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This review first appeared in the April 2011 issue of hi-end hifi magazine fairaudio.de of Germany. You can also read this review of the ISOL-8 MiniSub 2 in its original German version. We publish its English translation in a mutual syndication arrangement with the publishers. As is customary for our own reviews, the writer's signature at review's end shows an e-mail address should you have questions or wish to send feedback. All images contained in this review are the property of fairaudio or ISOL-8 - Ed.

Reviewer: Jörg Dames
Sources: Fonel Simplicité, laptop with foobar2000 and Northstar USB dac32
Amplification: Integrated - Fonel Emotion; pre/power - Funk MTX Monitor V3b, Audionet AMP monos
Loudspeakers: Thiel CS 3.7, Sehring S 703SE
Cables: Low-level - Straight Wire Virtuoso, Vovox; high-level - HMS Fortissimo, Reson LSC 350
Power delivery: Hifi-Tuning Powercord Gold incl. IeGo terminations, MF-Electronic power strip, Oehlbach Powersocket 808, HB Cable Design Horizon PowerStrip
Review component retail: €799


Pure cosmetics? Besides the fact that hifi is often more smoke than fire whilst burning green backs like paper, our hobby and nicotine smokers not only have in common that their coolness factor belongs to the past but that real addicts do it filterless. Music listeners view filters with suspicion, usually relative to dynamics. And admittedly my prior exploits into cleaner power delivery didn’t really take off in earnest either. That was due to the usual side effects or because the necessary investment wasn’t compadre with audible benefits.


Today’s MiniSub 2 from the British—now here comes a slick mouthful—performance power conditioning specialist ISOL-8 does reach €799 deep into your purse. Compared to many others though that seems near pocket change, particularly because six power sockets eliminate an extra outlet strip. It's something for which many slam further smackers on that hard counter.
Nic Poulson is the brains behind it. His professional career began in the BBC’s sound department at the tender age of 17. Some will recognize him from ISOTEK which he founded in 2001 but left three years later to, as he put it, focus more on his own concepts. This led to ISOL-8. In the late 90s Poulson had also started Trilogy Audio Systems. That's an amplifier firm still active today.

To get on topic, why are AC filters even necessary? The obvious answer is (hoped-for) sonic gains. Whether the MiniSub 2 complied we’ll find out shortly. Because nothing is more practical than a good theory, let’s first cover more ground. For typical power disturbances Poulson cites among others radio-frequency emissions from digital components which distort the silicon layers of transistors; high-energy spikes from switch contacts (think light switch transients); rectifier diodes and their fog-layer effects; and finally the vagrant shadows of inductive industrial users loading down your domestic AC network.

All this influences the workings of hifi kit whose music signal is little more than modulated wall power. It’s not just about shielding against external attacks though. It's also about isolating components from each other. This theme of cross contamination where individual boxes pile on dirt at one another is of particular concern to the ISOL-8 people.
The London conditioners distinguish between two core types of disturbances to be dealt with. The difference is whether the disturbance propagates on just one conductor of the current loop (phase or ground) or symmetrically in phase on both relative to ground.


The first is differential mode noise. It occurs with conductors physically not closely coupled such as internal wiring or where specific circuit parts cause distortion. Here the disturbance circulates in a local current loop.


The second is common mode noise. This typically occurs when a bi-directional conductor pair runs in close proximity. Here effects don’t remain contained locally. They seek the path of least resistance and drain to earth ground via stray capacitance.


According to the ISOL-8 team most manufacturers ignore asymmetrical power disturbances i.e. differential mode noise which, unlike common mode noise, has to be filtered on both legs with a combination of series-connected inductors and a paralleled shunt capacitor especially transparent to HF signal. It becomes clear too that the Brits insist on treating both forms of noise to mandate somewhat more complex filtering which then points mostly at their costlier models like the SubStation LC/HC [below] and isn’t as comprehensively addressed by the MiniSub 2.