Fosi Audio V3 Mono Amplifier Review

[Doodski]

Many holes... I gather cooling will not be an issue;

View attachment 360770


JSmith

I like that...

 

[virtua]

What a great time to be an audio enthusiast

 

[Doodski]

What a great time to be an audio enthusiast

If these TPA3255 ICs have such performance then Ti will make even better chips and voila!

 

[Golf]

I like that...

Definitely. Makes some sort of »Fozzie Bear Audio« appearance, no?

 

[Doodski]

Definitely. Makes some sort of »Fozzie Bear Audio« appearance, no?

Yes, now that you mention it... LoL.

 

[Extreme_Boky]

These Fosi mono blocks with their expanded XLR SINAD [compared to RCA] seemingly make a good use case for using my Oppo 105D XLR outs (wonder if a pre-amp would be needed?):
View attachment 360750

You need a pre-amp to control volume.

The only way you could connect OPPO analog out to Fosi directly, is by utilising OPPO's USB DAC feature... it will work no problem, but the volume would have to be controlled at the source... I used HQPLayerPro and JRiver when experimenting with my OPPO205. If you decide to try this, limit the maximum volume (in JRiver for example) to something like 50% and do NOT forget to disable all Windows OS sounds (!!).

Or... you could install a nice volume pot inside Fosi monoblocks.... if you know a bit about electronics. Even a 6-stepper attenuator will do nicely in preventing fully blasting the speakers by accident. Of course, you'd lose the warranty...

Another way is to see how Fosi implemented gain control... to modify the overall gain to something more sane... maybe between 16 and 20dB... which is more than enough with modern sources. Then you won't need a volume mod in Fosi monoblocks.

 

[sweetchaos]

How do 2 of these compare with stereo balanced amplifier, Topping PA5 II (about US$250 now)?

In other words, which is the better option, for which use case.

Thanks.

 

[Doodski]

How do 2 of these compare with stereo balanced amplifier, Topping PA5 II (about US$250 now)?

I have a feeling that commentary will be moved outside of the review thread. So wanna start a new thread?

 

[MacClintock]

It is really a pitty that I have no need whatsoever for a cheap, small amplifier.

 

[restorer-john]

It is really a pitty that I have no need whatsoever for a cheap, small amplifier.

You can never have too many amplifiers.

Well, that's not true. I have too many. Don't be like me. But I will say these little high performing things would be really easy to smuggle in to the house and hide wherever you wanted...

 

[Jimster480]

It has no volume controls? So how do you adjust the volume?
Otherwise the performance looks quite good especially at this price. Like I am really surprised. I think this is the #1 budget amp now?

 

[Bleib]

How do 2 of these compare with stereo balanced amplifier, Topping PA5 II (about US$250 now)?

In other words, which is the better option, for which use case.

Thanks.

Probably similar experience unless the loudspeakers have a low sensitivity

 

[amirm]

It has no volume controls? So how do you adjust the volume?

This is a power amplifier which means they usually don't have volume controls. You need a preamp in front of it or a DAC with volume control.

 

[Golf]

You need a preamp in front of it or a DAC with volume control.

Would a »streamer« (like Denon DNP-2000NE) also do?

 

[Doodski]

Would a »streamer« (like Denon DNP-2000NE) also do?

Use the variable line output for volume control.

 

[Kimbrough Xu]

Nice!! I normally don't care about components much, but I've been looking for another small amp for my center channel, and this looks amazing for the price.

How are you driving your LR channels?

 

[Golf]

Use the variable line output for volume control.

I believe those are meant for driving active speakers in the first place. Will that work with a power amp also?

 

[Tell]

This is nice! But personally I would like to see this performance in boards without the chassi and power supply for a cheaper price to build your own thing with. Both mono and stereo versions of course

 

[Doodski]

I believe those are meant for driving active speakers in the first place. Will that work with a power amp also?

Yes, that will work very well with a power amplifier.

Variable Output Level​

4.5Vrms

DNP-2000NE

DNP-2000NE

www.denon.com

 

[Urib]

This is a review and detailed measurements of the Fosi Audio V3 Mono class D amplifier. It was sent to me by the company. The price with the power supply I tested is US $139.99.
View attachment 360697
I must say the concept of a "monoblock" amplifier in such a small size runs foul of any expectation a longtime audiophile would have! But monblock it is even though it is a very small block. Controls are on/off/trigger audio and selection of XLR vs RCA inputs -- just like the big boys! I am not showing the sides of the amp but there are very large holes with attractive orange color grid showing through. Nice. Back panel is again a bit of a shock to the system seeing XLR input:
View attachment 360698

The power supply as noted, is quite beefy with 48 volts at 5 amps on tap (240 watts). The amplifier is stated to have PFFB implementation which for a class D amplifier means it should have no load dependency together with lower distortion. Let's see if we get these with our measurements.

Fosi Audio V3 Mono Amplifier Measurements
Let's start with XLR input:
View attachment 360699
Wow, I did not expect this class of amplifier to break through the 100 dB SINAD barrier but the V3 Mono does exactly that, placing it in our prestigious category of "excellent:
View attachment 360700
View attachment 360701

RCA input costs you some performance but I was relieved to not see any mains interference:
View attachment 360702

Distortion is still at provably inaudible -115 dB. I like that the gain is nominal 25 which is my new recommendation for amplifiers.

Noise performance is excellent and at full power, darn near approaches sate of the art:
View attachment 360703

Now the all important frequency response and load dependency test:
View attachment 360704

There is essentially no impact up to 20 kHz between the 4 and 8 ohm indicating very low output impedance, albeit with a bit of peaking. Compare that to non-PFFB amps such as Fosi Audio V3 stereo Amp:

Above we have 2 dB differential at 20 kHz.

Distortion is very low and only increases with frequency:
View attachment 360706

View attachment 360707

Let's see how much power we can get out of this little box:

View attachment 360709

View attachment 360710
Efficiency must be quite high as we get essentially the power we put in (the power supply likely has some headroom).

There is decent amount of power even with 8 ohm and with very low noise:
View attachment 360712

As note though, distortion does rise at higher frequencies:
View attachment 360713

Fortunately it is good where our hearing is very sensitive (below 5 kHz).

I also threw my suite of my punishing reactive loads at it:
View attachment 360717

Translating into watts:

View attachment 360716

Amazing that this little amplifier can handle even 2 ohm load! Note that these are short term power ratings.

There may be a bit of power on noise:
View attachment 360718

Conclusions
All I can say is wow! It is incredible how far these small amplifiers have come. It is the result of a manufacturer listening to our needs, implementing features such as balanced and trigger inputs, and proper feedback mechanism to essentially eliminate load dependency. I can't imagine asking for more from Fosi when it comes to such an amplifier. Everything is as good as you could possibly want.

It is my pleasure to recommend Fosi Audio V3 Mono amplifier.

-----------
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/

I saw that it is possible to connect one 48v power supply to 2 monoblocks with a splitter cable. Will it reduce the power of both amps?