This is a review and detailed measurements of the ifi DC iPurifier DC (power) filter. It is on kind loan from a member. The iPurifier costs US $99. Looks like there is an updated, iPurifier2 now.The ifPurifier is an inline DC filter. Power goes in, power goes out. I received a set of adapters with it, not sure if these come with it or not. If not, you definitely need it as these barrel connectors come in a few sizes of outside diameter and inside.The unit itself is a bit chunky so may not mate with some devices:The challenge with these devices is not that they don't do anything. They do. The issue is if that change materializes in sound you hear.For testing I thought we rely on USB power. "Everyone knows" that USB power is "dirty" so surely this is a perfect input to iPurifier to clean up. I used my Topping D50s as the target DAC since it has independent power that can be provided from USB. For digital data to it, I opted for Toslink optical so we are not dealing with ground loops and such.Here is our Topping D50s with straight USB power as described above:Note that there is half to 1 dB of variation in every snapshot of SINAD (metric of noise and distortion). I then inserted the ifi DC iPurifier in the path:Not a thing has changed. Output voltages are identical at 1.973 and 1.961 volts (Right and Left). Frequency of the tone is right on the money at 1 kHz with 5 digits after the decimal point. Distortion and noise as reflected in THD+N or SINAD are the same (sans the run to run variation).Even our noise floor at whopping 140 dB (as represented by FFT gain) is also the same.Let's zoom in even more to see if there is a difference in ultrasonics or even deeper in the noise floor:Those tiny differences are just not material. If you look at the DAC differently you get such changes.Let's get rid of our signal and boost the bandwidth to an incredible 1 MHz (1000 kHz) or 50 times our best case hearing range:There is no question the output of the DAC is remaining the same. As it should since DACs have their own internal filter for DC input. Indeed they regenerate the DC input to get the proper voltages they need internally.Let's get rid of the DAC altogether and just hook up the USB power to the audio analyzer. Yes, I can do that but you should not do it with your audio gear or you will blow up your speakers good. Here is the comparison now:Now we see that the iPurifier is indeed cleaning up the USB power. It is lowering its noise and getting rid of fair amount of very high frequency spikes. Why did we not see this effect when testing with the DAC? Again, that is because the DAC was also performing this filtering so it did not benefit from it being beforehand. No decent DAC assumes USB power is clean.As electronics and audio theory would tell us, a device like iPurifier does nothing useful for the sound you hear. Marketing material talks about what the device does as far as filtering. But nothing is shown as far as the measured impact on the output of an audio device. And rightfully so because there likely isn't any improvement.Of course, if you bought this device and plugged it, you immediately hear better bass, more air, more microdynamics and resolution. All of that happens not because the device made these changes, but because when you focus on what a device does, you listen differently. When the sound waves coming out of an audio device has not changed, the only thing that must have, is your perception.Needless to say, you should not waste your money on such tweaks. You can get a great DAC for the same price as this dongle that doesn't care about USB power quality.At the risk of stating the obvious,If you have to throw away your money, give it to a needed charity.------------As always, questions, comments, recommendations, etc. are welcome.Yes, we have a new pink panther model! Sadly it did not come cheap. Given its size and rarity, it required significant pocket change to acquire. I hope I can count on you all to offset that cost byusing