elipsonfan
New Member
Fosi Audio has launched a Bluetooth tube (headphone) amplifier. It is priced around €100 on Amazon but is also available through the Fosi Audio store. This amplifier converts Bluetooth audio streams from phones, computers, or tablets into an audio signal for your headphones or (bookshelf) speakers. Thanks to a combination of high-quality sound and features at this price point, the Fosi Audio T20 is an extremely attractive product.
Fosi Audio was a new brand to me in the hifi world. Many emerging Chinese hifi companies launch products that receive positive performance reviews at very affordable prices. Fosi Audio was so kind to send me this amplifier for a review. I myself own Rotel, Mission, NAD, Marantz, Arcam, Elipson, California Audio labs, Grado and IFI Gear.
This is a Bluetooth and RCA line-in desktop product, roughly the size of a passport. It is powered by a separate adapter. While it does not feature optical, coaxial, or USB connections, it is designed to stream music from your phone via Bluetooth. For streaming via Google Chromecast or connecting a CD player, you can use the RCA line-in at the back of the amplifier. There is a switch at the rear to select either Bluetooth or the RCA inputs. During testing, streaming was always uninterrupted, with stable performance as if it were connected by a cable.
Build Quality
The amplifier is compact and well-built, with a solid finish. It has an attractive metal casing, and the front features sturdy, high-quality metal knobs and switches. The amplifier measures 9.9 cm in width, 6 cm in height, and 18 cm in depth, including the power connector and Bluetooth antenna at the back. The height includes the two small tubes mounted on top.The supplied tubes are of the 5654 type from General Electric, and you need to install them by pressing them into the sockets on top. According to Fosi Audio, the tubes can be replaced with JAN 5654W, 6K4, 6J1, GE5654, 6AK5, 6ж1П, 6BC5, 403A/B, EF40, or EF95. Fosi sells replacement tubes for €20 should you wish to upgrade. A blue LED lights up beneath the valves when the amplifier is turned on.
On the front, there is a 3.5mm jack socket, which is positioned about 3mm deeper into the front panel and accommodates a jack plug up to 9.5mm thick at its widest. In addition to the on/off button and volume knob, there are two rotary knobs for treble and bass control.
However, if your 3.5mm plug features a plastic connector that is wider near the metal connector, it may not fit properly. This was the case with my Grado SR80 headphones, as well as the newer SR80x, both of which have connectors measuring 11mm wide at the plastic part. I ordered a "dual female audio cable Y splitter 3,5mm" for €1,60 on Aliexpress to solve this problem.
The headphone output supports headphones with impedances between 16-64 Ohms. If you use headphones that are less sensitive, such as those from Beyerdynamic (250 Ohms), you may want to consider a different headphone amplifier that can drive more demanding headphones.
The amplifier uses the TPA3116 Texas Instruments Class D chipset for excellent audio performance, delivering 2x50 watts (4 ohms), with circuitry to protect the speakers from DC current in the event of faulty capacitors. More information is available here: [https://www.ti.com/lit/ds/symlink/tpa3116d2.pdf].
The Bluetooth chipset is from Qualcomm (QCC3031), supporting Bluetooth 5.0 and aptX and aptX-HD audio. The streaming range is up to 12 metres. An antenna for Bluetooth is located at the rear of the amplifier. Considering the quality of the materials and sound, it's remarkable that Fosi Audio can offer this product for around €100.
In addition to Bluetooth streaming, there is a stereo RCA line input at the back. Audio output is secured by either the 3.5mm jack plug or the small speaker connectors at the rear. If your speaker wire is 2.0mm² or thinner, or you use banana plugs, you can connect passive (bookshelf) speakers to the terminals. The amplifier can deliver 50 watts RMS with 4-ohm speakers. No software installation is required on your phone or laptop. When powered on, the amplifier will automatically connect to BT HIFI AUDIO, streaming all audio directly to the amplifier. The T20 can handle hi-resolution audio files from services such as Spotify, Tidal, Qobuz, Deezer, and others.
The supplied adapter has a cable length of around 2 metres, so you don’t need to be close to a mains outlet.
