How do I integrate P4 into a audio system?

First, connect P4 to your audio sources via RCA cables, then connect P4 to an amplifier via RCA cables, and lastly, use speaker cables to connect the amplifier to the passive speakers.

What is the function of the Bypass switch?

This is the bypass function for turning the tone control on and off. Sliding it up bypasses the bass and treble adjustments while sliding it down enables the bass and treble controls. The bypass switch won’t function on the volume control.

What are the benefits of the high-precision motorized analog potentiometer in the P4?

It ensures smooth, precise volume control, and enhances usability while reducing noise and distortion. When adjusting the volume with the remote, the potentiometer‘s motor syncs with the physical knob, providing a seamless and intuitive experience.

What can the pre-out port used for?

Allows for easy connection to external powered subwoofers or additional amplification. It ensures seamless integration with your audio system, enabling enhanced bass response or driving additional speakers for a more immersive listening experience.

Fosi Audio P4 Mini Preamp with 3 RCA Inputs, EQ/Bypass, Treble & Bass Tone Control with Remote Control - Fosi Audio

Fosi Audio P4 Mini Preamp with 3 RCA Inputs, EQ/Bypass, Treble & Bass Tone Control - Fosi Audio

Product Highlights

RCA Inputs

≥ 110dB

SNR

≤ 0.003%

THD+N

≥105dB

SINAD

Product Highlights

RCA Inputs

≥ 110dB

SNR

≤ 0.003%

THD+N

≥105dB

SINAD

Fosi Audio P4 Mini Preamplifier

Name: Fosi Audio P4 Mini Preamplifier
Brand: Fosi Audio
SKU: P4-12V
Price: 99.99 USD
Availability: InStock

$99.99

148 total reviews

Features

Triple RCA Inputs
Bass, Treble, and Gain Control
Motorized Pot for Smooth Adjustment
Bypass Function for Pure Signal Path
Op-Amp Rolling: SS3602, MUSES02, OPA2134PA

Product variants

Review Videos

Finally! What We’ve All Needed! Won’t Stay in Stock…

cheapaudioman

P4 is a home‑run preamp, combining quality and utility.

Old Guy Hifi

Practical review: P4 integrates neatly into entry‑level Hi‑Fi.

Matt Coykendall

Deep dive: P4 + V3 Mono synergy explained.

Pieces of Vinyl

Comparative test: do you really need the P4 preamp?

Mad Audio

Is P4 the best budget analog preamp available?

Techder Audios

Finally! What We’ve All Needed! Won’t Stay in Stock…

cheapaudioman

P4 is a home‑run preamp, combining quality and utility.

Old Guy Hifi

Practical review: P4 integrates neatly into entry‑level Hi‑Fi.

Matt Coykendall

Deep dive: P4 + V3 Mono synergy explained.

Pieces of Vinyl

Comparative test: do you really need the P4 preamp?

Mad Audio

Is P4 the best budget analog preamp available?

Techder Audios

Another Masterpiece Driven by Voice of Customers

The P4 is a mini preamp self-developed by Fosi Audio based on extensive feedback from users worldwide after the launch of the V3 stereo amp.

Input: RCA x3; Output: RCA, Pre-Out
SNR≥ 110dB; THD+N≤ 0.003%
Frequency Response: 20Hz-20kHz(±0.1dB)

High-Precision Motorized Analog Pot

Offer smooth volume adjustment while reducing noise and distortion for a purer soundscape.

Pre-Out Port

Expandable connection for powered subwoofers/powered speakers.

3-Level Gain Adjustment

Match different output levels from audio sources for improved sound quality.

Tone Control Bypass

Bypass the tone control circuit to enjoy the purest high-fidelity sound.

Enjoying a Convenient Audio Experience

Easily adjust the volume, switch sources, and control the tone without leaving your seat.

P4 & ZP3 Comparison

Thinking about a new preamp? Let’s line up P4 and ZP3, and see what makes each one special.

Product details

Description

Mini Control Hub: The P4 supports up to 3 RCA inputs, allowing easy connection to CD players, streamers, DACs, cassette decks, and turntables with built-in phono preamp. Switch between sources with a click for seamless audio control.
Practical and User-Friendly: Equipped with volume control, bass and treble adjustment with bypass function, three-level gain control, and a remote. The preamplifier offers convenient audio setup and optimization, making every listening session effortless.
Motorized Potentiometer: Featuring a high-precision motorized analog pot, the P4 delivers smooth volume adjustment, reduced noise, and minimal distortion for a purer and more refined sound experience.
Compact and Solid: The P4 stereo preamp features a sleek, minimalist design that saves space and provides robust resistance to electromagnetic interference, ensuring reliable performance over time.
Exceptional Performance: With a low noise floor, high signal-to-noise ratio, and extremely low distortion, the P4 pre-amplifier delivers pristine audio, ensuring accurate sound reproduction and enhancing the listening experience for audiophiles

Specifications

Channel: 2.0
Input Mode: RCA*3
Output Mode: RCA, Pre-out
SNR: ≥ 110dB
Dynamic Range: ≥ 110dB
THD+N: ≤ 0.003%
Crosstalk: ≥ 105dB
Noise Floor: ≤ 9μV
Tone Adjustment Gain: ±12dB
Frequency Response: 20Hz-20kHz(±0.1dB)
Power Supply: DC 12V/1.5A

What‘s in the box？

Fosi Audio P4 Mini Preamplifier x 1
12V/1.5A Power Supply x 1
User’s Manual x 1

Which Product is right for you?

Compare products to find the best one for your needs.

From $199.99

Fosi Audio ZP3 Preamplifier

Learn more

Type

Preamp

Input

RCA x2, XLR

Output

RCA, XLR, Sub-Out

Bass & Treble Control

Yes

THD+N

≤ 0.0007%

SNR

≥ 115 dB

From $99.99

Fosi Audio P4 Mini Preamplifier

Learn more

Type

Preamp

Input

RCA x3

Output

RCA, Pre-Out

Bass & Treble Control

Yes

THD+N

≤ 0.003%

SNR

≥110dB

From $79.99

Fosi Audio P3 Tube Preamplifier

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Type

Preamp+Headphone Amp

Input

Bluetooth, RCA

Output

RCA, 3.5mm Headphone Jack, AUX

Bass & Treble Control

Yes

THD+N

≤0.02%

SNR

≥103dB

From $199.99