iFi's iSilencer and iDefender are designed to tackle different issues afflicting USB audio and the current versions, iSilencer3.0 and iDefender3.0, are being replaced by new, improved models – the iSilencer+ and iDefender+.

Using a computer as an audio source, whether laptop, tablet or desktop, is pretty standard these days. Moreover, most will hardwire the source to hi-fi gear via USB, generally because USB interfaces can pass hi-res audio data at maximum resolution. Furthermore, when done via an asynchronous port, you get bit-perfect transfer of the original source data.

However, as iFi points out, USB was designed to carry both power and data and is susceptible to electrical noise, which can adversely affect sound quality.

iSilencer+

iFi says that the iSilencer+ solves CRC (Cyclic Redundancy Check) errors, which can cause latency and signal distortion issues, by removing electrical noise (including EMI/RFI) at the source. We're told that it accomplishes this by combining passive filtering with iFi's ANC II (Active Noise Cancellation II) circuit.

ANC II has been developed from military radar technology and is not dissimilar to how active noise-cancelling headphones work. ANC II generates a signal identical to that of the incoming electrical noise but in the opposite phase, actively cancelling it out. Apparently, this is effective at removing low- and mid-frequency noise, while passive insulating filters deal with higher frequency interference.

As well as noise removal, the iSilencer+ also reduces the occurrence of jitter and re-balances the signal via iFi's REbalance technology. iFi states that all this ensures that the digital signal received by the DAC is identical to the original source, no matter which audio format is being played.

The new iSilencer+ sports upgraded circuitry over the previous iteration and adds low-ESR (Equivalent Series Resistance) Tantalum capacitors for
input and output filtering. The Stockport-based brand says this further elevates the iSilencer+'s noise-busting abilities with a 10-fold increase in filtering capacitance.

Finally, iFi adds that as well as plugging an iSilencer+ into the active USB output between computer and DAC, more iSilencer+ 'sticks' can be plugged into spare USB ports to further reduce radiated EMI. Furthermore, every time the number of units (and therefore the number ANC II circuits) is doubled, noise reduction capability also doubles. Also, the iSilencer+ can be used between external hard drives and music servers, too.

iDefender+

The iDefender+ is a more specialised USB audio device than the iSilencer+, specifically designed to tackle ground (or earth) loops that can cause issues with some computer-based systems, typically resulting in an irritating buzz or hum from the speakers.

When plugged into the source device's USB socket, the iDefender+ detects whether there is a ground loop problem, caused by the presence of multiple earths that add noise. The iDefender+, says iFi, breaks the ground loop by 'intelligently' disconnecting the computer's earth. As well as eradicating audible ground-loop hum it also lowers the system noise floor, resulting in improved resolution and dynamic contrast.

If you are using a DAC that relies on power via USB, say from a computer, the iDefender+ has another trick up its sleeve. Plug in an external AC/DC power supply into the USB-C socket, and it blocks power from the computer in favour of the external supply to feed the DAC. Naturally, using a high-quality, low-noise power supply will have increased benefits and iFi suggests its iPower or new iPower X.

Like the iSilencer+, the iDefender+ upgrades the performance of the outgoing iDefender3.0 with the addition of low-ESR Tantalum capacitors for input and output filtering. Additionally, both are available in three options – USB-A to USB-A, USB-C to USB-A, or USB-C to USB-C. The USB 3.0 and USB 2.0 standards are supported, and the connectors are gold plated.

Price and availability

The iFi iSilencer+ and iDefender+ are available from Amazon and other selected retailers from Friday 13 March. Both products have an RRP of £49 inc. VAT.

For more information, check out iFi Audio.