Fosi Audio BT20A Pro Amplifier Review

[Talisman]

@Fosi Audio Do you have reason to believe that with the bt20a pro there may be overheating problems with 48V power supply? Have you conducted durability tests at high power output levels?

 

[Fosi Audio]

My query was more around any known issue with using 36v psu, rather than necessity.
I have used 32v/36v/48v with other manufacturer’s tpa3255 amps and observed more heating with 48v even on lower volume (6 ohm load), but had no issues using 36v.
I am not suggesting it might be similar with your product.

May I know how many amps your 36V PSU has?

 

[Fosi Audio]

@Fosi Audio Do you have reason to believe that with the bt20a pro there may be overheating problems with 48V power supply? Have you conducted durability tests at high power output levels?

Yes, we have conducted durability tests at high power output levels with the 48V PSU. It does not have overheating problems.

 

[Guddu]

May I know how many amps your 36V PSU has?

36v 6a

 

[grogi.giant]

My query was more around any known issue with using 36v psu, rather than necessity.
I have used 32v/36v/48v with other manufacturer’s tpa3255 amps and observed more heating with 48v even on lower volume (6 ohm load), but had no issues using 36v.
I am not suggesting it might be similar with your product.

With the improved cooling, I really don't predict the overheating issues, and with that no point in going for 36v PSU.

 

[Guddu]

With the improved cooling, I really don't predict the overheating issues, and with that no point in going for 36v PSU.

Okay, thanks.
3 out of 4 different TPA3255 amps I have had similar observations, will see how this one goes when tested.

 

[Ultratek]

@Fosi Audio
For when the improvement / update in the BT30D PRO,
could be:
Input power 48V would be great for the tpa 3255 twins, perhaps getting a little more Watts of power and gaining a little more SNR would not be unreasonable, don't you think?
Also the set Japanese NCC Capacitors 63V/2200uF, Japanese Sumida Audio Inductors, German WIMA Output Capacitors,Japanese ELNA Capacitors ; They could eliminate some of the noise and THD that the source the requirement of those 48V can generate. that added to replaceable op amps would be a home run for the product with incredible power it would be nice to see it reviewed by @amirm. I would already buy it.
I only say it as a thought and of course it is subject to discussion in this forum.

 

[Fosi Audio]

@Fosi Audio
Found answer to PSU query, Product page says "Power Supply: 32V/5A, 48V/5A". Wondering why not 36v?
Also, any interest towards balanced design? and/or dual input?

What‘s in the box？
1. V3 ×1
2. User Manual × 1
3. 32V/5A or 48V/5A Power Supply × 1

By the way, which of your devices has balanced output?

 

[grogi.giant]

By the way, which of your devices has balanced output?

DSP Processor (t.racks DSP 4x4 Mini).

 

[Fster]

@Fosi Audio
Hi! If my wife wants to turn on music from her phone via bluetooth, what will she need to do if before that I was listening to music from my phone?

 

[Fosi Audio]

I'm waiting for the era of cheap surround decoding with noise levels as low as DACs. With built-in adjustable digital crossovers with time delay please. And whipped cream with a cherry on top.

OR the era where "subwoofer outs" all have corresponding built-in highpass filters...

Do you mean a DAC with built-in EQ such as virtual surround sound? Or a DAC which can decode Dolby?

And could you please describe more clearly why do you want time delay?

I agree with your HPF for the amps with subwoofer outs, and we are working.

 

[Fosi Audio]

@Fosi Audio
Hi! If my wife wants to turn on music from her phone via bluetooth, what will she need to do if before that I was listening to music from my phone?

She can press the volume knob for about 5 seconds to disconnect your phone from BT20A PRO, then she can connect via her phone.

 

[Guddu]

By the way, which of your devices has balanced output?

Topping D10 and E50.

 

[JktHifi]

I can't believe what some CLOWNS on here demand from a budget amp. If you have money to spare, JUST BUY A DIFFERENT AMP for tons more. On a budget, you can't do better. And that's what Fosi / Douk / Aiyima et al are aimed at

It’s only a wish. If nothing, it’s okay.

 

[JSmith]

JSmith

 

[Joe Smith]

JSmith

Always loved that cover photo... Lots of Sinatra albums where he's pictured with a mic, but this was the best IMO. Not a bad cover of the song, either, as I recall.

