Info - What is balanced isolated power

[Guest " "]

A good explination can be found at http://www.equitech.com/faq/whatis.html

What is balanced power?

When 120-volt AC power is balanced, one side of the circuit has +60 Volts to ground while the other has -60 Volts to ground. (Across the circuit, the usual 120 Volts is still present. Fig. 1) A European 230 Volt balanced power system has +115 Volts and -115 Volts to ground on the conductors.

Standard unbalanced AC power systems have a "hot" conductor and a "neutral" conductor. In the US, the "hot" conductor nominally has 120 Volts to ground and the "neutral" conductor has 0 Volts to ground. (Fig. 2) Europe has a similar system but with 230 volts on the "hot" and 0 Volts on the "neutral."

In a balanced power system, the voltages on the system's two output terminals are 180 degrees out of phase to each other with respect to ground. The system reference (ground) originates at the output center tap of an AC isolation transformer. In other words, the system's grounding reference (zero position) is located at the system's mean voltage differential or zero crossing point of the AC sinewave. This is a far more effective way to establish a reference potential for an AC system. The center tap is then grounded to Earth for electrical safety and for referencing shields.

There is never any voltage or current present on the ground reference in a balanced power system. Transient voltages and reactive currents which normally would appear on the neutral and ground wires are also out of phase and likewise, sum to zero at the ground reference thereby canceling out AC hum and noise.

A balanced AC Power system works the same way as a balanced audio circuit but with a higher amplitude. Both balanced audio and balanced AC incorporate phase cancellation or common mode rejection to eliminate noise.

[Guest " "]

If you were to setup a new HT room with balanced isolated power, the layout would look something like this.

Note the center tapped step down transformer. This slpits the 120 into 60 - 0 -60.

[Guest " "]

The outlets are also wired differently...here is a normal out let.

[Guest " "]

Here is an outlet wired for balanced isolated power.

Not the grounds...not connected to the outlet box frame...it goes back to the service box as indicated in the schematic.

[Guest " "]

Now, if you don't have 4100 bucks for a service box with the required step down center tapped isolated transformer, plus the 1500 bucks in labor, heres a popular short cut.

A lot of line conditioners provide a few out lets that are blanced isolated power outlets. Take a look at the case schematic for the HTTPS 7000, not the 2 isolation balanced transformers at the lower right, which supplies power for the last 3 banks of out lets.

[Guest " "]

Here are power readings on a normal outlet from hot and neutral .

[Guest " "]

Here are readings on a normal outlet from hot to ground

[Guest " "]

Here are readings on a normal outlet from neutral to ground.

[Guest " "]

now here are readings on a balanced and isolated power outlet across the former hot and neutral connections. It looks normal (120), but it is actually two out of phase 60 volt sources that when brdiged provide 120 (60 - 0 - 60). Take a look at the next pic.

[Guest " "]

Now her are readings on a balanced and isolated out let across the hot and ground connections. Note it says 60, which is one half of the sine wave.

[Guest " "]

Now here are reading on balanced and isolated power across neutral to ground. Note is indicates 60, but it is the opposite part of the sine wave. When bridge with the other half, the 60 - 0 - 60 provides 120.

[Guest " "]

Here are some claims, from the same web site, note the last paragraph.

Why do I need balanced power?

Power standards for electrical distribution were adopted many decades ago and haven't changed significantly since. With the advent of sensitive electronic applications, electrically induced interference has become a matter of concern to engineers. When electrical interference is present in any sensitive electronics, equipment performance will be limited by the noise. The problem is critical in many areas of high-tech electronic engineering, among them, the sound recording and video industries. A very low noise level is crucial in these areas because literaly, the noise can be seen and heard.

The dynamic range of the entire electronic signal chain determines the quality of the final product in all recording environments. The presence of any electrical interference at all lowers the S/N ratio of the recording. This limits the subtle detail and realism of the sound or image. Low level signals are lost in the noise floor of the system.

