Fosi Audio V3 Amplifier Review

[Jeromeof]

It would be a good bit of analytics to generate the 10K - 20K impedance of various speakers that have been tested. Sort of a 'Class D' impedance match spreadsheet, since as far as I can see all these class D amplifiers (or the TPA3255 ones anyway) have a similar load dependancy graph.

I am planning on using this in my converted garage with a PolK ES20 that I have currently hooked up with a Fosi Audio BT20A Pro (with a MiniDSP/Dirac doing some room correction) and looking at the Polk impedance in that range its like 4-5 ohm so will be bright, but then my 50+ year old hearing has probably slightly compensated from that brightness in that range anyway

 

[Multicore]

I have a pair of Mission Cyrus 781downstairs doing nothing. Could get it up and running with one of these and a WiiM, why not?

 

[alvigg]

Yes, the adhesion between the caps and PCB is not steady enough. We had noticed the problem and had taken measures to fix this.

Is there anything that should be done with the current crop of amps?

 

[leelee]

Load dependency always means poor rating for me. I don't think it's an acceptable issue to have in these little budget amps anymore.

Can one really hear a noticeable difference of + or - 1db at 20khz? I'm presuming that most people spending $100 dollars on an amplifier are not hooking them up to expensive speakers with ruler flat frequency responses.

 

[Jeromeof]

Can one really hear a noticeable difference of + or - 1db at 20khz? I'm presuming that most people spending $100 dollars on an amplifier are not hooking them up to expensive speakers with ruler flat frequency responses.

Exactly and I know I can't really hear beyond 15khz anyway so for me (and a good few people here) the difference in the effective audible range will be tiny.

And yes I think these are a good match for cheaper speakers (maybe up to $500), if your speakers are beyond that price range, they probably deserve a more expensive amp.

 

[gr-e]

Thanks for including this measurement.
>200uV idle noise seems a bit high but totally understandable considering the amp's power capability. Still, I'd be worried about hiss in a nearfield setup. The datasheet mentions output noise <85 μV, but I guess it's lower because of A-weighting.

 

[Hiten]

asking again...
how difficult it would be to implement PFFB ? And how much cost would it add to the total. I dont think it would be costly.
regds.

 

[Alex.san]

Again, we'd like to share an exclusive promo code with ASR members to save $12: FAV3ASR12

This promo code applies to all sales channels including Amazon, Aliexpress, and our official shop.

I wanted to use this promotional code when buying an amplifier on AliExpress, but, unfortunately, it does not work.

 

[Kimbrough Xu]

As for the efficiency test, how to understand it?

 

[Rubberducky]

And is some second hand class AB amplifier (like Yamaha A-S301) generally a better amplifier than these cheaper class D ones?

 

[Talisman]

asking again...
how difficult it would be to implement PFFB ? And how much cost would it add to the total. I dont think it would be costly.
regds.

This is a question I often ask myself too, what is the cost or the engineering challenge. It seems that no budget amplifier can do this

 

[Ultratek]

Hello everyone, I would like to thank Armin for this review of V3 and you for your instructive and enlightening comments.
Let me tell you that I am in a position to acquire a Fosi amplifier and I would love if you can help me decide between the BT20A Pro and the recently reviewed V3. regarding the latter I'm still not sure what "load dependency problems" means and how I could minimize that (I have to translate all ASR content to my native language) sorry.
Its use would not be for such an audiophile environment, if an advanced and growing listener.
The premises would be a balance between power, distortion, quality and theoretical duration of components.
I plan to connect them to two 3-way boxes with speakers, if possible of medium or high sensitivity, perhaps the bass design is with reflex. in the future some second amplifier only for sub woofer.
to the input I would connect a DAC Fiio KA5 dongle, or Tempotec HDII (humbly it is what I have) playing only music in high resolution MQA and Flac. I am subscribed to Tidal.
Thank you for your time, I hope you can help me with the choice, any comments are welcome.

 

[Xduoo Audio]

This is a review and detailed measurements of the Fosi Audio V3 stereo amplifier. It was sent to me by the company and costs US $89.99 with stock 32 volt supply. Price goes up to $109.99 with the 48 volt supply. There is a $10 discount coupon right now.
View attachment 293692
Despite its budget price, the V3 manages to look elegant with the hole pattern on top and large and smooth feeling Volume/On/Off control. Power supply is external and as noted, you get a choice:

View attachment 293693
As you will see later, you really want the 48 volt version:
View attachment 293694

Yes, it is a larger supply but you are going to hide it behind your desk anyway so might as well live the good life with the increased power there.

The amplifier is based on TI TPA3255 class D amplifier IC. There are replaceable op-amps for those of you who have nothing better to do than mess with the design.

