Fosi Audio BT20A Pro Amplifier Review

[delta76]

I have now mounted my Fosi BT20A Pro with a pair of Q Acoustics 3030i as my new, passive desktop setup (replacing a pair of ADAM A5 active speakers).

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The first thing that strikes me is how high I have to turn up the volume on the Fosi, considering my ears are less than 1 meter away from the speakers, and they're 88db into 6Ohms. I got the version with the 32V-5A standard power supply. Having said that, the sound is really good (had to turn the bass down and the treble up a bit). I'm using the output of my OPC soundcard for the time being.

The Q 3030i were previously set up in my bedroom (4 by 5 meters), connected to my Aiyima D03 (36V-6.5A). In that setup, I only had to turn up the D03 to about 45% for a slightly louder than comfortable volume. On the Fosi/Desktop, it's more like 60% for comfortable listening (PC output at 100%).

Would it make sense to order a 48V power supply for the Fosi?

no. unless you crank up to max and it is still not loud enough, or if you hear clipping. the volume setting is not very "comparable" between different amps

 

[Talisman]

I have now mounted my Fosi BT20A Pro with a pair of Q Acoustics 3030i as my new, passive desktop setup (replacing a pair of ADAM A5 active speakers).

View attachment 279181

View attachment 279182

The first thing that strikes me is how high I have to turn up the volume on the Fosi, considering my ears are less than 1 meter away from the speakers, and they're 88db into 6Ohms. I got the version with the 32V-5A standard power supply. Having said that, the sound is really good (had to turn the bass down and the treble up a bit). I'm using the output of my OPC soundcard for the time being.

The Q 3030i were previously set up in my bedroom (4 by 5 meters), connected to my Aiyima D03 (36V-6.5A). In that setup, I only had to turn up the D03 to about 45% for a slightly louder than comfortable volume. On the Fosi/Desktop, it's more like 60% for comfortable listening (PC output at 100%).

Would it make sense to order a 48V power supply for the Fosi?

The fosi audio bt10d has a linear pot, you'd be happy if you only had to turn it to 11 o'clock and have a very powerful sound, but this does not indicate a more powerful amp, it just indicates that it delivers everything at once.
A logarithmic potentiometer has FINALLY been implemented on this one, this means as you turn the knob initially the power will increase slightly and then progressively more and more, but don't confuse this with power.
This implementation will allow you to manage the volume in a much finer way even with a 2V line input.

 

[Deleted member 48726]

please show me a "not terrible"/significantly better amp for ~100$/100EUR

I'll wait.

Yeah, that's a tough one. Incredibly competitive.
BUT I wonder how it will last with this output and in an enclosure that's sealed off like that. Why don't manufacturers make them so convection can work proper?

 

[jaudio]

How does the soft start thermistor work? Fosi mentioned that the on/off toggle is not just a standby but a complete power off. My actual question is if it would be ok to turn the amplifier on/off via the AC mains (to the power supply brick)? This method was not recommended with the Aiyima A07 as the power surge would be straining the PSU filter caps too much. But this could potentially be solved here. Anybody know?

 

[delta76]

Yeah, that's a tough one. Incredibly competitive.
BUT I wonder how it will last with this output and in an enclosure that's sealed off like that. Why don't manufacturers make them so convection can work proper?

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The enclosure can actually act as a heatsink too, if properly designed. With high efficiency of class D + speakers usually draw less than 10wpc from amp, it would not be a problem. In most cases at least.
If you have a demanding speaker and you like to play it loud, it makes senses to look at amps with higher output and/or better thermal design. But really hard to ask for more at 70$

 

[ClassicGuy]

How do we know if the units we buy will be of the same quality Amir receives, in terms of sound quality and how the tone controls behave? Not trying to discourage manufacturers sending units for testing, but would like to get a sense whether the test unit is specially calibrated.

 

[Joe Smith]

How do we know if the units we buy will be of the same quality Amir receives, in terms of sound quality and how the tone controls behave? Not trying to discourage manufacturers sending units for testing, but would like to get a sense whether the test unit is specially calibrated.

On a $100 item? Doubtful.

 

[Joe Smith]

I have now mounted my Fosi BT20A Pro with a pair of Q Acoustics 3030i as my new, passive desktop setup (replacing a pair of ADAM A5 active speakers).

View attachment 279181

View attachment 279182

The first thing that strikes me is how high I have to turn up the volume on the Fosi, considering my ears are less than 1 meter away from the speakers, and they're 88db into 6Ohms. I got the version with the 32V-5A standard power supply. Having said that, the sound is really good (had to turn the bass down and the treble up a bit). I'm using the output of my OPC soundcard for the time being.

The Q 3030i were previously set up in my bedroom (4 by 5 meters), connected to my Aiyima D03 (36V-6.5A). In that setup, I only had to turn up the D03 to about 45% for a slightly louder than comfortable volume. On the Fosi/Desktop, it's more like 60% for comfortable listening (PC output at 100%).

Would it make sense to order a 48V power supply for the Fosi?