Specifications
- Amplifier type: Hybrid based on Class D (Texas Instruments TPA3116 chipset) with tubes
- Input: RCA, Bluetooth
- Output: Speaker terminals, 3.5mm headphone jack
- Dimensions: 9.9 cm width, 6.0 cm height, 18 cm depth
Sound Quality
To test the sound quality, I used a pair of Audio Technica ATH-TAD500 headphones from a friend. These headphones are sensitive and easy to drive, similar in nature and quality to the Grado SR80 I own. Having used the amplifier for two weeks, my phone and the amplifier now connect via Bluetooth as soon as the amp is powered on. Normally, I listen to the iFi Zen Dac Air, connected to my laptop via USB. The iFi is a headphone amplifier in a similar price range. When the T20 is not receiving an audio signal, it is completely silent, with no background noise.The Fosi Audio T20 clearly outperforms the internal DAC and amplifier in my Lenovo laptop, sounding more detailed, clearer, with a slightly warmer midrange, deeper bass, and better instrument separation and timbre. Listening directly through my laptop is unpleasant, especially if you’re used to a good external DAC/headphone amplifier.
When comparing it to the iFi Zen Dac Air, which is a DAC/headphone amplifier in a similar price range, the sound quality is comparable. Listening to Saint-Saëns' Le Carnaval des Animaux, I am impressed by the dynamics and its ability to reproduce the power of the piano and other instruments. The music seems more dynamic than when listened to via the iFi Zen Dac Air, and the instruments are more defined and precise, with a bit more clarity. Both amplifiers have a touch of warmth, but the Fosi Audio has a more pronounced midrange and a forward-sounding character, with bass that reaches deeper. While the bass isn't overwhelming compared to the iFi, it seems to handle lower tones with greater depth. Violins and high piano notes are precise, without being sharp or unpleasant. The overall presentation is natural and engaging.
When listening to the medieval classical La Folia de la Spagna, followed by Dementia Preacox Angelorum, the difference between the iFi and the Fosi becomes clear. The Fosi offers more power, a slightly more pronounced midrange, and enhanced highs and deep bass, making the presentation more energetic. The iFi, on the other hand, sounds more harmonious and less forward. The Fosi also delivers more detail without excessive treble, giving a sense of precision in the music.
Both amplifiers are excellent, making listening to quality headphones a real pleasure. It’s noteworthy that I never felt the sound quality was diminished when streaming audio over Bluetooth. To test this, I connected the Google Chromecast Audio, a small DAC, to the RCA line-in at the back. The Chromecast Audio provided a slightly smoother, less grainy sound, particularly in the higher frequencies, compared to Bluetooth streaming. However, the differences were minimal and not distracting. Streaming via Bluetooth is highly convenient, and for higher sound quality, you could pair the amplifier with higher-end headphones, such as those from Audeze.
To test its midrange, I listened to These Days by Ane Brun. The Fosi highlights her voice, lifting it out of the music and positioning it right in front of you. The drum rolls are well performed, while the iFi has more trouble, making them sound a bit muffled.
Listening to Crazy Love by Paul Simon and Norman Fucking Rockwell by Lana Del Rey, I can hear distinct vocals, precise highs and lows, and a very spacious presentation. The sound is incredibly enjoyable through this amplifier. Although I can’t clearly hear the tubes, the amplifier presents the sound with detail, good separation, a forward character, and deep bass.
After switching between the Chromecast Audio DAC and Bluetooth, the advantage of Bluetooth became evident. It is easy to connect, and the audio quality is just as good as using the line-in. The difference might be more apparent with higher-end headphones. For €100, it’s simply remarkable what Fosi Audio offers.
Bright Red by Laurie Anderson sounds transparent, with well-defined treble and deep bass that enhances the song. When switching to The Moon is a Harsh Mistress, the piano sounds rich and powerful, with the forward presentation accentuating Radka Toneff’s voice. It’s an engaging and impressive presentation.
Listening to Lou Reed’s Walk on the Wild Side, I can clearly hear the contrabass strings vibrating, the saxophone is well-defined, and Lou Reed’s voice sounds natural.
For bass testing, I played Bright Lights Bigger City by CeeLo Green and Therefore I Am by Billie Eilish. The bass in the Billie Eilish track is fast and punchy. The amplifier performs well with electronic dance music, though the limitations of the headphones are apparent in the bass frequencies.
Conclusion
If you listen to music on Spotify, Tidal, Qobuz, Deezer, Amazon, or YouTube and don’t mind using your phone for streaming, this is an excellent upgrade for your system.If you are in for an amplifier with the possibility to adjust bass and treble and love an engaging, some deep bass and detail, slightly warm and forward presentation, then this is the amp for you. You won’t regret it.
Fosi Audio’s T20 Tube Amplifier demonstrates that even at a price of around €100, you can get an outstanding headphone amplifier that can also drive speakers or connect to a CD player, iPod, or cassette deck. There’s no need to open your laptop to play music; it can be streamed directly to the amplifier with similar quality. This compact, well-designed device offers a brilliant way to get the most out of your headphones and enjoy music as it was meant to sound, without breaking the bank.
Hopefully I helped you with my review. if you have questions, let me know.
