Fosi Audio T20 Review



Fosi Audio T20 Review



Fosi Audio is a Chinese company is specialized reliable and easy-to-use Budged HiFi solutions such like DAC’s, Preamplifiers, Bluetooth Amplifiers and Speakers. The T20 is a Bluetooth Tube & Headphone Amplifier that features Qualcomm’s QCC3031 BT SoC that supports the aptX and aptX-HD codec’s. The device is equipped with 6J4 vacuum tubes and offers up to 50 watts per channel for Passive Speakers. Moreover, the Fosi T20 comes with independent hardware volume, bass and treble controls.



I would like to thank Fosi Audio for providing me the T20 for review purposes. I am not affiliated with Fosi Audio beyond this review and these words reflect my true and unaltered, opinions about the product.


Price & Availability:

The actual MSRP price for the Fosi Audio T20 is about 89.99 US$. More information’s can be found under the link below;


Package & Accessories:

The Fosi Audio T20 came in a rectangular box with some brandings and their motto “HiFi Made Fun” on the top.

Inside the box are the following items:

  • 1 x Fosi Audio T20 BT Tube & Headphone Amplifier
  • 2 x 6J4 Vacuum Tubes
  • 1 x 24V/4.5A Power Adapter
  • 1 x Bluetooth Antenna
  • 1 x User Manual


Design & Build Quality:

The Fosi Audio T20 is a solid looking device with its all metal casing that has a quite compact design and a small size with dimensions of 5.06 x 3.86 x 1.35 inches.

The surface of the metal housing has a black finish with slightly rounded corners.

On the front of the device is the control panel that sports a power On/Off switch, a 3.5mm headphone output and the Bass, Treble and Volume knobs. The knobs do offers a pretty precise feedback with just a very low amount of imbalance that is on a tolerable level for a device at this price range.

On the top of the T20 are the seats for the Vacuum Tubes that do glove in a nice Blue color.

At the rear side of the device is a Bluetooth / Aux switch, the Bluetooth Antenna (RF) interface, the Left & Right Audio inputs, the Left & Right Speaker outputs and the DC input interface.

At the bottom of the device are fours stands made from some sort of rubber material.

The build quality of the Fosi T20 meets my expectations for a product at this price level.



Technical Specifications:

  • Model                                     : T20
  • Bluetooth SoC                        : QCC3031
  • Amplifier Class                       : Class D
  • OP-AMP                                : Texas Instruments TPA3116
  • Max Power Output                 : 50W x 2@4Ω
  • Frequency Range                  : 20Hz – 20 kHz (±1 dB)
  • Terminating Impedance         : 2 Ω – 8 Ω
  • Headphone Output                 : 16-64Ohm
  • THD                                        : ≤ 0.04%
  • SNR                                       : ≥ 99dB
  • Input Sensitivity                      : ≤ 280mV
  • Bluetooth Codec’s                  : apt-X and apt-X HD
  • Bluetooth Trans. Distance     : Up to 12m 39 Ft
  • Output                                    : Passive Speaker & Headphones
  • Analog Inputs                         : RCA
  • Analog Outputs                      : 3.5mm Single Ended, Speaker
  • Power Input                            : 12V – 24V DC Input Range
  • Dimensions                            : 5.06 x 3.86 x 1.35 inches



Amplification and Audio Parameters:

The Fosi Audio T20 is equipped with 3.5mm Single Ended headphone output that has a SNR (Signal to Noise Ratio) value of 99dB and a THD (Total Harmonic Distortion) of approx ≤0.04% that are on an acceptable level for a Tube Headphone Amplifier at this price range.

The Fosi Audio T20 comes with a Texas Instruments TPA3116 OP-AMP K5 Pro is a pretty powerful OP-AMP with up to 50W per channel for Speakers, while I couldn’t find any value for the 3.5mm Headphone output.

The T20 came with 2x 6J4 vacuum tubes that do produce a pretty lush and warm tube. The background of the device shows a relative audible amount of background noise while listen to In-Ear Monitors. Headphones on the other are more tolerable, especially harder to driver planar headphones such like the HiFiMAN Edition XS.


Bluetooth Connectivity:

The Fosi Audio T20 is equipped with Qualcomm’s QCC3031 SoC that supports aptX and aptX-HD codec’s that do offer 24-bit music quality over Bluetooth. The T20 offers a quite stabile Bluetooth connection up to 12 meters.


Equipment’s used for this review:

  • Sources                     : Fosi Audio T20, ASUS TUF FX504GD, Samsung Galaxy S22 Ultra
  • IEM’s                          : Moondrop Blessing3
  • Headphones             : HiFiMAN Edition XS, SIVGA Luan



Albums & tracks used for this review:

