"Awesome little amp! I have E5, T2, PA2V2 & Total Airhead, this beats them all"


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Objective2 Headphone Amplifier

Objective2 Headphone Amplifier
O2 is an opensource amplifier designed by brilliant engineer NwAvGuy, with emphasis on benchmark performance and low cost. O2 arrives fully assembled, hand tested, and ready to enjoy.

Objective2, Front ††† Objective2, Top

The Objective2 (O2) is an open source headphone amplifier designed by NwAvGuy, with emphasis on benchmark performance and low cost. This item includes a fully assembled and hand tested O2 amplifier, ready for use. You will only need an AC adapter suitable for your region.

The O2 has created a stir in Head-Fi.orgís do-it-yourself community. After being banned from Head-Fi for heated discussion, he proceeded to design O2 for maximum benchmark performance to prove his points. Itís large and heavy, so hardly worth consideration as a portable amp, however, O2 lives up to its name.

For more information on the O2, please refer to NwAvGuy's O2 Details article.

Objective2 Features

Our Objective2's are assembled 100% in accordance with NwAvGuy's default, high-performance specifications.

Reference Grade Sound

Objective2 achieves vanishingly low THD and noise performance for audible perfection.

Low Output Impedance

O2's extremely low output impedance ensures transparent frequency response for all headphone loads.


At over 600mW, Objective2 provides enough output power to drive all dynamic headphones on the market with authority.

Amplifier Performance

Frequency Response +/-0.1 dB (20Hz-20kHz)
THD 1 Khz 150 Ohms 0.0016%
IMD CCIF 15 Ohms 0.001%
IMD SMPTE 0.002%
Noise (ref 400 mV) -105 dB
Max Output (33 Ohms) 613 mW
Max Output (150 Ohms) 355 mW
Max Output (600 Ohms) 88 mW
Output Impedance 0.54 ohms
Crosstalk (15 ohms) -65 dB
Channel Balance (50% volume) 0.6 dB
Battery Run Time 6-8 Hours


Case Dimensions (mm) 108.50 x 80.00 x 29.50
Case Dimensions (in) 4.27 x 3.15 x 1.16
Weight 11oz


Input 3.5mm or RCA*
Output 3.5mm or 6.35mm*
Power Battery or 14-20VAC


Gain 2.5x and 6.5x*
Volume Potentiometer Taper Alps 15A or 3B
Batteries 2x9V LSD NiMH
* Custom Configurations Available

Package Contents

  • Fully Assembled O2 Headphone Amplifier
  • 2x Tenergy 9V NiMH, Low-Self-Discharge Batteries
  • Free Set of Rubber Feet
  • Instructions Guide

Jack Configurations

Black and Silver Edition: Default configuration, featuring front mounted 3.5mm (1/8") headphone jack, 3.5mm input jack, and AC power jack.
Customize: Choose a 3.5mm or 6.35mm (1/4") headphone jack, front or rear mounted AC power jack, 3.5mm or RCA analog input jack, and custom gain levels. Customized units ship within 1 business day, exclusively in black!


O2 requires an AC adapter to charge its batteries. Power adapters are sold separately, as we ship worldwide. Be sure to select one of the following:

North America: US 15VAC Adapter
Europe, Australia, Great Britain, Singapore: GEZ AC Adapter
Other: Please refer to our O2 Power Adapter Guide

Default gain levels of Objective2 are intended to work well with over 95% of headphones on the market. We use the stock O2 with headphones as low as 16 ohms @ 1 dB/mW, and as high as 600 ohms (very high and very low efficiency, respectively).

There is no reason to change the stock gain unless you regularly listen at extremely low volumes. Gain can easily be changed by removing two resistors.

We can set gain of 1.0x/6.5x or 2.5x/1.0x upon request. Other combinations are also possible, but may delay shipment by 1-3 business days. Simply make your special request(s) during checkout.