HiFi Subjectivist ¦ Audio Forum ¦ NVA User Group

I’ve decided to purchase an NVA BMU (balanced mains unit)

A key point in the review, I feel.

Daniel Quinn wrote:Good review with no hyperbole. Just missing the 30 day try or return sentence.

Lots of detail about me and NVA is wrong, especially the history. The real history - Tresham started in 1978 called PA:CE Studio Ltd with me running it. I bought it away from them in 1980 and the name changed to Tresham Audio. Sold to Tannoy 1982. The far eastern currency crisis in 1997 meant I had to reduce size as 80% went export to the far east - 2000 got finally fed up with the industry and by then was spending more time teaching Tai-Chi, so closed it and put it in storage - 2005 Nadia was nagging me to get rid of stuff blocking up our house (it had came out of storage) so signed up at ebay and finished and repaired old stuff and sold it - Orders kept coming in so I had to start building new again, starting with cables, and it sort of grew from that. I was happy to start again as dealing direct was MUCH better than trying to deal with retailers and the market!

I knew it was going to be a small review and I am very happy with it. I hate over the top FOTM reviews, and this is just like one of your ones, basically "I liked it so I bought it".

If I didn't have a UPS/Regenerator I would be tempted myself. My mains isn't poor but the super cables made sod all difference however modifying the mains wave shape to a consistent sine wave and steady voltage made the system seem smoother. I don't have loads of gadgets to introduce crap and the SMPS I have do not ruin the sound.

If you do get clicks, pops and buzzes well worth trying.

Different thing altogether alfer, I've got both! The regenerator cleans and quietens the mains the BMU, something else entirely.

Well I have largely given up on promoting it as a mains filter or purifier, pops and clicks are not what it is about. I am not even sure it is functioning that way. It is very simple it is a box that makes the musical window on any system cleaner and more enjoyable. Five or six out there so far and all customers agree, apart from the loan prototype at Maccas and he is still unsure if it is worth it.

It did nothing to quieten my noisy mains at all, hence why I got the regenerator back in place. Funnily enough though, without the BMU the regenerator made an audible difference to the sound but with the BMU I can't tell the difference, (sound wise), with or without. The AG1500 is purely there to keep things mechanically quiet.

In my experience the BMU and AG500 do something very different. The AG500 (yes NOT a 1500) made things sound harder or shriller, it was sidelined after a few weeks. The BMU cleans things up for me - removes a sort of audio mush that I didn't really notice until it's was gone - and continues to do that.

I keep getting email questions about the BMU that are hard to answer accurately, and it shows the lack of knowledge that they are being asked in the first place. So I will direct people to this answer.

QUESTION

Hi Richard, I couldn't see in your advert how many watts the balanced mains supply is rated at (230V), and is it equally distributed across the four outlet sockets? Is the inlet an IEC socket, or captive lead? What are the dimensions of the unit, and does it require 'ventilation' room? Is the transformer silent?

Regards Alan

ANSWER

It has a captive lead because it has to legally as it is Class II appliance construction.

It requires no special ventilation.

A transformer circuit (which is what BMU is) is rate 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.

The full capability of the BMU can go to one or all the sockets, they are all in parallel.

Happy New Year to you all!

Richard, in a discussion with MartinT on TAS he mentioned that he'd still be intrigued to trial the BMU. Is this still possible, or has too much water gone under the bridge?

Cheers. Bill

He re-instates my membership and then I will talk to him about it.