Don't connect caps line-to-ground on the primary side. If you use those, do it on the secondary side.
Using a 20 amp Schurter line filter on the primary. Using the x2 caps on secondary outlets.
The limit is 15 amps overall on line side and secondary, allowing a few amps of overhead for parts with higher ratings.
Glen B, do you like what balanced power does for you system and sound? It must be a significant improvement to be using it for 8+ years.
The limit is 15 amps overall on line side and secondary, allowing a few amps of overhead for parts with higher ratings.
Glen B, do you like what balanced power does for you system and sound? It must be a significant improvement to be using it for 8+ years.
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Looking good. I also get enclosures from Par-Metal Corp, and reinforce the bottom plate with additional sheet metal. I used that very 2,000VA transformer from Toroid Corp. in one of my early builds and found it extremely susceptible to power line DC offset/harmonic distortion. Whenever the household washing machine was running, the transformer buzzed like a chainsaw, in time with the machine's agitation. I used a 20A Carlingswitch hydraulic/magnetic breaker, Pass & Seymour dead-front GFCIs. I initially used EMI/RFI block filters, including a Qualtek 20A unit on the primary side. In careful listening sessions, to my ears the block filters imparted a veiling of the sound when in the circuit, even though they do not function in the audio range. I eventually eliminated the block filters.
In my current setup, I use a large Equi=Tech transformer and two small Toroid Corp transformers each feedin its own duplex outlet. I side-mounted the two small trannys, to get them to fit in the enclosure.
BTW, Par-Metal Corp. does custom chassis hole cutting, such as for duplex outlets, power inlets, etc. for a small charge. Just provide them with a detailed drawing of the hole positions and dimensions.
An externally hosted image should be here but it was not working when we last tested it.
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And the point of this is exactly what? I worked in a facility that had the entire technical area done in balanced power. The reason THEY did it was because of the AC line filters in all the gear treats the power as balanced and ties 1000pF caps from line and neutral to protective ground setting up loop currents in the ground. It was easier to go balanced than to change the filters in nearly a thousand items plugged in. When they built a new facility they didn't go balanced and just added a few differential video DAs for the feeds that came from gear on a different power phase.
It's the filtering that causes the problems if you use balanced filters on unbalanced power (by far the most common).
It's nice looking work.
G²
G^2,
Not sure about your question. Might be rhetorical...?
However, I found it odd that caps are used on the secondary receptacles. Isnt that what the differential of balanced power (BP) suppose to do? I read in one place that BP only filters out up to 10khz? Perhaps the cap filters the rest of high freq noise. I was going to try with and without caps, on digital and non-digital gear.
Nice work, Glen B.
Not sure about your question. Might be rhetorical...?
However, I found it odd that caps are used on the secondary receptacles. Isnt that what the differential of balanced power (BP) suppose to do? I read in one place that BP only filters out up to 10khz? Perhaps the cap filters the rest of high freq noise. I was going to try with and without caps, on digital and non-digital gear.
Nice work, Glen B.
I don't know the schematic of the particular Schurter you are using, but I am assuming that it uses line-to-ground caps. Not good. This will contaminate your ground line if used on the primary, or unbalanced side. If you use it, install it on the secondary side.
What's a P&S dead front GFCI? Think I was looking for something like that, instead of a GFCI with outlets.
Pooge, it does have a cap to ground. Damn.
Pooge, it does have a cap to ground. Damn.
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A dead front GFCI is the same as a regular GFCI, just that it is switch rated and does not have slots to accommodate plugs. You wire your transformer hots to it just like a standard GFCI, and feed downstream outlets, which will all be protected. They are most commonly available from Leviton, P&S/Legrand, and Cooper/ArrowHart.
Specification Grade Dead Front GFCI, White, 2085W | by Legrand
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Strange, I have a bunch of Maryland Transformers Medical grade isolation transformers both here and at work, they meet all of the safety requirements of UL or IEC 60601 and do not have grounded secondaries, further they carry CE, CSA and UL approvals.
Floating secondaries in properly designed low capacitance isolation transformers have leakage currents measured in the very low uA range. The only return path for leakage currents is the very low ground to winding capacitance of these transformers, and that is a large part of what makes them safe. Grounding the secondary removes this aspect of isolation transformer operation. There is an effective safety ground provided on these transformers and that should always remain connected and available for devices with 3 wire cord sets.
Further think about the typical isolation transformer you may have on your bench, the one you might use for example when restoring an AA5 radio receiver or an amplifier you suspect has a transformer issue - you will find they all have floating secondaries. (For reasons I hope are obvious)
Floating secondaries in properly designed low capacitance isolation transformers have leakage currents measured in the very low uA range. The only return path for leakage currents is the very low ground to winding capacitance of these transformers, and that is a large part of what makes them safe. Grounding the secondary removes this aspect of isolation transformer operation. There is an effective safety ground provided on these transformers and that should always remain connected and available for devices with 3 wire cord sets.
