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Fostex HP-P1 Headphone Amplifier & DAC for Apple

The HP-P1 provides the ultimate listening experience for your iPod/iPhone/iPad in a portable, battery-powered device.

The Fostex HP-P1 is a portable DAC and headphone amplifier designed to receive digital input via a 30-pin iPod/iPhone/iPad dock connector. The HP-P1 also provides a digital-to-digital conversion function that allows the iPod/iPhone/iPad digital output to be converted into an S/PDIF signal for no-compromise recording or playback through another converter.


The beautifully designed HP-P1 weighs just over a half-pound, measures 2.9 inches wide x 1 inch high x 5.1 inches deep and is housed in a striking aircraft-grade-aluminum alloy chassis. The heart of this device is the high-performance, 32-bit AKM4480 DAC. The lithium-ion battery provides approximately seven hours of use per charge, and the device can alternately operate via a USB power source. A full charge takes five hours.

The HP-P1 + an iPhone: for 24-bit mix references on the go!

Input is on the front panel via a Type A USB connector that allows the unit to be connected to the 30-pin iPod/iPhone/iPad connector, or via a stereo mini analog input jack. If both the analog input jack and USB connector are plugged in, only the analog input signal is active. Also on the front panel are a stereo mini headphone output jack and a power indication LED. The volume control also powers the unit on and off. The headphone output has a 20 Hz to 20 kHz +/- 0.3 dB frequency response (at 32 ohm load, 80 mW output power) with a maximum output power or 80 mW + 80 mW and an applicable load impedance of 16 ohms or greater.

The rear panel includes a stereo mini Line Out jack with a -10 dBV nominal output level, an S/PDIF optical output jack, a threeposition Gain switch that allows the unit’s headphone output level to be matched to your headphone’s sensitivity, a Filter switch and a USB mini B connector for DC input. The Filter switch is one of my favorite features of the HP-P1, as it allows you to select between two filter types. Filter 1 is a conventional digital filter called “sharp roll-off filter” and Filter 2 is AKM’s newly developed digital filter called “minimum delay filter.”

I generally find that I prefer the sound of Filter 2, but they both sound fantastic so I typically give them both a listen and make a decision based on the source material and how they translate in the headphones I’m using. The Gain and Filter switches only alter the headphone output signal, not the Line Out or S/PDIF outputs.

In Use

The HP-P1 is straightforward and easy to use. To charge the battery, you simply connect the USB cable from a computer or USB power source to the HP-P1’s DC-IN port. The status indicator notifies the user when the device is fully charged and the battery charges whether the HP-P1 is powered on or off. In just a couple months of use, I’ve fallen in love with the HP-P1. Between my Ultimate Ears custom in-ear reference monitors, my Future Sonics M5 Atrio earphones and my Audio-Technica ATH-AD700 headphones, the HP-P1 has put me in complete audio bliss.

I’ve been copying my 24-bit mixes to my iPhone at the end of the day and using the HP-P1’s line out to reference them using my car stereo’s mini jack iPod input during my drive home and then listening through my Ultimate Ears custom in-ear reference monitors when I get home. Underpowered headphone amps make my ATH-AD700 headphones sound thin and hollow but when used with the HP-P1, the AD700s sound absolutely fantastic. Unfortunately, “i-devices” still don’t support high-resolution sample rates, so if you are mixing to 96 or 192 kHz, you’ll have to sample-rate convert, but the advantages of 24-bit over 16-bit are still massive.

As instrument apps for the iPad and iPhone have continued to evolve, they can now be considered legitimate performance options. When a musician pulls out his iPad to play an overdub (this has actually become quite routine as app sound quality and interface logistics continue to improve), using the S/PDIF or line output of the HP-P1 results in a sound far superior than that of the iPad’s built-in output. While the included carry case is handy, it only offers limited protection, so I picked up an Otter 2000 case, which, after adding a small piece of foam, fits the HP-P1 perfectly and provides complete protection while carrying the device in my computer bag.


While the price tag may be hard for some users to justify, the sleek HP-P1 is the only device I’ve encountered that provides on-the-go audiophile listening quality for the iPod/iPhone/iPad.

Price: $799

Contact: Fostex (American Music and Sound, U.S. distributor) |

Russ Long is a Nashville-based producer, engineer and mixer as well as senior contributor to PAR.