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Post by tony on Jan 3, 2016 17:26:35 GMT
A couple of years ago we had a wee Scottish bakeoff at Garys place. There was a power regenarator Brian had brought along and a BMU Ali had built from scratch that needed two people to carry. Garys mains wasnt too bad so we werent expecting much but were keen to learn.
The power regenerator went in first and made a noticeable improvement, lowering the noise floor and letting more detail through.
When Ali plumbed in his BMU we all sat with mouths agog!!! After much head scratching and patient explanation by Ali we all came to the conclusion that mains treatment really can make significant improvements to the sound.
I went home and ordered an Airlink BMU after a quick call to Ali to make sure what size would do the business.
The BMU stays in my system supplying whatever I have on the mains. A very cost effective upgrade to any system that once bought can stay with you on the long haul.
Thats my tuppence worth -usual caveat my ears/room/equipment/music.
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Post by Deleted on Jan 3, 2016 17:27:00 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? You have dropped the input considerably away from mains voltage/current by doing that. The wall wart is normally designed to Class II.
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Post by Deleted on Jan 3, 2016 17:35:19 GMT
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Post by ChrisB on Jan 3, 2016 17:43:05 GMT
I thought that's exactly what I did say:
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Post by pinkie on Jan 3, 2016 17:43:31 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. Kevin The issue is not what electrical class the balanced unit is. The issue is "what electricity does the connected appliance see"? Lets make it specific - reference the SOS article I linked to - "what electricity does my Quad 405-2 see when it is plugged into balanced mains?" And "what electricity does it expect to see"? To help, the following is taken from page 8 of the instruction manual FusesThe main fuse is 2.5amp surge resisting (2.5AT) type for 200-250v volt supplies while a 5 amp surge resisting (5AT) fuse is required when operating 100 -125v supplies. That one fuse whose value is dependant on the voltage seen, is present only on the brown wire coming into the unit. Where in the instruction book does it anticipate 115v on each of 2 legs? Again, see the SOS article "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" I see no reference to a distinction between class II and class I equipment in the term "virtually all commercially available electrical equipment" And the point is completely irrelevant in the case of RCD protection. Again - I don't want to make it sound like using one of these devices is like having a bomb in the house - just that it "spoils" a safety measure which is thought to be helpful - namely an RCD on the main consumer unit. If your dog chews through the wire of your class 2 device and that device is plugged into the wall socket at my house, the RCD will blow and the dog will carry on leaving hairs all over the carpet. If the dog chews through the same wire coming out of a BPS unprotected by RCD's on the output - that dog will be buried or cremated depending on the owners preferences, with the bonus of no more hairs on the carpet Of course, if the dog chews through the wire in a house with old wiring which does not have an RCD on the consumer unit its dead too, regardless of whether you used a BPS or not. The RCD is an ***optional new safety device. It seems a shame to bypass it My house in France has 2 circuits each protected by their own RCD and MCB, as well as mcb's on each of about 30 radial circuits. So the French seem to think RCD's are a good idea too. Note - that wire the dog chewed through doesnt care if it is connecting to a class II or a class I device. It still carries a voltage on it (or 2 voltages if plugged into a BPS) ***optional is probably not the right term now they are a requirement of current wiring regs. Perhaps supplementary would be a better term
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Post by pinkie on Jan 3, 2016 17:44:53 GMT
You are back on the bone that said you were not going to chew Richard. That's both true and fair, although in true playground style I would point out "DSJR started it". I'll stop. Unless asked again
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Post by pinkie on Jan 3, 2016 17:46:43 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? You did ask! No - they only output a low voltage, not 2x 115v. And you can't plug a hairdryer into them if you try to. So not the same.
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Post by ChrisB on Jan 3, 2016 17:50:35 GMT
You are back on the bone that said you were not going to chew Richard. I'll stop. I like that part of your post
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Post by Deleted on Jan 3, 2016 17:51:42 GMT
I was thinking of a component failure, as I really can't remember the last time I witnessed a chewed through/broken mains cable. Where I was going wrong is that I don't have a dog.
