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Fosi Audio BT20A Pro Amplifier Review

Rate this stereo amplifier

  • 1. Poor (headless panther)

    Votes: 1 0.4%
  • 2. Not terrible (postman panther)

    Votes: 30 10.6%
  • 3. Fine (happy panther)

    Votes: 170 60.1%
  • 4. Great (golfing panther)

    Votes: 82 29.0%

  • Total voters
    283

GrayA

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Apr 26, 2023
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Hi all,

I'm waiting for the BT20A pro to come back into stock with Amazon UK so I can order but whilst I'm waiting I had a question about adding a subwoofer. I assume I need a powered sub to connect via the 3.5mm subout?

I have a pair of floor standers I'll try first but as I like a more bass heavy profile I'm thinking of adding the SW so my question is more of a "planning ahead" one.

thanks
If you want to use a passive sub, the BT30D Pro is excellent. That's what I have with my passive sub.
 

spiketeam

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May 18, 2023
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Many thanks to Amir’s honest review and measurements. Happy Easter to Amir and all ASR fans!

We really appreciate ASR which allows us to listen to and gather users’ feedback on our old models. We absorbed a lot from the voices and develop this BT20A Pro. It’s not a perfect amp but we will keep making effort to improve it.

Here we want to give an exclusive 20%-off discount promo code for the BT20A Pro to all ASR fans. (Valid from today to April 30.)
20APROASR20

Hope you will be interested in this new amp!
Any chance for a new code? Its my birthday in 2 days and I am building a budget stereo setup for myself.
 

Palladium

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Anyone able to hear a very faint flapping noise coming from the tweeter when their BT20A Pro is idling, when the volume knob is set between 12 o'clock to max?
 
Last edited:

Palladium

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Yes, everything stock, with the 32V power supply. The flapping is only evident when I move my ear quite close to the tweeter (but it is there).

I have to put my ear an inch to the tweeter to even hear it, so its not really a problem.

I tried the 32V and 48V stock PSU, and swapped the NE5532Ps for OPA2134PAs, all of those made no difference to that flapping.
 

Jeromeof

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I have to put my ear an inch to the tweeter to even hear it, so its not really a problem.

I tried the 32V and 48V stock PSU, and swapped the NE5532Ps for OPA2134PAs, all of those made no difference to that flapping.
I had a similar problem with a different but similar class D amp - it turned out to be the plug and not being correctly grounded.
 

Jeromeof

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The FOSI PSU has a two-pronged plug, so the amp is not really designed to be grounded via the PSU.
OK well as I said it was a similar noise problem but a different amplifier / manufacturer - I haven't had any problems with my BT20A Pro using the stock PSU.
 

Palladium

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Sound quality wise, I subjectively prefer this with tone defeat on than the LM4562 A07 on my Diamond 12.2s. Sounds richer and more full bodied.
 

Kimbrough Xu

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May 18, 2022
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Is this a good upgrade from the tb10d or a07? I don't care about bt
Seems fosi audio V3 is more suitable for you.

 

TheBatsEar

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Is this a good upgrade from the tb10d or a07? I don't care about bt
To be honest, i don't see it as an upgrade.
An upgrade would be a NC252MP module based amplifier, or maybe a class AB (Yamaha, Rotel, Nad, Denon and so on).
 

TheBatsEar

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What are the differences with the bt20a potentiometer? In terms of sound, I mean
None, it's just a question of "feel" or ease of control. doesn't matter in terms of sound quality.
 

Maiu95

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May 5, 2023
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None, it's just a question of "feel" or ease of control. doesn't matter in terms of sound quality.
The only "problem" are the treble. I find them fatiguing with Elac Debut Reference listening rock... Even with the A07. Very clean but harsh
 

Talisman

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What are the differences with the bt20a potentiometer? In terms of sound, I mean
No difference in terms of sound. Simply the linear potentiometer of the tb10d brings the volume to very high levels very quickly, furthermore the minimum volume in which both channels play at the same volume is high enough, so as not to be able to listen to low volume background music.
The logarithmic potentiometer of the BT20a pro is logarithmic, the volume increase is initially much more gradual and allows listening at low volume without particular difficulties
 

TheBatsEar

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The only "problem" are the treble. I find them fatiguing with Elac Debut Reference listening rock... Even with the A07. Very clean but harsh
Cheap class D amps tend to be unstable with certain loads, and that sometimes manifests itself in overly prominent highs. My A07 sounds fine with my ATC SCM19v2, but not so good with my Mission LX-.3 MKII.
If you get an opportunity, borrow a class AB amp from friends or buy one. You may find that they sound a lot better with your particular load.
A friend of mine in the US got a Yamaha R-S700 for $120 recently, he said his speakers sounded different to him now, more bass, more body, less harsh. It's a very solid amp, even at $200. If you are in Europe, 160€ to 220€ is realistic for the R-S700.
If you are interested in AB amps, we have a thread called "Inside Yamaha amps" where you can look inside them. Denon, Marantz, Rotel and other AB amp manufacturers look very much the same.
 
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