What you described re your tone control settings is not what's in your picture above - treble is down, bass is up...? I think we're all used to bass being left, treble right, but a lot of the Chinese amps seem to have them in the opposite order..

For my Aiyima A07, with their 32v/5a supply, it gets quite loud at the 10 o'clock volume position. I would be deaf if played at 1 or 2 o'clock...

 

[delta76]

How do we know if the units we buy will be of the same quality Amir receives, in terms of sound quality and how the tone controls behave? Not trying to discourage manufacturers sending units for testing, but would like to get a sense whether the test unit is specially calibrated.

valid skeptic. Amir addressed this with other manufacturers (I recall Topping, not sure if there were other) as they offered that Amir to order from a retailer and they reimburse the cost. Amir thought that is unnecessary and he decided to test the sent in unit.

It's unclear about the situation with Fosi, but I would say that cherry pick a golden sample is pretty difficult thing to do.

 

[Joe Smith]

The Fosi representative active here hinted that they might have some new design coming up with a vented case. I'll be interested to see how that develops. If paired with a board design that lets the caps be further away from the power chip and heat fins, plus quality caps and inductors, could be what a lot of us have been looking for...

 

[Fosi Audio]

Yeah, that's a tough one. Incredibly competitive.
BUT I wonder how it will last with this output and in an enclosure that's sealed off like that. Why don't manufacturers make them so convection can work proper?

View attachment 279192

We featured quality capacitors, inductors, and relays in BT20A Pro to enhance longevity. So please do not worry about it.

 

[Fosi Audio]

How do we know if the units we buy will be of the same quality Amir receives, in terms of sound quality and how the tone controls behave? Not trying to discourage manufacturers sending units for testing, but would like to get a sense whether the test unit is specially calibrated.

We keep optimizing our products based on users' feedback, which means what you get will be better than the test unit.

 

[Fosi Audio]

The Fosi representative active here hinted that they might have some new design coming up with a vented case. I'll be interested to see how that develops. If paired with a board design that lets the caps be further away from the power chip and heat fins, plus quality caps and inductors, could be what a lot of us have been looking for...

I should say we are making what you are looking for.
Here is a leaked photo of it.

 

[laudio]

Have to rate this one as great. Quality construction, tone controls, good SINAD numbers, and real measured power. Get the 48V while you are at it. For the price surprised it didn't rate higher in the review.

 

[Kimbrough Xu]

I have now mounted my Fosi BT20A Pro with a pair of Q Acoustics 3030i as my new, passive desktop setup (replacing a pair of ADAM A5 active speakers).

View attachment 279181

View attachment 279182

The first thing that strikes me is how high I have to turn up the volume on the Fosi, considering my ears are less than 1 meter away from the speakers, and they're 88db into 6Ohms. I got the version with the 32V-5A standard power supply. Having said that, the sound is really good (had to turn the bass down and the treble up a bit). I'm using the output of my OPC soundcard for the time being.

The Q 3030i were previously set up in my bedroom (4 by 5 meters), connected to my Aiyima D03 (36V-6.5A). In that setup, I only had to turn up the D03 to about 45% for a slightly louder than comfortable volume. On the Fosi/Desktop, it's more like 60% for comfortable listening (PC output at 100%).

Would it make sense to order a 48V power supply for the Fosi?

So fosi audio finally used a Taper A volume control.

With the Taper A, the volume will increases logarithmically, very slow at first and then higher and higher, very suitable for human ear.

By the way, the 32V version is enough for your Q Acoustics 3030i.

 

[asnow]

I should say we are making what you are looking for.
Here is a leaked photo of it.

I just purchased the 48 volt version of the BT20A Pro, any chance it will come with the new vented case?

 

[Kimbrough Xu]

The fosi audio bt10d has a linear pot, you'd be happy if you only had to turn it to 11 o'clock and have a very powerful sound, but this does not indicate a more powerful amp, it just indicates that it delivers everything at once.
A logarithmic potentiometer has FINALLY been implemented on this one, this means as you turn the knob initially the power will increase slightly and then progressively more and more, but don't confuse this with power.
This implementation will allow you to manage the volume in a much finer way even with a 2V line input.

Yes, and it sounds more stable and comfortable when you adjust the volume.

 

[Fosi Audio]

I just purchased the 48 volt version of the BT20A Pro, any chance it will come with the new vented case?

Sorry, but the vented case will be used in our next new model only.

 

[Kimbrough Xu]

How do we know if the units we buy will be of the same quality Amir receives, in terms of sound quality and how the tone controls behave? Not trying to discourage manufacturers sending units for testing, but would like to get a sense whether the test unit is specially calibrated.

I have an idea, maybe you can send your unit to Amir to have a test.

 

[Deleted member 48726]

We featured quality capacitors, inductors, and relays in BT20A Pro to enhance longevity. So please do not worry about it.

Sure. But it still doesn't change rhe fact that there at all times is standing still air inside. This is inherently bad. Still air doesn't transport much heat. Still air gaps actually insulate. I don't get why there isn't just a handful of drilled holes.
Makes it seem like a work of haste. -Or an oversight.