account by equipment designers. Switching both sides of the line would become standard practice, for one.

bcarso makes the point about poorly designed equipment that can work well, and then become mysteriously bad as mains conditions change; this really backs up my point about equipment design.
All my designs (and I'm far from alone in this) make use of good quality mains transformers that really dont care if the incoming power is one legged, floating or triangular as long as the RMS voltage is within 10% of the nominal.
Is there really modern equipment out there that is that sensitive to mains conditions? (I'm talking about audio... video is another story!)

[quote author="TedF"]
Is there really modern equipment out there that is that sensitive to mains conditions? (I'm talking about audio... video is another story!) [/quote]

The point I was trying to make earlier is that in my experience, in a professional video facility, I have seen few such problems. Balanced power is not something I would consider necessary in my plant.

[quote author="bcarso"]

As far as the tearup: in an ideal world the electricians could work with little disturbance, and then make that changeover as you describe in little time indeed. I suspect though that most of the time, mismanaged as such projects tend to be, it would be significant downtime.
[/quote]


This kind of thang would blow your average electrician's mind. Be careful because most sparkulators are nuts-n-bolts kinda fellas and not theory heads.

A few years back, a local studio hired me to repair their electrical system. Besides some usual Tom Foolery, the biggest thing we did was beef up their grounding. This made a huge ass difference in the signal to noise ratio.

[quote author="Butterylicious"]
This kind of thang would blow your average electrician's mind. Be careful because most sparkulators are nuts-n-bolts kinda fellas and not theory heads.
.[/quote]

That's precisely what I was trying to allude to, as diplomatically as I could :grin: There are exceptions to every rule, and some of them are our fellow DIYer's in here (like you if I recall), but I have had some seriously challenging experiences with electricians.

In fact---I won't even get started!

> It may not be necessary to change the power lines in the room.

I started thinking, and realized that I was wrong. Several key NEC rules must be broken.

White wire MUST be groundED. That means you can't have 60V on a white wire. There are old exceptions, none of which seem to apply unless specifically invoked. Interestingly, the 1999 and 2002 revisions that specifically allow balanced power do not specifically address the white issue, but do say "shall be identified as to system at all splices and terminations by color, marking, tagging or equally effective means." So you MUST go through the whole system and mark it.

Breakers MUST be double-pole. A good short on either side of a balanced line must be broken. In fact the conductor size must be reconsidered in light of the lower voltage available in a line-to-ground short.

I had wondered if "60V" might be considered "safe". Since it is not cirrent-limited, it is not; in fact the code specifically requires GFCIs.

You must have a conventional (one side groundED) outlet near every balanced outlet. (This means the room field can't be perfectly balanced.....)

The system is installed only in commercial or industrial occupancies.
The system's use is restricted to areas under close supervision by qualified personnel.

Kids, don't try this at home.

The fact that it made it into the NEC suggests that there IS some significant need, enough to agitate the usually conservative NEC committees.

[quote author="bcarso"]I have had some seriously challenging experiences with electricians.

In fact---I won't even get started![/quote]

As an employeer, I have too. Before I started my own company, I was the head douchbag for a company of 60ish guys. I can't even relive that in my mind w/o wanting to slap somebody. I'm much happier with 3 journeymen and 3 helpers. Consistency and QC are now kept in line which falls in line just behind safety.

I did gander at the link Ethan provided and I can't see dropping that kind of dough on one of their systems unless you have some sort of special needs (what those might be, I could only guess). Maybe a single circuit version might be novel to have around.

Breakers MUST be double-pole. A good short on either side of a balanced line must be broken. In fact the conductor size must be reconsidered in light of the lower voltage available in a line-to-ground short.

Click to expand...

That's an interesting point. I don't see a need to alter conductor size since it's based on load, but the over current protection device might need to be 1/2 of the specified size? Consider a 5 ohm load at 120 volts is 24 amps, enough to eventually trip a 20A breaker, but a 5 ohm case short at 60 volts is only 12 amps. Ah! That's why GFCI's are required. Nevermind.

The more I think about it, the less I like it. If noise is a problem, beef up your grounding. If current is a problem, add a new clean circuit.

[quote author="PRR"]

Kids, don't try this at home.

The fact that it made it into the NEC suggests that there IS some significant need, enough to agitate the usually conservative NEC committees.[/quote]

I think it did take the Equitech folks quite a lot of time and lobbying.

Aaaaahhh! Now you're talking!
We engineers back in the old 'Alice' company in the 1970s used to wander about the building muttering "Earth is NOT earth! (ground is not ground)."
Ground paths and good grounds are the single most important factor in audio... and probably the second and third most important too! :grin: