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Post by pinkie on Jan 3, 2016 14:03:26 GMT
Again, as Martin T now appears to acknowledge - this balanced connection, and a Balanced Power Supply CANNOT REMOVE NOISE ON THE INPUT TO THAT CONNECTION. So all the noise on the mains, whizzing round the cables in your walls, WILL NOT BE REMOVED or CLEANED by a Balanced Power Supply. I said the effect of balancing cannot remove noise being input into the system, it can only cancel noise picked up by the system. but that's not the whole story. Running a BMU clearly does remove some of the noise, so there is more going on and I have already suggested that the efficiency of the transformer coupling may be dramatically lower at high frequencies, thus filtering out RFI. There is also the issue of magnetic storage, which may explain why dynamics and impact are improved when using a BMU. It's complex. But we are talking specifically about a balanced unit - and as I referenced the claims made were that it cleans mains by virtue of being balanced. And in that context, balanced is balanced, and identical for interconnects and power supplies - as defined in my earlier post. And a balanced connection cannot clean mains in the way described A transformer as a low pass filter maybe does (although it is going to depend on the type of transformer and its grounding arrangements - chances are most of the noise will be capacitively coupled to the secondary). The issue here was whether, as claimed on this forum, and in current marketing, the device "cleans noise from the mains by phase shift cancellation by virtue of a balanced connection" I think we agree it doesn't. But it brings me on nicely to "like noise cancelling headphones". I'll put it in a separate post
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Post by DaveC on Jan 3, 2016 14:07:53 GMT
. The Pip for example takes a centre tapped transformer to provide +18v -18v into the bridge rectifier. That is a balanced connection. Balanced in what way ? Your right. It's not. It's an example of a centre-tapped transformer and adds nothing to this discussion Pinkie you said it was, and now you admit you are wrong. This begs the question of how many other things you are wrong about ?
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Post by pinkie on Jan 3, 2016 14:10:38 GMT
Your right. It's not. It's an example of a centre-tapped transformer and adds nothing to this discussion Pinkie you said it was, and now you admit you are wrong. This begs the question of how many other things you are wrong about ? You have the technical knowledge and genuine expertise to know the answer to that very many times. The way you choose to use that knowledge, and the nature of your posts I find unhelpful - almost mocking. I am fortunate to have others with at least equivalent knowledge and expertise who are much kinder and more giving about sharing it with me. I realise at times it is a thankless task for them. My "phd friend" trys to avoid it like the plague. I understand - its like me explaining FRS102 requirements for valuing financial instruments to someone who can't understand the double entry for a cash purchase of stationary. But my "phd friend" does his best with a good grace and generosity of spirit. Normally, as at the moment, I avoid asking him by phone or email - because I appreciate its a bit less painful face to face (and I can ply him with red wine, and he dotes on my German Shepherds). The one exception, where I called in some favours, was to get him urgently to explain the safety issues to me and ensure I correctly understood them - because I persuaded him that there was some urgency where those matters were being discussed - and as far as I could tell incorrect statements directly relating to safety were being made. So yes - I am likely to make mistakes. But the conclusion that I only make mistakes may be an extrapolation too far.
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Post by pre65 on Jan 3, 2016 14:12:47 GMT
As I understand things (with my pea sized bwain) the balanced transformer has +120v and -120v and a centre tap instead of plain old 0-240v.
And my understanding is that if distortion is present on both legs they cancel each other out ?
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Post by pinkie on Jan 3, 2016 14:22:57 GMT
"like active noise cancelling headphones"
This (active noise cancellation) happens to be a particular specialism of my phd friend. I think it was intended as an honest and useful analogy / explanation. And in one way it undoubtedly is. But - probably unintentionally it could be considered deeply misleading
Where it is good, is that it is a great way of illustrating how 180 degree shifted phase signals (or noise) cancel each other. The noise on a balanced connection is identical on both connections, but 180 degrees out of phase which cancels it. The noise in a noise cancelling headphone, is shifted 180 degrees out of phase and added to the music, so that the 180 degree shifted noise and the real noise cancel each other. This idea that out of phase signals can cancel makes the noise cancelling headphone analogy a good one. Perhaps another good one, would be like putting one speaker deliberately out of phase and bringing the 2 speakers close with the drivers facing and hearing the bass cancelled
Where it is NOT a good analogy, is that the cancellation in headphones does not rely on a balanced connection. It does not cancel the noise on a connection. It samples or "listens to " the noise OUTSIDE the connection / environment and REMOVES that noise by inverting its phase and replaying the 180 degree shifted noise with the real noise at a gain level which cancels it. It actually DOES clean the existing noise up - in a way which the phase shifted balanced connection of a Balanced Power Supply does NOT do.
