Balanced Mains Units are used extensively in professional studios and are starting to make their mark in domestic audio situations. Janine Elliot gets her life in balance and plugs in the Russ Andrews BMU 3000 costing £3599.
Reviewing cables, mains conditioners and balanced mains units is bound to irk some hifi addicts, particularly engineers. I, like most reviewers, have suffered the displeasure of the few who believe all wire sounds the same and that travelling past your local Homebase for mains taming devices is quite simply a waste of money and petrol. Luckily my ears, like I’m sure yours, can perceive the finite differences in sounds between cabling to see that there is more to creating a good audio set up than tons of flashy lights and chrome knobs. So, to be asked to review the Russ Andrews Balanced Mains Unit coming in at 100 pennies short of £3600 is probably going to cause a few swear words from a few non-believers.
Russ Andrews (and me, too) has had his name bounded about internet forum sites enough over the years to take it all in his stride, as he – like I – can hear for himself just how effective products like these are in controlling and ultimately upgrading your hifi. And that is it; these heavyweight (23.4kg) boxes don’t profess to do anything other than feed you pure mains. Yes, the mains supply travels numerous miles to get to your house, so why should the last few feet matter at all? Well, quite simply the last few feet make the most difference because of interference from your freezer and hair drier, and God forbid, those of you pushing audio, wi-fi or HDMI around their 13A mains sockets. Whilst you can use mains conditioner to remove RFI’s and EMIs, they are really like Paracetamol; they make something painful a little bit more manageable, but only when you are able to actually replace that defective liver or kidney, will all things be totally well again. And that’s what the Balanced Mains Unit does. For this reason, professional recording studios around the world use balanced power supplies to ensure the purest starting point for their music, speech or video.
In its simplest form, normal mains is single ended, with around 230V at the live terminal and 0V at the neutral. By changing to a balanced unit you can split the 230V mains signal into two halves, putting +115V on the live and -115V in the neutral. These add up to 230V, but any noise or distortion in the mains will have appeared in both legs and will be cancelled out when joined together, similar to the process used in noise cancelling headphones.
The BMU3000 is like the BMU1000 I reviewed a while ago, which I hinted then that whilst being an effective upgrade for your hifi, was limited in only having two 13A sockets. Daisy chaining extension leads will only undo any good you have done. This unit therefore has five, which should furnish all your hifi needs. With two separate 1500V ‘SuperSilent’ transformers; one for two and the other for three UK or Euro (Schuko) UltraSockets giving a total of 3KVA of power across the five sockets, this should be more than enough for most people. Each transformer is individually wound on a silicon steel core and all is wired internally with Kimber Kable, obviously.
This heavyweight is actually very good looking and looks petit considering what is inside, and it even comes in a plastic suitcase to protect it all in transit, which you can then use when you go to off to Menorca. It does require a 16A IEC socket to use it, as opposed to a conventional 13A ‘kettle lead’, and so a PowerKord 300 was kindly packaged for my review.
This unit is in many ways identical to the BMU1000. You can adjust the unit to your incoming voltage without the need for meters, simply by listening to any “hum” caused by mismatching of input to output voltage. The unit comes as standard at 225V but this can be adjusted in small increments with TAP connections inside the unit. The brown live cable is connected to a grey/white cable, and can be reconnected to purple, black or yellow tappings on the secondary for 240V, 250 or 260V respectively. At the default 225V setting I found it was too noisy, though this reduced when I set up as 240V. The process for doing this is fairly simple though does mean undoing 12 Phillips screws and pulling out the right-hand ABS plastic top panel. The unit comes supplied with the live brown connector connected to the white/grey cables, so, with the unit switched off and unplugged I swapped the white/grey leads for the purple. This didn’t totally reduce the humming but brought it to an acceptable level, especially when I placed a heavy rubber mat on top of the unit. Whilst I love the ease of access to the top by removing the ABS panel – and they are held fairly tightly in place – they still do vibrate and so it will be a good idea to put something on the top to catch that sympathetic vibration. ABS is chosen by Russ not to keep the weight down, but due to him and his team finding that it gave a better sound quality than metal boxes. I have always been confused about whether there should be any form of metal Faraday cage to prevent further EMIs in a balanced MU, or indeed whether there was any point, it being self-cancelling. Russ agrees, and the team having done extensive testing on this. The “SuperSilent” transformers are particularly well made with very few stray fields. It actually sounds better without any cage or foil, which is why there’s isn’t one.
“We’ve long been fans of the use of non-metallic boxes for equipment – in terms of sound quality, subjectively the sound becomes more open and spacious, and metal casework sounds rather ‘closed-in’ in comparison.”
