Fosi Audio BT20A Pro Amplifier Review

[Fosi Audio]

@Fosi Audio
I'm glad to see that you're responding to our suggestions. If I may offer two suggestions for power amps and one for DACs:

Power Amps:
Please offer a High Pass Filter for the main speakers and a sub-out (pre-out that adjusts with the volume knob works too, but line-out that is independent of the volume knob is not good for connecting to a sub). Multiple settings for the crossover frequency and slope is great, but if you had to offer just one setting I'd recommend 80hz at a -24db per octave slope. I have a powered subwoofer with its own low pass filter, but finding a stereo speaker amp with a high pass filter seems nearly impossible!

Second, if you're offering a display on the amp then please allow the user to turn off the screen. A feature where the screen turns itself off after 5 seconds is best. I will not buy anything with a screen that is always on, it's so distracting when watching movies. Also, bright blue LEDs are the worst.

DACs:
If your DAC uses an ESS chip then please give the user the option to adjust the DPLL setting. If the DPLL setting is too strict, then the DAC will be unusable with certain TVs with high-jitter optical outputs.

Wow, HPF, sub-out, Multiple settings for the crossover frequency, got it.

How much power do you want?

 

[Down South]

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

I wa going to buy from Fosi direct but buying from audiophonics (I live in France) has to be the best option.

 

[GrayA]

@amirm Thanks for your hard work! At 83, is this your highest rated amp at <$100? Do you have a searchable link to your graph of all amps, or the detail in a document somewhere?

 

[gafortiby]

@amirm Thanks for your hard work! At 83, is this your highest rated amp at <$100? Do you have a searchable link to your graph of all amps, or the detail in a document somewhere?

Click on review index on top menu.

Master Audio Review Index

www.audiosciencereview.com

 

[gafortiby]

Please take a glance at our next new model- the V3 @sound67

Fosi Audio V3

Using a minimalist design language, focusing more on enhancing the sound quality and performance of the product, making it the best-sounding power amplifier of Fosi Audio to date.

www.fosiaudio.com

I posted a separate thread to talk about the new V3 amp.

Fosi Audio V3 amplifier discussion

Fosi Audio is releasing their new V3 amp. The model name is a bit confusing but oh well. Functionality it is like the Aiyima A07. Amp with RCA in, sub out, volume and power switch. Nothing else to distract you. I am not sure why it is on Kickstarter to launch, but I backed it since I was...

www.audiosciencereview.com

 

[Head_Unit]

RMS 300W? That is really high power, the power transformer may be too big.

Too big for what? 300W/4 ohms times 2 or more channels won't be tiny, that's true. I think most people don't need so much power, unless they play very loud. But my point is I see people discuss "upgrading" to some 140x2 Emotiva or whatever, well, that is not really much more peak power if at all than a big AVR.

 

[GrayA]

Click on review index on top menu.

Master Audio Review Index

www.audiosciencereview.com

Thanks so much! Looks like the answer to my question is yes. The only other one under $100 is the Aiyima A07 (83) but it doesn't have bass/treble control which I'd want. The only question is if the Aiyima A07 Pro would rate higher.

 

[SuperLuigi]

Sorry for the silly question, but could you use something like this to power a buttkicker mini? RMS is only 50 watts on them, or do I need a specific sub amp?

 

[Extreme_Boky]

This is my wish list:

XLR input (at least one input... two XLR inputs would be perfect
USB/optical/coax/ (HDMI) input....yes, an inbuilt DAC would be excellent
Class D amp... the same specs as in this BT20A Pro, but with speakers' binding posts lined up horizontally on the back plate, i.e NOT on top of each other
Headphone output
XLR output

.... something like fiio k7, but balanced throughout (ins and outs) & with Fosi BT20A Pro amplification (keep the tone controls!!!)... I'd buy that in a flash.

 

[Down South]

I'm about to order this amp but I have a question about the PSU. having read right through this thread is the 48V going to cause heat problems. Seeing as there is no venting on the case top I would anyway drill venting holes. Once I get some definitive answers I will know what PSU to order.