So meant to be helpful, and helpful in one context, but potentially misleading in other contexts. Particularly if used near to a phrase like
This is due to the distortion and noise being present on both legs of the split rail but one side is 180deg out of phase with the other so they effectively cancel each other out, a very simple solution.
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Post by pinkie on Jan 3, 2016 14:26:23 GMT
As I understand things (with my pea sized bwain) the balanced transformer has +120v and -120v and a centre tap instead of plain old 0-240v.
And my understanding is that if distortion is present on both legs they cancel each other out ? Sort of. Which noise? The noise whizzing around on the copper in the walls, with all that nasty SMPS and microwave oven gunge is NOT cancelled out. That is effectively part of the "signal" in the video I posted. That noise is divided into 2 180 degree shifted legs, and then put back together again at the other end (inside the connected equipment) and "rebuilt" into the original noise in the same way that the original signal was cut in half and then rebuilt. The noise that is added to the connection - ie the noise ADDED to the wire from the BPS to the equipment ( a tesco kettle lead in my house) - that bit of noise IS cancelled. Refer back to my earlier Wire A Wire B post (Oh how post numbers would aid x-ref's)
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Post by Mr Whippy on Jan 3, 2016 14:40:24 GMT
And what if? What if the improvements a BMU brings, according to those who have tried one, has bugger-all to do with how noise may or may not be handled? I don't really understand why it is such an issue for anyone.
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Post by pinkie on Jan 3, 2016 14:57:32 GMT
And what if? What if the improvements a BMU brings, according to those who have tried one, has bugger-all to do with how noise may or may not be handled? I don't really understand why it is such an issue for anyone. Absolutely. At no point have I said that a BMU or other BPS cannot bring enjoyment and an improved listening experience to the user. That is a subjective appreciation and a completely valid one. That doesnt meant that how things work isnt interesting. I wouldn't wish to stop anyone trying and enjoying a BPS (I have to briefly qualify a statement like that as subject to them understanding any safety related issues). But equally others may be interested as to WHAT is happening and whether there are other ways to do it. For example - Martin bought up that the device will block DC. That may not matter very much - unless there is a noisy toroidal somewhere - but if it matters for any reason, it is worth appreciating there are other ways to skin that cat I feel that what amounts to a paranoia about brand attacks , and perceived "objectivism" is amounting to censorship of legitimate discussion about how things work and WHY things happen. That would be a shame But nothing in a discussion of how things works precludes you from enjoying BPS or shakti stones for that matter both are used in recording studios. As are cocaine and marijuana from time to time.
