Subjective impressions of Fosi Audio BT20A Max

[Joe Smith]

I think this varies by unit. I hear no rattling in mine when the fan is running....

 

[Dr Schweinsgruber]

I returned mine though it was free: could not get the potentiometer knob off without damaging anything (don't have a pipe wrench), and did not have the right to nut driver. I am testing gear and am a consumer advocate, but I am not a plumber.

And no paying early adaptor should have to undergo this procedure either paving the way for the "Pro" model 3 months down the road that addresses the shortcomings.

A fan in an amplifier is unheard of (pun intended). I made sure all my computers are fanless...and I would never put this thing on my desk. Burson does it right, they increase the chassis' surface by their corrugated design and therefore get an effective heat dissipation without fan.

The fan in my unit was probably to specs, but once the unit got hot, there were all sorts of metallic vibrations ("ringing") joining the regular fan noise.

So much to measurements...there's much more to a product evaluation than that. In this case, measurements are completely irrelevant except perhaps the SPL.

Life's too short and sometimes free can be too expensive. Although I get a lot of free review gear, most of the stuff I actually use I bought myself...and I spent good money on it.

A positive word on Fosi's customer support: they were very responsive and tried to help, but couldn't really. And, yep, I agree that the BT20A Max sounds pretty good.

 

[Joe Smith]

I returned mine, though it was free: could not get the potentiometer knob off without damaging anything (don't have a pipe wrench), and did not have the right to nut driver. I am testing gear and am a consumer advocate, but I am not a plumber.

And no paying early adaptor should have to undergo this procedure either paving the way for the "Pro" model 3 months down the road that addresses the shortcomings.

A fan in an amplifier is unheard of. I made sure all my computers are fanless...and I would never put this thing on my desk. Burson does it right, they increase the chassis' surface by their corrugated design and therefore get an effective heat dissipation without fan.

The fan in my unit was probably to specs, but once it got hot, there were all sorts of metallic vibrations joining the regular fan noise.

So much to measurements...there's more to a product evaluation than that. In this case, measurements are completely irrelevant except perhaps the SPL.

Life's too short and sometimes free can be too expensive.

Gee, I'm always pretty good with "free." I too was a reviewer/tester for them and have been happy with the unit so far. It is IMO fine for setups that are non-nearfield.

(I drew this thread to Fosi's attention so they would know that experiences with the fan and fan noise are varying widely among users.)

I generally like passive cooling too, I think this amp is a bit of an experiment for them to address people who were jumping up and down for "more cooling!" But we shall see.

 

[dtaylo1066]

Whether in an amp, desktop PC power supply or my refrigerator, I generally determine that a fan will cause issues down the line, if not a raquet, and I do not enjoy replacing them. Ball bearings or grease in an amp, no bueno.

 

[ovitus]

Does anyone have disassembly instructions for this amp? I'm having trouble getting the front plate off so I can slide it out as the OP has shown. I want to swap out the op amps on mine.

Thank you!

 

[Balinus]

Does anyone have disassembly instructions for this amp? I'm having trouble getting the front plate off so I can slide it out as the OP has shown. I want to swap out the op amps on mine.

Thank you!

Here's the video Fosi sent me when I told them my fan was making unusual noise

https://drive.google.com/file/d/1ryzRDZ-i4eHXpaDRMymBKajoZWoXJASh/view?usp=sharing

 

[Joe Smith]

By the by, I recently swapped things around (because I am testing something for Fosi), so put Fosi gear back into my main workroom system. I am using the 48v/5a GaN power brick with the Fosi V3 amp and P4 preamplifier, and the V3 gets a bit warmer than when using the 36v/5a brick, but not by very much. I'm of the opinion that the active cooling fan was not something that was really necessary for the BT20A MAX, but was an additional product feature that some users said they wanted ("even more cooling to extend the life of the device") and Fosi was happy to oblige.

 

[Guddu]

Let me add my 2 cents here on Fosi BT20A Max

BT20A Max chassis is a notch up than their other ones, has decent weight overall with slightly stylish looks comparatively. its heavy enough not to be dragged by heavy cables.
Tone knobs has middle/center hold to make is easy to put on position. Tone Bypass (on the back) bypasses Bass & Treble, however Volume Control remains variable.
Motorized volume works nicely, responds to remote without any issues.
Sub out is volume controlled.
Remote is plastiky but still decent overall, works fine.
Active FAN under the hood makes faint noise which is mildly audible when nothing is playing.

