Fosi Audio V3 Amplifier Review

[Freezak]

This amp + S.M.S.L SU1 dac is incredible deal.

 

[badspeakerdesigner]

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.

That's not what happens with real speakers. This is what happens with real speakers, it will vary with load but this is what I got from an aiyima a07. I tested three a07's and got different rising responses towards the top end with each one but similar behavior of things starting to rise around 5khz (just the tweeter here and it's passive network, c note speaker).

While I'm not a big fan of the youtuber Andrew Robinson, he put out a video documenting the same problem, but he wasn't sure what the cause was, just that he was getting totally different HF responses with different amplifiers.

Same tweeter with amp that doesn't have load dependency (had woofer connected for this one, can ignore below 2k,). This seems like a good opportunity to market "non-load dependant" amplifiers from the budget amp makers. I've had people tell me it's just these speakers that an outlier, nope found plenty of commercial offerings with very similar impedence charts, like kef q150. Most people are pairing these speakers with cheap amps, I wonder how many complaints about brightness are because of this issue. I will continue to rate any amplifier with this issue as poor as I don't consider it acceptable and it is a design flaw in my eyes.

 

[totti1965]

Amir, do you have a short explanation for this picture?
I didn´t like, that the picture shows multiple values on the y-axis correspond to one value on the x-axis if there is more than 30 Watts output!
I saw this the last time, the day you have testet the increadibly expensive Devialet Expert 200 in March 2020.
I hope the Fosi Audio V3 amplifier performs significantly better than the Devialet in terms of volume control and other parameters. After all, for you guys, it should be at least be possible to set up something better for US $100,-- than the French did for US $9,650! I don´t want to throw my money away!

​

 

[Michael Kelly]

Fun fact - Buying a slightly less powerful PSU from a reliable fully approved vendor in the US (Meanwell [email protected]) costs ~$75! Makes me wonder about the long term quality of what they provide.

 

[natna]

Great news! I was looking for a good TPA3255 amp.
And it measures better than Allo V+ D amp!
OPAMP rolling (for example OPA1622 ) is a good thing, since that everybody do it in other budget 3255 implementations like AIYIMA'S

Nice work @Fosi Audio. I see that on amazon.de I cannot choose a 48v power supply.

Nice review @amirm.

What about crosstalk? I believe that because of the use of 1 TPA3255 chip, measuring the channel crosstalk is essential.

There might be an idle hiss noise with the 8ohm titanium tweeters of my speakers, though.
Looking forward to hearing impressions of actual owners about idle noise

And one more question. Does it offer soft start circuit?

 

[leelee]

That's not what happens with real speakers. This is what happens with real speakers, it will vary with load but this is what I got from an aiyima a07. I tested three a07's and got different rising responses towards the top end with each one but similar behavior of things starting to rise around 5khz (just the tweeter here and it's passive network, c note speaker).

While I'm not a big fan of the youtuber Andrew Robinson, he put out a video documenting the same problem, but he wasn't sure what the cause was, just that he was getting totally different HF responses with different amplifiers.

View attachment 293761

Same tweeter with amp that doesn't have load dependency (had woofer connected for this one, can ignore below 2k,). This seems like a good opportunity to market "non-load dependant" amplifiers from the budget amp makers. I've had people tell me it's just these speakers that an outlier, nope found plenty of commercial offerings with very similar impedence charts, like kef q150. Most people are pairing these speakers with cheap amps, I wonder how many complaints about brightness are because of this issue. I will continue to rate any amplifier with this issue as poor as I don't consider it acceptable and it is a design flaw in my eyes.

View attachment 293762

Very interesting, and that's a pretty big difference. I'll definitely be doing some REW measurements once I recieve my V3. Hopefully it does not have the same behavior as the aiyima. My current Fosi tb10d version 2 doesn't seem to have any major peaks or dips in the upper frequencies when measuring it with 8 ohm speakers as compared to any other amps I have.

 

[badspeakerdesigner]

Very interesting, and that's a pretty big difference. I'll definitely be doing some REW measurements once I recieve my V3. Hopefully it does not have the same behavior as the aiyima. My current Fosi tb10d version 2 doesn't seem to have any major peaks or dips in the upper frequencies when measuring it with 8 ohm speakers as compared to any other amps I have.

What speakers are you pairing the amp with?

 

[leelee]

What speakers are you pairing the amp with?

