Review: i.Fuzen Case, External Battery Pack, And Headphone Amp For iPhone 4.

Being an audiophile in the modern digital world while also considering mobility is almost impossible. At uncompressed bitrates, single CDs can easily approach 600-900MB in size. With the standard MP3 player only containing ~16-32GB of storage, such a lifestyle doesn’t exactly bode well for diversity. But times are a changin’. Audiophile equipment is getting smaller and becoming more efficient. And slowly but surely, device storage is growing. But what if you want the ultimate in portability while not sacrificing too much sound quality or battery life? Products such as the i.Fuzen made by Auzentech are right up your alley. Featuring a 3-in-1 design, this little case/extended battery/headphone amp is pretty awesome. Jump inside for the full rundown…

Case Construction & Design

Being sold as a case means that it should offer at least some basic level of protection. All too often, we see multi-function “cases” offer pretty terrible protection. In the case (no pun intended) of the i.Fuzen, we found protection to be adequate/slightly better than your average. However, there is room for improvement. Our biggest gripe considering protection is that the phone sticks out past the case meaning that if the case and phone lands face down, a cracked screen is all but guaranteed.

Protection around the rest of the device is quite good. The i.Fuzen is made out of a harder plastic, so sharp edges and other blunt force trama should be repelled without much sweat from the case itself. Shock protection from longer drops, however, is also something we’d worry about.

As far as layout goes, everything is pretty straight forward. On the front of the device you have an LED notification light that tells you what headphone mode you’re in (more on that later) as well as two touch-sensitive volume up/down buttons. When audio is listened to via the line-out dock on the iPhone, the on-screen volume controls are deactivated. Down below there are two headphone ports and a miniUSB port that handles syncing (pass through USB supported) and charging. Moving ’round to the right is rather uneventful as there’s nothing to be seen except for a cutout to the iPhone’s silent switch and volume up/down buttons. Finally, on the back of the device you’ll find the single power on/off button and 4 small LEDs that display the charge status of the i.Fuzen.

Extended Battery

The i.Fuzen features a 1,650mAh battery built into the case. According to the company’s own specs, that’s good enough for an extra 44 hours of audio playback, 11 hours of video playback, and 8hours of talk time. The stock iPhone 4 battery is rated at 1,420mAh, so the i.Fuzen should theoretically double your time away from the wall. In our testing, we found that to be more or less true. We could easily leave our iPhone off the charger for a solid 36 hours before we started to get panic alerts from our beloved glass-encased fruit. Mind you, during this 36 hours we had a mixture of ~60 minutes phone use, ~300 text messages, ~250 emails, ~3-4 hours of web browsing, ~60 minutes of video playback, ~6 hours of audio playback, and many hours of standby. Consider us impressed.

Headphone Amp

While protection and extended battery life are two very important factors to consider in such a case, the added headphone amp had us the most intrigued from the start. Getting sound quality that approaches audiophile levels in such a small package is more often a massive failure than something worth praising. But for the audiophiles and slightly less obsessed music junkies, we have to give the i.Fuzen props. The headphone amp is good.

For starters, the i.Fuzen is rated at 180mW (90mW + 90mW) — quite a bit higher than your average ~20mW/channel mp3 player rating. Other specs include:

  • Frequency Response: 5Hz ~ 100kHz, +/- 0.23dB
  • Input Sensitivity: 1.25 Vrms
  • Maximum Gain: +9dB
  • Input Impedance: 50kO
  • Load Impedance: 32 ~ 300 Ohm
  • Total Harmonic Distortion: 0.002%,@1kHz into 32O
  • Signal to Noise Ratio: 113dB (A-weighted)
  • Maximum Input Current: 800 mA
  • Output Voltage: DC 5V
  • Output Current: 500 mA

The headphone amplifier itself is a proprietary amplifier designed and built by parent company, Auzentech. It features a J-FET OP-AMP to deliver tube-like sound (read: warm sounding) as well as a ZX-Driver for low distortion and 180mW power.

