Fosi Audio BT20A Pro Amplifier Review

[TheThreat]

It does run hotter than I'd hoped. Switched on but not playing it gets pretty warm, which makes me wonder what the idle power usage is. My S.M.S.L SA300 doesn't get warm and I'm happy leaving it on 24/7, I wonder if the Infineon MA12070 just runs cooler.

I have it with the 48V power supply purchased directly from Fosi and mine also idles a lot warmer than I expected. I don't have a precise way to measure the temperature but my digital room thermometer is sitting on top of it and with no music playing it says 35C in a 21C room, power supply is not noticeably warm. I'm a little concerned with the longevity so I might crack it open this week and see what the culprit is.

Edit: Had a quick poke and I'm not sure what else I expected it to be but its definitely the amp chip as the heat sink was very hot. Nothing else within poking distance was even close to being hot.

 

[renaudrenaud]

I have a pair of elac debut reference. I've tried various class AB around $400 but I prefer the TPA 3255. Unfortunately I find the mid-high frequencies a bit sharp (like drum cymbals in the new Metallica's album, or some electric guitar). With the a07 the problem is more evident, especially with LM4562 (I like more OPA2134 which is more "dark"). With the fosi BT20A Pro I can fix it by keeping the highs at 10 o'clock but never swapped op amps. I have a 36v Mean Well but I was thinking of going down to 24v to get sweeter highs, does that make sense? I listen to low volume music in a small room.

You can read the specs from TI about the TPA3255.

https://www.ti.com/lit/ds/symlink/tpa3255.pdf?ts=1683467056933&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTPA3255

There is no difference in sound at low level, but with less power distorsion comes early in watts.

 

[potfur]

I have it with the 48V power supply purchased directly from Fosi and mine also idles a lot warmer than I expected. I don't have a precise way to measure the temperature but my digital room thermometer is sitting on top of it and with no music playing it says 35C in a 21C room, power supply is not noticeably warm. I'm a little concerned with the longevity so I might crack it open this week and see what the culprit is.

Edit: Had a quick poke and I'm not sure what else I expected it to be but its definitely the amp chip as the heat sink was very hot. Nothing else within poking distance was even close to being hot.

Mine has the 32V power supply and is barely warm to the touch when idling/playing music at a reasonably restrained volume. So perhaps the chip consumes considerably more energy when fed 48V. Power consumption (as measured by a smart wall outlet) at idle does not exceed 4 watts, which is consistent with it being at most lukewarm. All these readings pertain to the European (230 volt) power grid, but this should be of no importance beyond the PSU, which is separate from the unit itself.

 

[trivium]

So I decided to pull the trigger on this amp to drive my PC hitmakers, I bought it last week and Fosi has not sent me an order confirmation or anything, my card is charged aswell. Im going to try their online chat later this evening which correlates with their published Bussiness hours.

 

[isaac507]

Can the BT20A Pro operate stably for extended periods when using a 48V power supply? I previously had an aiyima A07 which also employs a TPA3255 chip, and when powered by 48V ps and connected to my 4-ohm speaker to play music, it would automatically shut down after just few minutes. Eventually, the device was spoilt after a month. I'm curious about the reliability of this BT20A Pro in comparison.

 

[Deleted member 48726]

Can the BT20A Pro operate stably for extended periods when using a 48V power supply? I previously had an aiyima A07 which also employs a TPA3255 chip, and when powered by 48V ps and connected to my 4-ohm speaker to play music, it would automatically shut down after just few minutes. Eventually, the device was spoilt after a month. I'm curious about the reliability of this BT20A Pro in comparison.

Who knows?
The market for small chip amps seems like The Wild Wild West.

 

[TonyJZX]

i suspect your speakers go down to 3 ohms and really i doubt any of these amps is suffficent outside of a sabaj a20 but then wr're talking real money

 

[Fosi Audio]

Can the BT20A Pro operate stably for extended periods when using a 48V power supply? I previously had an aiyima A07 which also employs a TPA3255 chip, and when powered by 48V ps and connected to my 4-ohm speaker to play music, it would automatically shut down after just few minutes. Eventually, the device was spoilt after a month. I'm curious about the reliability of this BT20A Pro in comparison.

We have incorporated high-quality components in the BT20A Pro to ensure its long-lasting and stable performance. Our rigorous testing confirms that when using a 48V power supply and a 4-ohm load, the BT20A Pro can operate reliably for extended periods without issues.