Diy 2 way bookshelf speakers. Morel tweeter and dayton woofer.

 

[Matias]

Amir, do you have a short explanation for this picture?
I didn´t like, that the picture shows multiple values on the y-axis correspond to one value on the x-axis if there is more than 30 Watts output!
I saw this the last time, the day you have testet the increadibly expensive Devialet Expert 200 in March 2020.
I hope the Fosi Audio V3 amplifier performs significantly better than the Devialet in terms of volume control and other parameters. After all, for you guys, it should be at least be possible to set up something better for US $100,-- than the French did for US $9,650! I don´t want to throw my money away!

​

It starts to come back when a protection circuit reduces power.

 

[Mike-48]

I wonder when the cheap Class-D designs will get rid of that load dependency?

 

[Talisman]

Diy 2 way bookshelf speakers. Morel tweeter and dayton woofer.

the nominal impedance of the speakers does not give you any useful information, in this case you actually have to calculate what the impedance curve of your speakers is between 10 khz and 20 khz, that value will tell you how the amplifier will sound together with your speakers

 

[ocinn]

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.

Not hard. TI outlines it in their own paper and even hand-feeds you the values for the components.

https://www.ti.com/lit/an/slaa788a/slaa788a.pdf

Does not solve the load-dependency issue, at least in TI's implementation. The other performance benefits are massive, esp when handling complex loads.

 

[leelee]

the nominal impedance of the speakers does not give you any useful information, in this case you actually have to calculate what the impedance curve of your speakers is between 10 khz and 20 khz, that value will tell you how the amplifier will sound together with your speakers

Yes, I get that. Just saying I have not seen any impedance dependancy issues with the fosi tb10d and my speakers. With the tb10d, the top end measured pretty closely to winpcd's predicted response. I think I also did see the Andrew Robinson video and he did note that the fosi did sound better than the aiyima amp.

 

[sarumbear]

I wonder when the cheap Class-D designs will get rid of that load dependency?

When they get more expensive.

 

[Jeromeof]

So only really because I had it lying around but I decided to compare the 'cost' of leaving it plugged in with both the 48V and the 32V power supply (I had a 32V one from the BT20A Pro) - so according to my 'energy meter' the 48V is constantly pulling 6W of power and the 32V is pulling 3.2W of power. I do find it amazing that even when playing very loud this amp only went up to 6.3W with the 48V power supply. I imagine I am just not playing it loud enough

Anyway, if you are planning of putting this somewhere where it's plugged in all the time it might be worthwhile just using the 32V power supply.

 

[Verig]

Ouch. That real world 5k+ rising response coupled with 32V psu will result in some very nasty sound when clipping. 34W (@8) before total obliteration (Yes I'm being hi-fi dramatic) is not much power. I hope the measurement is accidentally the worst case scenario.

But then again with the 48V PSU and right speakers this could still be very good $100 spent.

 

[Verig]

I wonder when the cheap Class-D designs will get rid of that load dependency?

This chip is from 2016. I have no idea how much progress has been made after that. All these cheap amps seem to use quite "old" tech. It would be interesting to know if there is a cheap option available but not utilized because buyers don't care or some other non-technical reason.

 

[DSJR]

A repetitive question with apologies -

The hf response goes a bit awry into 8 ohm loads. Lower in frequency, is the output basically the same level?

I ask this as presenting a simulated speaker load (hence my repetitive question) with a perfectly usual roller-coaster impedance curve would make a typical valve-tube amp with output impedance of 2 ohms or higher act like an equaliser at all frequences as the output tracks the speaker's crossover impedance rise and fall (best I can describe it but Stereophile reviews are telling in this respect). Would an amp like this as tested by Amir ONLY deviate above 10khz or so with varying load? Hope the description above and question now is understandable.

Something else which I don't *think* is covered in these reviews - what about max current output? I come from a period where many cheaper far eastern amps had plenty of 'voltage watts' per channel at low distortion, but give them a more difficult load and they often fell flat as the power supplies complained and with audible results sometimes.

 

[Kevinfc]

Such an amazing value when I consider the thousands I’ve paid in the past for inferior equipment.

 

[BostonJack]

A lot of value there. I really like the big volume knob. Good to have a quick "chicken switch" if a manual screw up has you driving the speakers too hard.
I can see this little amp as being more than good enough for many applications.