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Fosi Audio T20 Tube AMP Review


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Fosi Audio T20 Tube AMP Review

Fosi Audio T20 Tube Amp is a class D hybrid amp which has Line input (RCA connection), speaker output (Banana connection), headphone output (3.5mm stereo connection). It also has Bluetooth 5.0 (with APT-X and APT-X HD support) connection via its BT module and antenna. Although headphone support is stated as 16-64Ohm on the specs I have tried up to 250 Ohm headphones without any issues. Speaker terminating impedance is 2 Ohm - 8 Ohm. Maximum speaker power output is 50W x 2 and Total Harmonic Distortion is stated as THD ≤ 0.04%. Signal to Noise Ratio is also very good at SNR ≥ 99dB. Lets get in to the story and review:


(Above photo: My music angel mini statue shines with deep blue led lights coming from the bottom of the tubes)

Recently I bought a hybrid amp for my desktop setup. I am excited at this time on a level to need an urge to write a review and start a thread. Since I could not find any review about this little amp in head-fi I think this thread can be informative to the community.


I have been using Beyerdynamic DT-150 after recommendation from @Lorspeaker . I am glad that I bought that headphone at that time. I really liked the headphone with some music -especially with orchestral music. Some live acoustic recordings also sounded very nice on these... But I never think that it is an allrounder and I never got permanently attached to it. Until now :beyersmile:

I have been in a research to set up a cost effective, minimalistic and good quality desktop setup. I do Lightroom, Photoshop, Premier Pro and Davinci Reslove work a lot so spend a good amount of time on my desk.


I first purchased a Mac Mini M2 16GB with 250GB ssd. Then I have purchased Asus ProArt PA32UCX-PK monitor, Logitech MX Keys Mini, Logitech MX Master 3S Black mouse, a wide mouse and keyboard pad with wrist rest, a Huion HS610 graphics draving tablet, 2 Orico NVME M2 SSD enclosures which support 10Gbps. Then I have purchased Crucial 1 TB NVME M2 SSD P3 and a Kingston Black 1TB NVME M2 SSD Gen4 and Raid connect these two external SSD's through Thunderbolt cables. Finally I bought 2 Tannoy Mercury MX1 dark oak bookshelf speakers and located them on self made sponge dampers on my desk. At the building period of this desktop system I was looking for an amp which have Bluetooth 5.0 HD Audio support and RCA inputs. Also this amp should deliver both headphone and speaker (at least 2 fronts) output. All these should be in the very limited budget that left for the amp. I also wanted to try hybrid amp sound so I was looking for an amp which have tube and solid state parts on it. I also wanted this amp to have a small footprint. Then I came across Fosi Aduio T20 Tube Amplifier on Aliexpress. Although it is written as tube amp on it it is a hybrid amp. Knowing all these I push the purchase button.


I bought the amp without a power source so it needed an adapter. I first tried it with my old Asus laptop adapter which meets the requirements. Unfortunately the amp delivered a buzzing background noise. So I have ordered a new adapter from an Amazon seller. With the new 24V 5amp adapter background noise completely eliminated. The reason was the ground connection caused the background noise with the Asus power supply. Now I am enjoying the pure audio. In fact after some burn-in and the adapted change the sound quality exceeded my expectations. This is why I wanted to start a review about this amp.

PS: For best performance from the amp you need to let it run for at least 50 hours. So yes it definitely benefits from burn-in !


My setup is like this: Mac Mini M2 3.5mm Stereo out -> 3.5mm to RCA Custom Made Cryoed Copper Aduio Cable -> Fosi Audio T20 Tube Amp -> Beyerdynamic DT150 or Tannoy Mercury MX1 bookshelf speakers.


With this simple and minimalistic set up I am getting great sound quality.

My experience with speakers are limited so could not make comparisons but before this little amp I have tried the Tannoy's with my Pioneer VSX-609RDS and Yamaha RX-V663 home cinema receivers (both have pure direct output which eliminates fancy surround or equalisation effects) and Fosi T20 delivered better audio quality through the Tannoy's ( I am talking about quality here not the SPL). The headphone out on the Fosi T20 is incomparably better than the mentioned receivers as well.


(Above photo: I think my mini music angel found a new place between the tubes!)

When it comes to headphone out Fosi T20 delivers better sound quality compared to my Darkvoice TH336SE or direct output of the Mac Mini M2 when I use Beyerdynamic DT150 with it. The sound quality synergy is unbelievable!