Idle power usage is about 16 watts when no music is playing, also remains around 16watts under low volume listening volumes as well.

While I can not measure frequency response flatness, but here is quick look at difference in frequency response with 3e A7 and Aiyima A20, in my setup & room, UMIK-1 stays at the same location and sweep levels were voice-matched. It does tell me somewhat that there isn't any considerable high freq. peaking.




Fosi BT20A Max vs 3e A7 vs Aiyima A20, HPF OFF




Subwoofer-Out and HPF: 80 Hz




Subwoofer-Out is main volume controlled and has roll off starting around 80 Hz to 150Hz complete cut-off
When HPF is ON, subwoofer-out has 4-5 dB higher gain compared to when HPF is Off
Performance wise, it did work very well for Revel M16 speakers with subwoofer out.

Bluetooth Output - I never had any issue at all connecting with any devices I used with like iPhone 16, Windows Laptop, nVidia Shield Pro, Google TV box etc.
Sound quality wise, surely inferior compared to a nice DAC connected on RCAs but that’s reasonable. It is more like a convenience feature than HiFi.

Overall, pretty good. I totally liked 2 RCA inputs which is more practical in my opinion. Making it good option for me to compare 2 different RCA inputs like 2 DACs, Pre-Amps etc.

 

[ovitus]

Here's the video Fosi sent me when I told them my fan was making unusual noise

https://drive.google.com/file/d/1ryzRDZ-i4eHXpaDRMymBKajoZWoXJASh/view?usp=sharing

Thanks.. I got impatient and ended up de-soldering/cutting the cables on the back. Waiting to get another Sparkos op-amp and then I'm going to install it with a quieter Noctua fan, without those tiny holed grills. Also replaced the knobs

 

[Balinus]

Thanks.. I got impatient and ended up de-soldering/cutting the cables on the back. Waiting to get another Sparkos op-amp and then I'm going to install it with a quieter Noctua fan, without those tiny holed grills. Also replaced the knobs

I would be interested to see the final product you came with the Noctua fan (like them, I have that in my custom PC build). Will you try to change the dimension of the fan? Alternatively, I'm wondering if I should just get the 36V PSU and simply remove the, as people seem to report that it runs cooler with the 36V PSU.

 

[ovitus]

I would be interested to see the final product you came with the Noctua fan (like them, I have that in my custom PC build). Will you try to change the dimension of the fan? Alternatively, I'm wondering if I should just get the 36V PSU and simply remove the, as people seem to report that it runs cooler with the 36V PSU.

Seems to fit perfectly, it has the same dimensions as the stock fan. I have yet to put it all together and test it out because I needed to order a new Bluetooth antenna cable.. shouldn't of cut it.. whoops. I also upgraded to a 48V PSU

Links to everything I ordered:
https://sparkoslabs.com/product/dual-discrete-op-amp-ss3602
https://www.amazon.com/dp/B00NEMGCIA
https://www.amazon.com/dp/B0CN6PTR35
https://www.amazon.com/dp/B0D48JNKD2
https://www.amazon.com/dp/B0DK2QK7C7
https://www.ebay.com/itm/372806499045

 

[robbiekhan]

I just got this today for a subjective take on it compared to my Topping PA7. Did not know it had an active fan, that should be interesting as time goes on given dust getting in the fan and heatsink will result in more air turbulence over time and less thermal control.

My PC setup is also deathly silent so any form of fan noise is often annoying to my ears which are sensitive enough to be annoyed by Chinese wall warts plugged in across the room if they have poor circuitry causing cap noise whine etc.

Will be interesting to see if there is any audible difference in noise floor too given it has no balanced connectivity, and how imbalanced low volume listening levels are.

Going by all reviews online it appears to be a mostly transparent amp with a slight lean on warmth and good staging, whilst the PA7 is undeniably transparent with swathes of headroom/power.

Should be kinda fun I guess.

 

[Joe Smith]

I just got this today for a subjective take on it compared to my Topping PA7. Did not know it had an active fan, that should be interesting as time goes on given dust getting in the fan and heatsink will result in more air turbulence over time and less thermal control.

