Fosi Audio V3 Mono Amplifier Review

[DavidM1]

I’m curious about this preoccupation with heat. We have a Denon receiver that has been on for the last 22 years inside an entertainment unit. It has always had an obvious amount of heat rising through the vents on top and less than an inch of clearance all around but more or less open at the back.

If Fosi is happy with the heat dissipation of the V3 monos and if the heat tolerance of electronic components is far greater than what we might consider warm to touch then why are people keen to MacGyver solutions that drop the temperature only a few degrees? Perhaps it’s time to sit back and enjoy some music.

 

[Cal_Cobra]

Without realising it Fosi have created a very good convection cooling system - instead of using the units flat, use them virtically, they are stable. First remove the pretty but useless orange pieces (they slide out) and place the units on two pieces of any suitable non magnetic material 10-15mm wide/25 mm deep/80-100mm long. Once the units are in opoeration they will naturally create a convection current (heat rises) with cooler air being drawn in from the bottom.

Fosi could easily create a couple of pieces with secure clamping features making the whole arrangement completely stable. They could have done this from the beginning so that the toggle swtches etc. operated virtically along with the logos and then they would take up even less space.

Sounds like a good opportunity for someone to make a CNC machined aluminum holder for these. Maybe a 3D printed holder would work too?

 

[Down South]

I’m curious about this preoccupation with heat. We have a Denon receiver that has been on for the last 22 years inside an entertainment unit. It has always had an obvious amount of heat rising through the vents on top and less than an inch of clearance all around but more or less open at the back.

If Fosi is happy with the heat dissipation of the V3 monos and if the heat tolerance of electronic components is far greater than what we might consider warm to touch then why are people keen to MacGyver solutions that drop the temperature only a few degrees? Perhaps it’s time to sit back and enjoy some music.

If you read some of the white papers written in the 1950s you wouldn't make that statement. The lower the operating temps. the longer components last. and operate within their design limits. Topping has problems that a lot of people on this forum are well aware of. Is your Denon built into a tiny case with no effective means of heat escaping? The monos have a very attractive but ineffective means of heat exiting the enclosure. If Fosi had made a top plate with lots of holes for heat to escape then OK.
It's so easy to implement this idea without in any way modifying the enclosure that it's up to you to try or not. Any one who cn measure the operating temperature can suck and see.

 

[I_L_Music]

Hi there from Portugal!
For those concerned about the shipping arrival, my V3 monos (2 x 48v 5a) just arrived and quickly joined their new partners: Wiim Mini - Fiio Br13 dac - Heco Aurora 300's - active Sub Jamo C910 and AC Infinity fans.
View attachment 377302
(Also came with two extra opamps).
They have replaced a Fosi Bt20a Pro (48v 5a), and so far, I'm happy with the upgrade.
Probably, I'll replace the Mini and the Fiio for the Wiim Ultra, just for the sub out and the room correction features, thou I don't really have complains about the room, because this is an (one side) open space; speaking of that, it's very common here to go higher than 40 C (104 F), so the fans were very useful to prevent the Bt20a Pro from reaching "melting temperatures".
View attachment 377303
I'd like to thank you all for the great information I've found in this forum that helped me to build this system.
Best regards
Juan

Hello - does fans adds to the vibration to the unit or not? Pls confirm your experience

 

[Sokel]

Hello - does fans adds to the vibration to the unit or not? Pls confirm your experience

Vibration is one thing fans can do (depending on the frequency it may be unnoticeable )
Electric interference on the other hand is a whole different matter:

Strange polarity issue with new amplifier (Topping PA5 II Plus)

Due to improper encapsulation, heat death will catch up to it eventually. You will probably lose one channel first. Maybe I'm just lucky, but enjoying my ~2 year old PA5 original used almost daily. Ampguy conveniently didn't mention that he already had one PA5 replaced, and is one of the...

www.audiosciencereview.com

If anyone got these for their SINAD alone better measure them before/after fans.

 

[Down South]

Hello - does fans adds to the vibration to the unit or not? Pls confirm your experience

Fans -what fans? how are they applied?. For my Bada hybrid amp I had made, a slate box - no top, no back plate, lined with bitumous sound damping sheet material. The fan was a Papst 4412 FGL adjustable speed using 1.25W.It was sited on cork/soft rubber feet. I did'nt need to run it anywhere near max speed. The bottom plate of the Bada was removed. There was no vibration or sound issues.

Even though I have bought a laptop cooler (to arrive) I may well use this Papst fan and the slate box, it's just big enough to take both the monos. With my Dutch friend Harry we worked out the best way to use PC fans. Was there a 'sound' difference with the Badas ( we both had the same amp) yes, a slightly warmer more liquid sound and a real drop in operating temperature.

The only change I will make in the monos is to change the output wiring to the speakers as I did in the stereo version. No point in posting on this as this is a non-starter on ASR.

 

[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/

Is it possible to connect 48v 10a power supply to each monoblock? Will it improve the sound?

 

[Jtabos]

Hello - does fans adds to the vibration to the unit or not? Pls confirm your experience

No, they don't.

 

[Bleib]

Is it possible to connect 48v 10a power supply to each monoblock? Will it improve the sound?

Yes it's possible, some purchase them that way. As for the second question, that's questionable.

 

[antcollinet]

Is it possible to connect 48v 10a power supply to each monoblock? Will it improve the sound?

