CONNECTED FIDELITY AC-2K BALANCED POWER UNIT REVIEW

Connected-Fidelity AC-2K Balanced Power unit costs just shy of £2000. Ken Stokes plugs it into his system to report back for HiFi Pig.

When I was first asked if I’d like to review this Connected-Fidelity AC-2K mains balance unit I leaped at the chance. I’ve wanted to try mains balancing for some time and this was that chance! I know balanced mains units, in fact, almost any kind of mains filtering or conditioning has critics, however, I know of people who use mains balancing, mains regeneration, and countless other types of mains conditioning and many swear by the effectiveness of these products. I’ve tried a few myself and some I liked, some not so much. Mains balancing was something new for me and my rig. I’d heard mains balancing units in use before at shows of course, but not on my system and nor with a chance to conduct any comparative listening tests.

I already have a basic mains conditioning unit in my system – overload cut out to protect my kit from any mains surges and it incorporates some filtering, but the unit I have is very basic. The unit from Connected-Fidelity is, I know, something different from anything I’d had the opportunity to try before. I was pleased to discover on chatting with Michael Osborn at Connected-Fidelity that I could use this unit in conjunction with the unit I already have. In fact, it really is a simple inline box that plugs via an IEC type mains lead (not supplied) directly to your wall socket and with a three-pin gold plated output socket for UK users to your normal mains plugboard (alternative sockets are available for overseas users). All I needed to do was plug this into my wall socket with a plug-in mains lead and transfer my lead from my existing plug board/conditioning unit from the wall socket into the back of the AC-2K. Simple!

I was very intrigued by what a Balanced Mains Unit (BMU) might do and I was aware that these types of units can, in some cases, generate significant transformer noise. Given that this unit has a very substantial transformer weighing in at approaching somewhere close to 14kg I was concerned about the possibility of intrusive noise or hum. I was reassured that the Connected-Fidelity BMU is made specifically to sit close to domestic HiFi units within the listening space and I was assured ‘hum’/transformer noise should not be an issue due to the inclusion of substantial isolation inside the units.

It was agreed that in order to get a unit out to me as fast as possible, a pre-production unit would be dispatched. This pre-production unit was to be identical to the available production units in every respect except for some elements that had no bearing on function; graphics, the location of an on/off switch, and a lack of transit bolts (See comments at the end of this review)

CONSTRUCTION

When this Connected-Fidelity BMU arrived it was extremely well packaged in double cardboard boxes and substantial hard foam packaging, given that these units weigh in at a substantial, almost 14kg, good packing is clearly a must! I was pleased that when I opened it nothing was damaged and the packaging was very reassuring.

So what is in the box? To be fair there isn’t a huge amount to see, but you do get a well-made, solid black case with a polished aluminium front faceplate (I’m told that a black front faceplate may be a future option), a small LCD front display that offers outgoing voltage readout in red (can be turned off) and at the back are high-quality incoming and outgoing sockets (again options are available for overseas and for additional output sockets). The unit has some good-quality feet underneath.

These units are essentially very simple plug-and-play devices and it takes literally a few seconds to set up. I initially plugged in and sat the unit alongside my rig, next to my wall socket.

I placed the unit on an old wooden board as a plinth, mainly to match my other units. I was a little disappointed at first to discover I could hear hum from the unit, not outrageously loud, but just audible. However, I solved this issue very quickly once I realised the issue had more to do with the wooden plinth/board I was using that was vibrating. Simply adding some old Sorbothane pads under the unit solved the issue 100% for me. I did note that stood on the carpet this unit was also absolutely silent. These units run cold so placement on the carpet should not be an issue. I only mention this cautionary comment regarding hum purely as advice to bear in mind should this be an issue for any readers, additional isolation or a small carpet pad should easily rectify. I should also add that the transformer inside the case is extremely well isolated, held on a separate metal plate that is acoustically isolated from the unit casework, any issues should really be rare.