When I took the amplifier out of the package, I noticed something rattling in there. Fearing the worst, I took the unit apart. Turns out one of the two large power supply caps had lost its adhesion to the PCB. The putty used is to keep the cap glued to the PCB was too flexible and had broken loose. No harm though as the cap is laying on its side and can't go anywhere. The sound I was hearing was it moving just a hair up and down and hitting the top of the case. Suggest company use a different material to fix this.

I will post the pictures of the insides later. For now, a large aluminum couples the amplifier IC to the case. There is no thermal grease but the amp ran cool enough that I don't think you need to worry about it. But if you are, this you can remedy yourself. Despite me pushing the amp to max power repeatedly, it just got warm to touch. The protection circuit was the best kind with high tolerance of clipping and audio-restart.

Fosi Audio V3 Amplifier Measurements
I performed the low power tests using the 32 volt supply. The rest is done with both. So let's start with our usual dashboard:
View attachment 293696

Distortion is nicely kept to -100 dB so we are noise limited causing SINAD to land around 88 dB. This is well above average for all amplifiers tested:
View attachment 293697

Notice how many amplifiers it beats to the right of it!

Noise performance is also quite good for the class, almost clearing the hurdle for 16 bit content at just 5 watts:

View attachment 293698

Frequency response shows load dependency which all class D amplifiers in this price range show:
View attachment 293699
In English, this means that depending on which speaker you use, the sound may be a bit bright or a bit dull if your hearing extends to 20 kHz. You can counter with EQ (which you better have for good sound in your room).

Multitone and 19+20 kHz show good performance for the class:
View attachment 293700
View attachment 293701

Let's see how much power we can get out of this little box into 4 ohm:
View attachment 293702
You normally wouldn't expect to get more power with a 48 volt supply compared to 32 volt when their current ratings are the same. But as I noted in the picture at the start, the larger power supply is conservatively rated and is able to pump out more current for peaks. We can see this in our short-term power measurements:
View attachment 293703

View attachment 293704

With 8 ohm volt, we are more in need of voltage so naturally we get tons more there as well with the 48 volt supply:
View attachment 293705

Transfer function is quite good for class D and I was especially impressed with its ability to pump out same power at high frequencies as many amplifiers go into protection there:

View attachment 293706

There is some pop noise when turning on and off but it is very mild:
View attachment 293707

The amplifier is stable on power up:
View attachment 293708

Some of you have been aiming at creating more work for me by asking for for efficiency tests. I developed a test that is semi-automatic and provides reasonable accuracy (within 5%):

View attachment 293709

Note that part of the heat is dissipated in the power supply and part in the amp. The X axis is power per channel, not total (amp is driven in stereo).

Conclusions
State of the art DACs run on highly performant silicone that when well implemented, produces the best performance we have seen. We are seeing similar development with these class D IC amplifiers. Noise and distortion is quite low and beats many amplifiers in the market. They bring two drawbacks: external power supplies and load dependencies. If the latter is resolved, these amplifiers would obsolete large segment of the audio market!

The Fosi Audio V3 is well implemented and brings nice looks and design at a bargain price. Company is also quite receptive to customer input and is a delight to work with behind the scenes. I don't know what else we could ask for!

I am going to recommend the Fosi Audio V3 stereo amplifier.

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As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

Thank you for Amir's test, it is a brilliant amp for that price, I don't know what else we could ask for too, maybe XLR input.

 

[Kegemusha]

Great review and nice amp for desk. I am checking here in amazon and it states: Fosi V3, 300W x 2 Power.
Very tempting.

 

[Verig]

And yes I think these are a good match for cheaper speakers (maybe up to $500), if your speakers are beyond that price range, they probably deserve a more expensive amp.

Commercially speaking I think you start to get better crossovers and tweeters at about $1000/pr. Not a likely pair for a $100 amp.

I need to try one of these in action. I'm not worried about the 20kHz. There's very little recorded information above 12kHz anyway and in my forties I can't hear up to 20kHz. But I'm interested in how the audibility comes across in general "feel" of the upper register. Or does it. Older chip amps were horrible but that was mostly because of weak power and abrupt nasty clipping. Here there is plenty of power so we'll see.

 

[Kimbrough Xu]

Great review and nice amp for desk. I am checking here in amazon and it states: Fosi V3, 300W x 2 Power.
Very tempting.

It stiil copies the power from TPA3255. All of these TPA3255 amplifiers state 300watts x2, it is hard for the company to state the RMS power.

 

[Matias]

Impressive little amp. The 2 versions of power supply managed to get into best values in both low power and >150W in my spreadsheet below.

Amplifier SINAD list ASR + 3rd parties

docs.google.com

 

[geekosa]

This amp + su-1 can offer a great budget system ($200)

 

[ModDIY]

I have a pair of Mission Cyrus 781downstairs doing nothing. Could get it up and running with one of these and a WiiM, why not?

Yes no problem.

 

[ModDIY]

Very very good for a low budget amplifier. I voted Fine...it would be great if there was the PFFB, as Toku mentions, also no load dependency.