Yes it is possible. And no, it won't

 

[cfwotzka]

Is it possible to connect 48v 10a power supply to each monoblock? Will it improve the sound?

of course you can or should connect each amp to a dedicated PSU. in my opinion "mono is mono" means nothing is shared. about sound quality improvement you will find many different opinions and my is it will!

 

[early rejecter]

of course you can or should connect each amp to a dedicated PSU.

I think the question there was a difference between two 5a PSUs vs two 10a PSUs, not one PSU vs two PSUs.

 

[DavidM1]

If you read some of the white papers written in the 1950s you wouldn't make that statement. The lower the operating temps. the longer components last. and operate within their design limits. Topping has problems that a lot of people on this forum are well aware of. Is your Denon built into a tiny case with no effective means of heat escaping? The monos have a very attractive but ineffective means of heat exiting the enclosure. If Fosi had made a top plate with lots of holes for heat to escape then OK.
It's so easy to implement this idea without in any way modifying the enclosure that it's up to you to try or not. Any one who cn measure the operating temperature can suck and see.

No, I’m not going to read articles on component longevity from the 1950s. Given the heat of vacuum tubes I’m sure they were important in their day but it’s 3/4 of a century ago and I have no ability to assess the relevance.

Thanks to ASR, we all know about the Topping PA5 issues but these seem to have been remedied with the PA5ii. The PA5 lemons left some people nervous about overheating but the failures were due to Topping encapsulating components in goop to protect IP.

The V3 monos have been designed with heat dissipation as a higher priority. Fosi has explained how the case is used as a heat sink and the layout takes the heat producing chip away from the rest of the circuit board. Cooling doesn’t depend on ventilation slots alone.

Time will tell, of course, but I’m happy to leave the temperature control decisions to Fosi for now.

 

[effj]

Sounds like a good opportunity for someone to make a CNC machined aluminum holder for these. Maybe a 3D printed holder would work too?

I was thinking of workshopping one with wood… but a machined one would be particularly nice and easier to design safely.

 

[I_L_Music]

Vibration is one thing fans can do (depending on the frequency it may be unnoticeable )
Electric interference on the other hand is a whole different matter:

Strange polarity issue with new amplifier (Topping PA5 II Plus)

Due to improper encapsulation, heat death will catch up to it eventually. You will probably lose one channel first. Maybe I'm just lucky, but enjoying my ~2 year old PA5 original used almost daily. Ampguy conveniently didn't mention that he already had one PA5 replaced, and is one of the...

www.audiosciencereview.com

If anyone got these for their SINAD alone better measure them before/after fans.

Are vibrations or electrical interference in audible range? Any idea.. based on the response, I will decide whether to buy fans or not

 

[JimBean]

Well, with the 20% off deal Fosi has going on, I decided to order a pair of these with two 48v/5amp power supplies. Not that I really need more power for my speakers (small space, pretty nearfield), but it's too good a deal to pass up. Plus the benefit of PFFB, which may or may not make a noticable difference. Now I just have to wait a month or so before they ship.

 

[Down South]

No, I’m not going to read articles on component longevity from the 1950s. Given the heat of vacuum tubes I’m sure they were important in their day but it’s 3/4 of a century ago and I have no ability to assess the relevance.

Thanks to ASR, we all know about the Topping PA5 issues but these seem to have been remedied with the PA5ii. The PA5 lemons left some people nervous about overheating but the failures were due to Topping encapsulating components in goop to protect IP.

The V3 monos have been designed with heat dissipation as a higher priority. Fosi has explained how the case is used as a heat sink and the layout takes the heat producing chip away from the rest of the circuit board. Cooling doesn’t depend on ventilation slots alone.

Time will tell, of course, but I’m happy to leave the temperature control decisions to Fosi for now.

You didn't read my post or decided to ignore it because it doesn't suit your take on heat issues. I used a computer fan to lower the operating temperature of mosfets and power resistors. Active cooling systems have been used in PCs for years now. The monos use what is in reality a closed system. Little heat will escape the metal enclosure and using the side panels with admittedly attractive copper coloured mesh isn't going to do much either since heat will always seek an upward path. People have already supplied the forum with temperature info which members can use or discard, it's their choice.

A lot of gear could be designed to operate vertically with air vents with or without fan assistance, last longer and with the bonus of using less space.

I prefer my gear to work at or around room temperature. Some components are designed to maintain performance at high temps. aka Z foil resistors @ 70C. No they are not cheap but not only are they 'transparent' but will potentially outlast the people who use them - they are the exception. Those white papers that you cannot be bothered to read state clearly that substantially lowering the operating temperature of caps and resistors will double or triple their operating lives. There are those who change their gear frequently (bad economics) for them this doesn't matter,for others it does.

 

[renoxd]

Is it safe to use 1 different op amp in each monoblock? I will have 2x MUSE 02

 

[avdoc]

Is it safe to use 1 different op amp in each monoblock? I will have 2x MUSE 02

That's how Fosi recommends using the op amps, one of the MUSE 02 and one of the original OpAmps. See video starting at 10:08 here:

Of course, you can replace both op amps if you purchase 2 more MUSE 02s. AFAIK, no one has done that yet to see if there's any difference.

 

[Bleib]

That's how Fosi recommends using the op amps, one of the MUSE 02 and one of the original OpAmps. See video starting at 10:08 here:

Of course, you can replace both op amps if you purchase 2 more MUSE 02s. AFAIK, no one has done that yet to see if there's any difference.

This should be tested whether there is any measurable difference or mere placebo