Fosi Audio BT20A Pro Amplifier Review

[AaronJ]

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.

Thanks for the explanation.

 

[Joe Smith]

Looks like a nice board with better positioning of the caps and the chip/heat sink, so that's hopefully better for longevity than the Aiyima A07...

It would still be nice to see one of these guys made with a vented top case to allow more heat to get out...

Thumbs up for the center tone defeat on the tone controls and nice selection of power supplies. Also cool re the volume knob swappability.

On my SMSL AO100, I do like that it's an easy one-press-switch between BT and line inputs.

Great price. Well done, Fosi folks!

P.S. Oh, by the by, what Op-Amps are in it as stock? 5332s?

 

[specshifter]

Sorry if I missed it, but could someone please confirm if the pre-out is variable with volume or fixed? Thanks!
And thanks for the review @amirm !

 

[Fosi Audio]

DONT GET ME STARTED ON TONE CONTROLS

OK...i am an audiophile by osmosis only, with no real knowledge of electronics. But I have met a few who do.
My good friend was in business with Dick Olsher from Stereophile and another Stereophile reviewer lives up the street. I have been in on testing Ongaku amplifier clones. and on and on.

I have seen people, including myself spend hours and hours and thousands of dollars all trying to discern minute differences, in test that took way too long to even remember what the first tone sounded like.

Things like... (all quite fun by the way)

upgrade capacitors in amps and speakers
roll tubes!
change cables.
change cartridges.
mix and match so much equipment it would make your head spin.

And every once in a while, I would say in my wise-ass way, if you want a different sound why don't you use the tone controls.

oh yeah ... audiophile equipment does not have tone controls, I would hear.

SO, 3 CHEERS FOR TONE CONTROLS

Thank you for sharing, as per the tone controls, do you mean a device like a EQ?

By the way, the equiqment without tone controls is in the final stages of development, it will be released soon.

 

[Jeromeof]

Sorry if I missed it, but could someone please confirm if the pre-out is variable with volume or fixed? Thanks!
And thanks for the review @amirm !

It is variable with the volume - so you can connect a powered Sub and control volume on device.

 

[sound67]

Great review. Looking forward to receiving mine on Thursday.

 

[leelee]

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!

Hi, what is the amperage of the 48v power supply and where can we buy the fosi 48v power supply?

 

[sound67]

Well, you can by a 48V/5A power supply from Fosi Audio: https://fosiaudioshop.com/collections/power-adapter/products/power-supply-adapter-48v-5a

Whether it's actually necessary is another question entirely.

 

[holbob]

I strongly recommend you get this from Amazon due to the much higher power in the Amazon variant.

The upgraded version of Fosi Audio BT20A

Fosi Audio BT20A Pro 600W TPA3255 Bluetooth 2.0 CH Amplifier​

 

[Hipster Doofus]

Thank you for sharing, as per the tone controls, do you mean a device like a EQ?

By the way, the equiqment without tone controls is in the final stages of development, it will be released soon.

Just saying we all try many things to get a noticeable difference, when tone controls do the trick nicely. Nice discount offer by the way it came to $108 with tax with the 48v power supply. A screaming deal. I almost bought 2 to power my biamped speakers.

 

[mhardy6647]

So -- I am curious as to what market niche a product like this fills. Bear with me; I'll explain.
It has one input (well, maybe 2 -- I guess -- if one counts BT), which makes it seem like a power amp.
But -- it has tone controls, and a volume control. Is it therefore an integrated amp?
It's not very integrated, other than the tone controls.

I am just a little puzzled as to its raison d'être.
Maybe it's just me(?).

We are practically in the pocket change category <$100 bucks.

Toting around 99 bucks in change would require pretty robust pockets.

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.

The ST70 runs kinda toasty, too.

OK -- I'll stop now.

 

[amirm]

@Amir, how hot did the unit get during testing? I didn't see any vents in the case.

I don't recall it getting warm during testing but it has been a couple of weeks since I tested it.

 

[amirm]

So -- I am curious as to what market niche a product like this fills. Bear with me; I'll explain.
It has one input (well, maybe 2 -- I guess -- if one counts BT), which makes it seem like a power amp.
But -- it has tone controls, and a volume control. Is it therefore an integrated amp?
It's not very integrated, other than the tone controls.

It is for modern desktop use where you have just a DAC feeding it, powering a pair of bookshelf speakers.

 

[amirm]

I strongly recommend you get this from Amazon due to the much higher power in the Amazon variant.

I put a lot of blame at the feet of TI (the chip maker) which has post those outlandish power numbers.

 

[mhardy6647]

It is for modern desktop use where you have just a DAC feeding it, powering a pair of bookshelf speakers.

Ahh, that modern thing!
In all seriousness -- thanks. That does make sense.

 

[NewbieAudiophileExpert]

I do own a Fosi Audio BT20A-S and it's definitely OK for what it is, but I'm not sure that I'd purchase this particular 'PRO' model over a Loxjie A30....

Has anybody used it and heard the difference between the 'pro' and 'non-pro'?

I sorta put this in the same league as an AAiyima a07 and the like - it's good if you need a cheap class-D amp with tone control and op-amp swapability.

 

[JSmith]

op-amp swapability

No one needs that...


JSmith

 

[Fosi Audio]

It would still be nice to see one of these guys made with a vented top case to allow more heat to get out...

Our next new amp may give you a surprise then.

 

[TonyJZX]

see this is what I like... I have a few Fosi peices already... I buy them because they are cheap and they fill a need... and are really very good. Not as good as a $200 piece but close enough

but when they respond to customer advice it makes us excited to see what is coming up next.

 

[Soulsounds]

5 amps.

Hi friends.. one question: what's the audible difference between using the 48v 5a power supply vs. 24v 10A power supply.. if both of them have 240watts..

Please let me know..