Fosi Audio T20 Bluetooth Tube Amplifier Unboxing, Review and Teardown
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- Опубликовано: 22 апр 2020
- Unboxing, review and basic teardown of the Fosi Audio T20 Bluetooth Tube Amplifier.
It really does sound amazing and sounds better with the GE Jan 5654W tubes, I've now ordered some Mullard M8100 NOS tubes.
It drives my 86db Tibo Harmony 2 and 89db Polk S50e speakers really well, it can play very loud without distortion.
This amp uses the tubes for the pre-amp buffering, the tubes do run at 100vdc, the TI TPA3116 is used for the Class D amplification.
Speaker Start Delay Project:
• Make A Speaker Start D...
Specs:
CSR64215 Bluetooth 4.2 core support aptX low latency
50W RMS X 2 (4 ohms, 20 Hz - 20 kHz, 0.04% THD)
6J4 tubes, tubes can be replaced by 6K4, 6J1, GE5654, 6AK5, 6ж1П, 6BC5, 403A/B, EF40, EF95
Headphones output: 16-64ohm
Amplifier Chip: TI TPA3116
Audio input: RCA input + Bluetooth input
Audio output: 1 set of Banana Speaker Jacks
Frequency: 20Hz-20KHz
Class D power amp
Tube pre-amp
Purchased from: www.amazon.co.uk/Bluetooth-Am...
Fosi Site: fosiaudio.com/collections/fro...
GE Jan 5654W Tubes: www.watfordvalves.com/product...
Aiyima version:
www.aliexpress.com/item/32990...
Music: www.bensound.com 
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I really like the way you reviewed. Great job.
I'm really pleased with it! Makes my LP120XUSB sound way better thru my Edifier speakers :)
The tubes are in circuit for most of these style of amplifiers. They often use the tubes as buffers though. They use solid state for most of the leg work and the tubes are just there to add the characteristics of a valve amp, the secondary harmonics and such.
Got this in my recommended. Really like your videos. Subscribed!
Thanks, glad you like them!
I just bought Fosi Audio bluetooth tube pre-amplifier + Fosi Audio 50wattsx2 TPA3116 amplifier (total price around $100). Sound amazing
Sounds rather good even over YT.
good detailed video! Thank you!
Thanks for the review. I already have a little solid state amp so a I may just as get the passive version of one of these, seeing as it uses a solid state amp anyway.
Thank you for your review. I bought one on ebay for $62.99. I will receive the package at the weekend.
I'd be interested to know if you have the same clicking sound when you turn on the amp, thanks
@@Ratti3 I used it for two days and it worked great.
Great video ... Can you tell me what Bluetooth codecs are available in it for streaming? For instance ldac? Do the tubes help with Bluetooth sound quality? Thanks!
Bluetooth is v5 (according to current model on Amazon, aptX and aptX-HD). Bluetooth quality will always be less than line in. Sound quality is a subjective thing, this only uses the tubes for the preamp, the headphone amplification is done via NE5532 and the speaker out via a TI solid state IC.
Great video. This guy answers every question needed.
Just a few questions required for my personal set up, which are similar to your setup, I am also running Polk audio treated at 150watts. Does your setup every clip out at max.
I'm planning on replacing my 5.1 amplifier with this -mainly because I just want a simple 2.1 . I have a powered sub that I plan on connecting using the daisy chain method
My speakers connected to this are 100W and are made by Tibo and were only £40. I personally would not connect expensive Polk speakers to this cheap and unprotected output amp.
I’ve never tried playing it at max volume, looking at the size of the heatsink and how hot the whole thing gets, I would say it will have a short life if played at max volume for long periods.
@@Ratti3 thanks man
Any ideas the safest way to attach a little fan to help circulate air (power wise). Was thinking cutting the bottom to attach a pic fan to keep it cool but unsure how to connect power using its board
@@raymondkhan2709 I'm not sure it would be worth the effort.