Sound quality can also be affected by intermodulation distortion occurring as a result of the presence of ac noise in the audio or digital signal bandwidth. Even if the noise level is inaudible, it is likely that program material will be colored by the presence of electrical interference.

In more sophisticated areas of application, for example high-end digital signal processing (such as broadcast automation or even MDM recording), unacceptable error rates are often attributed to background electrical interference. Digital jitter is the "smoking gun" that points to high frequency AC noise. Digital jitter is caused in part by high frequency electrical interference approximating the bit stream rate of the digital signal.

Balanced power eliminates all of these problems because there is never ac interference present on the ground to invade signal circuits. Balanced power often increases the dynamic range of a recording system by 16db or more. When balanced power is applied, ground loops and hum problems, even subtle ac noise coloration becomes a thing of the past. The difference can be astonishing.

[djk]

A 10dB improvement is more typical.

Using a 10K:10K input transformer on your power amp inputs will sound better and cost a whole lot less.

See the notes at the Jeff Rowland site.

[Guest " "]

djk

There are a lot of articles at http://www.equitech.com/articles/articles.html. Many of which is for the recording studio industry. In reading some of the letters provided eguitech by past customers, most are studio setups, which I would have to assume are using balanced inputs already, if not optical. There is quite a bit of focus on reduceing the "noise floor" using balanced isolated power which leaves one with the impression of greater dynamic range.

In my setup, input transformers are not applicable since all my componets can and are optically connected. There is info at this site that reports reduced ditigal errors when using balanced isolated power.

In my excercise to evaluate these claims, I put my source media server as well as my HT reciever on seperate isolated balnced power circuts.

I am starting to understand these claims and can recognize the reduced noise floor often refered to as well as the greater dynamic range as a result.

I am impress by the greater detail, which combined with the reduced noise floor, greater dynamic range and horns, results in an amazing listening experience.

This is certainly something to demo if we ever have a klipsch gathering for the north east area.

I'll be building a 1.6 KVA balanced isolated power unit so i cam put every thing in my HT setup on balanced and isolated power. Using the info and approach at http://home.comcast.net/~thomasw_2/CheapskateBP4.html, total cost is projected to be less than 400 bucks. On my DIY project, rather than going 110 to balanced isolated 110 (60 - 0 - 60), I will be using 220 and take that down to balanced and isolated 110 (60 - 0 - 60).

[Coytee]

I'll be building a 1.6 KVA balanced isolated power unit so i cam put every thing in my HT setup on balanced and isolated power. Using the info and approach at http://home.comcast.net/~thomasw_2/CheapskateBP4.html, total cost is projected to be less than 400 bucks. On my DIY project, rather than going 110 to balanced isolated 110 (60 - 0 - 60), I will be using 220 and take that down to balanced and isolated 110 (60 - 0 - 60).

Would you consider documenting your journey for me, if not everyone else?

I'll be working on my big room soon and this stuff is GREEK to me so the more I can read about it and see it working in real life, the easier I'll be able to comprehend some of it.

Better yet... why don't you just mosie on down my way and just finish my room for me?

[]

[Guest " "]

Coytee

Will probally order the parts this weekend.

[Guest " "]

I bought this item today. Monster HTP 2500 power filter.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ih=019&item=290032764770&rd=1&sspagename=STRK%3AMEWN%3AIT&rd=1

It is a 300 dollar monster line conditioner (really a filter). Paid 60 bucks for it.

Bought it basiclly since it is a very nice looking case and has all the outlets installed already.

Cost of an equiv empty case at parts express was 89 bucks. With out the outlets, switch, cord, filters, etc.

I am going to put 2 isolated balanced transformers in it. Here is the part number for the ones I will be using.

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=122-720

Cost will be 90 bucks each plus shipping. Total cost will be 240 plus shipping to me, and my time.

This is about 100 bucks less than the big daddy balanced isolated power conditioner in the earlier link (350 bucks).