If the technical alphabet soup doesn’t mean much to you, walk away with this: It’s awesome. Out testing was done with a pair of Beyerdynamic DT-880 Pro headphones with 80ohm impedance. They’re not the hardest cans to drive, but using the stock headphone out port on the iPhone 4 proves to be a small struggle for the device to handle. Out of the i.Fuzen by way of the iPhone’s line-out dock, however, is quite another story.

Volume was more than ample. Soundstage was noticeably increased (music didn’t sound like it was being beamed though a tiny tube towards our heads), separation in complex music was also very good. In Muse’s Exogensis: Symphony Pts. 1, 2, and 3, the various symbols, piano, stringed instruments, and percussion could be individually heard instead of a massive pile of thrashing metal and distortion. Songs with more bass such as Link Park’s “My December” or any typical dubstep song were hard hitting, grabbing every low note with ease and authority. We’ve been listening to tons of music over again and it is honestly like the first time we’ve heard it. We couldn’t possibly be smiling any bigger than we are now — it’s that awesome. And remember, this is all in an easy to transport and use iPhone case.

Of course, what’s even better than one awesome portable music experience? Two of course. The i.Fuzen features dual headphone out ports giving your the ability to share all the awesome audio quality with a friend.

Headphone Amp Features

What makes the i.Fuzen headphone amp unique outside of its dual-output design and outstanding quality are the different sound modes that can be activated depending on the headphones being used. In total, there are four separate modes that can be toggled headphone/sound mode button on the bottom left side of the case.

  • Mode 1 (Blue LED Blinks Once): Low Power/Gain Multimedia Headphone
  • Mode 2 (Blue LED Blinks Twice): Low Power/Gain Multimedia Headphone with Cross Feed Filter
  • Mode 3 (Blue LED Blinks Three Times): High Power/Gain High Performance Monitoring Headphone
  • Mode 4 (Blue LED Blinks Four Times): High Power/Gain High Performance Hi-Fi Headphone

In our testing, we found Mode 2 to sound the best (to our ears) with our Beyerdynamic DT 880 Pros. Your mileage can and will vary greatly depending on headphones used and of course, because all of our ears are shaped differently, and therefore affect perceived differences in audio quality and music.


Should you buy the i.Fuzen? Well, if you’re in the U.S. you can only pre-order at this point as the device isn’t yet available here. As of writing, the price sits at $129.99. It may seem like a lot for a case. But you have to remember, this is a case, extended battery, and headphone amp all in one. In our eyes, it’s quite a bargain.

The only things we didn’t like about the i.Fuzen is the fact that the iPhone’s screen is left rather exposed to drops and damage and that you cannot use the headphone amp while charging. The latter is a pretty big issue if you’re constantly using the built-in headphone amp. (This isn’t an issue with the i.Fuzen itself, but more-so a restriction Apple places on “Made for iPhone” accessories.) But we have a feeling that the group of people who would use this case and headphone amp also have at least one other headphone amp or separate setup for home use. As such, we don’t see it as a complete deal breaker.

Outside of the U.S., availability is as follows:

U.S. Residents can pre-order the i.Fuzen here. (Available starting April 2011)

Photobucket Pictures, Images and Photos


  • Small and pocketable
  • Awesome sound quality that you can share with a friend
  • Close to doubling of iPhone runtime

Didn’t Like

  • Screen protection is almost non-existant and subject to drops
  • Cannot use headphone amp while charging

Gadgetsteria Rating

  • Design: 8
  • Protection: 7
  • Headphone Amp/Audio Quality: 9
  • Price: 7
  • Gadgetsteria Rating (not an average): 8

Scores based on 1-10 with 1 being utterly terrible to 10 being other-worldly


  • Batterie externe iPhone

    extended battery life are two very important factors to consider in such a case, the added headphone amp had us the most intrigued from the start. Getting sound quality that approaches audiophile levels in such a small package is more often a massive failure than something worth praising

    • Mike

      Very true. I was happy with the results though. The i.Fuzen is a pretty sweet little package.