Great review! Thanks! Did you ever try out the Aiyima amp? (it does look identical to the Fosi one) How did that work out for you? Also, wondering if you considered replacing the opamp with higher end ones, such as those from MUSES. Thanks a lot!
It's the exact same amp with the same problems. See the pinned post above. You can't replace the op amps as they are sop8 SMT soldered to the board
Ratti3 Thanks! Indeed - just wondered if you liked the other one after a month. Re op-amp: I was thinking of desoldering / replacing the existing NE5322, but all things considered probably not worth the trouble.
@@kuangx9489 I wouldn't like to try it, anyway it sounds great to me as is.
Ratti3 would you happen to have a link for the aiyima amp? I can only find models without the headphone jack in the front
@@sackofclams953 I've updated the description, check near the bottom, other sellers have them too, you also need to buy the PSU from them seperately.
Thanks for the careful review! Do the speakers turn off when the headphones are plugged in?
Yes they do
Good afternoon, thanks for the video! I use an internal Creative card to listen to my music from the PC on the headset. Do you think that adding this amplifier will make a difference in terms of quality and sound signature?
Sound reproduction is a subjective thing, if you are using a PC sound card that already is high quality. Feeding that into the tube amp will change the sound slightly, now you may or may not notice this. I use mine with a DAC and external speakers, I got it because I like the look of these tubes and wanted to drive speakers. This amp is not hifi, if you want a hifi tube amp you need to pay a lot more.
@@Ratti3 Thank you
Thanks for the video, I'm looking to buy this amp however by looking into amazon I saw t Douk Audio P1 that looks to be the same + USB, do you happen to know that unit? I'll be using mainly with headphones (X2HR and DT770 80ohm)
I did consider it before buying it, it is a different build, it uses a different BT chip and has a USB DAC. I've not bought one so can't offer an opinion on quality or perfformance, you may be able to find reviews if you keep searching. I did not go for it as it looks a bit garish to me.
I'm not entirely sure, but these types of amps *may* struggle of high impedance headphones (64ohms +).
The Douk Audio P1 is only a preamp, you cannot connect it to speakers without connecting it to a power amp first.
Bought one. Sounds great especially for $90.
Bel video, io ho questo amplificatore da un anno e mezzo e suona molto bene, l’ho accoppiato con le elac debut 5.2 ho cambiato l’alimentatore e le valvole e sto usando la porta rca perché lavora molto meglio del bluetooth.. suona da dio, ci sono possibilità di migliorare cambiando il chip o la scheda? Per curiosità
I just bought a LG tv and want a small amp like this to connect to Boston Acoustic bookshelf for a small two channel television sound system. Would you recommend this? We sit close and personal to display.
If the speakers are passive then yes it will work fine.
Hey quick question will it work with some dt 990 pro 80 ohms? Or will I need a different amp
The manufacturer website says 16-64 ohms for headphones.
@@Ratti3 just read that thanks, do you have any amps for headphones that you could recommend that aren`t too expensive
@@blogger115 no sorry the only other amp I have is a Denon AVR-X2600H. If you head over to the Head Fi forums you'll find plenty of people talking about headphone amps.
Hi, I am thinking about buying this Amp. I have seen that there is a T20X model too. Do you think it is a worth upgrade?
Thank you for the video.
The new version has a more powerful silicon Class D amplifier. It's not something I would buy myself in 2024 or in the future, just my opinion. They are not true valve amplifiers. At the time of making the video I did not know much about valve amps, things have changed now and I build my own power valve amps.
Hello does the Fosi Audio T20 had a phono pre-amp on it? thanks. M
It won't have enough gain.
Could you please tell me the screwdriver size to unscrew the back ones?
2mm Hex rear, 2.5mm Hex front
Great video buddy I’m looking to buy one. May I ask what speakers would you recommend
I would not connect very expensive speakers to this amp, it's not hifi (still sounds great) and there is no protection on the output. I was lucky and was able to buy a pair of Tibo Harmony 2 speakers for £40, I have reviewed them look them up. I bought this amp to use with my PC to give me a break from using headphones and to listen to music whilst I work from home. There are many speakers to choose, have a look at some of the dedicated speaker review channels.
