Fosi Audio BT20A Pro Amplifier Review

[I know (almost) nothing]

Perfect amp for my less-than-audiophile project of bypassing the defunct amp of my very old audio engine A5’s

 

[DavidM1]

What I mean is that 99% of the population listen to bad music recordings (which also have dynamic range < or << 10 dB). For them this amplifier is more than enough. And cheap loudspeakers with cheap crossovers and...

It is not appropriate for this a very good album.

https://twitter.com/x/status/1646962697156608000

Just listened to this through Apple earbuds and the Apple lightning dac. Classic blue note. Thanks! Why wouldn’t it be appropriate with this Fosi?

 

[Fosi Audio]

Can you post here when new and improved model arrives?

Of course we will post here.

 

[delta76]

The comparison with the tube amp at the end.... brutal. The class D amp sounded like someone squeezed Nora's throat with both hands and forced her to sing at the gunpoint. Ouch.

Right, because Youtube audio equipment comparison videos are so high quality and trust worthy now

 

[Extreme_Boky]

Right

 

[Deleted member 48726]

Right, because Youtube audio equipment comparison videos are so high quality and trust worthy now

I guess you somehow think the algorithm causes the sound differences?

Actually now I'm curious; do you hear a difference with headphones on?

 

[Talisman]

I guess you somehow think the algorithm causes the sound differences?

Actually now I'm curious; do you hear a difference with headphones on?

I guess you somehow think that a chain made up of his listening system, plus his environment, plus his microphone, plus his adc plus youtube compression, plus your listening system are able to tell you how a "sounds" amplifier

 

[DavidM1]

Yes, they have. Because a lot of them


Cheap class D amps have problemas with HF. Usually > 1 kHz (phase). The range 1-4 kHz is very important, our ears are very sensitive and it is convenient that the frequency response is as linear as possible, horizontal or inclined, but linear.

They also suffer from a phase change, which should be constant throughout the audio range (with class A and AB it is not a problem and it is usual, the merit is that it is < 1º at 20 kHz). Also distortion tends to increase with high frequency.

If you listen to poorly produced music, without physical instruments, voices adulterated with Autotune... then those inconveniences are much less. But if you listen to a jazz quartet, folk, orchestral mass... then it does matter. The point is that today very few listen to this type of music or similar, so it is stupid to spend a lot of money on music equipment. So FOSI does very well by focusing on that 99% of the population.

In class D, the only one that convinces me is the Hypex Nilai500DIY, much more than Purifi (perhaps only better with electronic music).

Thanks for the detailed response. Virtually all of my listening is classical and jazz and acoustic realism is a high priority.

 

[Deleted member 48726]

I guess you somehow think that a chain made up of his listening system, plus his environment, plus his microphone, plus his adc plus youtube compression, plus your listening system are able to tell you how a "sounds" amplifier

In _that_ video I prefer the sound from the tube amp. I also mentioned earlier that we don't see the setup but that doesn't change the fact that I prefer the sound from the tube in that video. I will never claim that you can tell how an amplifier sounds on a youtube video but in THAT VIDEO I prefer the sound from the tube and can hear differences between the opamps. And that was the point. I'm very well aware that you can not tell a particular sound from a youtube. But the differences are clearly there to hear. And when I much prefer the sound from the tube amp (in that particular video on youtube) I wonder if that's the case for many others and then wonder why Fosi Audio lets that fly in a marketing point of view.

I'm very well aware that room, speaker, mic, setup and compression colours the sound. I've done about hundred of REW measurements with different speakers and subs in my own room.

Hope that clears it up..

 

[delta76]

I guess you somehow think the algorithm causes the sound differences?

Actually now I'm curious; do you hear a difference with headphones on?

Except very very few trusted youtubers you can't trust a random guy with their "comparison" videos. Especially if he is trying to prove a non sense thing (class D sounds dry etc. ) there are so much they can do to "prove" their bias.

Then you have equipment issues. And yes youtube compression

 

[Deleted member 48726]

Except very very few trusted youtubers you can't trust a random guy with their "comparison" videos. Especially if he is trying to prove a non sense thing (class D sounds dry etc. ) there are so much they can do to "prove" their bias.

Then you have equipment issues. And yes youtube compression

I'm well aware. Trust me. I've clarified above.

