Fosi Audio BT20A Pro Amplifier Review

[amirm]

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..

To drive high impedance loads (e.g. 8 ohm speakers) you need high voltage. Even with 4 ohm speakers you want the 48 volt. The 24 volt one will produce much lower wattage and its extra current would be left unused.

 

[Kimbrough Xu]

The more amps, the

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..

The more amps, the more heat due to the equation (Q=I²Rt).

 

[Jacob8275]

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?

"Thumbs up for the center tone defeat on the tone controls" means the tone controls can be turned off when it in the center position?

 

[amirm]

"Thumbs up for the center tone defeat on the tone controls" means the tone controls can be turned off when it in the center position?

When set to the center they created the essentially flat in audible band response you see in the review. Whether it is calibrated to that or it really bypasses the tone controls, I don't know.

 

[AudioSceptic]

And less with above discount code.
But it doesn't accept shipping to Belgium or France...

The price at audiophonics is still very reasonable <https://www.audiophonics.fr/en/search?search_query=Fosi+Audio+BT20A+>

 

[Sister_Ray]

Switching to 8 ohm we naturally see the biggest hit to power:

View attachment 278425

Although to be fair, I put the cursor at an earlier point than for 48 volt supply (not enough measurement points there).

@amirm You say 69 watts but X=98.84? Is this a mistake? I just bought this little amp with some 8 ohm outdoor speakers (B&W AM-1), so 99 or 69 makes a big difference.

 

[Sister_Ray]

The price at audiophonics is still very reasonable <https://www.audiophonics.fr/en/search?search_query=Fosi+Audio+BT20A+>

Watch out, this is with the 32V power supply.

 

[AudioSceptic]

Watch out, this is with the 32V power supply.

Yes, understood.

 

[Fosi Audio]

Very nice little amp. With the 48V power supply it is a best value in its price x performance x power category.

Can't wait for chip amp makers like TI and Infineon to improve their current offerings. Then hopefully we would get excellent performance chips like the DAC industry already has with ESS and AKM, and we would get plenty of excellent performing cheap amps like we have with 120+ SINAD DACs nowadays. Chip amps are still not there yet compared to high end Purifi and NCoreX, but maybe one day.


As long as it is optional, like a board that the user can install him/herself, those who value this could buy without affecting those who do not want it, right? Fosi could order a batch of LDAC BT boards and offer for sale, and let the market decide.

Thank you for your suggestion, I have forwarded it to our R&D, we will consider it carefully and let you know once we have desicion.

 

[Fosi Audio]

About LDAC

I guess it could be a (paid for) optional firmware update. LDAC is a Codec, so probably purely software.

It needs different bluetooth module.

 

[Fosi Audio]

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.

Thanks Tony, can you tell more details about how good a $200 piece is? We will try if we can reach that good.

 

[shadracko]

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.

Unless you're into vinyl, a single streamer unit can well be the only input you need for a music-only situation. (It is for me). So this pairs wonderfully with a Wiim-type streamer (and a DAC if you're so inclined) for nearly any room. I feel like "integrated" has lost most of its value in a world where I really don't care about tuner, CD, tape, phono, or anything but digital.
It's missing remote volume control, if you want that and don't want upstream app-based volume. But i'd rather not have another remote to lose anyway.

It is probably best as a music-only unit, rather than with a TV. But even there it's feasible with a separate pre-amp.

 

[shadracko]

Thanks Tony, can you tell more details about how good a $200 piece is? We will try if we can reach that good.

Agreed. One of the main appeals of these ~$100 units is that to get something better, you get way up in price (~$800+ pretty quickly. I don't see anything in that middle $200-600 range that gives you any meaningful improvement, unless you really want an integrated DAC.

 

[amirm]

@amirm You say 69 watts but X=98.84? Is this a mistake? I just bought this little amp with some 8 ohm outdoor speakers (B&W AM-1), so 99 or 69 makes a big difference.

Oops. Will correct layer...

 

[Talisman]

Thanks Tony, can you tell more details about how good a $200 piece is? We will try if we can reach that good.

Since you seem to be listening, I want to give you this suggestion that nobody seems to think about.
For 200 it would be enough, maintaining these amplification characteristics, to insert a display, two or three analog inputs (we are all full of DACs anyway) and A HIGH PASS FILTER OPTION for the loudspeakers, with RCA sub output.
You would probably sell thousands just among forum users.
And if with these characteristics it were possible to make the response independent of the load, I would put 300 euros on the plate.

 

[Kimbrough Xu]

Since you seem to be listening, I want to give you this suggestion that nobody seems to think about.
For 200 it would be enough, maintaining these amplification characteristics, to insert a display, two or three analog inputs (we are all full of DACs anyway) and A HIGH PASS FILTER OPTION for the loudspeakers, with RCA sub output.
You would probably sell thousands just among forum users.
And if with these characteristics it were possible to make the response independent of the load, I would put 300 euros on the plate.

Agreed, and add a remote control, and if the two or three analog inputs have a XLR input can be better.

 

[kemmler3D]

Less than $1/watt with decent performance and bluetooth input, that beats SINAD performance of some known brands... maybe you've heard of Rotel or Yamaha, check out the chart. That's quite a coup when you think about it.

Basically with this and some reasonable monitors you can put together a kid's bedroom system for less money - that would make the "mini-component" systems of my youth (in the 90s) sound like boiled dog crap in comparison.

Not in the market for one at the moment but it's good to know these bad boys are out there. You could take a bunch of these, whatever speakers you want, and a WiiM and do a whole-home system with considerable oomph for about $200 per room plus speakers. Don't get too comfy, SONOS...!

 

[isaac507]

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...

Also happy to see quality caps and inductors are integrated. This could make it more reliable than the A07 (which of mine spoilt within a month...)

 

[tomtoo]

Opened

Maybe you win one?

 

[JktHifi]

We are entering the era of cheap amplifiers. Sometimes it’s very difficult to me to accept this kind of reality.
Waiting for the next era of cheap loudspeakers which is also small sized but big sound.