Ratti3 Thank very much for the advice keep up the great videos
One question please: I'm considering buying a tube amplifier. But I listen to all my music through bluetooth from Spotify and my phones are also wireless. Can I both transmit AND listen via bluetooth with these amplifiers?
You can connect one device to the amp to send music, I don't about Spotify or your phones (headphones?)
An update on this amp...
I somehow missed the annoying loud thump when you plug in the power, as I had the toggle switch in the off position. The toggle switch does not get rid of the thump when using headphones, so very annoying and bad for speakers. I also started to notice loud clicking sounds on the speaker when turning on, this stops after about 4 clicks, this was not there when I tested. It was so annoying I sent it back to Amazon. I then ordered the same amp but made by Aiyima from AliExpress which was £20 cheaper. It has the EXACT same thump and clicking sound.
Here is the speaker start delay circuit: ruclips.net/video/oUH6x4hy9Ck/видео.html - and just to clarify, it's probably fine to leave the amp connected I believe the current draw is small. I prefer not to leave too many electrical items on in my house, also the toggle switch on the front works fine protecting the speakers. I just wanted to make my own speaker protector.
I also looked into the 100v voltage booster IC used, it is the UC3843B that is commonly used for this type of thing. I actually made my own version of it for a tube amp that I'm making, the chip can output high voltages, I managed to get 360v when testing. Here is a video of the 100v booster I made: ruclips.net/video/WjKtIpr8MAg/видео.html
Hi there, firstly thanks very much for a valuable information about the amp. I have seen the other video you posted about the speaker start delay. My question, if I was to use the amp as is and to avoid the horrible thumb never to unplug it, what is the power consumption with the switch 'off'? Any other potential problems you can think of as a result of leaving the amp plugged in? I simply don't have time and resources to make the speaker start delay you suggest. Thanks in advance.
@@jakubbachniak5448 No issues leaving it on, it's just a personal preference. I have too many devices in my house that are constantly on, I don't want to add to it.
I've used various amps, synth keyboards, receivers, turntables since the 70's and my experience has been that powering on, plugging in, etc. often causes a pop or thump. With my T20, plugging/unplugging with power toggled off has no sound. Toggling power after it's plugged in produces no sound. Have had no clicking sounds. There is a fairly significant sound when plugging in the toggled-on T20, though, which I would expect from any amp..?
@@mrpixelator You get what you pay for, I get no thumps on my Denon, the output is controlled by relays on the Denon.
So the amp cant be turned of any other way than unplugging the power? Was looking into this one but thats kinda a dealbreaker
It turns off the tube circuit and the power amp, but there seems to be some power going to other components, I say this because it feels slightly warm with the toggle switch in the off position. I have an inline switch on my power supply which I installed, so not a problem for me.
Hello Friend! Will the tube have any influence on the sound signature in the headphones?
A very small amount and it is something very subjective. Some people can't tell the difference. Others will laugh at this device. At the end of the day you get what you pay for. A proper tube amp costs a lot more.
@@Ratti3Tks my Friend
Would you say it's worth it over a it's identical solid state amp?
For a bit of fun yes, I would not classify it as a proper amp. I have a separate more powerful amp for serious use.
Is it possible to change the 2 op amp on this please ?
Thank you for the nice review !
Nie - są przylutowane. Ale Aiyima ma taki sam model i tam są wymienne. Ale na tych które są gra bardzo fajnie:)
The OP AMPs are SMD, so would be quite hard to replace.
Thank you for a through review. I was surprised how much better poor quality MP3 sounded through this amp and there was enough power for my bedroom. What tubes will give it a warmer sound like a macintosh has?
All EF95/6AK5 tubes will work. The popular ones are GE Jan 5654W, Mullard M8100, Voshkod 6ZH1P-EV etc. I've got about 8 different brands now. There's information on compatible tubes with reviews on the Head-Fi Forum, search for "Little Dot Tube Amps Vacuum Tube Rolling Guide".
