Basic specifications

• A headphone amplifier with single-ended input and output
• Input: 3.5 mm 3-pole
• The output uses a 4.4 mm jack, so you can enjoy clean sound free of anti-phase crosstalk
• The NJM8830 from Nisshinbo Micro Devices is used in the output stage
• No volume control, to avoid degrading the sound
• Gain fixed at ×3
• Suited to earphones and headphones with a sensitivity of 98 dB or more (at 96 dB or less, some models may not reach enough volume)
• About 30 hours on new 750 mAh rechargeables
• AAA batteries. Fujitsu white batteries recommended; for alkaline, Fujitsu Premium S

Power	75 mW @33Ω
Frequency response	3 Hz – 5 MHz (−3 dB)
Output impedance	1.03 Ω
Suitable impedance	Up to 250 Ω
Dimensions	18 × 57 × 107 mm (including protrusions)

Note: the numbers do not always match the impression you get by ear.

Precautions

• Turn your player's volume down and connect from the headphone output (phone out) or a variable line output. A line output without volume control plays at full volume and can damage your hearing and your earphones or headphones.
• If you take the board out of its case, never put it down on metal. The batteries could short-circuit, causing burning or damage.
• Batteries other than NiMH, NiCd, alkaline or manganese are used at your own risk. Any resulting fault is not covered by the warranty.
• If the LED dims and noise appears, the batteries are running low. This is not a fault.