Normally with our mains supply, we have a “live” wire and a “neutral” wire, both of which carry the current with the neutral wire earthed at the source, plus an earth wire – the three wires we see when we wire a plug. The BMU has two outputs of 115v (total 230V) that are out of phase – essentially two live wires but out of phase with each other which are earthed. The live and neutral lines are essentially “partially” isolated which reduces DC entering the chain and potentially causing audible issues. Look, I’m no electrical engineer and if you want to get into the whole “what is it?” then Google is your friend. However, the Connected Fidelity unit is basically a 2.0Kva mains transformer in a damped non-magnetic case with surge protection that is taken out of the circuit once powered up. The double-pole power switch (30 Amp) likewise switches on after the transformer has powered up. Fit it, forget it.

As mentioned there are options with the Connected Fidelity unit and you can choose to have UK or Schuko plug sockets as standard. In addition and at extra cost you can have a double UK socket instead of the single, four Schuko sockets instead of the single, or double US sockets (obviously with the appropriate 120V input/output transformer). In addition, you can opt for a multi-tapped transformer that offers 220, 230 and 240V.

Around the back of the AC-2K.

Suffice to say I believe these units are well made, look neat, and are easy to install. I am impressed by the construction and feel these units are very well put together. I can also add that I had a peek inside the unit I received, as I was sent a pre-production unit that didn’t have the production unit transit bolts, this meant I needed to open in order to remove some travel blocks. Of course, I couldn’t help having a good nosey. All looked very neat and solidly put together. Note production units are fitted with transit bolts so there is no reason to open the units as I needed to do.

SOUND QUALITY 

The section I expect most are interested in now we have covered the basics, so without any more preamble – did I notice a difference? The answer to that is a simple yes. In fact, although yes, an apparently subtle difference, it was addictive and the more music I played the more aware I became. Differences were not about a more forward top-end or bigger bass, in fact, the timbre of my rig didn’t really feel as if it had changed much, which is maybe a little misleading, because differences there are. My wife coined an expression I think fits very ably, she said ‘Everything feels bigger and louder’. Maybe a simple observation, but a very good starting point.

The soundstage feels bigger, the music feels to have more vibrancy, it’s more agile, leading edges of drum kicks feel, well, more real and they have more bite. Nothing was in fact louder, I checked with a dB meter! Volume remained exactly the same. That sense of the music being louder was entirely something I attribute to a greater sense of soundstage and realism. Unplug the unit and everything felt very much ‘smaller’, soundstage shrunk back towards speakers and the music felt sluggish. I’m struggling to put it into words and this upgrade was not, for me anyway, quite like anything I’ve tried before. Music sounded ‘faster’, but of course, it wasn’t! Songs were the same timings, but everything gained what I can only describe as more attack, a greater sense of immediacy.

And from the side.

I unplugged and replugged lots of times using different music, different genre and at different times of day, amp warm, amp just turned on and cold. I was conscious that my incoming mains has always fluctuated, being at the end of a row of cottages and with a shared supply. I wanted to ensure I tried this unit on and off as much as possible at different times of day, peak periods, and during periods of lower demand. I have always been conscious that occasionally my rig ‘just doesn’t sound right today’ and I put that down to either mood or maybe incoming mains. I’ve not noticed that phenomenon since I installed this unit which I think speaks volumes. In over a month I’ve not thought, my system just doesn’t sound right tonight. There is a level of consistency to the sound quality of my rig I’ve simply not had before and that is surely a very positive outcome.

CONCLUSION

So to draw this review to its conclusion, these are well-made, solid, robust units that operate silently provided they are set up correctly. As the saying goes, it does what it says on the tin! They are available with different options for overseas and UK applications and fit neatly alongside other kit. Small these units may be, but unsubstantial is not a word I’d use to describe them. They look every bit like a piece of quality kit.

I really didn’t know what to expect of the AC-K2, several of my friends really rate balanced mains and I know they’d not be without them. I wanted to hear what the fuss was all about. I expected a lot and being honest, at first I probably expected an unrealistic outcome. However, yes I noticed a difference in sound quality, although it wasn’t exactly as I’d expected. Was I disappointed though? The answer is a resounding no!