Using 2 transformers will provide me with 1.6KVA (1600 VA's or 1920 watts, 16 amps total).

So this will basiclly be open heart surgery.

The HTP 2500 will be dis-assembled, and re-assembled to incorporate the balanced isolation transformers.

Here is the link with the construction over view.

http://home.comcast.net/~thomasw_2/CheapskateBP4.html

[scotrajode]

I have to interject. Wow, someone is feeding you a line of mostly crap. Where do I start. Let me start by saying that I am a licensed electrician and graduated valedictorian in my class of 151. My overall average was 97.92% and a 98.70% in AC theory. I don't want to sound like a pompous *ss, but I want to make sure you know I am not just talking out of my *ss.

Let me start bu saying that all AC power is balanced. If it is not, there is a ground fault. What they are talking about is a center referenced transformer.

Current, not voltage is what induces voltage on on wire, circuits, etc. Since current flows one way on the hot and the opposite on the neutral, they are 180 degrees out of phase with each other on the cable and cancel each other out so no voltage is induced onto the ground wire. This is true no matter where the ground is referenced on the power supply.

The ground is only there as a safety. It does not matter where it is referenced on the system. Be it one pole or the other or the center, it there only to give the current a path back to the source, in the event of a fault, so that an over current condition will exist on the circuit and the breaker will trip. That will help prevent people from getting electrocuted. A neutral fault will not trip the breaker unless there is ground fault protection. The breaker will sense that the current on the neutral is not equal to the current on the hot because about half of it will go back on the ground.

AC power always has a 60hz (or 50 hz) hum. That is why it is AC instead of DC.

What does cause noise is harmonics. This is caused by non linear loads. Power supplies are the most notorious. 3rd order
(triplen) harmonics are usually the result. Harmonics can induce slight voltages on the ground and make "dirty" power. Coincidentally, audio equipment makes great use of power supplies. Sounds like a catch 22, huh? The best solution is a dedicated circuit for your audio system with and isolation transformer with an isolated ground for each piece of equipment and phase them identically.

At the utilization device, it is true that a center referenced power supply has the current 180 degrees out of phase with each other when referenced to ground, they are zero degrees out of phase when referenced to each other. Unfortunately, this also true of standard ground referenced system. They talk about the voltage being out of phase with each other, which is different than a standard grounded system, but that is meaningless since voltage does not induce current or voltage on the ground. That puts a little kink in their nice theory.

Just to clarify, VA is also called apparent power. W is also called true power. The only time watts are as much as volt/amps is in a purely resistive load which makes the power factor 100. If there is any inductance or capacitance in the circuit, true power decreases while apparent power stays the same and the power factor goes down. So, if you have a total of 1600VA available, the best you can hope for is 1600 watts, or 13 1/3 amps at 120 volts. If there is any inductance or capacitance in the circuit, it will be less. Example: if the power factor is 90 and there 1600VA, there is only truly 1440 watts or 12 amps available.

If you would like clarification on anything, please don't hesitate to ask. It is not very often I get to impart my electrical knowledge, so I am happy to when I get the chance.

Scott

[Guest " "]

Thanks for your questions. Lets focus on one of your fundament statements which was that all ac power is balanced. Actually all 110/120 is unbalanced.

All AC is balanced going into a home via the 220/230 run, but becomes unbalanced at the main's bus where the 2 phase are split to provide 2 single phase of 120. In most homes, it is an educated guess on the part of the electrician how to load both split and unbalanced phase of 120 as they wire the breakers into the homes service requirements. In my home the load balance is not even close, there are 20 breakers, 6 are high draw and frequently used circuts which were put in with 4 low draw circuts while the remaining 10 circuts have draws that are occasional and very little use. The voltage difference across the two phases are measurable.

A balanced power black box device that runs off 220/230 and brings the power down to 110/120 via the use of 2:1 step down transformers and converting the service outlet power to 60-0-60 while using both phase of the inbound 220/230 serivce to the home results in fully balanced power to the service outlet.

