Fosi Audio V3 Amplifier Review

[Eric Natural]

... I just leave the Fosi orange vol control turned up to 11 & adjust level with my preamp - plenty loud for my room
best of luck

 

[Subway2400]

Hi,

I've been using a Fosi V3 for 2 about weeks, with the 48V PSU. I'm using it to power a pair of Wharfedale 12.0 speakers for desktop use, connected on a Realtek ALC1220-VB.

I'm pretty satisfied by this little amplifier. I use it at no more than 2 o'clock, the volume control is ensured by the Windows setting. There is no background noise, even with when the GPU is under load. I can't testify about its power, as desktop use isn't really power-demanding and bass below 90 Hz is handled by a subwoofer. Music listening really is enjoyable with the Diamond 12.0 and the Fosi doesn't seem to alter sound in any way. It perfectly fullfils its role. As for temperature, it gets moderately warm to the touch. It runs colder than my Denon X2500H AVR (without Eco mode) and warmer than my ex Yamaha A-S500 (which I really liked).

The only downside to me is the lack of separate power button that forces me to currently use some tape to mark the exact volume pot position. I really wish it had a power button. Plus using the pot when not really needed just add to wear and tear for nothing.

I did some measurements of the frequency response of the speakers using white noise to compare the V3 with my Denon X2500H which uses standard A/B amplifier. Despite a load dependency of the Fosi V3 amplifier, I did not detect any noticeable difference on graphs between the Fosi V3 and the Denon X2500H. The speaker frequency response is the same between the two amplifiers, not showing elevated treble.

I'm pretty happy with this amplifier !

 

[NSacchetti]

No!
Capacitors are glued to the PCB, probably you wouldn't have the same problem with rattling capacitor like @amirm with test example.
Thermal paste is for the metal part on the TPA3255 and the case. Not needed of course, but can be useful in better transfer of heat to the case.


A few more parts and as simple as is proposed from TI.
View attachment 293989
The biggest problem is a gain of (only) 19 dB with PFFB (like with Topping PA5). It will be a lot of complains from customers and @Fosi Audio wouldn't like that, I presume.

@Fosi Audio, you announced a new model after V3 with double XLR inputs, so when we can expect that product?
I hope you will ditch that 32V/5A PSU and you will start with a 36V/6A as a basic PSU.

Hello,

What should I do to replace input opamps by an unbalanced input tube buffer in the Fosi V3? How to find exactly board points to replace opamps outputs by tubes outputs? What is the V3 input impedance?

All help will be much appreciated!
Thank you guys!

 

[antcollinet]

Hello,

What should I do to replace input opamps by an unbalanced input tube buffer in the Fosi V3? How to find exactly board points to replace opamps outputs by tubes outputs? What is the V3 input impedance?

All help will be much appreciated!
Thank you guys!

You shouldn't. You are very unlikey to be able to make such a mod work.

If you really want to have a tube sound input to the amp, if there even is such a thing (I don't know why you would - but it takes all sorts to make a world) then use a tube based pre-amp or buffer.

 

[am_dew]

I have been using this amp (with 48v/5A PSU) now for a few weeks and am very pleased. While I am not what you would call an audiophile, I do know and appreciate good sound. The V3 is being fed by the preamp output of my vintage Kenwood KA-7300 integrated amp (which I bought new in 1977 and has served me very well but has issues with the power amp section in one channel), which has various input souces (Schiit Modi 3 DAC, Amazon Echo Link, etc.) fed into it. The vast majority of the time I am using the Echo Link to stream music from Pandora or Amazon (I know, not the greatest quality; but it's very acceptable to my aging ears). The V3 powers a pair of custom built JBL speakers my dad built in the early 60's, each with a JBL D130 15" driver and JBL 075 tweeter with a custom 3K crossover. These are very efficient (103 dB spl).

I have the Kenwood's volume set to about 10 o'clock, the FOSI's volume pot set to about 2 o'clock and I have the streaming gain set pretty low, which starts things at a fairly low volume but gives me the flexibility to raise the volume using Alexa from my phone , if desired, to very lould levels without touching the volume pots on the V3 or Kenwood. Call me lazy.

I turn the V3 on and off using an Alexa controlled smart plug but only after the componets upstream from the V3 have been turned on and are stable. I presume that doing this does not harm the V3.

Alll in all, I am quite pleased with the V3 and for the money and my ears, it is a great deal.

 

[CRTguy28]

I've got a pair of Definitive Technology ProCinema 80 speakers and I want to use them for TV viewing at normal listening levels (occasional movies and music as well). I need an amp to power them and was thinking of buying the Fosi Audio V3 for this purpose. I know I could buy a used receiver for cheap but I want the small form factor of the Fosi V3. The pro cinema 80 speakers have a sensitivity rating of 89dB and I'd be listening from a distance of about 7 feet. I typically don't listen to speakers really loud so my average dB level for listening would be between 60-70dB and maybe slightly louder if I'm watching an action movie. My question is, would the Fosi Audio V3 with the 32V adapter be enough to safely power two Definitive Technology ProCinema 80 speakers?

 

[nathan]

I've got a pair of Definitive Technology ProCinema 80 speakers and I want to use them for TV viewing at normal listening levels (occasional movies and music as well). I need an amp to power them and was thinking of buying the Fosi Audio V3 for this purpose. I know I could buy a used receiver for cheap but I want the small form factor of the Fosi V3. The pro cinema 80 speakers have a sensitivity rating of 89dB and I'd be listening from a distance of about 7 feet. I typically don't listen to speakers really loud so my average dB level for listening would be between 60-70dB and maybe slightly louder if I'm watching an action movie. My question is, would the Fosi Audio V3 with the 32V adapter be enough to safely power two Definitive Technology ProCinema 80 speakers?