Having lived with this unit for the best part of a month its effect is addictive. I really don’t want to remove this from my rig, it is plain enough what it does once removed. I’ve unplugged and plugged back so many times I’ve lost count. A real reflection that these units work. Every time I unplugged I couldn’t wait to plug it back into my system!

It seems I am now used to a new ‘normal’ sound quality, a new level of realism, a new depth and soundstage, and a new vibrancy to everything I play. Matters not if my source is my CD spinner, streamed or ripped files, everything is benefiting and I don’t want to remove this unit from my rig!

The effects may be subtle, but unavoidable in my rig, but there is no going back for me now – once heard it’s a tough one to let go. My wife and I both agreed that we like what this unit does. I am told that most will experience some level of improvement to their systems, but that this can be system-dependent. All I can say is that in my rig I love what this small but heavy box does.

How much do I like it? Let’s just say this is the second Connected-Fidelity product that has me having a peek inside my wallet!

AT A GLANCE

Build Quality: 

These are well-made, solidly constructed units

Neat and well finished

No issue at all with the unit I received, be prepared to lift with a straight back though!

Sound Quality:

I was told the effect could be subtle, which I would not entirely disagree with, but once you’ve tried I found it addictive

Music gained more attack, more vibrancy, and especially a bigger soundstage with greater separation and clarity between instruments

Value for Money:

Not cheap, but I’d suggest that these are units that are keepers, change boxes, change speakers, change from vinyl to digital and I can’t see many deciding to move these boxes out of their systems.

We Loved:

Solid build, fits well alongside most rigs, and is easy to install

A consistent and predictable lift in sound quality and soundstage

We Didn’t Love So Much:

Not exactly a major issue, but we’d prefer a blue LCD display if only because it would match other kit we have and black rather than a polished aluminium faceplate (I’m told that a black fascia plate may be a future option).

These units are heavy, but that is not really a fault, they are built around substantial transformers so it’s inevitable. They do need to be located on a solid area.

Price: £1995 as tested

Elevator Pitch Review: I’d wanted to try balanced mains for some time and having had a chance to review the Connected-Fidelity AC-K2 I’d have to say I’m not disappointed. This unit lived up to expectations even if what I initially expected was a little off the mark. This unit grew on me and I became addicted to what this brought to my system – a new level of transparency and detail, greater depth and width to the soundstage. I love it and I’d urge others to try it. I don’t want to return this unit which I think speaks volumes.

SUPPLIED BY CONNECTED-FIDELITY

Ken Stokes

Review Equipment: Roksan Caspian M2 CD player (transport only), MacBook Pro using Audirvana for ripped uncompressed flac files and Qobuz Studio for streamed. Benchmark Dac3 Pre / Dac to Nord NC500 MK2 spec’ Dual Mono Power Amp, Vienna Acoustics Beethoven Baby Grand SE Speakers, Chord Epicx speaker cable, Tellurium Q Black XLR, Chord EpicX digital coax and Chord EpicX USB, mains – Belden DIY Screened Mains Cables.

*UPDATE & STATEMENT FROM CONNECTED-FIDELITY

“There have been some recent product developments to our AC-2K range of balanced transformers. There are now two options, the ‘AC-2K Studio’ and ‘AC-2K Reference’.

The AC-2K as reviewed above is essentially the ‘Reference’ option, but now has a twin (RCBO) electronic trip switch on the balanced output side. This addition has not made any discernible audible change to the output but adds a 100% level of safety (monitoring overload, short circuit, and earth leakage) that we have been asked for, from time to time.

Our high-quality bespoke transformers are manufactured by a specialist UK Company who have supplied 1,000’s of balanced transformers to radio and TV stations for outside broadcast units and recording studios around the world and has never had a transformer fail; an RCBO is not really required for this reason. If a cable carrying balanced power were to be damaged, cut or wired incorrectly, the RCBO would also trip of course.

The ‘AC-2K Studio’ option is a less expensive design using the same high quality cryogenically treated transformer in the same casework.”

Michael Osborn (Connected-Fidelity)