DIY Audio Hybrid Tube MOSFET Headphone Amplifier Simple Circuit

The hybrid tube MOSFET line amp, which, because of its musical sound, became a very popular amplifier “Low-Voltage TubeMOSFET Line Amp,” which also appears on borbelyaudio.com under Spe cial Articles. DIY amateurs wished to use it in many different applications, such as CD buffer, I/V converter, power amplifier, and headphone amplifier. It worked very well in all line-level ap plications, but the second stage was not laid out for high-current operation, so driving headphones was not possible. I have therefore redesigned the circuit to allow high-current operation.

The result is the EB-804/421, a single-ended (SE) pure Class-A amplifier, ca pable of driving headphones between 32 and 600Ω. The amplifiers need ±15 to ±24V regulated supplies at 160/100mA and 6.3V DC at 300mA for the tube heat er. I recommend feeding the amps from separate supplies. The PCB for one amp is 90 x 80mm.