I'm putting together another tube headphone amplifier with DAC, using boards and a custom case. I'm also making a speaker protector circuit for the T20 as it makes a popping sound when turning on, I'll post the video for it. I now feed the input using a Topping D50s DAC.
@@Ratti3 Ja polecam 6j38p oraz GE 5725
6BA6 tube？
Did you notice any improvement with replacing the tubes ?
I would say it's very subjective, and depends on the persons hearing. I believe I noticed a difference with Russian tubes, so I prefer them over other tubes.
I switched the stock tubes to the GE tubes and burned them in for over 100 hours and without question I preferred the stock tubes. The GE sounded too dark and lacked the dynamics and bass of the stock tubes.
worth upgrading the up amp chips?
would be easier and cheaper to buy a better amp
What vacuum tubes should I use for the best sounding amplifier?
That is very subjective, since posting this video I've got hold of the analog discovery 2 and took some measurements; I compared a 1950s Mullard vs a 2021 Russian modern tube, the results we're almost identical, both tubes sounded the same to me too. Sure you can have bad tubes that may give you the impression that another brand/tube is better.
Also don't forget this is not a "proper" tube amplifier, it has op amps for buffering and headphone out and the loudspeaker amplification is done by a class D silicon chip. The tubes are buffers.
My most up to date opinion is that these are gimmicks and nothing more, just something nice to have on your desk.
I am currently building a KT88 tube power amplifier, the only silicon in the audio path is the digital volume control that adds only 0.0002% distortion.
Polecam wymianę lamp na rosyjskie 6j38p - wtedy dopiero będzie porządny bas i przestrzeń !!!
cuidado, yo tengo el mismo pero de otra marca y a los tres meses estube cambiando los tubos para probar el cambio de sonido como habia hecho un par de veces semanas atras, y en uno de los cambios de los tubos con el aparato apagado del interruptor pero conectado a la fuente de alimentacion, pues se escuchó un ruido y las luces azules se qencendieron estando el interruptor en of, y los tubos ya no se calientan y el sonido (que era fantastico para auriculares) ya no está amplificado, el lunes lo devuelvo, y mañana me llega otro igual que he comprado por que es fantastico.
lo mejor es no tocar los tubos, y si se hace que sea con el aparato desconectado de la fuente, de todas maneras prové unas jan 54.?w de ge que todo el mundo aconseja , pero yo prefiero las que trae que son las 6j4? los agudos tienen mas cuerpo y los graves mas impacto y apretados y en general mas volumen.
Los op amp se desmontan con la mano? O están soldados?
OP Amps are SMD mounted
this is work to 18 to 20v battery or no boss
I think it will work with a lower voltage, output power will be lower.
Do you know if Fosi Amps actually utilize the tubes or are they just aesthetic and use transistors? I've heard that's the case with many sub-$100 tube preamps. Thx!
Did you watch the video? Yes it's used as part of the pre-amp so not a proper tube amp, they cost a lot more and have big transformers. 100vdc is supplied to tube screen and grid.
@@Ratti3 Guess not
@@Your-BestNightmare The tubes are in the circuit. If you pull the tubes, you literally get no signal from the headphones or outputs.
Be careful, I have the same but from a different brand and after three months I was changing the tubes to test the sound change as I had done a couple of times weeks ago, and in one of the tube changes with the device off the switch but connected to the power supply, because a noise was heard and the blue lights went on with the switch on, and the tubes no longer heat up and the sound (which was fantastic for headphones) is no longer amplified, on Monday I return it , and tomorrow another one will arrive just like I bought because it is fantastic.
it is best not to touch the tubes, and if it is done with the device disconnected from the source, in any case I provided some jan 54.?w de ge that everyone advises, but I prefer the ones that are 6j4 ? the trebles have more body and the bass more impact and tight and in general more volume
Yes parts of the circuit is still powered even with the toggle switch turned off. I prefer Russian 6AK5 tubes. I have a selection of 20 tubes. I'm currently making my own tube amp, I'll post a video if I can successfully make it.
