Fosi Audio BT20A Pro Amplifier Review

[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.

 

[Freezak]

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

Will it have at least as much power as the BT20A Pro has at 8 ohm with 48V psu?

 

[ClassicGuy]

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

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

The most pressing question is: would it come with the orange knob ?

 

[gafortiby]

@Fosi Audio , I registered for this forum just to say I would like an orange knob on the v3 amp.

Also, why are you using kickstarter when you can sell direct?

 

[sokool0]

First of all, I'm a satisfied user of the fosi tb10d amp.
At this time, I'm looking forward to upgrading the amp to the next level, and have found you have a new amp w/quality components inside the amp.

Would it be an upgrade to the tb10d?

I don't have interest in blue-tooth, etc but want to have a minimalist amp just for amplifying signal.

BTW, you found a good way to dissipate heat w/o using a big heat sink.
Same technique's got found in the 3e audio tpa3255 board which has a big bottom plate for heat dissipation.

One more question, you don't have a plan to sell the v3 on the aliexpress, do you?

 

[Fosi Audio]

First of all, I'm a satisfied user of the fosi tb10d amp.
At this time, I'm looking forward to upgrading the amp to the next level, and have found you have a new amp w/quality components inside the amp.

Would it be an upgrade to the tb10d?

I don't have interest in blue-tooth, etc but want to have a minimalist amp just for amplifying signal.

BTW, you found a good way to dissipate heat w/o using a big heat sink.
Same technique's got found in the 3e audio tpa3255 board which has a big bottom plate for heat dissipation.

One more question, you don't have a plan to sell the v3 on the aliexpress, do you?

We believe the V3 could be the right one you are looking for.

We'll certainly sell the V3 on Aliexpress after we release it, probably in late May or early June. We're going to launch the crowdfunding on Kickstarter next week and if you back the project, you'll be one of the first users to get this robust amp.

 

[Fosi Audio]

@Fosi Audio , I registered for this forum just to say I would like an orange knob on the v3 amp.

Also, why are you using kickstarter when you can sell direct?

We'll provide the option of an orange knob on the V3 amp.

 

[Fosi Audio]

Will it have at least as much power as the BT20A Pro has at 8 ohm with 48V psu?

Yes, it'll have a similar power to BT20A Pro.

 

[Fosi Audio]

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.

May I know if your subwoofer is an active one?

 

[Extreme_Boky]

I hope the V3 model will come with XLR inputs.

I also like the fact that you used through-hole capacitors... so, I do believe that blurb from your website: For audiophiles from audiophiles. I think you may have tuned the V3 version to sound & be more like that valve amplifier sound, while still providing very good measurements. This is a big plus in my book.

I'd love to see the speaker binding posts placed horizontally (all 4 of them) so that I could connect my speaker cables which are quite rigid. Placing binding posts on top of each other is simply an instant pass for me (but I also understand that it helps with space-saving... and I'll be cool with that).

 

[JktHifi]

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

Request for V3:
Speaker impedance 4 - 16 ohm capability

 

[Wembley]

May I know if your subwoofer is an active one?

I still think about which way to go. Passive + separate amp or active sub with plate amp.
Currently I only have a pair of speakers on my desktop but I plan to expand to a 2.1 system.
This is why I think about the differences between these two amplifiers.

 

[Fosi Audio]

I still think about which way to go. Passive + separate amp or active sub with plate amp.
Currently I only have a pair of speakers on my desktop but I plan to expand to a 2.1 system.
This is why I think about the differences between these two amplifiers.

Most people use active subwoofer, but also some may use passive subwoofer, that why we developed fosi audio BT30D PRO, and also the total power of BT30D PRO is higher than BT20A PRO because BT30D PRO adopts 2 pcs of TPA3255.

