Fosi Audio V3 Amplifier Review

[peng]

I agree, it is a bit of "having your cake and eating it too." I think Fosi made the V3 in part due to our comments here and other top audio boards about amps such as the Aiyima A07, and wanted the more savvy user to buy it. But when all of the competing amps are pushing the high power ratings, if they don't do so, then the less savvy might not even consider the V3. Given the state of competition right now for these companies, and the tight profit margins, it's kind of a tough spot.

Problem I see is, it gives the numerous Youtubers talking points, some are fair and are somewhat knowledgeable while others would say things that may have negative impacts on Fosi's sales.

Reality is, advertised numbers aside, $72 for a legit 30 W/50 W, 8/4 ohms (being conservative), or actually about 46 W/84 W at about 0.1% THD+N that other power amps including some so called high end ones based their ratings on, makes this amp a no brainer to buy. For those who want more, $89 for twice as much output with the 48 V PS is an even better value.

 

[Mordor]

I prefer 2x50 with quality then 150x2 with worse sound....

 

[fernandocuello]

How should I decide between this amp and the Fosi BT20A Pro?

 

[potfur]

How should I decide between this amp and the Fosi BT20A Pro?

Quite easily. If you need Bluetooth or tone controls, BT20A Pro. If you need neither, V3.

 

[fernandocuello]

Quite easily. If you need Bluetooth or tone controls, BT20A Pro. If you need neither, V3.

I could give up bluetooth if the V3 sound significantly better. Do you think it does?

 

[Talisman]

I could give up bluetooth if the V3 sound significantly better. Do you think it does?

No

 

[Mordor]

V3 its better....

 

[peng]

Today I ran REW again, this time I quit Dirac Live first, and as expected max. SPL increased by about 15 dB:
So, at about 1 meter, with everything set to maximum, that is, the V3 amp's volume control, the DAC analog output, and windows10 at 100%.
I am happy with that, considering the LS50 can't really do better than 106 dB at 1 meter anyway. That's with the 32 V power supply. I should be getting one with 48 V PS in 5 to 10 days.

I only ran REW for the range 200-12,000 Hz, to avoid damaging the speakers.

With variable smoothing:

No smoothing:

 

[WillBrink]

Problem I see is, it gives the numerous Youtubers tlaking points, sone are fair and are somewhat knowledgeable while others would say thing that may have negative impacts on Fosi's sales.

Reality is, advertised numbers aside, $72 for a legit 30 W/50 W, 8/4 ohms (being conservative) makes this amp a no brainer to buy. For those who want more, $89 for twice as much output with the 48 V PS is an even better value.

That really bugs me however. It's borderline enough to prevent me from getting one.

 

[peng]

That really bugs me however. It's borderline enough to prevent me from getting one.

On the other hand, if you go with 0.1% THD that many more expensive power amp manufacturers regularly based their rated output on, the Fosi V3, 32 V power supply could do about 46 W 8 ohms, and 84 W 4 ohms. With that, I guess it is the one of the best, if not the best value in terms of W/$, one just have to know that it is not going to do 300 W, or even half that. And all that for $71!!

I have been listening to it for hours now, it sounds neutral, transparent, and I can imagine listening to a $5,000 amp that wouldn't make a difference. I bought it purely out of curiosity, because of what was presented in that unusual Scientific Audiophile Youtube video review, and it turns out to be a keeper, without a doubt.

 

[Bruce Morgen]

FYI, "nekkid" (no power brick) V3s are going for fifty dollars and change from Fosi via eBay. I'm tempted to pick up a couple even though the two old A07s in my little 7.1 system are more than adequate for their surround/ambience job -- what a bargain!

 

[Joe Smith]

That really bugs me however. It's borderline enough to prevent me from getting one.

It's a good amp, everyone in this sector plays the power game.

Aiyima apparently has a new Pro A07 coming soon, I will be interested to see what they have done, partially in response to Fosi...

 

[Fosi Audio]

An output low-pass filter is essential for Class D amplifiers. However, it is inserted in series with the speaker circuit and has a great influence on the frequency characteristics. It has long been known that this problem can be solved by adopting the PFFB method, in which the feedback signal is extracted after passing through the output filter. However, PFFB has only been approved for use by some companies due to patent applications.
Therefore, other manufacturers had no choice but to get feedback from the front of the filter.
However, the patent expired several years ago, and recently, products using PFFB have also been sold. Certainly Topping PA5 is one of them. TI, which manufactures the device, has recently started to provide technical materials on how to incorporate the PFFB.
There are some technical difficulties in incorporating PFFB into existing products, but the characteristics are clearly improved.
I expect Fosi Audio to work towards introducing PFFB as well.

