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Fosi Audio BT20A Pro Amplifier Review

Rate this stereo amplifier

  • 1. Poor (headless panther)

    Votes: 3 1.0%
  • 2. Not terrible (postman panther)

    Votes: 31 10.3%
  • 3. Fine (happy panther)

    Votes: 177 59.0%
  • 4. Great (golfing panther)

    Votes: 89 29.7%

  • Total voters
    300

Guddu

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I've received my BT20 Pro today. I can confirm there's no seal or anything on the box. Ordered on Amazon, shipped from China, arrived in 10 days(!). I was not expecting it to provide such volume to my Elac DBR62! The volume knob is barely turned from its lowest position. Which brings me to my next question.

I'm using the BT20 with a Topping E50. My problem is that the BT20 has no remote, so I can't change the volume easily while watching TV. Can I switch my E50 to pre-amp so I can use the volume control on there? Or is it not recommended?
If you want to control volume on E50 then change it to pre+DAC, it should work well.
 

Martinvb

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I've received my BT20 Pro today. I can confirm there's no seal or anything on the box. Ordered on Amazon, shipped from China, arrived in 10 days(!). I was not expecting it to provide such volume to my Elac DBR62! The volume knob is barely turned from its lowest position. Which brings me to my next question.

I'm using the BT20 with a Topping E50. My problem is that the BT20 has no remote, so I can't change the volume easily while watching TV. Can I switch my E50 to pre-amp so I can use the volume control on there? Or is it not recommended?
Yes this is indeed possible. I would advice to turn the volume on the Fosi up to the max you expect to listen to on a regular basis (e.g. 12 o’clock), then to use the E50 to adjust to the right volume. This reduces the chance of accidental high power output to your speakers when the volume on the E50 is accidentally reset to 0 dB (in the 2,5 years that I use my setup this has not happened even once, but I know that some members warn for this).
 

louwii

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Oct 21, 2023
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Thanks @guddu @Martinvb !

I've set that up and it works totally fine. I couldn't here a difference in the sound quality either. No idea if that changing the E50 from DAC to DAC+pre would even affect that.

Just to make sure, the "neutral" setting for treble and bass on the BT20 it 12 o'clock right? Where the "notch" is?

I can't believe how small that stack is, for driving the DBR62. I can finally get rid of the old Denon home theater receiver I was using.
 

louwii

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Oct 21, 2023
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Yes. I also prefer to keep bass/treble neutral and suppose that these Elac's do not need any tone adjustment either, do they?
They're very good out of the box indeed. I've only lowered down the bass a bit because I don't want to piss off my neighbors too much.
 

ripmixburn

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Late to the party here, but I own the BT20A Pro and the SMSL SA300 which is Infineon-based. Comparing several speakers in different rooms and DACs, the BT20A Pro is significantly more fatiguing than the SA300. There is a sharpness to the lower-treble/upper-midrange that is unpleasant even at moderate volume levels. It is apparent though that the Fosi has more power, even with the stock A/C adapter.

Unless changing op-amps can change the tonality of the Fosi, I'll likely sell it locally.

I have a calibration mic and an old-school SPL meter. What's the best method to show a comparison?

And another question… does the SMSL AL200 bring more power to the party with the latest generation of Infineon chipset?
 

peng

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Late to the party here, but I own the BT20A Pro and the SMSL SA300 which is Infineon-based. Comparing several speakers in different rooms and DACs, the BT20A Pro is significantly more fatiguing than the SA300. There is a sharpness to the lower-treble/upper-midrange that is unpleasant even at moderate volume levels. It is apparent though that the Fosi has more power, even with the stock A/C adapter.

Unless changing op-amps can change the tonality of the Fosi, I'll likely sell it locally.

I have a calibration mic and an old-school SPL meter. What's the best method to show a comparison?

And another question… does the SMSL AL200 bring more power to the party with the latest generation of Infineon chipset?

I could listen to mine for hours and wouldn't find it fatiguing at all. If you have a good mic, you can use REW to check it's frequency response against the SMSM SA300. I have done my BT20APro with my V3 and my NAD class AB amp for my desktop use. I am not sure such a comparison proves anything, but it does provide some useful info nonetheless.

If I compare the Fosi amp with my other amps such as my separates, such as Marantz vintage, Parasound A21, buckeye NC502MP, VTV Purifi etc., the results will most likely look very similar. I know that because I have done those comparisons between those amps a few times in the past. Amps can certainly sound a little different, but by themselves they shouldn't differ to the point that one would sound much more fatiguing than another (yes I know people said they had such experience, and I wouldn't know why, without being there). If you can get kind of differences, it would be interesting to try isolating the real causes.



1698611212604.png


NAD distortions:

1698611410143.png



1698611442765.png
 

wiziloo

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Nov 4, 2023
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Hi all!