Russ therefore chose ABS and I measured no EMIs. After setting the unit voltage correctly there were still quiet hum noises, but these are due to several reasons. Firstly, any object with wire, metal, current and magnetic field is going to act like a speaker. Also, I mentioned in the BMU1000 review that some hum is caused by the fact that the core laminations in the transformer are extending and contracting as they are magnetised, called Magnetostriction, and that this will happen twice in each 50Hz UK current cycle giving a gentle 100Hz hum. Getting the correct voltage reduces this, though there is still a minute amount of residual hum, but importantly it was considerably reduced further with damping of the cabinet. Placing the unit on a solid base or rack, preferably not of glass, and also placing the unit on more generous rubber feet will absorb any of the vibration from the rack and other audio equipment. Plus, if your hifi has good power supply stages, it almost totally disappears. The unit will look great in the lowest part of a rack with the mains leads from hifi equipment being fed neatly into it from above and this, too, will aid in reducing induction between cables and more important to audio cables close by. But, if the unit is on the rack it is therefore essential that you spend all the time to set it up correctly. For example, the 8 rubber feet on the BMU3000 are less deep than the lower lip of the front Aluminium faceplate, so if you sit the unit faceplate within the shelf, you need to use bigger feet. In my case I used four 30kg strength rubber semi-circular pods. Also it would perhaps have been better, bearing in mind the anorexic feet, that the 13A IEC sockets were designed fitted upside down, since they would be fed from your components above. Having them with the earth ‘pin’ at the top means the cable exiting the inserted mains plugs is bent around tightly and can touch the shelf, and can therefore act as a carrier of vibration from the BMU. In an ideal world you should in any case place the unit away from your rack and hifi, though looking as good as it does you might be tempted not to.
Once I set up the review sample on my own pods all was good and I had no worries about the noise, nor did I need to add my own mains conditioners. Indeed, should you really, really feel the need to add a RA or other mains conditioner – Russ recommends you don’t use any, even though he makes a number of them – then you should only use them before the BMU3000. Also, the unit is fitted with an internal and resettable thermal breaker on each of the transformers. If the unit trips, then you need to unplug everything, get out a Phillips or Pozidrive screwdriver and unscrew 12 screws from the back panel to get inside the unit and reset it. I still wish a thermal breaker unit could be fitted to the rear of the box.
With its twin 15000VA transformers, totalling the 3kVA for the five sockets, I had no fears in winding up my power thirsty Krell power amp and connecting the multi power supply equipped KPS20i CD player. Wow, I always thought the KSP20i was one of the best ever CD players, and still very analogue and musical playback, particularly in the bass, but connected to the BMU3000 showed me why I needed to have a balanced life. The extra detail, speed and most important, the extra bandwidth of sound particularly at the top end was quite extraordinary. The difference between this and the 1000VA version was really evident in my power-thirsty American kit. Where a lower specified unit could cause the audio to sound a bit compressed or even to add mechanical noise, this was like an over-specified engine in a car; there was always something in reserve when you needed it. Playing vinyl the result hinted at better speed accuracy and an increased excitement and improved timing. Everything was tight, controlled, and exact. Interestingly, whilst the sound was more clinical and flatter, the lowest-frequency pedal organ notes when playing Saint-Saens Organ Symphony (Jane Parker-Smith, LPO, Serge Baudo) through my Wilson Benesch Torus subsonic generator as indicated by 2 blue flashing lights was greater through the BMU than solely through my own designed mains conditioner which showed just one blue light, but which appeared to have the greater lower bass. The BMU quite simply made the sound clearer and more accurate. And then, connecting up my old Quad 303/33 wired up to my aged iconic Chartwell LS3/5a’s for use in reviewing the new Graham Audio Chartwell LS3/5 I couldn’t believe just how deep that bass could get.
So, would I recommend the BMU3000? Well, it’s a bit like choosing between Sainsbury’s Basics custard or Birds. Whilst both will work well with mum’s apple pie, the latter taste better and has more goodness. But it is more expensive. Ouch. So it is too with the BMU3000. Yes, some engineers and non-believers will suggest going to the local DIY or electrical store, and yes, you will get a knockdown price and it’ll be okay. Most likely the internal engineering won’t be so exact, the amount of effort put into its design and suitability for audio/visual probably won’t have been in the forefront of its build, and – for me very important – it won’t look so drop dead beautiful in its rack-friendly 10mm thick anodised aluminium front panelled box. Perhaps their 13Amp sockets won’t be as classy as the five SuperSilent’s, but most importantly the cabling and cores probably won’t be as good, and there is an awful lot of wiring in these toroidals. Each of the two transformers within the unit use 77m of wire on the primary and a total of 80m of wire on the secondary. That all adds up to a total of 314 metres, meaning the BMU3000 costs just over £11 per metre, which in context actually isn’t an awful lot. As Russ explained to me;
“The wire is carefully chosen for its performance – the primary wire, for example, is of a type that allows 11% increased density than conventional wire, leading to better performance and a quieter operation. The secondary wire consists of two trifilar wires (ie six in total), again chosen specifically for its performance”
I liked the BMU3000 more than I thought I would. The amount of extra information, precision, depth of sound and frequency extension at the extremes that I got from my kit was audible, and should be considered as a very cost effective upgrade for all your kit. If you are spending a lot on your hifi, that probably means your cables as well, so it should also include your mains taming. But, if you still are sceptical, buy one from Uncle Russ and if you still aren’t impressed he gives a money-back guarantee.
Build Quality: High quality build throughout but would have preferred better and more substantial feet
Sound Quality: A significant improvement with more detail, speed and bandwidth in evidence
Value For Money: Not cheap but then not cheap to build
Speed and detail of sound
Lower noise floor and a cleaner sound
Excellent components including mains sockets and wiring
The best looking mains adapter
Some will still need converting to the benefits