Hi Toku, recently we have been working to introduce the PFFB. Luckily we solved the load dependence. However, we encountered some problems. The distortion becomes serious. Do you have any suggestions on this?

 

[TurtlePaul]

Did you copy the TI values? 33 dB gain seems like the feedback is way too low / gain too high.

For example, TI's PFFB datasheet shows results which end up with quite low gain.

TI Datasheet

TI claims that the SINAD should increase. Given the amount of business you are doing with TI, I am sure that you should be able to get a call with an engineer for them to help your implementation. Unfortunately, it looks like both the engineers who wrote this paper have moved on from Texas Instruments, but I suspect their analog audio department has a pretty deep bench of engineering knowhow on these specific chips.

 

[Jazzrocker]

Regarding volume:

My listening chain is: Fire TV Stick with Spotify -> HDMI input of the TV -> Via tosling to a miniDSP Flex 8 -> 2 x Fosi V3 with 48V power supply with volume set to max -> 2x Dynaudio Emit 10 (driven by 1 Fosi) + 2x DIY Subwoofer (driven by 1 Fosi).

If I set the miniDSP to -50 dB, it's already a medium volume. At -40 dB it is loud. -30 dB is too loud for an appartment. The Emits are rated at 86 dB (2.83 V / 1 m), so not very sensitive. Impedance is 6 Ohm.

So I can't see how power can be a problem. For my setup it is more likely too much power. I lose 30 dB SNR from the miniDSP DAC. I could set the volume of the Fosis to a lower level, but then I have to be very careful not to touch the control.

 

[stoyansbg]

I just got my V3 with 48V PSU and I like how it sounds very much. It did feel a bit weak though at max volume with a pair of 6 Ohm speakers so I plugged in an old Sony TA-F535R amp, which is rated at 110W/4Ohm and 90W/8Ohm, to the same speakers. Without any measuring equipment, and using the same audio source, the Sony drove the speakers a lot harder. I did not expect this amp to give out 300W but am kind of disappointed it did not match the lower wattage rated amp from last century. Also bummed what causes the apparent difference. According to the review, V3 should be able to put out 100W. Could the Sony be rated less than what it's capable of?

Edit: On a second thought my audio source sound level may be too low and I guess Sony's integrated preamp probably does a better job lifting it up before passing it down to the amp. Could that be it?

 

[Juampa1989]

I just got my V3 with 48V PSU and I like how it sounds very much. It did feel a bit weak though at max volume with a pair of 6 Ohm speakers so I plugged in an old Sony TA-F535R amp, which is rated at 110W/4Ohm and 90W/8Ohm, to the same speakers. Without any measuring equipment, and using the same audio source, the Sony drove the speakers a lot harder. I did not expect this amp to give out 300W but am kind of disappointed it did not match the lower wattage rated amp from last century. Also bummed what causes the apparent difference. According to the review, V3 should be able to put out 100W. Could the Sony be rated less than what it's capable of?

Edit: On a second thought my audio source sound level may be too low and I guess Sony's integrated preamp probably does a better job lifting it up before passing it down to the amp. Could that be it?

To get all the power out of it you have to use a source with 2 vrms output. I bought the smsl c100 dac. And with 8 ohm speakers, 88db sensitivity. 32v 5 amp power supply gives me a maximum of 105db, which is quite a lot when listening loudly, I never exceed 95 because it becomes unbearable. My area is 120m2 and it can be heard loudly throughout the house with half a knob. I repeat, I use the 32v supply and 2 vrms dac. It is not recommended to use a more powerful DAC because it distorts

 

[TheBatsEar]

Could that be it?

Only measurements can truly give you insight into that. While your impressions might feel self evident and absolute, they might be wrong regardless. Humans aren't measurement instruments, they aren't repeatable or reliable.

Only measurements can truly give you insight into reality, mate.

Welcome at ASR

 

[TurtlePaul]

Power is how many watts the device can output with low distortion and no clipping.

Gain is how loud a device gets when the volume knob is all the way clockwise.

You are confusing power and gain. The Fosi V3 can have more power but less gain than your existing amp.

 

[stoyansbg]

Power is how many watts the device can output with low distortion and no clipping.

Gain is how loud a device gets when the volume knob is all the way clockwise.

You are confusing power and gain. The Fosi V3 can have more power but less gain than your existing amp.

Thank you for clarifying! I am not very familiar with the terminology. I guess I am a bit confused. Given the speakers are the same, would not more power into them translate to more gain/loudness?