Further think about the typical isolation transformer you may have on your bench, the one you might use for example when restoring an AA5 radio receiver or an amplifier you suspect has a transformer issue - you will find they all have floating secondaries. (For reasons I hope are obvious)
Here's a couple of articles from the Equi=Tech website. Please read the next to last paragraph (highlighted in red) of the first article that mentions grounding. With a balanced isolation transformer used in a household setting, you will want to have the center tap tied to the household ground, in order to quickly clear ground faults in equipment powered from that transformer.
http://www.equitech.com/articles/rep1.htmlhttp://www.equitech.com/articles/bpng.html
Balanced Power: The Next Generation
http://www.equitech.com/articles/rep1.htmlhttp://www.equitech.com/articles/bpng.html
Balanced Power: The Next Generation
You have a 'ground' on the output that is nothing at all. If either line shorts to an actual ground (water pipe, building ground) nothing will happen. Will it kill you? It depends. If you use a 2 wire plug, all you've done is add an isolation transformer. A lot of work for no benefit and a potential safety hazard. Look into medical grade line filters if filtering is your goal.
G²
G2, are you talking about the schema on post #4 or #10 or both?
Are you pointing out something that no one else already has pointed out?
Feel free to post a schema that you feel works.
Are you pointing out something that no one else already has pointed out?
Feel free to post a schema that you feel works.
A few years ago I worked on an installation for a large recording studio, on a boat.
We were several miles from the sub-station in a residential area, so the decision was made to implement balanced mains- 120v-0-120v.
When we wired the units in, I commented that we needed to ground the center taps- the site electrician didn't have a clue and so we rang the manufacturer.
When we asked the chap on the other end of the phone, he nearly fell off his chair laughing.
Of course you need to ground the center tap. And fuse all the neutral legs in the equipment.
And it would have been a good idea to place all the switch mode stuff on seperate spurs too.
BTW. we had 3 balancing units, 3.5kva each unit. And a huge servo controlled rheostat to ensure a smooth 240v.
Bernie.
We were several miles from the sub-station in a residential area, so the decision was made to implement balanced mains- 120v-0-120v.
When we wired the units in, I commented that we needed to ground the center taps- the site electrician didn't have a clue and so we rang the manufacturer.
When we asked the chap on the other end of the phone, he nearly fell off his chair laughing.
Of course you need to ground the center tap. And fuse all the neutral legs in the equipment.
And it would have been a good idea to place all the switch mode stuff on seperate spurs too.
BTW. we had 3 balancing units, 3.5kva each unit. And a huge servo controlled rheostat to ensure a smooth 240v.
Bernie.
Balanced power is not permitted for residential use per NEC, regardless of UL/CSA or any other certification. I find few people who care, especially in audio circles.
If you find balanced power improves your audio system, you have a marginally operating system. The problem isn't with the 'purity' of power, it's with your system. The reason balanced power is even considered in commercial applications is to address the difficulties in different pieces of equipment with varying filtered front ends being fed off multiple outlets/circuits in large power applications. A residential application can easily overcome these difficulties with intelligent design and layout.
There are 3 or 4 threads you can search here to find this same argument made over and over again. The trend is to ignore the Code, do it your own way, and use the argument that it makes things better therefore it's the best way to go.
As a licensed PE practicing for decades, floating systems are to be avoided. Fix the problem, don't band-aid it with an isolated power source. Ground the center tap, but to meet code, there should be a neutral and a hot for 120V service. +/- 60V is not permitted in the home, nor is it needed.
If you find balanced power improves your audio system, you have a marginally operating system. The problem isn't with the 'purity' of power, it's with your system. The reason balanced power is even considered in commercial applications is to address the difficulties in different pieces of equipment with varying filtered front ends being fed off multiple outlets/circuits in large power applications. A residential application can easily overcome these difficulties with intelligent design and layout.
There are 3 or 4 threads you can search here to find this same argument made over and over again. The trend is to ignore the Code, do it your own way, and use the argument that it makes things better therefore it's the best way to go.
As a licensed PE practicing for decades, floating systems are to be avoided. Fix the problem, don't band-aid it with an isolated power source. Ground the center tap, but to meet code, there should be a neutral and a hot for 120V service. +/- 60V is not permitted in the home, nor is it needed.
The discussion is about point-of-use balanced power, not wired installations. Those in audio circles employ balanced power to reduce AC line-borne common-mode-noise. How does "intelligent design and layout" eliminate this noise? Your opinion goes against the grain of all the intelligent audiophiles, product reviewers, and engineers who manufacture or use balanced power systems, and find their use beneficial. In every thread like this there is always that one person who throws their credentials around, thinks they know everything and everyone else is uninformed. I guess the engineers at Equi=Tech, Plitron, Torus, Furman Sound, Toroid Corporation of Maryland, Blue Circle, etc., who manufacture balanced power supplies are all wrong and you are right.
