The OPA2134 with JFET’s is a high-end DIY stereo amplifier for dynamic headphones. It was designed with an emphasis on maintaining simplicity in the signal path, and utilizes an all-discrete, fully-complementary topology featuring a JFET input stage, current-mirror VAS (voltage gain stage), Sziklai complementary feedback pair (CFP) output stage, and no global negative feedback.
It is also ideal as a pre-amplifier line stage. Just add multiple inputs and a selector switch. Its low output impedance and high output current capability allows it to drive a power amplifier over long interconnect cables without signal degradation.
Designed to be a compact AC-powered desktop unit, it provides high performance with relatively minimal complexity for an all-discrete design. In conjunction with an off-the-shelf enclosure solution, the amplifier is simple and inexpensive to build.
Based on the Kumisa III by Benny Jørgensen, it adds several significant enhancements by Alex Cavalli. Alex and AMB teamed up and performed SPICE simulations and fine-tuning, as well as printed circuit board layout. The project was conducted with community participation, in an open-source manner , and the result is an exceptional amplifier you see here.
Amplifier is designed to be easy to build, but is not recommended as a first-time project for the beginner.
pcb is FR4 1.6mm 2oz Blue (HASL)