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Post by MartinT on Dec 12, 2015 11:16:42 GMT
NVA BMUThe loan BMU arrived this week and, after removing all the packing, turned out to be smaller than I expected but weighty and very nicely finished. It has a captive power lead (there goes that possibility for experimentation) so I plugged it in and let it settle. I had been warned that it might trip the circuit breaker but nothing happened. There is no mechanical noise or hum emanating from the unit. It has four top mounted outlets and there is my only beef with the design: those 13A modular sockets tend to pop out if a heavy power cable is used at an angle or the cable is inadvertently yanked. I'm not sure if they are the only way in but otherwise I'd be asking to have them more permanently fixed in place.  My first try-out earlier in the week was very interesting. I powered only my Belles power amp from the BMU, being the heaviest current draw and allowing me to switch fairly easily between raw mains, BMU and my P10 regenerator. The P10 is set to high regulation mode, Multiwave mode 6 and 235V output, my usual settings and those that work best for me. I listened in order of Raw -> BMU -> P10 with only the Belles being swapped around. I started with the Belles into raw mains (my mains is quite distorted at around 2.3% with a somewhat triangular waveform and runs high, often at over 250V). It didn't sound as usual but represented a baseline performance level. I had a good listen to three favourite discs and formed a mental image. Next up was the BMU. There was an immediate improvement in structural solidity, tighter and deeper bass (in reality, bass that was better resolved). Because the presentation was cleaner, the whole sound improved but in all my notes it was the bass that improved the most. For a £5.2k amp to respond so well to a £500 BMU was certainly impressive and was a no-brainer for those without any mains treatment in their system. Next I plugged it back into the P10. Now the sound took on all of the strengths of the BMU but there was far more resolution of fine detail, greater dynamics and overall even greater potency from the bass end of the spectrum. I did try the whole CD replay system into the BMU, and the differences I had already observed remained, only more pronounced. Much shuffling around pretty much confirmed the early ranking order and that the BMU is considerably better than raw mains, but not up to a serious regenerator. Quite as it should be, really. Let's remember in all this that we are comparing a £500 BMU with a £4500 regenerator, a not inconsiderable price difference. I have been saying how good regenerators are, but they are undoubtedly not cheap. In that regard, the BMU is a relative bargain and should be tried out by anyone with no mains treatment who wants to start significantly improving their system sound quality.
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Post by MartinT on Dec 12, 2015 11:23:13 GMT
Would all members who either own a BMU or have loaned one please add their findings to this thread? Thanks.
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Post by ChrisB on Dec 12, 2015 11:26:04 GMT
The think the fixed mains cable is a bonus rather than a setback myself, but there you go!
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Post by zippy on Dec 12, 2015 11:26:47 GMT
I'd be interested to hear a like-for-like pricewise comparison - e.g. BMU versus AG1500.
Is the P10 worth £4500 more than the BMU ? It's a big price jump.
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Post by MartinT on Dec 12, 2015 11:43:02 GMT
Is the P10 worth £4500 more than the BMU ? It's a big price jump. It's an irrelevant question to me, as I'll buy the best I can afford. If I couldn't have afforded a P10, then I would look seriously at a BMU. |
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Post by Deleted on Dec 12, 2015 12:02:30 GMT
I'm not going to be in the market for a BMU anyway, but I'd have been far less put off if the sockets had been on the back or even side rather than the top. I can't bear wires sprawling all over and I can imagine it looking the the Medusa when it's connected up. Pity, because the case is very attractive, as are all NVA IMO. Anyone else put off by this aspect or is it just me being OCD?
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Post by ChrisB on Dec 12, 2015 12:11:38 GMT
I think it might make it a little more tricky to accommodate in some installations.
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Post by accudazed on Dec 12, 2015 12:31:41 GMT
Thanks Martin for your really helpful test. I have terrible mains power issues where I live; big housing area near a large industrial estate. The effects are so bad sometimes I switch to listening to one of my cheaper CD players. Why use the Ayon's valves when the crappy mains supply negates any of the machine's benefits over cheaper CD players? The cheaper machines sound pretty lousy too when the mains supply is just not up to it. At midnight during the summer is when my hifi sounds at its best! Not conducive to good family relations though...
The BMU sounds like a real bargain and heaven knows, the world of hifi needs more of those!
How about doing the test blind? I'm not saying for a minute that I don't trust or doubt your judgement. Doing it blind adds another useful angle to your really helpful test.
I've tried my own blind tests for a bit of fun really and found it a bit of an eye or, is it 'ear' opener?! Apart from the tension caused by not knowing what I was listening too and of course my 'judgement' was on trial - well, that's my excuse(!) - I noticed that the gaps between equipment seemed to close...
Regards,
Steve
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Post by Deleted on Dec 12, 2015 12:31:51 GMT
Even having all 4 sockets At the rear of the top plate and facing the rear would help. I'm sure the internals will likely limit such things, but the idea of mains cables sprawling out of it in different directions is a real spoiler for me.