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Post by Deleted on Jan 3, 2016 14:58:46 GMT
"let them kill themselves if they want to". Sorry, I have to take this up again. It's been shown that if a BMU goes awry inside, either the fuse in the master mains plug blows or the consumer unit trips, the body of the BMU being Perspex posing no safety threat at all. Dave - remember you asked. Its not whether the unit is inherently dangerous. Its whether the way it changes electricity for things plugged into it compromises safety. Its a bit like whether not wearing seat belts is a compromise to safety. I think it is. But if the car I choose not to wear seatbelts in as an Audi, it doesnt make Audi's dangerous. It just means not wearing a seatbelt is compromising safety Whilst a switch might be a convenience item or a safety item I conclude a fuse exists for reasons of safety alone. If an equipment designer decides it is appropriate to protect his equipment with a fuse, whether an internal case fuse or a recommendation that the appliance should only be used with a 3 amp cartridge fuse in the mains plug that is for safety reasons. Connecting it up without a fuse, say just with a metal bar instead compromises safety. Putting a voltage on the blue wire - the neutral rail - where the equipment designer didn't expect it to be, and so didn't put any fuses, compromises safety That has nothing to do with how inherently safe the BMU as a device is in isolation. Its about changing the electricity that is experienced by the things plugged into it. Its a bit like one could design a transformer with appropriate windings to supply 1000v instead of 240v. The transformer could be in a perspex box and bomb proof - but supplying 1000v to a device expecting 240v would compromise safety. Like any transformer a BMU or any other BPS also prevents a fault on a device plugged into it (an earth leak type fault - such as potentially a human electrocution) from tripping the RCD on the household consumer unit. Since current wiring regulation insist that the electricity in a house must be protected by RCD's on the consumer unit, I consider that a device which renders that protection inoperative for anything plugged into it compromises safety. It's not saying the unit is inherently dangerous. Just what it does to consumer unit RCD's and connected equipment fuse arrangements interferes with those safety measures in a way which amounts to compromising safety Like choosing not to wear a seatbelt. Not a certificate of instant death. But a significant identifiable increase in risk Could I ask at this juncture if you have any qualifications at all in respect of electrical safety or indeed any knowledge at all beyond a very basic understanding of the physics involved? I ask this because you appear to be making assertions and casting doubt about commercially available products that one would assume have required safety certification. I am interested to know whether there is any credibility to the above statements whatsoever or if this is just more of the space filling misinformed waffle the internet is (unfortunately) stuffed with ...
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Post by pinkie on Jan 3, 2016 15:12:58 GMT
Could I ask at this juncture if you have any qualifications at all in respect of electrical safety or indeed any knowledge at all beyond a very basic understanding of the physics involved? I ask this because you appear to be making assertions and casting doubt about commercially available products that one would assume have required safety certification. I am interested to know whether there is any credibility to the above statements whatsoever or if this is just more of the space filling misinformed waffle the internet is (unfortunately) stuffed with ... I have no qualifications. I asked a friend who does - because I thought what I was hearing sounded potentially dangerous and wanted the opinion of an expert. The points are not really complicated ones though. Most people understand what a fuse is. How hard is it to see that if someone designing equipment wants to put a fuse on the live wire - they expect to know which wire is going to be live. On your regular plug thats the brown one only. In a BPS both the brown one and the blue one are live. The person designing and building my NAD 3020 didn't know there would be live voltage on the blue wire, he designed it and obtained its CE approval on the assumption only the brown wire would have a voltage on it. It is hard to make the assumption that if he wanted to put a fuse on the brown wire because he knew it carried a voltage, that if at the time you had said "oh by the way - I'm going to put a voltage on the blue wire too" he wouldnt have had similar reasons for sticking a fuse on that wire. I am hardly alone - google a bit, take a look on WigWam. The points are well enough understood and reported. Try this for one example sound on sound balanced mains safetyI'm not sure you really need a qualification in anything to understand that point.
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Post by AlanS on Jan 3, 2016 15:20:59 GMT
Instead of thinking and talking about BMU why not try one (after a chat)? I am sure they will put your mind at rest on all the things that concern you and you share with us. You do want one, not just to go on endlessly quoting your friend, I trust? www.russandrews.com/balanced-mains-units/ Why we really are "Happy to Help" We really do mean it! We are enthusiasts ourselves, and we love chatting to you and working with you to solve your Hi-Fi-related problems. It's no more than we would expect ourselves. So if there's anything you're not sure about, or you want advice on which product to try for a specific problem - or indeed anything that's Hi-Fi or Home Cinema related - give us a call! and they have 60 DAY MONEY BACK GUARANTEE 100% satisfaction - or your money back Ever bought a Hi-Fi product that sounded great in the dealers but not so good when you got it home? We know from experience that the only way to ensure a product is right for you is by having the time to trial it in comfort at your own home with your own system. We're so confident that you'll be happy with the performance of our products that we give you a full 60 days to try them at home - and if you’re not 100% satisfied with the improvements, you can send them back for a full refund. You can’t say fairer than that, can you? Why 60 days? All new cables and conductive metal parts need time to 'settle' before they perform at their very best - we call this process the Burn-In period and it can take anything up to 500 hours. By allowing you 60 days to test them you can be sure that you’re hearing the performance you can expect in the longer term rather than having to make a snap judgement based on a product the character of which may change. If you still have the curiosities after that try another supplier.
