{"product_id":"fosi-audio-box-x4-phono-preamp-headphone-amplifier-with-jan-5654w-vacuum-tubes-for-mm-turntable-phonograph-preamplifier","title":"Fosi Audio Box X4 Phono Preamp \u0026 Headphone Amplifier with JAN 5654W Vacuum Tubes for MM Turntable Phonograph Preamplifier","description":"\u003ch4\u003eThe Fosi Audio Box X4 combines dedicated phono preamplification with integrated headphone amplification in a single compact unit. Purpose-built MM cartridge input with low-noise signal conversion and grounding protection ensures pristine vinyl playback, while auxiliary inputs accommodate digital sources. Tube-based architecture supports multiple vacuum tube variants—5654W, 6K4, 6J1, 6J4, GE5654, 6AK5, and others—allowing personalized sonic tuning through component swapping. Dual output configuration enables simultaneous line-level and headphone monitoring. Package includes 12V power supply, documentation, and 18-month warranty with dedicated customer support.\u003c\/h4\u003e","brand":"Fosi","offers":[{"title":"Default Title","offer_id":47826639618100,"sku":"Box X4-12V","price":79.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0729\/7030\/5588\/files\/1_23f71b08-8ab3-4646-a3da-62a869a3e11b.webp?v=1779393805","url":"https:\/\/www.theheadphoneshop.com\/products\/fosi-audio-box-x4-phono-preamp-headphone-amplifier-with-jan-5654w-vacuum-tubes-for-mm-turntable-phonograph-preamplifier","provider":"The Headphone Shop","version":"1.0","type":"link"}