The Original Audio OPA-4A is a high quality tube and headphone amplifier combo, based on the joint use of two 12AU7 tubes for the power stage and two EL34 tubes for the single-ended output stage within a linear circuit. The OPA-4A reveals a warm, smooth and musical sound, typical of tube designs, without losing its vigor. Its architecture allows it to develop a power of 2x6W under 8Ω for the speaker output and 2x4W under 32Ω for the balanced headphone output or 2x900mW under 32Ω for its single-ended headphone output. An ALPS 27 potentiometer allows a fine volume control of the sound level.

For its connectivity, the OPA-4A offers a balanced input on stereo XLR and single-ended on stereo RCA, as well as a Bluetooth connectivity. The latter allows you to broadcast your music remotely, from a smartphone for example. It also supports the aptX transmission codec, allowing to reach a quality of restitution close to that of the CD.

On the output side, there are speaker terminals at the back, but also a balanced headphone output in XLR 4-pole format and a single-ended headphone output on 6.35mm jack.