**LME-Series Audiophile Portable Headphone Amplifier

Precision Triple-Stage Architecture with Dual-Rail Power**

Experience studio-grade transparency in a pocketable form factor. This amplifier is designed for listeners who demand a "black" noise floor and zero-compromise signal integrity. By combining high-performance LME-series op-amps with a dedicated LM4880 driver, this amp delivers effortless musicality for both sensitive IEMs and studio monitors. The Audio Path

Input Buffer (LME49721): A high-impedance Rail-to-Rail input stage ensuring your source (DAC or Phone) is never loaded down.

Active Baxandall Volume: Avoids the channel imbalance of standard passive pots, providing linear, precise volume control.

Power Driver (LM4880): A dedicated output stage delivering a clean 55mW per channel (@ 32Ω).

Hardware Safety: Equipped with 220uF safety coupling capacitors. This provides a physical DC-blocking barrier, protecting your headphones while maintaining a flat response from 22Hz to 20kHz.

Advanced Power & Battery Management

This design features a stabilized ±2.7V dual-rail system powered by the LM27762 charge pump + LDO.

Dual Power Modes: The unit operates seamlessly from an internal battery or via USB power (which also charges the battery).

Smart Logic: Integrated LTC2954 push-button control and TPS22917 high-side isolation.

Ultra-Low Standby: Off-state consumption is < 1uA, so your battery stays ready for months.

Battery Requirements: Compatible with any Single-Cell (3.7V) Li-Ion or LiPo battery.

Connector: Molex PicoBlade 2-pin.

Note: Battery is not included due to shipping regulations.

Precision Bass Boost

A toggleable +6dB (2x) shelving filter tuned to a 350Hz corner frequency. It adds musical weight and "body" to lean-sounding headphones without bleeding into the vocal midrange.

Technical Specifications

Op-Amps LME49721 (Ultra-low Distortion)

Output Power 55mW per channel (@ 32Ω)

Frequency Response 22Hz – 20kHz (@ 32Ω)

Bass Boost +6dB Shelving @ 350Hz

Power Consumption ~35mA (Active) / < 1uA (Standby)

Battery Connector Molex PicoBlade (2-pin)

Charging Integrated USB Charging (BQ-series)

**A Special Thanks

This project was made possible by the support of PCBWay, who sponsored the high-precision PCB manufacturing for this design. Their industry-leading fabrication ensures the tight tolerances required for our ultra-low-noise dual-rail power system.**

PCB measures: 75mm x 45mm x 12mm (L x W x H)