Fosi Audio Box X2 Tube Phono Preamplifier

About The Fosi Audio Box X2 Tube Phono Preamplifier

The Box X2 is a high performance MM phono preamplifier which uses a pair of Vacuum Tubes in its gain stage which brings a richness and warmth to the vinyl sound that many are looking for and which makes records sound more engaging than digital formats such as Compact Discs or Streaming Services.

This Fosi Audio phono preamplifier removes low-frequency noise and ensures clear sound quality by converting phono signals to line-level signals using high-quality components and low-noise integrated circuits.

3 Switchable Gain Modes

You can switch between 3 modes: 39, 42, or 45 dB which allows high compatibility and customizable control provided by the adjustable gain levels.

Combo Tube Phono Preamp and Tube Line Preamp

With a front 3.5 mm Aux input, it's also a tube line preamp which is a bit of a welcome surprise. So, if you have a Moving Magnet cartridge equipped turntable you should plug it into the RCA inputs on the rear panel and connect the earth lead (if required). However, if you would like to enjoy that warm Tube sound with another device with an analogue output such as a CD player or Streamer then you use an RCA to 3.5 mm cable which you plug into the front panel Aux input. This is a line level input that bypasses the phono stage and allows you to enjoy that warm tube sound using your other components. To go back to listening to your turntable, simply remove the 3.5 mm connector from the front panel socket, being sure to turn the Box X2 off before doing so.

Vacuum Tubes

The Fosi Audio Box X2 is supplied with a pair of highly regarded GE JAN5725W vacuum tubes used in the gain stage. These are military grade (Joint Army-Navy) versions of the 5725W which is pleasantly surprising in such an affordable phono stage. Tube rolling, however is a favourite pastime of tube amp owners and you can roll (replace) the stock tubes with a range of alternatives which will make your tube preamp sound different. Some differences you may prefer and some you may not but it’s very inexpensive and easy to try this out for yourself and quite a plot of fun. Compatible tubes include the 6AK5, 6K4, EF95, 6J1, 6J2, 5654W, 6J2P, 6AS6, CV4011, GL5725, and CK5725.

Our Review

The Fosi Audio Box X2 Tube Phono Preamplifier is all about adding a touch of magic to your vinyl sessions, wrapping your favourite records in that smooth, golden warmth only tubes can bring. It’s the kind of sound that makes you want to pull up a chair, sink into the music, and forget about the cold precision of digital formats for a while. With three adjustable gain settings and the bonus ability to double as a tube line preamp for other gear like CD players or streamers, it’s surprisingly versatile for something that looks so simple. Those stock GE JAN5725W military-grade tubes are a real treat, but the Box X2 also invites a little tube-rolling fun if you’re the adventurous type. Whether you stick with the originals or swap them out for something new, the experience is all about enjoying your music in a way that feels rich, personal, and just a little bit indulgent.

Main Features & Specifications

• Design: Compact High Performance Tube Phono Preamplifier
• Inputs
  • Rear Panel: Stereo RCA (MM) Moving Magnet Phono Input
  • Front Panel: 3.5 mm Aux Line Level Input
• Output: Stereo RCA Output
• Gold-Plated RCA Jacks
• 3 Gain Adjustment Level Settings: 39, 42, 45dB
• Output Voltage Level: 600 mV
• (SNR) Signal to Noise Ratio: ≥98dB
• (THD) Total Harmonic Distortion: <0.1%
• Power Supply: DC 12V 1.5A
• Included Accessories: DC 12V 1.5A Power Adaptor, 2 x Vacuum Tubes, 2 RCA to 3.5 mm Mini Jack Cable, User Manual
• Dimension (WxHxD): 98 x 42 x 118 mm (65 mm high with tubes installed)
• Weight: 0.3 kg
• Manufacturer's Warranty: 2 Years

Note: Features & Specifications Subject To Change Without Notice. E&OE.