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Post by dvh on Jan 3, 2016 15:47:26 GMT
Maybe Pinkie could get his 'PhD Friend' to join TAS.
MODERATION: Uncalled for personal comment removed.
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Post by Deleted on Jan 3, 2016 15:52:46 GMT
Maybe Pinkie could get his 'PhD Friend' to join TAS. MODERATION: Uncalled for personal comment removed.Again, out of order. Mods - is this a friendly forum or not?
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Post by Deleted on Jan 3, 2016 15:55:27 GMT
I agree. If I want to read sniping and personal digs, I can get a better "fix" on Wigwam
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Post by ChrisB on Jan 3, 2016 16:30:19 GMT
Thank you for pointing out the inappropriate comment. Come on guys, you know the rules.
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Post by ChrisB on Jan 3, 2016 17:02:07 GMT
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Post by Deleted on Jan 3, 2016 17:17:40 GMT
I think I can summarise the safety question. Is it safe to operate Class I (These appliances must have their chassis connected to electrical earth) to a Class II (double insulated electrical appliance is one which has been designed in such a way that it does not require a safety connection to electrical earth) balanced mains unit?
I am sure that the Class II BMU is a perfectly safe unit (if it wasn't RD would not make it) and is ideal for a system made up of Class II products (Such as NVA). What I don't know is how a BMU is wired up so if I class I component connected to it electrically fails to earth, does the Class I component case/chassis become live as the path to earth has effectively been cut? If the answer is no, then there is no safety concern for the entire system.
As a note, having pretty clean mains, I have no interest in a BMU or mains regenerator, but seeing this thread evolving rapidly I thought I would have a read. I would appreciate it if someone qualified could answer my question though.
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Post by pinkie on Jan 3, 2016 17:19:23 GMT
I'm not sure what you were suggesting they would help with, but I think they may miss the point. The issue is NOT the safety of the device itself. It is the safety of things plugged into it. You cannot anticipate that - but to help you I will tell you I would probably plug a class 1 Quad 405-2 into it. So the fact the unit itself is class 2 is irrelevant. The point is covered by the Technical editor of Sound on Sound (for professional musicians and studios) in the article I linked to The critical issue is that virtually all commercially-available electrical equipment is designed for exclusive use with standard unbalanced domestic mains supplies, and is consequently only fused in the live side because that is the only safe arrangement. This kind of equipment is inherently unsafe when used with unprotected balanced mains supplies since, if a fault develops and the internal fuse blows, the equipment will still remain live via the 115V still present on the 'neutral' leg — and it will therefore be potentially lethal. In the US the remaining mains voltage would be restricted to about 60V, which is obviously less lethal, although still not a good idea!
To counter these inherent risks, some manufacturers of commercially-available, self-contained balanced mains supply units incorporate individual current balance ('earth leakage' or GFCI) trips on each balanced mains outlet. These will detect fault conditions and isolate both sides of the mains supply to protect both the equipment and the user, and so this kind of device is safe to use with normal single-fused equipment. Some products provide current-balance trips for a group of outlet sockets, and although less convenient, this arrangement is still intrinsically safe.So RCBO's on both outputs would help - very substantially. Many BPS either off them as options or have them as standard. They are only the total fix implied by SOS article if fitted to EACH socket individually, and with an appropriate current rating for the "fuse" (mcb) element - but they are a great big dollop along the way to fixing the problems, and would probably do for me personally, if I felt I wanted balanced mains in the first place. I am a bit wary of the concept of "less lethal". You are either dead or not dead.
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Post by ChrisB on Jan 3, 2016 17:24:00 GMT
Is it not similar to powering a steel cased unit with a manufacturer supplied wall wart? Are these things (the psu) not also built to the same Class ll standards?
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Post by ChrisB on Jan 3, 2016 17:25:40 GMT
You are back on the bone that said you were not going to chew Richard.
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