When that is said I do enjoy some of NRD (New Record Days) binaural videos with headphones on. That's as close as it gets AFAIC. -In that room with that equipment and my headphones..

 

[okok]

what exactly does Fosi mean, Foxy?
@Fosi Audio

 

[Soulsounds]

How it sounds? BT20A Pro with Various Op-Amps Demonstration

View attachment 279379

I wrote:

1º OP249
2º OPA2604

It is surprising how well the familiar NE5532 stands the test of time.

The worst, RM4559

Hi friend
. Thanks you for that awesome video.. could you test the opa1656, the opa 2210 super-β and the LM4562NA... and compare with the op249 and the ne5532
Please!!!

 

[Fosi Audio]

what exactly does Fosi mean, Foxy?
@Fosi Audio

Good question.
We would like to define the word "Fosi" as "Full of sound & ideas".
Or extended to "Fidelity of sound immerses you in the audio world".
Do you have any suggestions?

 

[JSmith]

Do you have any suggestions?

Not related to the company name... but yes. One can only assume the optimal op-amp for the circuit has been used, however I see the company actively encourages op-amp rolling. Why is that... has the optimal op-amp been used for the design, or no? If so, why this advertising of op-amp rolling? My suggestion would be to let that go and not market your devices that way, as if you imply there are improvements to be gained from op-amp rolling, then it has a negative implication for stock parts used.


JSmith

 

[Fosi Audio]

You can always drill holes into the cabinet yourself.

Yes, drilling holes is fun, which we are doing on our new model.

 

[sound67]

Not related to the company name... but yes. One can only assume the optimal op-amp for the circuit has been used, however I see the company actively encourages op-amp rolling. Why is that... has the optimal op-amp been used for the design, or no? If so, why this advertising of op-amp rolling? My suggestion would be to let that go and not market your devices that way, as if you imply there are improvements to be gained from op-amp rolling, then it has a negative implication for stock parts used.


JSmith

Maybe because they realize that many so-called "audiophiles" aren't real adults but children who want to play with their toys.

Same as with smart phones. All kinds of people experiment with custom ROMs even when there's absolutely no reason to do it.

 

[Fosi Audio]

Not related to the company name... but yes. One can only assume the optimal op-amp for the circuit has been used, however I see the company actively encourages op-amp rolling. Why is that... has the optimal op-amp been used for the design, or no? If so, why this advertising of op-amp rolling? My suggestion would be to let that go and not market your devices that way, as if you imply there are improvements to be gained from op-amp rolling, then it has a negative implication for stock parts used.


JSmith

The stock ones are good enough to satisfy most users. However, we realized many audiophiles love to DIY. They are pleased to find an amp that allows them to roll the op-amps or other components to achieve their desired sound and functionality.

 

[JSmith]

The stock ones are good enough to satisfy most users.

to achieve their desired sound

In a way your reply concerns me even more now...

Rolling Op-amps in Gustard H20 Headphone Amplifier

I reviewed the Gustard H20 which is a high-end headphone amplifier yesterday. Its owner kindly sent me some high-end op-amps to "roll" in there to see what difference it makes. The task was pretty easy. The top screws come out of the H20 and if you tilt the unit, the lid falls out exposing...

www.audiosciencereview.com

Rolling (replacing) Op-amps in Topping D10 DAC

This is a study of whether changing op-amps in a DAC makes a measurable difference. Taking a lead form "rolling" tubes in tube products, a trend has started in replacing op-amps -- sometimes with much difficulty -- to improve performance of solid state products like DACs. A few months ago I...

www.audiosciencereview.com

Anybody OP amp rolling?

There are many products touting OP amp rolling capability. Anybody doing it? Is it snake oil?

www.audiosciencereview.com

Up to the company, but my suggestion to not appeal to this crowd stands. No one should need to replace any parts to achieve their "desired sound" and there should be no need to tweak a completed device after purchase. I hope you don't take this post the wrong way, as it is intended as constructive criticism.


JSmith

 

[sound67]

I'm sure if they had made the Op amps (which really are snake oil IMHO) fixed items, YOU would have complained why they weren't removable. You can't please all people all the time, and people like you always find a reason to complain about SOMEthing. What they did for under 100 bucks I (so far) think is marvelous. The fact that it's even doable nowadays is a reason to rejoice.