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Estimated price (community-sourced)
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About the X4
The Fosi Audio BOX X4 (often listed as Fosi Audio X4) is a compact, two-channel hybrid tube phono preamplifier and headphone amplifier for moving-magnet (MM) turntables. It uses two JAN 5654W vacuum tubes and includes volume, bass, and treble controls. The unit accepts an MM phono source or a 3.5 mm AUX source, and provides an RCA line output for powered speakers or a separate amplifier plus a 3.5 mm headphone output. It is a preamplifier rather than a power amplifier, so it cannot directly drive passive speakers. The product is still listed by Fosi Audio and multiple retailers; therefore, it does not appear to be discontinued.
Specifications
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