• Live sound reinforcement and stage use.
• Initial prototype uses an external passive dynamic microphone connected by XLR.
• Future revision may integrate a custom microphone capsule.
• Prototype priority order: reliability, manufacturability, RF performance, professional audio quality, then cost.

• Capture a balanced passive dynamic microphone signal at the transmitter.
• Transmit high-quality low-latency digital audio wirelessly.
• Receive audio and output a true balanced professional XLR signal.
• Operate from a single-cell Li-ion battery.
• Recharge through USB-C.
• Provide robust RF behavior with manufacturer-required antenna keepout.

• Transmitter PCB and receiver PCB in one project.
• DECT-class wireless audio module, selected provisionally.
• Low-noise balanced microphone preamp.
• True balanced receiver output line driver.
• USB-C Li-ion charging and power-path management.
• Battery fuel measurement where practical.
• Battery protection and ESD protection.

Diagram

• Preferred: DECT module with professional audio support.
• Provisional lead: Renesas DA14AVDDECT, pending exact latency, pinout, footprint, antenna keepout, and availability confirmation.
• Rejected: Bluetooth audio modules; they do not meet the handoff requirement.

• XLR female input.
• Pin 1 = shield/ground strategy, Pin 2 = hot, Pin 3 = cold.
• Low-noise balanced microphone preamp recommended: THAT1580-family or equivalent.
• Add RF/ESD input protection and phantom-power abuse protection in detailed revision.

• XLR male output.
• True balanced active driver recommended: THAT1646 or DRV134 family.
• Professional +4 dBu headroom may require boosted/split analog rails; this remains an explicit design decision.

• Single-cell Li-ion battery per unit.
• USB-C sink with independent CC1/CC2 pull-down resistors.
• Charger/power-path IC per unit unless the selected DECT module’s integrated battery management is used instead.
• Fuel gauge per unit if a host/controller is available to read it.

• USB-C power input per board.
• Battery connector per board.
• XLR female input on transmitter.
• XLR male output on receiver.
• RF module audio/control interface: TBD until selected module pinout is imported.

• Candidate battery: 800–1200 mAh single-cell Li-ion/LiPo depending on enclosure.
• Candidate charge current: 500 mA default for USB compatibility and thermal margin on a narrow PCB.
• Runtime target: several hours; exact value depends on RF module operating current and line-output rail strategy.

• Compact SMD design.
• 4-layer PCB recommended for RF/audio grounding and return-current control, though 2-layer may be evaluated only after RF module layout guidance is known.
• Prefer DigiKey, Mouser, and LCSC-stocked parts.
• Avoid NRND/obsolete RF modules for the main design.

• RF module control, pairing, audio routing, and fuel-gauge reading depend on the selected module and host/control interface.
• Firmware documentation is deferred until the RF/control architecture is locked.

• Maximum PCB width: 25 mm.
• Preferred length: about 60 mm, flexible if required.
• RF module should sit at the end of each PCB.
• Antenna keepout must be free of copper, vias, ground pour, components, and enclosure metal on all layers.

• Use DECT-class professional RF, not Bluetooth.
• Use a module, not a bare RF chip, to reduce RF certification/layout risk.
• Treat DA14AVDDECT as provisional lead; do not freeze PCB layout until exact module data is available.
• Use active balanced output rather than pseudo-balanced output.
• Use separate analog/RF layout regions and strong grounding discipline.

• The first prototype may use an evaluation-module-derived RF interface if the exact production module part is unavailable in Flux.
• Audio output level is assumed to target professional line input compatibility, but maximum output level/headroom still needs confirmation.
• The battery pack may include built-in cell protection; if not, board-level protection must be added.

• Initial specification created from the ChatGPT handoff.
• RF module selection identified as the gating item for production schematic and PCB layout.