 

[DavidM1]

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

SMSL C200

 

[cbrworm]

I have a question, I think the TPA3255 supports higher power output with higher current supplies. I have a high-quality 48v 10amp supply. I believe the chip has overcurrent protection, are there other components on the amp board that would not support the potential power delivery using a 10 amp supply? I have a range of speakers I would use from M&K S150s that are 4 ohms and happy with lots of clean power, to vintage Infinity speakers that have kind of rough impedance curves that need a lot of current. At this point it would really just be a test to see if these modern class D amps can be a stand-in for high-power class A/B amps. I wouldn't expect to drive them as hard, but I also wouldn't want the amp to fry. Ultimately, I would probably end up using the amp as a desktop amp for some smaller M&K S-90 monitors.

Also, for future desire for balanced input, I have a couple sources I would use, but the primary balanced source would be a MOTU audio interface. I believe the TPA3255 natively supports balanced inputs in 2 channel mode. I don't remember the 4 letter code for the bridging type.

Thanks

 

[Ibsen]

We believe the V3 could be the right one you are looking for.

We'll certainly sell the V3 on Aliexpress after we release it, probably in late May or early June. We're going to launch the crowdfunding on Kickstarter next week and if you back the project, you'll be one of the first users to get this robust amp.

Any chance to have a BTL mode for using as a mono amp?

 

[Fosi Audio]

I have a question, I think the TPA3255 supports higher power output with higher current supplies. I have a high-quality 48v 10amp supply. I believe the chip has overcurrent protection, are there other components on the amp board that would not support the potential power delivery using a 10 amp supply? I have a range of speakers I would use from M&K S150s that are 4 ohms and happy with lots of clean power, to vintage Infinity speakers that have kind of rough impedance curves that need a lot of current. At this point it would really just be a test to see if these modern class D amps can be a stand-in for high-power class A/B amps. I wouldn't expect to drive them as hard, but I also wouldn't want the amp to fry. Ultimately, I would probably end up using the amp as a desktop amp for some smaller M&K S-90 monitors.

Also, for future desire for balanced input, I have a couple sources I would use, but the primary balanced source would be a MOTU audio interface. I believe the TPA3255 natively supports balanced inputs in 2 channel mode. I don't remember the 4 letter code for the bridging type.

Thanks

Yes, you can use the 48V 10A power supply.

As for the balanced input, this V3 can not supports balanced inouts, but we are developing a model which supports XLR input. The TPA3255 can not bridged but can switch to mono channel and you get the double power from the channel.

 

[Fosi Audio]

Any chance to have a BTL mode for using as a mono amp?

Thank you for your suggestion, we are developing a model which can be switched between stereo and mono channel but not BTL mode.

If you switch to mono channel, the power can be twice.

 

[Wembley]

Most people use active subwoofer, but also some may use passive subwoofer, that why we developed fosi audio BT30D PRO, and also the total power of BT30D PRO is higher than BT20A PRO because BT30D PRO adopts 2 pcs of TPA3255.

Thanks for your reply. I probably will switch to BT30D Pro and eventually upgrade the power supply to e.g. Mean Well LRS 200 36v.

 

[Wembley]

I have a question, I think the TPA3255 supports higher power output with higher current supplies. I have a high-quality 48v 10amp supply. I believe the chip has overcurrent protection, are there other components on the amp board that would not support the potential power delivery using a 10 amp supply? I have a range of speakers I would use from M&K S150s that are 4 ohms and happy with lots of clean power, to vintage Infinity speakers that have kind of rough impedance curves that need a lot of current. At this point it would really just be a test to see if these modern class D amps can be a stand-in for high-power class A/B amps. I wouldn't expect to drive them as hard, but I also wouldn't want the amp to fry. Ultimately, I would probably end up using the amp as a desktop amp for some smaller M&K S-90 monitors.

Also, for future desire for balanced input, I have a couple sources I would use, but the primary balanced source would be a MOTU audio interface. I believe the TPA3255 natively supports balanced inputs in 2 channel mode. I don't remember the 4 letter code for the bridging type.

Thanks

I think a Mean Well LRS 200W 48V could be a price attractive alternative. It has passive cooling (silent) and can provide a lot of power for the short term.
Please correct me if I'm wrong: the amplifier will take as much power as it can "consume". If the power supply is able to deliver there is no negative impact if it's oversized. The amplifier will be the bottleneck.