The FX-Audio TUBE-03E is a 6K4 tube preamplifier. Affordable, it remains a very good preamplifier, complete and powerful, with a clean volume control. In addition to the classic RCA Stereo and 3.5mm Jack inputs, it features a 4.2 Bluetooth input for streaming audio files from a Bluetooth-connected device, such as your smartphone. The DAC in charge of digital-to-analog conversion is directly integrated into the Bluetooth A64215 chip and allows decoding of the quality signal. On the output side there is a Stereo RCA. All connectors are gold plated, ensuring very good conductivity and resistance to oxidation. Finally, there is a tone control on the front panel, which allows you to adjust the bass and treble reproduction according to your listening and audio system. The tone control uses two NN5532P AOPs mounted on DIP8 and interchangeable.