  • Adele – My Little Love (Spotify)
  • Randy Crawford – On Day I Will Fly Away (Flac 16bit/44.1kHz)
  • Hayley Westenra – Odyssey Album (Dezzer HiFi)
  • Dionne Warwick – Walk On By (Flac 16bit/44.1kHz)
  • Sarah McLachlan – Angel (Flac 24bit/48kHz)
  • Sertap Erener – Aşk (Flac 16bit/44.1kHz)
  • Edith Piaf – Non Je Ne Regrette Rien (Flac 16bit/44.1kHz)
  • Diana Krall – So Wonderful (DSF)
  • Aretha Franklin – I Say A Little Payer (Flac 24bit/96kHz)
  • Sonya Yoncheva – (Giuseppe Verdi) II Trovatore, ActI (Flac 24bit/96kHz)
  • George Michael – Don’t Let the Sun Go Down on Me (Flac 24bit/192kHz)
  • David Bowie – Heroes (Flac 24bit/192kHz)
  • Elton John – Rocket Man ((Flac 24bit/96kHz)
  • Barry White – Just The Way You Are (Flac 24bit/48kHz)
  • Isaac Hayes – Walk On By (Flac 16bit/44.1kHz)
  • Sting – Englishman in New York – (Flac 24bit/48kHz)
  • Eric Clapton – Wonderful Tonight (Flac 24bit/96kHz)
  • B. King – Riding With The King (Tidal Hi-Fi)
  • Dave Gahan – Kingdom (Tidal Hi-Fi)
  • U2 – Sunday Bloody Sunday (Flac 16bit/44.1kHz)
  • Muse – Hysteria (Flac 24bit/96kHz)
  • Rush – YYZ (Flac 16bit/44.1kHz)
  • Red Hot Chili Peppers – Nobody Weird Like Me (Flac 24bit/48kHz)
  • Bro Safari, UFO! – Drama (Deezer HiFi)
  • Rok Nardin – Berserks (Spotify)
  • Bear McCreary – Valkyries “God of War OST” (Deezer HiFi)
  • Armin Van Buuren – Vini Vici (Flac 16bit/44.1kHz)
  • Daft Punk – Doin’ it Right (Flac 24bit/96kHz)
  • Jo Blankenburg – Meraki (Spotify)
  • Lorde – Royals (Flac 24bit/48kHz)
  • Massive Attack – Angel (Flac 24bit/48kHz)
  • Toutant – Rebirth (Deezer HiFi)
  • Gogo Penguin – Raven (Flac 24bit/192kHz)
  • Gogo Penguin – Murmuration (Flac 24bit/192kHz)
  • Alboran Trio’s – Cinque Lunghissimi Minuti (Flac 16bit/44.1kHz)
  • Portishead – It Could Be Sweet (Spotify)
  • Max Richter – On the Nature of Daylight (Flac 24bit/96kHz)
  • Charly Antolini – Duwadjuwandadu (Flac 24bit/192kHz)
  • Ferit Odman – Look, Stop & Listen (Flac 24bit/192kHz)
  • Chopin – Nocturn No. 20 In C-Sharp Minor (Flac 16bit/44.1kHz)
  • Fazıl Say – Nazım Oratoryosu (Live) (Flac 16bit/44.1kHz)
  • Vivaldi – Le QuarttroStagioni “The Four Season” (Deezer HiFi)
  • Otto Liebert& Luna Negra – The River (Flac 24bit/192kHz)
  • Lunatic Soul – The Passage (Flac 16bit/44.1kHz)
  • Deftones – My Own Summer (Shove it) (Flac 16bit/44.1kHz)
  • Metallica – Sad but True (Flac 24bit/96kHz)
  • Opeth – Windowpane (Flac 16bit/44.1kHz)
  • Megadeth – Sweating Bullets (Tidal Hi-Fi)
  • Rush’s – Leave That Thing Alone (Flac 16bit/44.1kHz)
  • Slayer – Angel of Death (Spotify)
  • Liquid Tension Experiment 2 – Acid Rain (Spotify)
  • Yosi Horikawa – Bubbles (Spotify)



The Sound:

This review has been written after a burn-in period of about 50 hours. My sound experience below are based over the 3.5mm Headphone output paired with In-Ear Monitors like the Moondrop Blessing3 and headphones like the SIVGA Luan and HiFiMAN Edition XS. The Bass and Treble knobs of the device have been set to 12 o’clock, which are the default settings.

Bass / Midrange / Treble / Soundstage & Imaging:

The Fosi Audio T20 reflects the warm and lush sonic presentation of a Tube amplifier quite successful, especially for such a small device with an affordable price. The T20 shows a good subbass depth and extension with a pretty soft and slightly warm tonality. The bass knob is an efficient way to increase the intensity and rumble. The midbass region is a bit more highlighted compared to the subbass area. The midbass region of the T20 shows a good sense body and impact, while grade of texture and resolution generated in this area is quite good for such an affordable tube amplifier.

The Fosi Audio T20 offers a pretty smooth midrange presentation with a mildly warm tonality that reflects the character of a tube amplifier. The sense of air, transparency and resolution meets my expectation from a Tube Amplifier at this price level. Male vocals are reproduced with a good amount of body and fullness, while female voices do sound pretty lively and emotional, without to have problems such like sibilance or harshness. Instruments on the other hand are shown with a nice sense of warmth and fullness, which is a welcome coloration if you do like the typical sonic character of tube amplifiers.

The Fosi Audio T20 offers an efficient lower treble emphasis, which has a close to natural tonality. The lower treble area sounds in general relative transparent and spacious, with fairly controlled transitions. The upper treble range of the T20 is a tad less highlighted and detailed compared to the lower treble register. Instruments for example such like hi-hat in metal music are moderately pronounced, while the extension of this instrument is in general short.

The Fosi Audio T20 has a suitable soundstage for a fairly precise instrument placement. The soundstage has an average width, while the depth of the stage is pretty good for a Tube Amplifier at this price level.



The Fosi Audio T20 is a very compact Tube amplifier with Bluetooth connectivity option that offers a pretty good overall sonic performance for a device below the 100 USD price rage. Features such like Qualcomm’s QCC3031 BT SoC that supports aptX and aptX-HD codec’s, plus independent hardware bass and treble controls are very useful addition, which makes the T20 to a device that I can recommend to Tube Amplifier lovers with a limited budget.


Pros & Cons:

  • + The sonic flavor that comes from the Vacuum Tubes
  • + Independent Bass & Treble Knob
  • + Compact Size
  • + Good Build Quality
  • + Price Performance Ratio


  • – Not the cleanest background atmosphere (a common issue of budget tube amplifiers)
  • – Bass & Treble Knob creates distortion if you crank it to much


Thank you for the Read!



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