Fosi Audio SK01
- 20 reviews
- Fosi Audio
Fosi Audio SK01
- 20 reviews
- Fosi Audio
$25.42
- Authorized Dealer · Tech Support · 30-Day Returns
Why it stands out
Best for
Not ideal for
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Setup guide
How to connect
What you should know
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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 SK01 is a battery-powered analog headphone amplifier and preamplifier with 3.5mm line input, dual headphone jacks and adjustable three-band tone control.
Up to 2400mW at 32Ω in high gain, pure bypass, loudness and a 2500mAh battery make it flexible for desktop and transportable wired listening.
Why it stands out
High-power analog headphone drive
High gain delivers up to 2400mW at 32Ω for a broad 16–300Ω headphone range.
Three-band tone shaping
Separate treble, midrange and bass controls allow more precise adjustment than basic two-band designs.
Pure and loudness modes
Bypass removes tone processing, while loudness improves perceived bass and treble at low listening levels.
Headphone amp and preamp
3.5mm line out feeds an amplifier or powered speakers with the same volume and tone control.
Best for
- Powerful wired headphone listening
- Analog sources needing portable amplification
- Users wanting three-band tone control
- Preamp use with powered speakers or a power amplifier
Not ideal for
- USB digital audio or DAC conversion
- Bluetooth wireless playback
- Balanced headphone connections
EMiUZEK Buying Notes
- SK01 is analog only; USB-C is for charging and does not carry audio data.
- It cannot drive passive speakers directly; line out must feed an amplifier.
- High gain can become very loud—start at minimum volume before wearing headphones.
Frequently asked questions
Does USB-C carry audio?
No. USB-C is for 5V charging only.
Can it work as a preamp?
Yes. Use 3.5mm line out into an amplifier or powered speakers.
Can it drive passive speakers?
No. A separate power amplifier is required.
What headphones are supported?
Fosi specifies 16–300Ω.
Can tone controls be bypassed?
Yes. PURE mode bypasses the tone circuit.
How long does the battery last?
Fosi states up to about six hours, depending on use and load.
HOW TO CONNECT
Portable headphones
Source: Phone, DAP or dongle DAC
Connection: 3.5mm line in
Output: 3.5mm or 6.35mm headphone
Target: Wired headphones
Note: USB-C is not an audio input.
Desktop preamp
Source: DAC or streamer
Connection: 3.5mm line in
Output: 3.5mm line out
Target: Power amplifier or powered speakers
Note: SK01 controls level and tone.
High-impedance headphones
Source: Line-level DAC
Connection: 3.5mm line in
Output: 6.35mm headphone
Target: 16–300Ω headphones
Note: Choose gain carefully and start low.
Technical Specifications
Audio performance
| Feature | Specification |
|---|---|
| High / low gain output | 2400mW / 300mW at 32Ω |
| Headphone impedance | 16–300Ω |
| SNR | 108dB |
| THD | ≤0.001% at 1kHz / 770mV |
| Frequency response | 20Hz–20kHz (±0.05dB) |
| Noise floor / Crosstalk | 20μV / 83dB |
Connections and power
| Feature | Specification |
|---|---|
| Input | 3.5mm line in |
| Outputs | 3.5mm line out; 3.5mm and 6.35mm headphones |
| Tone adjustment | Treble ±8dB; mid ±10dB; bass ±11dB |
| Battery | 2500mAh |
| Charging | DC 5V USB-C; power only |
Recommended System Setup
| Setup | Connection |
|---|---|
| Portable | Phone/DAP → SK01 → Headphones |
| Desktop | DAC → SK01 → Headphones |
| Preamp | Source → SK01 line out → Power amplifier |
Additional Product Content
Fosi Audio product comparison
Compare the models by the differences that most affect system matching and everyday use.
| Feature | SK01 | SK02 | P3 |
|---|---|---|---|
| Product position | Analog headphone amp / preamp | USB/optical DAC headphone amp | Tube preamp / headphone amp |
| Digital DAC | No | Yes, ES9038Q2M | Bluetooth input only |
| Main inputs | 3.5mm line | USB, optical | Bluetooth, RCA |
| Headphone outputs | 3.5mm, 6.35mm | 3.5mm, 4.4mm | 3.5mm |
| Maximum output at 32Ω | 2400mW high gain | 755mW via 4.4mm | 150mW |
| Balanced headphone output | No | 4.4mm | No |
| Tone controls | Treble, mid, bass | No | Bass, treble |
| Battery operation | Yes | No | No |
| Line / pre-out | 3.5mm | 3.5mm line / optical | RCA, AUX |
| Best use | Powerful analog portable amp | Hi-res desktop DAC/amp | Tube Bluetooth preamp |
What's in the box, manuals and downloads
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