iFi’s new SilentPower range claims to tackle mains-related noise to improve audio/AV system performance.


Alongside its collection of audio devices for home and portable use, including class-leading DACs and headphone amps,British brand iFi makes a range of accessories to tackle common issues that affect the performance of audio systems. The prime objective is to reduce noise in the audio signal which may be engendered in various ways, from problems caused by USB interfaces to issues with mains electricity.


iFi’s latest collection of specialised ‘audio enhancers’ deals specifically with mains-related noise. The all new SilentPower range consists of four products at launch: the DC Blocker, the GND Defender and a pair of IEC power cables called Nova and SupaNova.

iFi SilentPower Audio Enhancers

iFi SilentPower Audio Enhancers, DC Blocker and GND Defender


These two little devices look similar – they both measure 68x37x32mm – but they are designed to tackle different problems that can result in an audible hum. They connect to the power inlet at the rear of any audio component, with the user’s power cable attaching at the other end. They can be used individually or together, depending on the issue(s) the user is attempting to solve.

The DC Blocker is a neat, solution to ‘DC on the mains’  a problem well known to affect the performance of audio equipment and a significant cause of irritating transformer hum. In theory, the electricity we draw from the sockets in our homes should be pure AC, with a perfectly symmetrical sine wave alternating between positive and negative phases. However, this AC voltage is affected by small amounts of DC voltage, present in the mains supply for reasons that are many and varied – this can cause the AC waveform to become asymmetrical, an effect known as ‘DC offset’.

iFi SilentPower Audio Enhancers

The iFi DC Blocker

The AC transformers commonly used in home audio equipment cannot tolerate the presence of significant levels of DC voltage without being compromised. Less than 500mV of DC – typical in an average household electricity supply – can be sufficient to cause toroidal transfers of the kind often found in amplifiers to become saturated, which adversely affects sonic performance and may also cause an audible mechanical hum. The DC Blocker is capable of cancelling more than 1000mV of DC voltage, thereby correcting the DC offset and rebalancing the AC sinewave. It does this ‘intelligently’, adjusting its performance according to the level of DC detected. This solves the problem of transformer hum caused by DC on mains and helps to optimise the sonic performance of the audio component to which a DC Blocker is connected.

If you can hear a hum or buzz through your speakers, it is likely that you have a ground loop problem. This occurs when two or more audio components in a system are connected to a common ground (or earth) point via different paths – for example, if two different wall sockets on the same circuit are used to power different components in a single audio/AV system in which the components are connected via electrical (as opposed to optical) signal cables.

If a problematic ground loop exists, the GND Defender resolves the issue by disconnecting the loop running through the connected component. By using one or several GND Defenders in a hifi system, the user can ensure that all components are connected to a common ground via a single path, eradicating the resulting hum through the speakers. Interference caused by ground loops can also affect picture quality in AV systems, resulting in issues such as visible scrolling bands. iFi says that the GND Defender will help to solve this problem, too.

iFi SilentPower Audio Enhancers

iFi GND Defender

Both the DC Blocker and GND Defender are constructed so that they do not compromise the RFI/EMI shielding or filtering that may be offered by the connected power cable or filtering device further upstream. They are solidly made, their casing has a high dielectric rating and they surpass the highest safety standards. And, with a voltage rating of 90V to 240V, they can be used all over the world.


iFi has made a number of clean-power products in its nine-year history to date, but these did not include an IEC mains cable for home audio components, until now. The Nova is a specialised power cable which iFi says is a serious upgrade over standard mains leads.

The Nova incorporates five conductors, each made from heavy-gauge, continuous-cast OFHC (Oxygen-Free High Thermal Conductivity) copper. Two pairs of live and neutral conductors are arranged either side of the grounding (or earth) conductor, which is positioned at the centre of the cable. This geometrically balanced configuration causes the magnetic fields generated by the live and neutral conductors to cancel each other out, ensuring the grounding conductor is unaffected by residual magnetism and unwanted induced voltage – iFi calls this design Ground Zero.

iFi SilentPower Audio Enhancers

iFi Nova

A further pair of air-dielectric delineators – polymer matrix tubes filled with air – are arranged on either side of the earth conductor, keeping the two pairs of live and neutral conductors apart whilst improving the cable’s overall dielectric performance and constructive solidity.

Each individual live and neutral conductor sports multiple layers of insulation and shielding. First, a dielectric made from a polymer matrix is extruded over the OFHC copper conductor. Surrounding this is an oxygen-free copper shield. And covering the shield is a further layer of polymer insulation. These individually shielded conductors, plus the air-dielectric delineators, are twisted in a circular helix around the central, untwisted grounding conductor, itself wrapped in polymer insulation – this twisted arrangement further aids RFI/EMI rejection. The cable is completed with a tough yet flexible polymer outer sheath and iFi’s audiophile-grade connectors, with oxygen-free copper conducting pins coated in tarnish-resistant 24ct gold.

iFi claims that the result of this mix of materials and construction is a power cable offering constant impedance and superior rejection of EMI/RFI, maintaining the purity of mains electricity feeding each component in an audio or AV system. It also complements iFi’s PowerStation mains-conditioning bar, which we reviewed and gave our Outstanding Product Award.


The SupaNova active power cable takes the Nova and adds a cylindrical housing part way down its length. This cylinder contains Active Noise Cancellation II – the latest version of iFi’s proprietary noisebusting tech – in combination with advance-filtering components.

iFi SilentPower Audio Enhancers

iFi SupaNova

Noise in the mains supply occurs at different frequencies, depending on the cause. Passive noise reduction systems are effective at the top end of the frequency spectrum but often less so at lower frequencies. In addition, passive systems need large capacitors to be truly effective, which make the best such products bulky and expensive. iFi’s Active Noise Cancellation II technology enables a power conditioning device that they say “is highly effective at reducing noise consistently across the entire frequency spectrum yet sufficiently compact and lightweight to position within the mains cable itself”.


iFi’s SilentPower range begins launching this month. The DC Blocker and GND Defender are available now, while the UK-plug versions of the Nova and SupaNova arrive in July. RRPs as follows:

iFi DC Blocker: £129

iFi Nova: £169 (1.8m cable)

iFi GND Defender: £99

iFi SupaNova: £349 (1.8m cable)

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