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Post by dsjr on Dec 12, 2015 16:55:01 GMT
I bought mine, so may I post a user comment - I have no dealings with making these AT ALL and still don't know how they're wired internally!
Mine came straight from (AOS mod) Macca. The box was opened as the BMU was in free movement and the Doc was concerned it might have been damaged or the transformer come adrift - it wasn't and it was the original loaner unit so not as heavily doped and stuck inside. The captive mains cable is far heavier gauge than the usual cables NVA use, but the current capacity of the cable should be more than enough for a full system to be wired through it with no degradation.
As an aside, the whole reason for sticking the sockets in place is due to the Class 2 regs, which Pinky got his knickers twisted over some time ago. NO metal parts outside to risk a shock from, even screw fixings, although if the sockets come away with fancy over-heavy mains cables, then fair enough - more and stronger glue please Doc 
Next point - yep, the thing is a bit bulky, but I solved it by putting it on its side with the exiting mains cable to the rear. No issues for me, but others with it on show may possibly feel differently about it.
Noise? The humungous one the Doc made for himself was awful, so the one huge transformer was removed and smaller one fitted instead (edit - I thought it was two smaller trannies, but apparently it's just the one) and the result in his room is silence. My own has less doping, being an early one, and it does hum gently, usually late at night surprisingly, but it's pretty well quiet during the day. My workroom PC is on much of the day as I use it for playing sound files via Foobar and the fan noise drowns out anything else, although these fans are vari-speed types.
As for sonics, all I can say is that the audio performance of the system connected to it doesn't seem to change 'cosmetically' or 'tonally' at all, but what I hear - and the TIS interconnect does this too - is improved subtlety in the WAY a singer sings a song, or a player plays their musical instrument. None of the workroom speakers I've used this year (LS5/9, Diamond IV and IMF Compact) have deep powerful bass, so I can't comment on bass reproduction as such, except to say that this greater 'freedom of expression' is very much there and appreciated by this listener anyway 
I hope the comments above can e taken as pretty well impartial in this particular instance. I didn't have to buy the thing, but using the setup without it gave me withdrawal symptoms, even with the mid-range amps and speakers I use and low cost sources, so I had to buy it rather than return it.
This is how I use mine, although it's been relocated and the wires from the numerous external drives nearby have gone as a larger single drive is used instead.
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Post by John on Dec 12, 2015 16:58:56 GMT
Good results and looks like a bargain in terms of SQ to cost ratio
I am looking to hearing what it do in my system
I have spent a lot on mains over the years and no longer feel like I have worked hard on eliminating mains issues so be a good test to see how far I traveled. IF it makes a reasonable difference I probably go for one.
I have used balanced mains in the past with good results but having the home rewire I found I did not really need one so really interested if this has changed
I have no issues with where the sockets are
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Post by gazjam on Dec 12, 2015 17:46:19 GMT
Would all members who either own a BMU or have loaned one please add their findings to this thread? Thanks. Big fan of BMU's, had mine in for a couple of years now. Never looked back, improvements across the board with the noise floor dropping away to practically nothing. Makes the best of the kit you have imo. Lengthy post of mine over on AOS when I fitted mine: theartofsound.net/forum/showthread.php?26471-Balanced-Mains-Transformer-WOW!-Hardwired-Installation-log-%28Pic-Heavy!%29&highlight=balanced+mains I'll be rewiring mine soon actually, have some rather good solid core French mains cable on a reccy from Marco which I'll be using to rewire the entire setup, from the CU to the BMU, through to the hydra feeding all my kit and on to IEC's feeding the kit. The idea being to have the same (good quality) cable throughout. At the moment I have various types and lengths of mains cables which annoys my audiophilia nervosa, as well as probably not being ideal sound quality wise. Back of my rack is a bit of a nightmare so rewire being done as part of a big tidy up. |
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Post by Eduardo Wobblechops on Dec 12, 2015 20:21:23 GMT
Yep, still remember what a big improvement it was when I brought my home built unit over to yours Gary, was like an entirely different system.
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Post by dsjr on Dec 12, 2015 21:23:46 GMT
Gaz - Are you sure a solid core mains cable is safe, as it could kink and snap, with possible disastrous results? That's the reason why domestic mains cables are stranded I believe - the solid core house wiring is fixed in position behind plaster or away from any human interference.
Please check it's legal and safe to use such stuff in your listening room (house insurance), that's all. In fact, the whole BMU technique should render mains cable differences much more irrelevant I hope.
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Post by Sovereign on Dec 13, 2015 2:53:40 GMT
Very interesting thread !
I think I should start off by saying to be able to buy any piece of high quality hi-fi equipment with this kind of looks , fit and finish and performance offered for £500 delivered, it has got to be the bargain of the decade, and if anyone is thinking about upgrading theere mains this would be £500 extremely well spent. As far as I understand NVA will tweak and custom the placement of sockets to fit although I may be wrong . Especially as NVA offer a complete money back guarantee should you not be satisfied.