Get the larger power supply for peace of mind, then yes this amp with the larger power supply puts out a similar amount of power to two speakers as do most AVRs in two channel mode.

 

[bgravato]

I've been a happy owner of a Fosi V3 for the last 9-10 month. I bought it with the 48V power supply directly from Fosi.

Yesterday I saw some comments of people complaining about their V3 getting too hot with the 48V/5A PSU, so decided to do some further investigation on mine...

Now that it's summer and it's hot, room temperature is about 25-26°C (77-79°F). After having it turned on for many hours I put my hand on it and it was warm to the touch, but not so hot that it was uncomfortable to touch, just a bit warm. So not sure if people are exaggerating on how warm it gets, or if some units just get warmer than others...

Anyway, I happen to have a 24V/10A PSU hanging around, so I decided to try it. Even after being on all day long, it's still pretty much as cool as if it was off. Not the slightest feel of warmth.

I didn't do any measurements, but on a quick subjective listening session, to my ears, my usual listening levels (which are fairly low) and my speakers (Dali Spektor 2), I couldn't really perceive any noticeable different in sound either... Which got me wondering if, for someone like me who doesn't push the volume up too much (at most I'll go up to 12 o'clock position on the knob, but that's only when the source audio is fairly quiet), is it worth going for the 48V PSU.

 

[GGroch]

I didn't do any measurements, but on a quick subjective listening session, to my ears, my usual listening levels (which are fairly low) and my speakers (Dali Spektor 2), I couldn't really perceive any noticeable different in sound either... Which got me wondering if, for someone like me who doesn't push the volume up too much (at most I'll go up to 12 o'clock position on the knob, but that's only when the source audio is fairly quiet), is it worth going for the 48V PSU.

Good test, good question.
Perhaps it is "worth it" to own the 48V power supply because you will have all of the power the amp can produce if you ever need it. BUT

Rated power on a very similar TP3255 amp predicts an output of about 60 wpc into your 6 Ohm Dali's using a 24v power supply. That should play very loudly. With a 48V 5A supply you might get double the watts, but that is only a few dB louder.

In your use case I would put the 48v back in the box and use the 24 volt until you need the 48v for the fall festivus party. There is no reason the 24 volt should not sound just as good in your room, and you are doing your bit to save polar bears

 

[Eric Natural]

I've been a happy owner of a Fosi V3 for the last 9-10 month. I bought it with the 48V power
Now that it's summer and it's hot, room temperature is about 25-26°C (77-79°F). After having it turned on for many hours I put my hand on it and it was warm to the touch, but not so hot . . .

similar V3 lifespan to yours here bg, and don't feel it's any warmer than any previous amplifier that I've driven this hard. Warm but not hot.

...is it worth going for the 48V PSU.

maybe but I'm getting good level out to the room & recycled the 32v box already : = )

peace

 

[bgravato]

and you are doing your bit to save polar bears

My initial thought too, but then I plugged it in through my power meter and realized the 24V PSU isn't very efficient... Idle (V3 off) consumes 5.2W, with the V3 on it draws 7.7W.
With the 48V PSU, I got only 0.3W idle and 6.1W with the V3 on.

So despite the V3 being less efficient under 48V, the PSU efficiency compensates that.

I could buy yet another PSU (lower voltage, more efficent), but buying more electronics might hurt the polar bears even more...

similar V3 lifespan to yours here bg, and don't feel it's any warmer than any previous amplifier that I've driven this hard. Warm but not hot.

Same here... My class AB vintage amp, not only is about 40x bigger than the V3, but produces a lot more heat (as expected)... I also tried an Aiyima T9 Pro before the V3 was released and it also warmed up quite a bit (buy given it had a couple of tubes in it, that was expected too).

I don't think the V3 gets hot either (just warm as you say), but it was interesting seeing the difference depending on the supply voltage... I wasn't expecting such a noticeable difference.

 

[Mordor]

Any advice about change those little chips for a different sound signature?

 

[antcollinet]

Any advice about change those little chips for a different sound signature?

My advice would be to not bother. The engineering says there is no sound signature change going to happen.

 

[Mordor]

Thank you for your feedback. Almost one year and super happy with it!

 

[loki85]

Has anyone got this outside? It's under a covered alfresco, so there's no direct rain/elements, but it does get very hot on some days where I live (45C/113F).

I'm concerned about whether it will be able to handle the heat in this situation?

 

[nathan]

Has anyone got this outside? It's under a covered alfresco, so there's no direct rain/elements, but it does get very hot on some days where I live (45C/113F).

I'm concerned about whether it will be able to handle the heat in this situation?

I would double check with the manual but I think that would be outside of safe OPERATING temperature for the unit. If you don't use it when it is that hot, it might be okay.

 

[musica]

can i use it only as a power amplifier?
do you hear any knocks in the speakers when turning the V3 on and off?

 

[nathan]

Sure, as described on the first post.

 

[antcollinet]

I would double check with the manual but I think that would be outside of safe OPERATING temperature for the unit. If you don't use it when it is that hot, it might be okay.

You'd also need to make sure there is no sun/heat getting through the the covering. If you can feel any radiation coming off the inside of that when the sun is shining, that will be much more problematic than air temperature.

 

[musica]

Can the Fosi v3 worthily replace the Denon pma 700 ae as a power amplifier, which I will use as a pre-amplifier?