Pro-Ject's Tube Box DS is a high-end MM/MC phono preamplifier featuring an unprecedented level of flexibility at its price point. Based on a dual-mono circuit topology featuring a matched pair of premium ECC-803 Golden Pin Tubes, Tube Box DS employs premium parts throughout the preamplifier circuitry including costly ultra-low noise semiconductors. Unique to this model is continuously variable control of cartridge input impedance loading. By being able to adjust anywhere within the range of from 10-1,000 ohms, you can dial in the perfectly appropriate impedance for your particular phono cartridge therefore achieving the cartridge's optimized performance. Gain adjustment is also selectable in three steps of 40/50/60 dB, covering a wide range of both Moving Magnet of Moving Coil cartridge brands. For Moving Magnet cartridges, input capacitance is also variable. A switchable subsonic filter is also provided that can filter out frequencies below 20Hz.