My PC setup is also deathly silent so any form of fan noise is often annoying to my ears which are sensitive enough to be annoyed by Chinese wall warts plugged in across the room if they have poor circuitry causing cap noise whine etc.

Will be interesting to see if there is any audible difference in noise floor too given it has no balanced connectivity, and how imbalanced low volume listening levels are.

Going by all reviews online it appears to be a mostly transparent amp with a slight lean on warmth and good staging, whilst the PA7 is undeniably transparent with swathes of headroom/power.

Should be kinda fun I guess.

I could hear the fan in a nearfield system with the amp about 1 yard away from my left ear. Once music was playing, I was no longer aware of it. My nearfield system also uses an older Lenovo tower running Linux, and I can hear its fan with no music playing, but it does not bother me. The BT20 works perfectly for a system where your head is not going to be very close to the amp. In my bedroom system now, I keep a little cloth cover on it between uses to keep dust from accumulating in the top vent.

 

[robbiekhan]

Alright used it all evening.....

... The annoying thing for me as due to sensitive hearing the fan airflow noise is a distraction for desktop use since the rest of my workstation is deathly silent. It's more audible than a standard laptop fan, but not audible when music is playing until you get to a quiet passage in the track etc.

It defeats the objective of having an amp/DAC etc that has a totally silent noise floor and the ironic thing is with other power amps that I have used or integrated amps, the RCA connections always have had a very faint noise floor hiss, not so here, it's blackness even with my ear right against the speakers regardless of volume setting, but you can hear the fan lol.

Another issue is that it has low volume channel imbalance which is typical of a potentiometer pot, the problem is that when you feed it a line level signal from a pre/DAC, you have very little room to modulate low volume, by the time you get sound that is channel matched, the volume is too loud, and that's on my Comete 40th, an easy to drive speaker that leaves loads of headroom on the table.

Edit*

video:

Oh yeah at the start when the power cord is plugged in notice there's a very faint ticking pulse noise coming from inside, this sounds like a ticking watch movement, it only goes away once you press the power button to go out of standby, but then the fan comes on lol.

 

[Denios]

For those of you considering changing the fan to a low noise one, I'd recommend Noiseblocker fans over Noctua.
I've been using them for ~12 years in computer systems now, and they're fantastic.
They also supply specific fan types for being super quiet while still maintaining decent cooling performance. This is one of the areas they are specialists in in large scale industrial applications.

 

[RandomEar]

@robertospeed When posting a video please add a short summary of it, as requested in the forum rules.

 

[robertospeed]

Here’s a demo video of the Fosi Audio BT20A MAX featured on my YouTube channel.
Fosi Audio BT20A MAX Description:

In this video, I'll share my experience with the new Fosi Audio BT20A MAX.

I'm not a technician, but simply an enthusiast who wanted to try this amplifier in my home environment to understand how it really sounds.

I listened to it for two weeks, connecting it to my Dali Spektor 1 speakers (in a 2.1 setup with a B&W ASW608 sub) and the massive Indiana Line Utah 5 speakers, to see how it handles different loads.

What we'll cover in this video:

• Feature Analysis: TPA3255 chip and PFFB technology.
• Testing the 80Hz high-pass filter.
• Testing the motorized volume and LDAC Bluetooth.
• My personal opinions on the strengths and weaknesses.

If you like the video, please subscribe to the channel and leave a like to support my future enthusiast reviews!

 

[HJCarballosa]

On ASR we appreciate objective results and hard, measured facts. The differences you claim do not sound plausible for amps which measure in the same ballpark (maybe excluding the vintage Sansui). Stating audiophile fairy tales like "sterile Class D sound" for which no one ever provided any objective evidence does not support your claims - on the contrary.

Unless you did double blind testing or provide measurements clearly showing differences in frequency response, distortion or SNR, your subjective impressions are likely flawed and simply another example of bias in humans. I appreciate you sharing your experience with Bluetooth stabilty, thermal properties and the remarks concerning fan noise but would consider any comments on the sound of a device which shouldn't have any sound whatsoever very questiona

Fosi Audio BT20A MAX – User Impressions / Review

Product: Fosi Audio BT20A MAX
Type: Class D stereo / 2.1 integrated amp
Chipset: TI TPA3255 + NE5532
Disclaimer: Pre-production unit provided by Fosi Audio. Opinions are my own.

