BMU

[Dr Bunsen Honeydew]

How does the 1kVA version compare with the 5kVA with the Cube Pro head units - apart from the buzzing!?

Cheers. Bill

Already explained in the BBBMU thread. There is little to no advantage and big disadvantage in acoustic noise from the transformer.

[akond_ze_skwak]

The difference is massive, if you don't have one, well then you should, and ahead of all other upgrades.

Planning for the Autumn (...)

So am I, maybe even a little earlier.

Version with Schuko sockets and plug is available, I suppose?

[Dr Bunsen Honeydew]

It is indeed.

[Dr Bunsen Honeydew]

So little understanding, and the confusion created by Pinky (with Muccus support) has spread across the web. Here is a typical email I am getting and my reply.

Hi, I am interested in your balanced mains unit but there doesn't appear to be much information contained on your website in respect of the specification of the unit.

I have read a bit about these and it would appear you need to have a transformer sized well over the demand of the equipment connected to it (some say 3 X the load connected ) not sure how true this is but I have six mono block switched mode power amps rated @ 500w running an active linn system, would your unit be capable of supplying this and has it got the necessary protection on both live and neutral legs in and out to guard against the possibility of live remaining on the neutral side of the supply in the event of a fault.

I have an NVA headphone amplifier which I purchased a few years ago and have been very please with it, I am sure the mains unit will be just as well made and appropriately built to do the job but there is so much misinformation around I thought it better to ask.

Regards

Mike


It is built to Class II double insulated appliance regs so is quite safe as nothing can ever get to the case. It is only Class I metal cased and fused units that need all that gubbins. There is earth continuity through the unit so any voltage drain to earth from either + or – legs on anything connected to it will take out the consumer unit fuse or trip, it doesn’t need a separate one https://en.wikipedia.org/wiki/Appliance_classes

A transformer circuit (which is what a BMU is) is rated in VA (volt/amps) which is a movable feast according to how and why the transformer is made and the parameters the manufacturer sets for HIS VA rating.

VA rating as a specification is not fixed as there are variables. Basically it is what temperature you allow the coils to reach and how long it takes the coils to reach that temp. A conservatively rated 1000va transformer could be rated as 2000va at the point of self destruct, there is that much variation. AND because it is a temperature related spec how the transformer coils are ventilated can make you think you have a better transformer than you really have. It is the thickness and quality of the wire coils and the quality of the winding process that dictate good transformers not some pulled from the air VA figure. On top of that the quality and thickness of the iron or steel plate in the core.

So I have no accurate fixed answer for you, all I can tell you is the transformer is a conservatively rated 1000va by the manufacturer but that is obviously not the whole story. Other manufacturers could rate it at 1500va or at extreme and still be quoting an accepted variance of the spec at 2000va. So pretty pointless question I am afraid.

The reason some people ask is they add up the quoted va ratings of all their systems transformers and say "I need this" which is caused by lack of understanding, well you don't. The NVA BMU will completely effectively supply ANY hi-fi system that is made today, be it valve or transistor.

Paul Messenger has a few thousand VA as well and uses just one of my units for the whole lot.

NVA

[Shuggie]

The mains in my house is a more than a tad 'flat-topped' eg the top and bottom of the sine wave is clipped. Please forgive my ignorance, but what effect would the BMU have on this? I'm presuming that it would still output a similar wave, minus the common mode stuff, but I'm keen to be educated.

[Dr Bunsen Honeydew]

Only AC goes through a transformer and it blocks all DC. What you describe is your mains has a DC element. But you could do this with any transformer and an isolation transformer will do this. Converting mains to balanced does more than this. Single ended is 0v - 240v balanced is -120v - 0v - +120v which = 240v.

Several types of noise and distortion are reduced with the use of these units. The key parameter is the reduction of 'common mode' noise, that is noise and distortion that is equal to both the live and neutral wires on the incoming mains.

BUT by far the main benefit is musical, and I don't and as far as I know no one knows why. As it cant be just removal of noise and distortion from the mains as it does this musical improvement with systems connected to bad mains and near perfect mains, so something else is going on. I have the beginning of a theory based on mains source impedance, but it is little developed yet.

[Shuggie]

Thanks for the explanation. I've been using a PS Audio P5 regenerator which does what it's supposed to, but even though it doesn't use the traditional high power amplifier circuit it still consumes a fair bit of power; however, more critically, there's something not quite right 'musically' with it powering the system. Take the P5 out and the effects of the distorted mains are worse than the 'unmusicality'. I think I'd be mad not to try a BMU - bearing in mind your various travails with courier services, do you allow customer collection?

[Dr Bunsen Honeydew]

Yes. By appointment.

[Shuggie]

I've ordered one from the eBay shop.

[selby]

What are the dimensions of the BMU?

Need to check if it will fit within a unit and would be good to get on the eBay listing and website.