 

[TheBatsEar]

Please take a glance at our next new model- the V3 @sound67

Fosi Audio V3

Using a minimalist design language, focusing more on enhancing the sound quality and performance of the product, making it the best-sounding power amplifier of Fosi Audio to date.

www.fosiaudio.com

How did you manage to get 600W out of a 240W (48V/5A) power supply?

 

[Freezak]

I'm about to order this amp but I have a question about the PSU. having read right through this thread is the 48V going to cause heat problems. Seeing as there is no venting on the case top I would anyway drill venting holes. Once I get some definitive answers I will know what PSU to order.

Perhaps wait for Fosi Audio V3, venting holes on both sides.

 

[GrayA]

I'd want V3 pro since I want treble and bass controls

 

[Down South]

Perhaps wait for Fosi Audio V3, venting holes on both sides.

I've had a look at the V3 - even if the bottom plate has stand offs to lift the PCB off the base plate there's no pathway to create a convection current. By creating venting on the side plates as well as the top plate would.

The Fosi site does'nt show Bluetooth capability or bass/treble controls with the V3. I have no need of Bluetooth but bass & treble would be nice because I'm going to keep my CDs but make digital copies of my LPs and the Puffin phono has DSP so the SSD flash drive will have all my LPs just the way I like.

I still would like an answer about heat issues with a 48V PSU. I use 90dB Heybrook Sextets with external x/overs.

 

[Kimbrough Xu]

Sorry for the silly question, but could you use something like this to power a buttkicker mini? RMS is only 50 watts on them, or do I need a specific sub amp?

The power is enough for your buttkicker mini.

 

[Kimbrough Xu]

I'd want V3 pro since I want treble and bass controls

I think you want Fosi Audio TB10D, they both TPA3255.

Fosi Audio TB10D Amplifier Review

This is a review and detailed measurements of the Fosi Audio TB10D stereo amplifier. It was sent to me by the company and is only sale for US $70 on Amazon including shipping. We have the typical compact desktop aluminum case. Controls feel nice for the class. Tone controls are not centered...

www.audiosciencereview.com

 

[TheBatsEar]

I expect load/impedance dependency in this class of switching amplifiers but here, the peaking is almost entirely out of band which is good:

A frequency response like that in any other amp would be considered defective.
Why do we allow almost 1dB deviation at 20Hz and 20kHz in an amp in 2023?

 

[Talisman]

A frequency response like that in any other amp would be considered defective.
Why do we allow almost 1dB deviation at 20Hz and 20kHz in an amp in 2023?

Because it costs less than $100 and delivers 100 watts of fairly clean power before clipping into 8 ohms. Seems like an acceptable compromise to me. Obviously it's not a very high fidelity amplifier, and it doesn't want to be, but for a "noisy" secondary system or to act as a power amp using the preouts of an AVR, it seems excellent to me

 

[solderdude]

How did you manage to get 600W out of a 240W (48V/5A) power supply?
View attachment 281858

PMPO ? using some reservoir caps this is not unheard of, not with 0.00something distortion though.
When you charge capacitors you can very shortly draw peak powers beyond the continuous rating.

 

[TheBatsEar]

Because it costs less than $100 and delivers 100 watts of fairly clean power before clipping into 8 ohms. Seems like an acceptable compromise to me. Obviously it's not a very high fidelity amplifier, and it doesn't want to be, but for a "noisy" secondary system or to act as a power amp using the preouts of an AVR, it seems excellent to me

Well, it costs almost as much as a Japanese AB here, if you take the better power supply, so i'm comparing it with those.
Yep, it's a defective frequency response.

PMPO ? using some reservoir caps this is not unheard of, not with 0.00something distortion though.
When you charge capacitors you can very shortly draw peak powers beyond the continuous rating.

The caps are 2x 2200µF. The mystery remains: how do you get that much power out of a that power supply and these caps? @Fosi Audio, can you explain how that works?