I am more then happy with this setup and suddenly Beyerdynamic DT150 became my main daily HP! :beyersmile:
If Fosi Audio adds a 6.5mm jack connection to this amp in the future that would be perfect for a range of full size headphones!!!




How can I describe the sound: Full, musical, detailed, holographic imaging, detailed, layered, very well defined bass, rich and life-like mids, non-fatiguing but very detailed highs, may be not very neutral but very very close. Tubes did certainly add some coloration to the sound but very ever so slightly and not in a bad way. I like this type of sound while working. I will experiment with different tubes in the near future. I need to test my other headphones and AB them... Apart from Beyerdynamic DT150, I have tried Sennheiser DH250 Linear-1 and AKG K-400 (MP) with the amp and they also sound very good. But with the Beyerdynamic DT-150 sound quality is on an amazing level! DT-150 soundstage became like an open headphone. I have A-B'ed it with AKG K400 and only strength of K400 is its soundstage is still wider but the depth, wideness and height of the DT150 soundstage is better than I have ever heard it and reproduction is so life like that sometimes I remove it from my head in order to be sure that the sounds are not coming from my Tannoy speakers but from the headphone! Transparency, realism and holography of the sound is that good!

I have tried Bluetooth APT-X HD connection and compared it to the wired connection. I have not tested any other speaker apart from Tannoy Mercury MX-1 but will try my Dali and Pioneers in the future.

I don't hear any popping sound as I turn the switch on or off. I don't hear popping sounds if I remove the mains plug while the amp is still on. So these do indicate that the power management is very nice with this amp. Also I have to mention my 220V->24V 5A adapter appeared to be audiophile quality. With the Asus 19V 3A adapter I do get popping sounds if I remove the main plug from electricity. So there has to be something with the adapter as well. I have seen that Fosi did not sell the amp alone anymore (I mean without the power adapter). You have to purchase the full package (with the Fosi original power adapter). May be they are aware of the 'aftermarket' or 'different' adapters causing problems so they only ship the amp with their original 24V 4.5A adapter. As far as I know their adapter does not cause background noises so I assume it is safe to purchase their full package.

You can ask and I will try my best to reply.

Please feel free to add your own comments about this amp.

Cheers, :beerchug:


Fosi Audio T20 AMP Specifications​

  • Model: T20
  • Power Adapter: 24V/4.5A, DC Input Range: 12-24V (I use 24 V 5A adapter without grounding)
  • Headphones Output: 16-64Ohm (I have tried up to 250 OHM headphones and it drives them well)
  • Terminating Impedance: 2 Ohm - 8 Ohm (I use it with 8OHM speakers)
  • MAX Power Output: 50W x 2 (this seems low on specs but in reality reasonbly high, never need to crank the volume to max)
  • THD ≤ 0.04%, SNR ≥ 99dB
  • Amplifier Chip: TPA3116, Input Sensitivity ≤ 280mV
  • Bluetooth Chip: QCC3031
  • Frequency Range: 20Hz - 20kHz (±1 dB)
  • Input Mode: Bluetooth and RCA
  • Bluetooth Transmission Distance: Up to 39 Ft(12m)
  • Bluetooth Version: Bluetooth 5.0 support aptX and aptX-HD
  • Tubes: 2 x 6J4 tubes (tubes can be replaced by JAN 5654W, 6K4, 6J1, GE5654, 6AK5, 6ж1П, 6BC5, 403A/B, EF40, EF95)
Mac Mini M2 Audio Specs:
Could not find detailed info on this. But from the online reviews and from my own experience I found the audio output quality from the 3.5mm connection to be excellent! It is better than every Mac I have. I have compared it to Macbook Pro 16" i7 (2019 model), Macbook Pro 13" M1 and Macbook Air M1. Audio quality of Mac Mini M2 is better than the mentioned computers.

Below are the audio specs from the Apple web site:

Audio Playback
  • Supported formats include AAC, MP3, Apple Lossless, FLAC, Dolby Digital, Dolby Digital Plus, and Dolby Atmos
  • Built-in speaker
  • 3.5 mm headphone jack with advanced support for high-impedance headphones
  • HDMI port supports multichannel audio output

My purchase link for T20 amp (from Aliexpress):

Special thanks to the Fosi Audio technical support team and representative Summer for their support on the endless questions that I have emailed them. The technical support rocks on Fosi Audio !