Fosi Audio P4
- Fosi Audio
Fosi Audio P4
- Fosi Audio
$119.00
- Authorized Dealer · Tech Support · 30-Day Returns
Why it stands out
Best for
Not ideal for
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Frequently asked questions
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Official product information provided by Fosi Audio
The following product descriptions, specifications and images are provided by the manufacturer.
Fosi Audio P4 is a compact solid-state stereo preamplifier that brings three RCA sources under one volume and tone-control stage.
Its motorized analog volume control, remote operation, three-level gain, tone bypass and separate pre-out make it a practical partner for power amplifiers and powered subwoofers.
Why it stands out
Three-source analog hub
Three RCA inputs allow convenient switching among a DAC, streamer, CD player or other line-level source.
Motorized analog volume control
The remote-driven analog potentiometer provides smooth level adjustment without replacing the analog signal path with digital volume control.
Flexible tone and gain adjustment
Bass, treble, bypass and three gain levels help match different source levels and listening preferences.
Low-noise preamplifier performance
High SNR and low THD+N support clean system control in a compact all-metal chassis.
Best for
- Systems with multiple line-level analog sources
- Power amplifiers needing source selection and remote volume
- Powered speaker systems
- 2.1 systems using the volume-controlled pre-out
Not ideal for
- Driving passive speakers directly
- Turntables without a built-in or external phono preamp
- Users needing Bluetooth or digital audio inputs
EMiUZEK Buying Notes
- P4 is a preamplifier and cannot directly power passive speakers.
- All three inputs are line-level RCA; a standard turntable requires a phono preamp.
- Pre-out is volume controlled and suitable for compatible powered subwoofers or powered speakers.
Frequently asked questions
Can P4 drive passive speakers?
No. Connect its RCA output to a power amplifier that drives the passive speakers.
Does P4 include Bluetooth?
No. It is an analog RCA preamplifier.
Can I connect a turntable?
Only if the turntable has a built-in phono stage or you use an external phono preamp.
What is pre-out for?
It provides a volume-controlled line-level output for compatible powered speakers, a powered subwoofer or downstream equipment.
Can tone controls be bypassed?
Yes. The bypass function provides a more direct signal path when tone adjustment is not needed.
What does the gain setting do?
The three gain levels help match differing source output levels and system sensitivity.
HOW TO CONNECT
Power amplifier system
Source: DAC, streamer, CD player or phono preamp
Connection: RCA input
Output: RCA output
Target: Power amplifier → passive speakers
Note: Select the source and use P4 for volume control.
Powered speaker system
Source: Up to three line-level sources
Connection: RCA input
Output: Pre-out or RCA output
Target: Powered speakers
Note: Begin with conservative volume settings on both devices.
2.1 system
Source: Line-level source
Connection: RCA input
Output: RCA output + pre-out
Target: Power amplifier and powered subwoofer
Note: Use pre-out for the powered subwoofer and confirm crossover settings.
Technical Specifications
Audio performance
| Feature | Specification |
|---|---|
| Product type | 2.0-channel solid-state preamplifier |
| SNR | ≥110dB |
| Dynamic range | ≥110dB |
| THD+N | ≤0.003% |
| Crosstalk | ≥105dB |
| Noise floor | ≤9μV |
| Frequency response | 20Hz–20kHz (±0.1dB) |
| Tone adjustment | ±12dB |
Connectivity and power
| Feature | Specification |
|---|---|
| Inputs | RCA × 3 |
| Outputs | RCA, pre-out |
| Gain adjustment | +3dB / +6dB / +9dB |
| Volume control | Motorized analog potentiometer with remote |
| Power supply | DC 12V / 1.5A |
Recommended System Setup
| Setup | Connection |
|---|---|
| Stereo separates | Sources → P4 → Power amplifier → Passive speakers |
| Powered speakers | Sources → P4 → Powered speakers |
| 2.1 separates | Sources → P4 → Power amplifier + powered subwoofer |
Additional Product Content
Fosi Audio product comparison
Compare the main Fosi Audio preamplifier choices by source support, outputs and the features that most affect system design.
| Feature | P4 | P3 | ZP3 |
|---|---|---|---|
| Product position | Compact analog preamp | Tube preamp + headphone amp | Balanced high-performance preamp |
| Analog inputs | RCA × 3 | RCA | RCA × 2, XLR |
| Wireless / digital inputs | None | Bluetooth 5.1 | None |
| Main outputs | RCA, pre-out | RCA, AUX | RCA, XLR, sub-out |
| Headphone output | No | 3.5mm | No |
| Speaker amplification | No | No | No |
| Tube stage | No | Yes, replaceable 5654W | No |
| Tone controls | Bass and treble with bypass | Bass and treble | Bass and treble |
| Remote control | Yes | No | Yes |
| THD+N | ≤0.003% | ≤0.02% | ≤0.0007% |
| SNR | ≥110dB | ≥103dB | ≥115dB |
| Best use | Three analog sources and powered sub expansion | Bluetooth tube preamp and headphones | Balanced stereo system integration |
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