Today i recieved my BT20aPro, i bought it from here: EBAY link
I have some problems:
1. It runs really hot.
2. When i turn the treble to the negative side, it makes high pitch "UFO like" noises. If it stays in the middle, or at the positive side its noiseless.
3. I checked the opamps, and i found these. They are clearly not ne5532. Are these fake or genuine muses02? :
IMG_20231104_2033291.jpg


IMG_20231104_204540.jpg


Thank you in advance for the answers!
 

NoMoFoNo

Active Member
Joined
Mar 1, 2020
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Hi all!

Today i recieved my BT20aPro, i bought it from here: EBAY link
I have some problems:
1. It runs really hot.
2. When i turn the treble to the negative side, it makes high pitch "UFO like" noises. If it stays in the middle, or at the positive side its noiseless.
3. I checked the opamps, and i found these. They are clearly not ne5532. Are these fake or genuine muses02? :
View attachment 323913

View attachment 323914

Thank you in advance for the answers!
First thought is that you received a returned device that a previous user had upgraded with Muses02 op amps. If there is a funky sound coming from one of the tone controls it could be caused by one of the Muses, especially if they are fakes. Unless you have some other op amps you could try in those sockets I'd return it for replacement.
 

Andysu

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Dec 7, 2019
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fosi DAC Q4 mini headphone amplifier

connected to optical output on stormaudio elite isp32 mk3 as the processor doesn't have headphone output on the front so mini headphone amplifier

398290192_10160953193700149_2868701510725688501_n.jpg
 

peng

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wiziloo

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First thought is that you received a returned device that a previous user had upgraded with Muses02 op amps. If there is a funky sound coming from one of the tone controls it could be caused by one of the Muses, especially if they are fakes. Unless you have some other op amps you could try in those sockets I'd return it for replacement.
Thank you for the answer!
Today i bought two genuine ne5532ap op amps, and replaced the propably fake muses2 op amps.
It solved all the strange noise and overheat problems, and sounds mutch better!
 

Holdt

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Jun 10, 2022
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Thank you for the answer!
Today i bought two genuine ne5532ap op amps, and replaced the propably fake muses2 op amps.
It solved all the strange noise and overheat problems, and sounds mutch better!
So you've know experienced the art of op-amp rolling that many swear to..;)
 

Vallory

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Is it a good practice to connect and disconnect the speakers rca cables, before and after you turn on and off your amp?
(To prevent the pop sound from damaging the speakers)
 

Guddu

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Is it a good practice to connect and disconnect the speakers rca cables, before and after you turn on and off your amp?
(To prevent the pop sound from damaging the speakers)
There is no need to disconnect RCA cables, in fact avoid touching any cables when amplifier is powered ON if possible.
If anything, lower down volume on amplifier before powering off if you are worries about pop noise.
 

TheBatsEar

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Is it a good practice to connect and disconnect the speakers rca cables, before and after you turn on and off your amp?
(To prevent the pop sound from damaging the speakers)
Welcome to ASR :cool:

If you make changes in your setup? Yes, i think it is.

Just for turning it on and off? There shouldn't be a pop, or rather, it should be very faint.
I don't have this particular model, is there a pop if you simply turn it on? Do all of them have the pop?

Anyway, i wouldn't care, if your speakers are regular sized bookshelfs or larger bookshelfs, they should be able to survive a pop with ease. I don't think we have heard about many pop-damaged setups, if at all. I certainly can't remember.

I would maybe think twice with delicate tiny speakers or very vintage gear.

Great measurements. :)
 

grogi.giant

Active Member
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Apr 30, 2021
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I purchased the BT20A and BT20A pro on offer during Amazon Prime day.

Has anyone else had issues with the BT20A pro giving a very feint beeping sound out of the speakers when the amp is on but there is no music playing? It is independent of the volume setting. It sounds like years ago when you would get some noise out of speakers when your phone is nearby. It's more noticeable in the left speaker (which is closest to the Bluetooth antenna) When I press and hold the volume button to turn off the BT the issue disappears. But when I power cycle the amp the BT is back on and so is the noise.
I don't actually have a need for the BT so I am tempted to return it and get the TB10D instead as their website says it has the same components but without the bluetooth.

The BT20A does not have this same suspected BT noise, but unfortunately the BT20A does a pop in the speakers when switched via a smart plug so that one doesn't fit my requirements either and will need returning.

This is probably Bluetooth module announcing itself and inducing some in circutry after volume control. It is noticeable with high sensitivity speakers...

Check if it continues if you take the BT antenna off.
 

pseudo

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Jul 14, 2023
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So I'm getting an Amazon refund for a faulty Aiyima D03 and thinking of trying this BT20A pro as a replacement. Is it still a good buy or has something better come out since? Has anything been done to fix the weird Bluetooth frequency curve?
I just need good sound quality with BT and aux input and sub out, up to $150 ish budget.
 
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