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Post by dsjr on Jan 3, 2016 17:54:37 GMT
As you know, I'm not qualified, other than to pass on that the Doc has had a couple of issues with gear plugged into his own BMU and even had a transformer fail. In every case, the rcu tripped out! 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 AlanS on Jan 3, 2016 17:54:39 GMT
With regard to the concern by Pinkie and others about earthing. If whoever has the unit at the moment or whoever gets it next has a multimeter it cannot be onerous to measure between the plug earth and one or all of the sockets for zero resistance or open circuit. Zero resistance move on to the next concern.
Do I have to explain further?
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Post by pinkie on Jan 3, 2016 18:04:55 GMT
I like that part of your post That's fine. In all the excitement did I miss somebody resolving the conflict between the claim that a balanced connection could "clean the mains" and the fact that we have established that a balanced connection cannot clean the mains?
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Post by MartinT on Jan 3, 2016 18:11:09 GMT
In all the excitement did I miss somebody resolving the conflict between the claim that a balanced connection could "clean the mains" and the fact that we have established that a balanced connection cannot clean the mains? No. What you missed was a "BMU could clean the mains to a certain extent". I'm not sure anyone ever claimed that a balanced connection could do that. This is the second time I've had to clarify.
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Post by pinkie on Jan 3, 2016 18:13:24 GMT
With regard to the concern by Pinkie and others about earthing. If whoever has the unit at the moment or whoever gets it next has a multimeter it cannot be onerous to measure between the plug earth and one or all of the sockets for zero resistance or open circuit. Zero resistance move on to the next concern. Do I have to explain further? Sadly the wrong test and misses the point. I'll only expand on that if specifically asked to .
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Post by pinkie on Jan 3, 2016 18:17:40 GMT
In all the excitement did I miss somebody resolving the conflict between the claim that a balanced connection could "clean the mains" and the fact that we have established that a balanced connection cannot clean the mains? No. What you missed was a "BMU could clean the mains to a certain extent". I'm not sure anyone ever claimed that a balanced connection could do that. This is the second time I've had to clarify. I was referencing the wording used when it was first introduced. I don't think that comment addresses the point. Are you saying "the claim in the post that a BMU cleans the mains by virtue of its balanced connection in the manner described was wrong, but its still does nice things to the sound and MIGHT clean the mains" (I assume you have no direct evidence that it does - you could look at those "before" waveforms on your regenerator plugged into the wall and compare them with "before" waveforms plugged into a BMU ). I suppose it depends on your definition of "clean" and where you think the noise is going. I think that was the point Jez was focussing on. It is a pity he couldn't have shared his technical knowledge without offending people, cos he sure knew what he was talking about.
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Post by MartinT on Jan 3, 2016 18:52:16 GMT
I've said what I wanted to say, Richard.
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Post by Eduardo Wobblechops on Jan 3, 2016 19:47:31 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? Yes, but you are generally only talking about 12-15v. Not a dangerous voltage.
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Post by Eduardo Wobblechops on Jan 3, 2016 19:54:51 GMT
With regard to the concern by Pinkie and others about earthing. If whoever has the unit at the moment or whoever gets it next has a multimeter it cannot be onerous to measure between the plug earth and one or all of the sockets for zero resistance or open circuit. Zero resistance move on to the next concern. Do I have to explain further? I may be wrong on this, but I don't think the unit in question has a through earth?
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Post by dsjr on Jan 3, 2016 20:53:41 GMT
YES IT BLOODY WELL DOES!!!!!! At great inconvenience, I struggled to get to the mains socket the BMU is plugged into (it's partly obscured by the PC workstation and pulled out the PC mains plug instead Anyway, I completely disconnected the BMU and tested for earth continuity from sockets to mains plug - perfect earth continuity on my meter!!!
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Post by MartinT on Jan 3, 2016 20:59:21 GMT
It would have to be, otherwise your kit could sit at an undefined potential.
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