 

[Head_Unit]

Do you mean a DAC with built-in EQ such as virtual surround sound? Or a DAC which can decode Dolby?
And could you please describe more clearly why do you want time delay?
I agree with your HPF for the amps with subwoofer outs, and we are working.

Currently the only way to decode surround (Dolby, DTS) is with an Audio-Video Receiver (measured performance some quite good but none state of the art), or quite expensive pre-pro, or quite complex Home Theater PC. With so many good and not-expensive DACs and power amps, it would be nice to have a surround decoder of really high performance but not a crazy price. This is a kind of vague wish I think many share.

What exact product, that is tricky. Just optic/coax outputs to feed multiple DACs? But the DACs then need synchronized timing and volume. That is a rather niche product, especially if expanded to allow multiple outputs for active DSP crossovers. (Ah the time delay would be for active crossover time alignment, I guess this is available from miniDSP and maybe others. The missing piece is the surround decoding-you can make some very high quality two-channel systems but the same quality level cannot be made in surround.)

Maybe more effective to integrate DACs, at which point you now have a conventional pre/pro. There is nothing wrong with a pre/pro; to gain market attention would mean really good sounding and measuring output sections and a price not crazy, where buyers would feel the performance would be truly improved over an AVR. Now in this very forum we see that at least from a measurement point of view I don't think there is any pre/pro whose performance is better than the best AVRs (??). Dispense with legacy inputs, inputs maybe 1 eARC HDMI, 1 HDMI for game console, 1 HDMI for a disc player. AirPlay 2 and Spotify Connect.

Great to hear about highpass filters. Even something fixed is fine at these low prices; subwoofers almost always have variable adjustment.

I guess another missing product could be a high powered clean performance amplifier at a low price. The market now seems to have tens of watts per channel for oh $100 but if you want like 300W/4Ω then suddenly it is thousands of dollars. Notice my stress on the FOUR ohms, since most speakers are now 4Ω even if they say 8.

 

[anotherhobby]

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

This looks like a really nice little amp too! When is it supposed to be available for purchase at places like Amazon?

 

[Kimbrough Xu]

Currently the only way to decode surround (Dolby, DTS) is with an Audio-Video Receiver (measured performance some quite good but none state of the art), or quite expensive pre-pro, or quite complex Home Theater PC. With so many good and not-expensive DACs and power amps, it would be nice to have a surround decoder of really high performance but not a crazy price. This is a kind of vague wish I think many share.

What exact product, that is tricky. Just optic/coax outputs to feed multiple DACs? But the DACs then need synchronized timing and volume. That is a rather niche product, especially if expanded to allow multiple outputs for active DSP crossovers. (Ah the time delay would be for active crossover time alignment, I guess this is available from miniDSP and maybe others. The missing piece is the surround decoding-you can make some very high quality two-channel systems but the same quality level cannot be made in surround.)

Maybe more effective to integrate DACs, at which point you now have a conventional pre/pro. There is nothing wrong with a pre/pro; to gain market attention would mean really good sounding and measuring output sections and a price not crazy, where buyers would feel the performance would be truly improved over an AVR. Now in this very forum we see that at least from a measurement point of view I don't think there is any pre/pro whose performance is better than the best AVRs (??). Dispense with legacy inputs, inputs maybe 1 eARC HDMI, 1 HDMI for game console, 1 HDMI for a disc player. AirPlay 2 and Spotify Connect.

Great to hear about highpass filters. Even something fixed is fine at these low prices; subwoofers almost always have variable adjustment.

I guess another missing product could be a high powered clean performance amplifier at a low price. The market now seems to have tens of watts per channel for oh $100 but if you want like 300W/4Ω then suddenly it is thousands of dollars. Notice my stress on the FOUR ohms, since most speakers are now 4Ω even if they say 8.

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

 

[Wembley]

Hello,
I just received the BT20A Pro (grey knob , but that doesn't matter).
Two topics I would like to mention ( @Fosi Audio ):
1) Since I would like to add a subwoofer, I think about a purchasing an additional mono amp OR the BT30D Pro.
The main difference is the capability of the BT20A Pro to be operated with a 48V PSU instead of 36V (BT30D).
I assume that total power output will be similar, but the BT30D has three channels, so it will be around 50% less power per stereo channel.
Is there from a technical point of view any indication for significant differences in terms of SINAD / THD? My assumption is, that these two are built with pretty similar components.
Or is there something else, that I don't see at this moment?
2) I would highly appreciate if a vented case will be available as a retrofit. Makes a lot of sense, also from sustainability point of view.