Formula xHD

About the Formula xHD

The Aqua Acoustic Quality Formula xHD is a flagship digital-to-analog converter (DAC) designed and hand-built in Italy, featuring a proprietary Optologic R2R ladder DAC architecture with no oversampling or digital filtering. It uses separate analog and digital power supplies with C-core transformers and discrete components such as BJTs, Mosfets, and J-FETs to ensure ultra-low noise and high sound quality. The analog output stage is direct-coupled with no capacitors in the signal path, and balanced outputs are transformer-coupled for superior tonal saturation and warmth. The DAC supports PCM sample rates up to 768 kHz and native DSD up to DSD256 (quad-rate DSD), with a fully floating, isolated USB decoding and clock generation implemented on FPGA with proprietary firmware. It includes multiple digital inputs such as USB 2.0, AES/EBU, coaxial, optical Toslink, and AQlink (I2S). The modular design allows for future upgrades and easy servicing. The Formula xHD is praised for its transparency, natural timbre, dynamic scale, and emotional musicality, with a long burn-in period required for optimal performance. It is compatible with Windows (custom XMOS driver), Mac OS (native X Core Audio), and Linux (USB Audio 2.0).