This is a review and detailed measurements of the ifi micro iUSB3.0 USB regenerator, power supply and battery bank. It is on kind loan from a member. It costs US $399. ifi says it was discontinued but then came back to market.The enclosure is just like everything else ifi makes:Which is to say it is confusing as heck. I have a full container of ifi products and every time I go looking for one, I have to spend 10 minutes reading the hardly legible print on the back to know which is which.This thing has more USB outputs than you know what to do with. Power-only, power and data. Port 1. Port 2.ifi positions this device for people with systems that cost more than $1,500:So I decided to test it with a top of the line DAC, the Topping D90. To see if it can deal with ground loops and such, I decided to test with unbalanced RCA output of it.I fired up the dashboard and as before, we see the fantastically low noise and distortion of the Topping D90 by itself, being powered by my very "dirty" desktop USB port:If there is any dirt, it is not getting in the eye of this DAC!Now let's run the USB through the ifi iUSB3.0 with the ground switch set to floating:Hmmm. We lose half a dB of SINAD due to extra spike around 16 kHz that was not there before. If I flip the switch it goes away and performance remains the same (i.e. the device is doing nothing useful).Zooming in further, let's look at jitter test:We better see the impact of floating the ground here with the same 16 kHz spike and addition noise around 6 to 12 kHz (little red pulses).If I ground it once more, then the additional noise goes away but we are left with the same performance as not using the ifi iUSB3.0.I have measured so many USB regenerators and filters and the outcome is always the same: they either make things worse or do nothing useful. Same is true of micro ifi iUSB3.0. Any audible improvements would have to come from your brain manufacturing it, not due to electrical improvements of your DAC.Please don't waste money on such things. Remember that not one of these companies shows a measurement of the output of the DAC improvement. Not one. ifi has Audio Precision analyzer. If there was an improvement there, they would have post it. Don't pay someone to excite your imagination for you.------------As always, questions, comments, recommendations, etc. are welcome.The beheaded pink panther is complaining that his arm is getting tired posing this way all the time. He wants either extra pay or massage service. Can't afford either one so pleaseusing