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Well Golly. People who make balanced transformers think you should buy them. I wish I could have said it as well as Zigzagflux but the man is spot on. As I said earlier, we installed balanced power commercially to deal with AC line filters but this is minimal to no problem at home. If the power supply in your gear CAN'T deal with common mode noise there is something seriously wrong with it.
As for 'intelligent audiophiles', some of them can be sold _anything_ with a good story attached. I had one who insisted changing the 4 one inch wires from the cartridge to the head shell made a difference. There are even some of you who are CERTAIN the digital signals through the expensive Monster cable is somehow better than the 99 cent Fry's cable. The sound is more 'detailed' and the nuances of the video are more subtle. Humbug. Run a pathological test signal and prove it one way or the other.
Happy New Year
Curmudgeonly G²
Why don't you just get a 3-phase power feed to your home and use a 3-phase (or 3 equal) transformer(s) and 3 rectifiers/filters and then it won't be such a problem. 🙄
Or you could build (buy) a quality SMPS that has balanced output and then also the line noise is filtered out.
Or you could build (buy) a quality SMPS that has balanced output and then also the line noise is filtered out.
Speak it...
These gimmicks will plain kill people. As a medium voltage engineer, EE and EE(electronic engineer). I am not a genius but the words isolation transformer and ungrounded do not go together unless in an R&D setting. The reason we ground things is to create high current faults directly to earth in order to operate fuses/safety protection! not energize the chassis or people. Without a bond/ground reference to earth, the device will simply not protect itself by causing a high current condition. Per the NEC... all ac power neutrals should be bonded to earth at the first point/means of disconnect when entering into a service. Menaing every house in the USA "Should" have its 120V neutral bonded to ground/earth. I do this when operating 40MVA generators during power testing all the way through to my house at the end of the line.
Anyone using ungrounded secondaries on anything should read more. The forum rules are against it, the NEC, IEC, ANSI and a few others are against it as well, in particular the whole free world. If you have "real, measurable" power quality issues, contact your power company, they are required to correct it at a certain point. If you "feel" like you can "hear" the electrical noise, consult a therapist. There are very few residential power quality problems in the USA due to power factors being high and the grid being massive and stable. Most problems are from factories or other large consumers of power. These are almost always realted to power factor and large variable frequency drives / inverters. Anything with rectification. If you live in a 100 year old house with 100 year old wiring and you are trying to use balanced power gimmicks to fix your problems, see my above statement... consult a therapist.
If anyone would like actual, real pictures of what happens when you remove the center tap let me know. A thief tried to remove some copper from our 100MVA medium voltage transformer. He knew a little bit about electricity. He shorted the hot side, removed the center tap to earth, then started cutting the neutrals. After his arm was blown off by cutting into the wires, (that he thought he shorted) he was electrocuted to death, extra crispy. During the investigation, I believe he only cut the center tap, then died as the center tap would have been instantly energized.
Do not get hung up on a UL or CSA stickers, that rating is for the device, not your whole creation! The manufacture places the sticker on a transformer to show he conforms to the UL/CSA code. That code does not cover any living organism that hooks it up incorrectly! Any XFMR has potential for direct earth shorts on both primary and secondary due to the conductive core!
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Does anyone one else want to chime in on the dangers of not grounding a transformer secondary? Anyone? Let it out now, because the rest of us have moved on. We get it.
Its one thing to educate, it another to do it in a condescending tone. Its because of people like you that I didnt learn a goddamn thing in school early on.
As for not hearing or needing balanced power to improve the sound of audio and video equipment, that's a matter of opinion. I heard one system with a $13k BP setup at the electrical panel. Have also heard the big Furman balanced unit and the systems sounded good to me and both owners feel there is a benefit. I'm not spending $13k let alone $2700 to see if I like balanced power in my system. Not going go demo a unit as that would cost as much as the transformer itself. I might be crazy, but I'm not stupid.
If you can add something to this project, I'd like to hear it. If you want to regurgitate what was said earlier about not grounding the center tap just save it. We get it. Its dangerous. Don't do it!! The center tap to should always be grounded to earth for safety.
I can see why this topic was never really covered on this forum. 🙄
Its one thing to educate, it another to do it in a condescending tone. Its because of people like you that I didnt learn a goddamn thing in school early on.
As for not hearing or needing balanced power to improve the sound of audio and video equipment, that's a matter of opinion. I heard one system with a $13k BP setup at the electrical panel. Have also heard the big Furman balanced unit and the systems sounded good to me and both owners feel there is a benefit. I'm not spending $13k let alone $2700 to see if I like balanced power in my system. Not going go demo a unit as that would cost as much as the transformer itself. I might be crazy, but I'm not stupid.
If you can add something to this project, I'd like to hear it. If you want to regurgitate what was said earlier about not grounding the center tap just save it. We get it. Its dangerous. Don't do it!! The center tap to should always be grounded to earth for safety.
I can see why this topic was never really covered on this forum. 🙄
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