In the last 10 years I have made maybe nine different types of balanced mains Transformers, I have also owned the power inspired 1500 regenerator . I must state that I have no real engineering or safety knowledge in this department at all but I do like to make things and mains power has all the always fascinated me,
Without going into too much detail, there was a difference between the AG1500 regenerator, and a basic balanced BMU that I had at the time. The balance of power supply gave more low-end information delivered thrust and a greater tonal quality to the music, taking away some of the background noise and just allowing a really good and well balanced sound to come through. However I noticed the AG 1500 regenerator perhaps allowed a cleaner sound with more fine separation and fine detail to the sound. I ran both the regenerator and the balance power supply together for about a year and there was a good accumulative effect, however I can't remember why but I needed some cash so I sold my balance of power supply and re-generator and when money became available I just made myself a huge balance powersupply and didn't bother with the regenerator in the end . But this new balanced Power supply I wanted to be the last one that I built so I was looking to make a real reference product and be done with it
Initially I would buy my balanced toroial transformers from Airlink but I always found that they hummed because they were not designed particularly well nor was the quality of the components that they used, so I began to look for other suppliers I was ideally looking for a company I could sit down and talk with and learn from . I found this out by speaking with a small local accompany that airlinkoutsource to, and Airlinks component list wasn't that great , after then I found a very small company who makes all the transformers themselves and we sat down together and they tried to design the best balanced toroidal for the purpose I was wanting to use it for. In the end we ended up making 3kVA balanced toroidial with the 5kVA iron core. It's a big mother in in the end I called the whole power supply the MTBPS (Mother Trucker Balanced Power Supply) because it is huge, i've got to say despite its size it sits there powered on and is as near quiet as a mouse. There are other design features to it which help this but as it's nearly 3 o'clock in the morning I can't be bothered to rack my brain for the individual design criteria, again this is not my design or knowledge or experience it is that of others who have been making to toroidals for 40 years. I have larger threads in more detail on the build on art of sound and audio chews.
In making the MTBPS I tried adding soft start circuits so it doesn't blow the house consumer unit , switches and DC blockers made by Nick Gorham. I haven't used 13 amp sockets on mine but rather 15 amp power con connectors they are all in a straight line on the back. This is then hardwired to the consumer unit dedicated for my hi-fi . I did find the use of an Nick Gorham DC blocker to be stunning in use, everything in my brain told me it wouldn't work and "it would kill The music, or lesson and squash the sound but it had the exact opposite affect, the DC blocker is still in use today in the MTBPS
That's me done and settled on balance of power now , I think I have tried every combination and trick in the book , The chap that made my final mother trucker I got him to try all sorts of weird things that I was reading about but none of them beat his original design , we used toroidals from 1kVA straight up to 5 kVA. And settled on one I use now.
I would love to compare my MTBPS with the NVA BMU, I have no idea what difference that will make, likewise with Martin's P 10 regenerator.
Happy experimenting !
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Post by John on Dec 13, 2015 6:14:01 GMT
Interesting post James and great to see you posting Hope the treatment going well and close to the end of the treatment
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Post by ChrisB on Dec 13, 2015 7:12:33 GMT
Thanks for that James. Very interesting.
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Post by ChrisB on Dec 13, 2015 7:23:34 GMT
Given that this device has 4 sockets and some people have big systems, what would be the best way of using it?
For example, I have 2 power amps, a pre, 2 turntables, a phono stage, a cd player, tuner, reel:reel......
Which types of component will benefit most (and which the least) from being plugged into it? Will plugging a 6 way extension block into one of the sockets be the way to go?
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Post by gazjam on Dec 13, 2015 10:43:41 GMT
Gaz - Are you sure a solid core mains cable is safe, as it could kink and snap, with possible disastrous results? That's the reason why domestic mains cables are stranded I believe - the solid core house wiring is fixed in position behind plaster or away from any human interference. Please check it's legal and safe to use such stuff in your listening room (house insurance), that's all. In fact, the whole BMU technique should render mains cable differences much more irrelevant I hope. Dave, A fair point and I hear what your saying. I'll be consulting a spark on this as well as speaking with Marco, who has plumbed this cable in already. As the solid core cable will be fit once and forgotten about, I'll be clamping it in place once all the layout and lengths have been worked out. I'm sure there's regs in place that say it has to be clamped every "x" distance along its length or something. Safety first. Part of the reason I'm doing it, apart from hearing first hand the difference a good mains cable can make in my own system, is that knowing the kit is all rigged up with the same cable, hardwired where possible, with no mess of wires and everything wired up as efficiently as possible I can "put to bed" the mains feeding my hifi, knowing that its "done". Thanks for the comment mate, a good point. |
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Post by MartinT on Dec 13, 2015 11:00:38 GMT
I would say that the key item is the power amp. If you have to lead off from the BMU, use a very high quality multiway strip for the lower power ancillaries and never have anything unused for the session plugged in.
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