 

[asnow]

Yes, I tested 3 ways to transmit Bluetooth audio to the Fosi BT20A Pro.
1) Direct Bluetooth to the Fosi
View attachment 283485
This is the frequency response 1):
View attachment 283486
2) Bluetooth to a cheap Aukey receiver/DAC connected to the Fosi RCA in
View attachment 283487
This is the frequency response 2):
View attachment 283488
3) Bluetooth to a S.M.S.L. DO100 DAC connected to the Fosi RCA in
View attachment 283489
This is the frequency response 3):
View attachment 283490
Differences are NOT due to different codecs because the transmitter was an Apple MacBook pro M1 which uses only the AAC codec.
The rise in the treble is due to the load (a Cornwall Loudspeaker) impedance. Apart from that the Fosi BT20A Pro produces a perfectly flat frequency response when fed through RCA by the S.M.S.L. DO100. The amp shows some 2dB bass drop when fed by a cheap bluetooth receiver/DAC. What is worrying me most, just like @asnow , is the bluetooth frequency response of the Fosi itself with its several dBs of deviation from linearity. Now I know it's not just my sample and I would like to ask @Fosi Audio if some improvement to their BT20A Pro is due sooner or later. I might like to buy a bluetooth-linear improved unit, hopefully with the mythical orange volume knob.
Currently, the need for an external DAC/receiver nullify the convenience of a small self-contained amplifier with Bluetooth connection.

Hello @Fosi Audio. Can you please comment on the not so flat frequency response curve for the BT20A Pro Bluetooth input?

 

[Ultratek]

Hemos incorporado componentes de alta calidad en el BT20A Pro para garantizar su rendimiento duradero y estable. Nuestras rigurosas pruebas confirman que cuando se usa una fuente de alimentación de 48 V y una carga de 4 ohmios, el BT20A Pro puede funcionar de manera confiable durante períodos prolongados sin problemas.

@ Fosi Audio

¿Podrías decirnos si tienes pensado actualizar/implementar una fuente de 48V para el Bt30D pro, en un futuro, alguna fecha estimada?

 

[staticV3]

@Ultratek Please use English on ASR.
You can use https://translate.google.com/ or https://www.deepl.com/en/translator to translate your posts before posting them.

 

[Ultratek]

@Fosi Audio

Could you tell us if you plan to upgrade/implement a 48V source for the BT30D Pro in the future, some estimated date?

 

[Fosi Audio]

Hello @Fosi Audio. Can you please comment on the not so flat frequency response curve for the BT20A Pro Bluetooth input?

Normally speaking, the frequency response curve is less flat when using a Bluetooth connection. There could be several reasons like the codecs utilized, audio compression, signal interference, and distance and obstacles. We're collecting the feedback our users gave regarding the BT20A Pro's Bluetooth. We will evaluate and consider replacing the Bluetooth chip to improve its performance.

 

[Fosi Audio]

@Fosi Audio

Could you tell us if you plan to upgrade/implement a 48V source for the BT30D Pro in the future, some estimated date?

You're very prescient! We are working on this actually. The BT30D Pro of the 48V version will probably be available in the third quarter of the year.

 

[Ultratek]

¡Eres muy clarividente! Estamos trabajando en esto en realidad. El BT30D Pro de la versión de 48V probablemente estará disponible en el tercer trimestre del año.

Gracias por su respuesta, quedamos a la espera de su salida, y cualquier avance que nos pueda dar.

 

[new666uk]

Hi all,

I'm waiting for the BT20A pro to come back into stock with Amazon UK so I can order but whilst I'm waiting I had a question about adding a subwoofer. I assume I need a powered sub to connect via the 3.5mm subout?

I have a pair of floor standers I'll try first but as I like a more bass heavy profile I'm thinking of adding the SW so my question is more of a "planning ahead" one.

thanks

 

[staticV3]

I assume I need a powered sub to connect via the 3.5mm subout?

A powered sub, or an extra Amp with passive sub would work.

 

[new666uk]

@staticV3 thanks for the super fast response. If only their stock replenished as fast

 

[GrayA]

Hi all,

I'm waiting for the BT20A pro to come back into stock with Amazon UK so I can order but whilst I'm waiting I had a question about adding a subwoofer. I assume I need a powered sub to connect via the 3.5mm subout?

I have a pair of floor standers I'll try first but as I like a more bass heavy profile I'm thinking of adding the SW so my question is more of a "planning ahead" one.

thanks

If you want to use a passive sub, the BT30D Pro is excellent. That's what I have with my passive sub.

 

[spiketeam]

Many thanks to Amir’s honest review and measurements. Happy Easter to Amir and all ASR fans!

We really appreciate ASR which allows us to listen to and gather users’ feedback on our old models. We absorbed a lot from the voices and develop this BT20A Pro. It’s not a perfect amp but we will keep making effort to improve it.

Here we want to give an exclusive 20%-off discount promo code for the BT20A Pro to all ASR fans. (Valid from today to April 30.)
20APROASR20

Hope you will be interested in this new amp!

Any chance for a new code? Its my birthday in 2 days and I am building a budget stereo setup for myself.