Fosi Audio Tube Phono Preamp – BOX X4
Give Your Turntable a Dedicated Place in Your Audio System
Bring your MM turntable into a line-level audio setup with the Fosi Audio BOX X4 tube phono preamp. Its compact metal body, tone controls and headphone connection make it a useful centerpiece for a personal listening station.
Key Benefits
- MM phono stage — Convert a compatible turntable signal to line level.
- Bass and treble controls — Adjust the tonal balance from the front panel.
- Headphone connection — Add another listening option to your desktop setup.
Make your record-playing routine feel more intentional, from selecting an album to setting the listening level. Use the BOX X4 with powered speakers or an appropriate amplifier; it does not directly power passive speakers.
Frequently Asked Questions
Can it drive passive speakers directly?
No. Passive speakers require a suitable amplifier.
Which turntable cartridge type is specified?
The phono input is specified for MM cartridges.
Are vacuum tubes fitted?
Yes. The description identifies 6J1 vacuum tubes.
Can I adjust bass and treble on the unit?
Yes. The front panel has separate bass and treble controls.
Does it have a headphone connection?
Yes. The product description and front panel identify a headphone connection.
SPECIFICATIONS
Brand Name: Fosi Audio
Certification: CE
Channels: 2 (2.0)
Control Method: Push button
FOSI AUDIO Model: X4
High-concerned chemical: none
Input: RCA+3.5mm AUX
Material: Metal
Maximum Power Per Channel: NO POWER
Model Number: BOX X4
Origin: Mainland China
Output: Powered Speakers
Output Power: 0
Package: Yes
Power Adapter: 12V with UL PSE Level 6 energy efficiency
Surround sound channel configuration: Others
Type: Tube Preamp Amplifier
feature: Desktop Audio Preamp,MM Phono Stage Amplifier

Fosi Audio Phono Preamp for Turntable Phonograph Preamplifier With Vacuum Tube Amplifier HiFi BOX X4
Notice:
1.The BOX X4 is currently equipped with a 6J1 vacuum tube.
2.BOX X4 is only a preamplifier, not amplifier, can not be connected with passive speakers directly, If you need connect BOX X3 with passive speakers, you need to connect it with an amplifier then connect the amplifier with your passive speakers.
Features:
1. Tube MM Phono Preamplifier: The BOX X4 phono preamp supports 3.5MM AUX and MM turntable input, converting phono signals to Line Level with low-frequency noise removal using high-quality components and low-noise integrated circuits. Protect your turntable with the grounding post feature
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2.Tube Headphone Amplifier & Preamplifier: The Fosi Audio BOX X4's versatile design includes a 3.5MM AUX headphone and RCA output, offering a range of usability beyond expectations
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3.Applicable Vacuum Tube Model: 6K4/6J1/6J4/GE5654/6AK5/66*In vacuum tubes, etc. Achieve a customized stereo system by replacing vacuum tubes. With different tubes producing unique sounds, it's a DIY opportunity worth exploring
Highlight:
Model: BOX X4
Power Adapter Output: 12V
Product Adapter Input Voltage Range: AC 100V - 240V
Output Voltage Level: 1kHz and 650mV
SNR ≥ 70dB
THD ≤ 0.1%
Frequency Response: Standard RIAA
Product Weight: 0.71 lb/320g
Product Dimensions: 3.97x4.72x1.37 inch (10.09*12*3.5 cm)
Input Mode: MM turntable input +3.5mm AUX
Output Mode: RCA output + 3.5mm headphone output
Applicable headphone types: 16 Ω - 300 Ω
Package Include:
*Box X4 Phono Preamp x1
*6J1 Vacuum Tubes x2
*12V Power Adaptor x1
*User Manual x1
QA
Q1:Can the headphone and RCA outputs be used simultaneously?
Yes. When both the 3.5mm headphone output and RCA output are connected, sound will be output through both the headphones and RCA connectors.
Q2:Can the BOX X4 be used with an MC cartridge?
NO.The BOX X4 is designed specifically for use with MM cartridges. However, our upcoming model, the BOX X5 is compatible with MC cartridges.