While there is a lot of confidence amoung folks the electrical industry in the electrical service provided to homes, folks in the audio industry have been faced with a myrid of issues attributed to the nuetral wire, the distributed grounding points which terminate at the outlet case, and un-isolated circuts in a home as well as un-isolated from adjacent homes.

"Power factor" issues are a concern if one subscribes to the notion that home appliance motors, lighting balast, and appliance transformers provide significant reflective inductance to lower a homes power transmission effectiveness. Ideal power factor rating is 100, panic rating is 85. "Power factor" ratings are significant concerns at industrial facilities which use hundreds of electric motors and at such facilities the factors involved in "power factor" computations are consistent thru out the service day to warrant the application of corrective measures such as baselining the current "power factor" of the facility and determining the cause, as well as the corrective action. Typically the cause of non forward power factors are induction motors and once evaluated the mitigation is the addition of capacitor banks using motor run capacitors. These capacitors store power between cycles and release it back into the motor circuts faster than the local power transformers can respond to the demnd. As a result, a facility's ower factor is improved.

In a home however, the opportunity to apply power factor correction technique is not as attractive as in industrial applications. Home motors are few and do not run constently. Most home motors actually have motor run capacitors attached to the motor units which engage when the motor's engaged. The needs for power factor correction pricipals in a home is less justafiable. As much as I would like to believe that transformers, ballast, and home applicance motors are contributing to a reduced power factor (less than 100), I think the case for it would be a weak one. If you have pool, spa, central air conditioners, large fixed base power tools that do not have motor run capacitors installed, a review of the data plate on the motor will usally indicate the devices power factor. Good news is that for a home, half farad (500uf) is rarely needed and typical correction needed is about 100uf. Placing the correction on the device with the switch between the capacitor and the service box would be ideal to avoid issues of a too forward leaning power factor which is believed to increase 5th and 7th order harmonics.

Issue of harmonics in a typical home electrical service is getting a lot of attention right now with the onset of power supplies that do not use isolation or step down transformers such as those found in home computer systems, laptop power supplies, LCD and Plasma displays entering the home market for entertainemnt use. These power supplies are being studied as a cause of harmonics that are reflected back into the electrical system in local distribution circuts between the home and the comunity step down transformers.

You will find this a growing area of intrest and certainly worth your furthru study.

[Jim E]

Scott,

I am in agreement with you. A clean run or multiple runs of power from the mains panel with a good ground has always worked for me. In a typical home the wall outlets are shared and all too often things like air conditioners, ceiling fans, dimmers, refrigerators etc. are on the same feeds. While this construction practice is legal and keeps the cost of building down, it does not always work for audio or other sensitive equipment. In my present system I have two 12 gauge (12/2 copper romex with ground) home runs to the mains with dedicated grounds and a supplemental copper rod earth ground spiked 15 feet into terra firma. It took me a full day to install and the cost was under a hundred bucks. It seems to work just fine for me as long as SoCal Edison is doing their job.

Most audio equipment generally have sufficient power supplies that do a good job regulating the AC into the proper DC voltages and filtering out 50/60 cycle hum. Many supplies also have MOV surge suppressors in their design to filter over voltage spikes and circuitry to minimize other line transients. Most audio equipment utillize a single primary stepdown transformer that is as far as I can relate not critical of line polarity (hot or neutral) so how the power is "balanced" would seem to be of no importance. What is important is if you have sufficient current and voltage available and is it clean. If not then dedicated power isolation devices and/or home runs may be the answer. If you are using large high output amplifiers on the same circuit as your other low wattage components be sure they are not pulling the line low. Some power amps can pull well over 20 amps at full tilt. If you have good clean power and still have noise, then check your equipment and interconnects. Also keep in mind that the requirements in a recording studio or other professional environment are somewhat different than the home audio setup.