This is a custom-made Oz design OZ-21010 tube microphone preamplifier. In addition to the standard version, it has a line input and an opto-compressor. The audio signal circuit uses vacuum tubes and transistors, the power supply circuit is fully discrete, the microphone input uses a Lundahl transformer, and the opto-compressor uses a Carnhill transformer for the line. The amplification section uses two 12AX7 and 12AU7 vacuum tubes, which were replaced with sovtek and mullard tubes around March 2025. The unit has been used about 10 times since then. ■ GAIN 20dB～60dB (9-step rotary switch with 5dB steps) ■ Phantom power ■ Phase switch (polarity inversion) ■ PAD (-10dB) ■ HPF (80Hz) ■ Input impedance: 1kΩ ■ Output impedance: 100Ω or less ■ Frequency response: 20Hz-60kHz ±2dB ■ Distortion (THD+N): 0.01 or less (1k / +13dBu) ■ S/N ratio: 89dB (Signal: 1V reference IHF-A) ■ Input terminals: XLR ■ Output terminals: XLR ■ Power supply voltage: 100V (adapter connection) ■ Included items: Main unit / Adapter ■ Weight: 3.2kg ■ Dimensions: 483mm x 44mm x 260mm