There is an endless array of DACs and Amps and DAC/AMP combos, headphones/speakers and, of course, high end audio cables. High fidelity audio does come at a hefty price, especially if you're looking for an endgame headphone setup. If you can't imagine spending hundreds or thousands on multiple variations of audio components, you actually don't have to. If you already own a decent DAC, tube amplifier and audiophile quality headphones, a USB audio purifier might be all you need to improve your listening pleasure!
As the saying goes, understanding a problem is the only way to find its solution. Like with all problems, there is always a solution. In the world of audio equipment, one common problem is the unwanted noise you can get when two or more devices are connected to a common ground from different electrical sockets, creating a noise that sounds like a low frequency hum - the infamous ground loop noise.
This humming or hissing noise is especially problematic with USB digital audio as it spoils the enjoyment of the audio experience. Since USB audio is transmitted digitally through a USB cable, the low frequency hum created by the ground loop will travel through the shielding of the USB cable, which is one reason to buy a quality USB cable with 90 ohm impedance rating that is properly shielded.
USB consists of power, ground and two data signals and the USB power output can also seep unwanted noise into your audio, making USB signal extra noisy. Fortunately, there are ways to clean up the interference that affect the USB audio signal and get better sound out of the usb connection with USB signal purifiers such as the iFi Audio iSilencer3.0 and iDefender3.0.
As the name implies, audio purifiers filter the noise interference in the audio by lowering noise floor and reducing audio jitter (playback distortions), which is not to be confused with clock jitter that happens during the re-clocking of the USB DAC sampling clock by the computer's own sampling clock. Most USB DACs today will either have an adaptive USB implementation or an asynchronous USB implementation, which creates less clock jitter. Jitter and ground loop noise are very difficult to eliminate completely so, the best course of action is reducing it so noises are no longer audible.
Both the iSilencer3.0 and iDefender3.0 accomplish the same objective of cleaning up the USB audio signal but the iSilencer3.0 does it slightly differently and more effectively by implementing Active Noise Cancellation (ANC) technology to minimize noise. ANC enables iSilencer3.0 to suppress electromagnetic/ radio frequency interference noise in real-time, justlike ANC headphones suppress background noise.
iDefender3.0 suppresses ground loop noise and noisy power supply by disconnecting the computer's USB port power connection, as well as ground connection via smart circuitry built-in that is capable of detecting more than one ground. Disconnecting the USB power connection is a smart way to remove power noise from battery powered USB DACs that don't need a power supply. If the DAC is USB powered, it will need power but using USB power would defeat the purpose of iDefender3.0.
Luckily, iDefender3.0 integrates a micro USB power port for USB powered DACs that is designed to plug in a power supply to disconnect the noisy USB power and replace it with low noise external power. A low noise power supply is not included unless you purchase the iDefender 3.0 bundle version. You could technically use any 5V power supply since the USB power port is rated at 5V but the iPower power supply by iFi audio is a purpose-built 5V/2.5A low noise power supply, which makes sense to use since using a regular power supply would only add to the noise problem.
Both the iSilencer3.0 and iDefender3.0 are USB 3.0 devices that are backward compatible with USB 2.0; hence they will work even when plugged in to a USB 2.0 port. They feature a female USB 3.0 port on the back end, and a male USB 3.0 gold plated connector in the front and are plug-and-play without any driver installation required. Both iSilencer3.0 and iDefender3.0 are compact and lightweight, weighing 6.5 grams and measuring 48 mm long, 18 mm wide and 8 mm thick. The effectiveness of the  iSilencer3.0 and the iDefender3.0 it's dependent on the noise filtering capability of the equipment as some DACs have an active filtering circuit built-in.
Both iSilencer3.0 and iDefender3.0 are an audio filtering and audio enhancing solution, improving the dynamic sound, vocal clarity in the midrange and soundstage across the audio frequencies without adding any harshness or distortion. How much of the improvement you notice will depend on your specific playback environment but you should definitely appreciate the smoothness and space the iSilencer3.0 and the iDefender3.0 provide.
Realizing that you are an audiophile can be one of life's little surprises but, if you don't want to spend the kind of money that goes with being an audiophile and still achieve a level of happiness with your current setup, getting a USB audio purifier might be the answer.