​

---

TL;DR

Feature-rich Class D amp with PFFB, strong Bluetooth implementation, and a slightly warm tuning. Sounds good for the price, but the always-on fan and idle heat are worth mentioning. Not perfect, but very solid value.

View attachment 507785View attachment 507786View attachment 507787

Features (relevant ones)

• TI TPA3255 output stage
• Post Filter Feedback (PFFB) → reduced load dependency
• Qualcomm QCC3095 Bluetooth 6.0
  • LDAC, aptX Lossless, aptX HD, aptX Adaptive, etc.
• Dual RCA inputs
• Subwoofer output (2.1 capable), with HPF switch at 80Hz
• Motorized analog volume pot + remote
• Bass / treble tone controls + bypass (useful if you have a preamp)
• 12V trigger input

Specs (manufacturer):

• 300 W × 2 @ 4 Ω (peak), 180 W × 2 RMS with the 48V/10A PSU (I got the 48V/5A, giving approximately 100Wx2 into 8 Ω).
• THD+N ≤ 0.003%
• SNR ≥ 112 dB
• 2–8 Ω load support

​

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Setup / Test Conditions

• Power supply: 48V / 5A (not the optional 10A)
• Speakers tested:
  • Paradigm Monitor 7 v2
  • Kanto YU4 passive
• Use case: nearfield (desktop use, Kanto YU4) + medium-room listening (Paradigm Monitor 7 v2)

View attachment 507788

Sound Impressions

Overall tonal balance is neutral-to-slightly-warm, which is not always the case with budget Class D amps.

• Bass: Deeper and more authoritative than my Aiyima A80, but still controlled.
• Midrange: Clean, smooth, slightly warm. Easy to listen to for long sessions.
• Treble: Clean and non-fatiguing, but some loss of micro-detail at very high volume.

Compared to:

• Aiyima A80: Fosi sounds fuller and warmer; Aiyima is more analytical.
• Sansui 9090 (vintage): Obviously not the same league, but the tonal balance is closer to that relaxed presentation than to a sterile Class D sound. Instrument separation is of course better on the Sansui, with a better instrument separation. Nonetheless, the BT20A Max is on the warmer side of neutral.

Speaker matching matters. With already warm speakers, this amp could sound slightly muffled. With my speakers, it stayed balanced.

At very loud volumes, clarity drops a bit—nothing unexpected for a compact Class D amp nearing its limits.

​

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Bluetooth Performance

Very good, does what is expected from it! Used an iPhone 14 for testing, so I haven’t tested every possible codec/protocol.

• Stable connection
• Low latency (tested using a YT video)
• Codec support is better than most Bluetooth implementations in this price range

Auto-reconnection is very fast when the unit if powered on.

View attachment 507789

Fan / Thermal Behavior

There is a fan:

• Always on
• No standby mode
• Quiet, but audible within ~1 m in a silent room

The amp also stays warm at idle, with little difference between idle and moderate playback temps. Under heavy load, thermal control is actually better than my Aiyima A80.

Personally, I’d rather see:

• A slightly larger chassis
• More passive heatsinking
• No fan or a way to disable the fan or a temperature gauge starting the fan only at loud volume (which should be warmer, hence starting the fan in conditions where you can’t hear the fan).

Long-term fan reliability of the fan is an unknown (dust, bearing wear, etc.). While testing the unit, the fan developed a more “pronounced” sound that can be heard between songs or low volume part. This is only heard if the amp is close to the ears (<1 meter) though, so it might be or not a concern depending on personal setup. Fosi support has sent me instructions on how to open the unit and tighten the screws. After re-tightening, the noise is gone. Also note that is is pre-production unit.

View attachment 507790View attachment 507791
View attachment 507792

​

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Power

Even with the 48V/5A PSU, power is more than sufficient for most use cases. Unless you’re driving inefficient speakers at high SPL, I don’t see the 10A supply as mandatory.

​

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Use Case / Final Thoughts

Despite being overpowered for them, this amp has ended up as my cottage amp, driving B&W speakers. My ideal use-case would have been for listening music while working, but the noise coming from the fan prevents me from doing that (I can’t position the amp farther away than 1 meter).

