In the past there was the worrying idea that all computer manufacturers would, sooner or later, block our machines with a completely closed digital music listening system, thereby preventing us from changing or customising anything. This fortunately didn’t occur thanks to the diffusion of soundcards that helped both, the emergence of increasingly high-performance sophisticated devices and the diffusion of liquid music.
Also, in recent times listening to music has been helped by the increased availability of devices that can use the USB port, so that more refined products such as DACs are now able to accept signals up to 32-bit / 384 kHz. In this regard, much has been said about the quality of the audio signal coming from a computer USB port due to the fact that the USB standard transmission was not originally designed for high-quality audio. In fact, the standard USB wires that carry the signal data, one for power and one for the mass, are woven together in a single cable which then allows easy connection to printers and other devices through the USB port. If this was replicated in a traditional stereo system the playback would be far from the optimum. In fact, electromagnetic interference problems could easily arise which would affect listening to the music. Of course the USB cable shield could improve the situation but, as regards one of the major problems with computer audio playback, which is electromagnetic noise interference aka EMI, this would not be an ideal solution. The EMI noise from electromagnetic interference is generated mainly by switching power supplies that are present within a computer and that incorporates a switching regulator to use electricity more efficiently. The noise generated by EMI may become very annoying and noticeable between songs. To solve this problem iFi Audio has decided to create a customized product called USB iPurifier that only does one job: it cleans and filters audio and digital power at the end of the chain just before the signal goes to the DAC. The main function of its specially designed circuit, is to restore the waveform of the original analog signal to an even more faithful and realistic sound output.
The iPurifier is sold in a tiny package that also contains the short illustrated manual and a USB to Mini USB converter. Its external structure is in die-cast metal with 4 tiny screws at the top. A small green LED located in the middle of the top shows when it is on and operating properly once connected. The iPurifier by iFi audio uses PurePurification technology to remove electromagnetic interference generated by the computer or by the USB cable. In addition, the so-called iPurifier also removes the DC offset. The term is an electronic one and refers to a mean amplitude displacement from zero. Extending this concept to the representation of a waveform, the DC offset can be regarded as the average amplitude of the waveform and only when the average amplitude of this waveform is equal to zero, there is no DC offset. The iPurifier is fully compatible with the USB 2.0 standard and is capable of handling high-resolution PCM signals of up to 384 kHz DXD and DSD signals at all levels. As reported by iFi audio, the use of iPurifier can reduce the level of electromagnetic noise by at least 5 dBs.
For the listening test, we included the iPurifier in our reference listening chain and for the USB signal we used a 5 volts stabilized, separated and dedicated power supply. The USB cable used for the test is made of pure silver occ. To convert the signal from USB to AES -EBU we just used the X-SPDIF by Matrix Audio. We let the iPurifier burn-in for at least 72 hours prior to any benchmark. We then had a rather long listening session with our usual reference songs before using the iPurifier in order to better identify any potential differences. We have to say that since the beginning its insertion in our listening chain, it has improved the sound clarity of the entire source making the noise less pronounced. The middle frequencies have been given greater definition and at the same time have become more balanced, while the low frequencies showed even greater accuracy. Also, high frequencies maintained and gained in naturalness. The sound stage is thus improved in its entirety. The source appears to be more precise both as regards focus and the separation between the two channels. We also enjoyed a slight but decisive improvement of transient articulation especially at low frequencies. When used with a dedicated power supply for the USB signal, the small iPurifier is surprisingly successful, thereby improving the quality of listening, especially with high-resolution sources compared to those in the classic audio CD format.
In recent years the progress made by digital audio through the use of the USB port has been quite remarkable. This product by iFi audio, even though it was built specifically, gives us the opportunity to send, at least in our view, a particular message. The USB audio playback system using a computer as a source, in order to better express its full potential, must take a number of proper precautions. First of all it needs a USB cable developed for applications in which the hi-fi audio data signal travels separately from the power signal to minimize as much as possible any potential interference. Usually the USB signal, that comes from a PC, doesn’t have a clean and stabilized voltage supply so it must be powered externally in a specific manner, even by batteries. Only in this way, as we have learnt from experience, the iPurifier’s role can be decisive even in a very high quality and refined audio listening chain. Its presence can make a difference, rendering the listening to USB sources virtually free from any interference and at their fullest potential.
Honestly, I must say that I was initially skeptical about the benefits of such a product. In fact, in the world of professional audio the use of the USB port has often been viewed with suspicion and for years the firewire port gained a better reputation. However, I had to change my mind thanks to the optimizations implemented in our studio. In this way the iPurifier has ensured a small but tangible improvement in sonic performance giving itself now a secure and well deserved place in our audio chain. To conclude, if you are looking for a small accessory with great potential you certainly won’t be disappointed when purchasing it. I can sincerly say that it’s a product that I would highly recommend.
- Sound quality 
- Bang fot the buck 
- Measures 
- Build quality 
- Versatility 
- Overall rating
- 1. iPurifier sound quality is really really good
- 2. The bang for the buck of the unit is high compared to the price
- 3. The measures show very interesting values
- 4. Build quality and aesthetics of the device are excellent
- 5. Versatility is very wide range in the world of USB audio devices