Fosi Audio BT20A Pro Amplifier Review

[neRok]

It would be interesting to see how the tone controls affect the freq response measurements. A measurement with them at max and maybe min to see the range.

It may be different per model? But someone asked this question in the BT30D Pro thread, and the Fosi rep said;

For the specs, it's ±12dB for Bass control and ±6dB for Treble control.

Another user added this info;

Assume sample TI implementation. https://www.ti.com/lit/an/sloa042/sloa042.pdf?ts=1676605234086.

I found similar results when testing the in room response of some speakers powered by BT30D (older non-Pro);

I have a question... how is the Bluetooth/RCA Input source switching done?

Presuming it is the same as BT30D models, it is not ideal IMO. Bluetooth is always on and has priority over RCA. This was confirmed by Fosi rep.

Yes, I understand what you mean. In fact, our team had a brainstorming session about whether or not to include a mode selector. Ultimately, we concluded that if a customer is looking for an amplifier with Bluetooth connectivity, Bluetooth is likely to be their preferred option for playing music. Therefore, Bluetooth connection should take priority over the RCA connection, and the user shouldn't need to select it. Nonetheless, we understand that many people still prefer having a mode selector. Therefore, we plan to create a new model in the future that will meet this demand.

 

[Kimbrough Xu]

I got one with only $70 by applying the 30% off early bird coupon. And thanks Amir, I just think I will get a 48V power supply now.

 

[Kimbrough Xu]

How extraordinary is it that we can buy a competent, cool-running stereo amplifier for $99.99?

The Dyna Stereo 70 power amp launched in 1959 at a price point of $99.95. For a kit.

In 2023 dollars, that's more than $1000.

This may not be a great time to be a boutique high-end hifi maker, but it is a pretty amazing time to be an audiophile.

Yes, its the best time to be a Consumer of Audio Products. It was the best of times for audiophiles, it was the worst of times for high-end hifi makers.

 

[Fosi Audio]

Here we also want to thank @mctron @Palladium @ftlbaby

Your advice of adding a tone-defeating function has been fulfilled on this new BT20A Pro. We'll keep listening to your voices and improve our products.

 

[Fosi Audio]

I have a question... how is the Bluetooth/RCA Input source switching done?

The Bluetooth connection will take priority. Let's say when a Bluetooth connection is built, it will switch from RCA to BT. If you want to switch back, you can press and hold down the volume knob for 5 seconds to clear the Bluetooth connection.

 

[Trasam Audio]

let the march of Class D continue!

nice, thank you

Yes, the class D amplifiers are much better today.

 

[JSmith]

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.

Good job, glad to see well implemented tone controls and a better overall design around the TPA3255. Also happy to see the product page showing some level of test measurements, as honest spec's mean a lot in my opinion (would also be nice to see a more realistic power output figure though).

Fosi Audio BT20A PRO

The Fosi Audio BT20A Pro is a new generation Bluetooth amplifier integrating the high-performance Texas Instruments 3255 amp chip, which can bring up to 300W power per channel and allows ultra-low distortion across the audio band and superior audio quality.

www.fosiaudio.com

Thanks for sending this in for testing and to @amirm for his time in doing so. Also very kind of Fosi Audio to offer ASR members 20% off, kudos.


JSmith

 

[gvl]

The next challenge for consumer audio is to make power supplies smaller than the amp.

 

[Fosi Audio]

The next challenge for consumer audio is to make power supplies smaller than the amp.

Actually, we are working on it. We may offer power supplies of smaller size with enough output power for our amps in near future.

 

[soundwave76]

Hmm, this seems to be the same amp, but the volume knob has a different color…?

FOSI AUDIO BT20A PRO Class D Amplifier TPA3255 Bluetooth 5.0 2x225W 4 Ohm - Audiophonics

The Fosi Audio BT10A PRO is a small, compact and powerful Class D amplifier, offered at a resonnable price. Its amplification stage uses a TI TPA3255 chip, capable of developing a power of 2x300W under 4Ω with a high efficiency.

www.audiophonics.fr

 

[Blumlein 88]

Maybe this is something you plan to cover in your dummy’s guide to amplifier measurements, but how can we tell when something is current limited by the measurements?