​

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Pros

• PFFB implementation at this price
• Clean, slightly warm sound
• Strong Bluetooth codec support
• Dual RCA + sub out
• Very good value for features

Cons

• Fan runs continuously, can be heard if the amp is positioned close. The fan developed a more “bassy” noise during my 2-week testing, which was settled by re-tighting the screws of the fan (needed to open up the case though). I will see if Fosi support can replace/repair the unit or not.
• No standby mode
• Slightly warm at idle (but moderately warm while listening, thanks to the fan)
• Loss of definition at high volume

​

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Rating

Good value, good sound, but not flawless. If you’re okay with a fan and want lots of features in a compact Class D amp, this one is worth considering.

​

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Music Used

• Harmonium – L’Heptade
• Miles Davis – Bitches Brew
• Michael Kiwanuka – Small Changes
• Pat Metheny – Secret Story
• Pink Floyd – Dark Side of the Moon
• Amy Winehouse – Back to Black
• Lou-Adrianne Cassidy – Journal d’un Loup-Garou

Steven Wilson – The Overview

I very much appreciate your post. Some complain that you expressed feelings and not data from a measurement device. Very, very weird; I thought humans, not robots, listened to music. I 'm just glad you're sharing your thoughts. Tha's very nice, so KUDOS to you!

 

[HJCarballosa]

On ASR we appreciate objective results and hard, measured facts. The differences you claim do not sound plausible for amps which measure in the same ballpark (maybe excluding the vintage Sansui). Stating audiophile fairy tales like "sterile Class D sound" for which no one ever provided any objective evidence does not support your claims - on the contrary.

Unless you did double blind testing or provide measurements clearly showing differences in frequency response, distortion or SNR, your subjective impressions are likely flawed and simply another example of bias in humans. I appreciate you sharing your experience with Bluetooth stabilty, thermal properties and the remarks concerning fan noise but would consider any comments on the sound of a device which shouldn't have any sound whatsoever very questionable.

Be Kind.

On ASR, subjective review =:

View attachment 513609

On the opposite end of the spectrum, Amir has measured a lot of low cost amps of late, and many measure quite respectably, and some post quite good measurements, and get high ratings. So good power is cheaper and more available than ever before in audio.

Fosi Audio BT20A Pro Amplifier Review

This is a review and detailed measurements of the Fosi Audio BT20A stereo class D amplifier based on TI TPA3255 IC. It was sent to me by the company and costs US $99.99 with 32 volt power supply. Despite its low cost, the case gives a feeling of quality. I am not usually fan of tone controls in...

www.audiosciencereview.com

How long? How long will they perform this well: months, years, days? Wish these new small, efficient designs success, but waiting to purchase until I know I can keep it 10 years (yes, 10!) without a worry because I pass on my gear to family and friends. I've passed on Infinity, Yamaha, and Def Tech without worries. Fosi? Well, my wallet's itchin to be used!!!

 

[HJCarballosa]

Every evaluation of a product is to some degree subjective as long as humans are involved, including measurements (as the chosen parameters are subjective and their informativeness is limited). Yes, it is useful to have an internally consistent series (what hardcore ASR disciples wrongly and obsessively refer to as "objective"), but this also does not tell us the whole story. And after all these observations ("measurements") follow the interpretations, which are entirely subjective.

I stick subjectively to my Questyle CMA 12 Master and subjectively tell you that you get what you pay for. Yep, it cost $2000 USD new ($1100 CAD 2nd hand for me) and I will be able to enjoy my bias and other inferred deficiencies without forced double blind testing but also without ASR compulsion for the next 20 years. I also have the FiiO K17, but it is not good enough to take full advantage of my Sennheiser HD 800S's capabilities.

I also have great gear that measures miserably according to ASR (not according to Stereophile, but obviously Stereophile's measurements are not "objective"), such as the AudioQuest DragonFly Cobalt dongle DAC, and it sounds better to my ears, that is more natural, than any of the many dongles I have tested for audioreviews.org. I must have had this delightful bias for 5 years now - and probably cannot be helped. My problem is my classical music education aberration: I subjectively know what a cello sounds like and I don't care too much about static sine waves...and only static sine waves can objectively and absurdly represent sound and sound quality.

But what do I know...at least I do not impose myself on others...

As to the forced title of this thread which is the result of bullying its creator: EVERY impression is subjective.

Yes. What you wrote, yes.