Is this a pre amp then?
yep, tubes do the first bit, then the rest using op amps and solid state power amp, you won't find a true tube amp for this price or size
L'ho appena preso, niente male la qualità audio, soltanto 2 cose non mi convincono:
-Anche quando viene spento resta alimentato (dovrei misurare il consumo per valutare quanto impatta in bolletta)
-Il jack cuffie é molto delicato, basta sfiorare il cavo, con una leggerissima pressione verso il basso che la cuffia sinistra non si sente più (provato con più cuffie) qualcun altro ha lo stesso problema o é difettato il mio?
Sì, ho detto che l'amplificatore non si spegne completamente. Non ho problemi di connessione delle cuffie.
@@Ratti3 Hai avuto modo poi di misurare il consumo alla presa per caso?
@@leonardodominicis498 Sfortunatamente no. Sarebbe necessario dividere un cavo di alimentazione CC di riserva per misurare la corrente. In caso contrario, utilizzare una sorta di presa di misurazione della potenza.
@@Ratti3 E' lo immagino, io il misuratore di potenza lo avevo pure ma si è rotto, non segna piu. Ora vedo se riesco a prenderne un altro, sennò lascio stare
@@Ratti3 Ho contattato il supporto via email e mi hanno chiesto di provare se il problema sussistesse anche con cuffie senza microfono. Ho fatto la prova a collegarlo con lo splitter che separa il microfono dalle cuffi e effettivamente cosi non da piu quel problema
What is the Bluetooth pairing name? Thank you.
I have the Aiyama version of this now, so don't know what it was on the Fosi. The Aiyama says "BT HIFI AUDIO". Hifi lol
@@Ratti3 why the switch to Aiyama?
@@TheEchomaker I thought there was something wrong with it, it was making clicking sounds during power on. Turns out they all do it including the Aiyima. See my comments above for more info. You basically get what you pay for. I'm still happy with it regardless of the problems.
This is 100 watts yes?
50W x2, the manufacturers website does not say into what impedance, so could be 50W x2 into 2ohms, if the speakers are higher impedance then the output power will be less. Regardless it will be loud enough for use in a small room.
I don't use this amp for my main, I have a much more expensive Denon AVR for watching movies.
Oh the non copyright music thanks to the Larry David's of the world
Fosi Audio T20 + Lompoo LP42... Tantissimo con pochissimo.... :)
Buonasera, ho appena acquistato le lonpoo e pensavo a questo amplificatore.. Il suono riesce ad essere caldo tipico valvolare? Riesce a smuovere bene le casse anche a bassi volumi? Grazie se vorrà rispondere.. Saluti
@@gabriele8150 Ia valutazione è ovviamente proporzionata al prezzo d'acquisto. Detto questo è un piccolo gioiellino, che muove egregiamente le lonpoo formando una accoppiata perfetta. Consiglio cavi segnale 2.5 mm con connettori a banana Amazon Basics. Come tutti i valvolari spinge bene a basso volume e accetta molte tipologie di valvole che ne possono modificare sensibilmente le caratteristiche sonore. In rete di trovano ottimi consigli.
Does it still work?
I have the Aiyima version of it now, yes it still works.
@@Ratti3 why is the aiyima better??
@@highhat5229 they are exactly the same, I returned the Fosi because I thought it was faulty.
@@Ratti3 what was the issue?
@@highhat5229 check my pinned comment
На выхлопе усилитель D класса в лампах нет некакого смысла
а лампы для красоты ???
The tubes do some amplification at the start, 100v DC is applied to them.
A Chinese scam, only the PRE-amplifier is assembled on the lamps, the output stage is a noisy transistor assembly TPA3116, which makes the presence of the lamps a decorative element.
Китайский развод, на лампах собран только ПРЕДуселитель, выходной каскад шумящяя транзисторная сборка TPA3116, что делает наличие ламп декоративным елементом.