If you have the same voltage, dropping impedance by half should double power.

So in this case the amp with 48 volts had 69 watts at 8 ohms and 146 with 4 ohms. You really wouldn't have expected more than 138 watts. So a bit odd, but not current limited.

With 32 volts the results were 40 watts for 8 ohm and 70 watts for 4 ohm. Without current limiting you would have expected 80 watts into 4 ohms. So mildly hitting the current limits of this amp's output capability.

 

[Blumlein 88]

Hmm, this seems to be the same amp, but the volume knob has a different color…?

FOSI AUDIO BT20A PRO Class D Amplifier TPA3255 Bluetooth 5.0 2x225W 4 Ohm - Audiophonics

The Fosi Audio BT10A PRO is a small, compact and powerful Class D amplifier, offered at a resonnable price. Its amplification stage uses a TI TPA3255 chip, capable of developing a power of 2x300W under 4Ω with a high efficiency.

www.audiophonics.fr

Amir mentioned in the review an orange knob is included if you wish to add some color.

 

[Talisman]

I guess the review is out now due to embargo issues as it has just come out across Europe using the coupon or I too bought one of these for around €70, glad it wasn't a waste of money other than a slightly load-dependent frequency response (but less so than other budget class D implementations with tone controls), it seems to me you can't expect much more from a product in this price range.
only small negative note, I never liked the Bluetooth implementation with priority over RCA, if they had inserted a physical control to activate and deactivate it, for me it would have been the perfect little amplifier.

 

[JktHifi]

Postman Panther vote from me.

 

[mcdn]

Nice to see the soft-start thermistor on the power input, and the 105c rated caps, and the quality output inductors. Should be pretty reliable.

 

[3125b]

And a pre-out, nice.
But what‘s the deal with the „225W“ power figure? That‘s the chips spec at 10% THD, not the amps actual output capability. Everybody in the chipamp space does it, but that doesn‘t make it any less disingenuous …

Power supplies could be made more compact and efficient with the use of GaN semiconductors, but they are currently quite a bit more expensive. An internal power supply also saves space but drives prices up because it means every model needs individual safety certification.

 

[TonyJZX]

https://www.fosiaudio.com/wp-content/uploads/2023/03/0181920_1080-1024x576-1.jpg

the BOM shows an included orange vol. knob for that splash of color

effectively you get 40w or 70w per ch. with the big psu

i think you're at a impass here... if you want sub $100 then youre going to have to put up with that kind of BT switching oddness

realise the Chinese audience probably loves Bluetooth and so there doesnt seem to be an easy or cheap way to switch inputs from BT to aux

OR

if these things really irritate you then you need to go up to $200+ where you can get an all in box with the psu inside and you get a remote which you can switch from BT to Aux to digital inputs at will

to me these sub $100 units will tend to be power amps... you probably got a dac that will act as a remote preamp

going to double that price then it becomes more of an integrated amp

 

[Talisman]

i think you're at a impass here... if you want sub $100 then youre going to have to put up with that kind of BT switching oddness

realise the Chinese audience probably loves Bluetooth and so there doesnt seem to be an easy or cheap way to switch inputs from BT to aux

OR

if these things really irritate you then you need to go up to $200+ where you can get an all in box with the psu inside and you get a remote which you can switch from BT to Aux to digital inputs at will

to me these sub $100 units will tend to be power amps... you probably got a dac that will act as a remote preamp

going to double that price then it becomes more of an integrated amp

I could link to dozens of products under €100 with both bluetooth and line inputs and physical switching

 

[Rja4000]

Thanks
How many Amps is the 48V power supply ?
There should be a bundle amp+48V PSU as well, ideally.

 

[VintageFlanker]

How many Amps is the 48V power supply ?

115.99$, ex VAT:

Fosi Audio BT20A PRO 300W x2 TPA3255 2 Channel Bluetooth 5.0 Power Amplifier

Experience Hi-Fi audio with the Fosi Audio BT20A Pro home amplifier. Enjoy 300W x 2 power output, upgraded Bluetooth 5.0 connectivity, and sound controls.

fosiaudioshop.com