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Fosi Audio V3 Mono Amplifier Review

Rate this amplifier:

  • 1. Poor (headless panther)

    Votes: 12 1.9%
  • 2. Not terrible (postman panther)

    Votes: 19 3.0%
  • 3. Fine (happy panther)

    Votes: 121 19.4%
  • 4. Great (golfing panther)

    Votes: 471 75.6%

  • Total voters
    623
Honest question here as I see people very happy about the phono input...
First, I am not a vinyl guy, but why would you want digitize the beloved vinyl/analog output?
Because analogue amplification is compromised, but most importantly you can't apply room correction, arguably even more important for vinyl. Ultimately though it just a nostalgia trip anyway, as every digital version sounds clearly better. I just love the looks, tactility and that it takes me back to my childhood, I've no interest in taking it seriously and haven't for years.
 
Because analogue amplification is compromised, but most importantly you can't apply room correction, arguably even more important for vinyl. Ultimately though it just a nostalgia trip anyway, as every digital version sounds clearly better. I just love the looks, tactility and that it takes me back to my childhood, I've no interest in taking it seriously and haven't for years.
Thanks...that I can clearly understand, but I wonder about others.
 
Fosi told me the monos are stuck in Spanish customs, and on the tracking it stop on Spain customs. Fosi ask me for evidences fromk kickstarter and credit card bill , and to send them . They told me to wait , and they assure the all duties. Last news was about 20 days ago...
Dear Galego.
I am more than sure that Fosi Audio will eventually respond for this problem. I can attest that their customer service is of an excellence rarely seen. I am really convinced that they will try by all means to solve your problem, but what you describe is strange, to say the least.
I am from Argentina and my V3 mono They left Hangzhou (China) passing through Shanghai, Sennan (Japan), Anchorage (Alaska), Oakland San Francisco (USA), Campinhas (Brazil) and finally arrived in my country. Throughout this itinerary there was no problem since all of them are transit places and not destinations.
It is not appropriate for ANY customs in ANY country to retain your shipment. The control must be done by the customs of your country.
Therefore, I believe that the problem lies with the logistics service provider and not with Fosi, although I repeat, you can be sure that they will respond.
Greetings!
 
It looks like 2 fosi monos with two 48V 5Amp power adapters is $280
2 fosi monos with two 48V 10 Amp power adapters is $420

Are the 10 Amp adapters worth the extra $140, if running Magnepan LRS? Thanks guys.
I use V3Ms with separate 48V/5A power supplies for my Magnepan MG2.5Rs in a very large open room with ~20 foot cathedral ceilings and have no problem hitting ~80dB peaks watching movies. Per Fosi, there is no benefit for the 10A power supply on a single amp.
 
I use V3Ms with separate 48V/5A power supplies for my Magnepan MG2.5Rs in a very large open room with ~20 foot cathedral ceilings and have no problem hitting ~80dB peaks watching movies. Per Fosi, there is no benefit for the 10A power supply on a single amp.
Can it hit 90db or is that asking a bit too much from these mini monos? Overall, I like it kinda loud, not a 70db listener. I am sitting about 11 1/2 ft away from a LRS+. Worst case, I could move closer to the speaker. I currently am using the high powered Emotiva class H, but, i don't like it that much.

Can you crank it to 90db on some metal and see what it does?
 
Can it hit 90db or is that asking a bit too much from these mini monos? Overall, I like it kinda loud, not a 70db listener. I am sitting about 11 1/2 ft away from a LRS+. Worst case, I could move closer to the speaker. I currently am using the high powered Emotiva class H, but, i don't like it that much.

Can you crank it to 90db on some metal and see what it does?
Below is the Stereophile measurement of the impedance of the Magnepan MG2.5R. It's impedance is 6 ohms or higher from 20 Hz to 2 kHz, which is where most of the power demand lies.
666MG25FIG1.jpg

Here is the max output the TPA3255 chip vs PS supply voltage in PBTL mode that the V3 Mono uses. At 48 Vdc supply, at 4 ohms the max output is ~250 W. Translating to 6 ohms, it is 250 * 4/6 = ~170 W.
The 48 Vdc 5 A power supply is rated to provide 240 W of power, and should be more than enough to power the V3 Mono to full output driving the MG2.5R. A higher current PS is only beneficial for driving loads that go substantially below 4 ohms at frequencies where there are high demands for power.
PBTL Output.png
 
Below is the Stereophile measurement of the impedance of the Magnepan MG2.5R. It's impedance is 6 ohms or higher from 20 Hz to 2 kHz, which is where most of the power demand lies.
666MG25FIG1.jpg

Here is the max output the TPA3255 chip vs PS supply voltage in PBTL mode that the V3 Mono uses. At 48 Vdc supply, at 4 ohms the max output is ~250 W. Translating to 6 ohms, it is 250 * 4/6 = ~170 W.
The 48 Vdc 5 A power supply is rated to provide 240 W of power, and should be more than enough to power the V3 Mono to full output driving the MG2.5R. A higher current PS is only beneficial for driving loads that go substantially below 4 ohms at frequencies where there are high demands for power.
View attachment 388706

Well, here is the LRS.
719MLRSfig1.jpg
 
You think you'll be driving the LRS with >240W?
I don't know, i'd rather not blow anything up. I was only thinking out load about your statement, "A higher current PS is only beneficial for driving loads that go substantially below 4 ohms at frequencies where there are high demands for power."

But, i could move my seat closer to 8 feet or something from the speakers.
 
Honest question here as I see people very happy about the phono input...
First, I am not a vinyl guy, but why would you want digitize the beloved vinyl/analog output?
Most people round here are perfectly aware that a ADC/DAC pair with competent electronics is 100% transparent** to the usual analogue sources - including vinyl.

**the analogue output from the DAC is 100% audibly identical to the "beloved vinyl sound" going into the ADC.
 
Honest question here as I see people very happy about the phono input...
First, I am not a vinyl guy, but why would you want digitize the beloved vinyl/analog output?

Because, from a purely technical standpoint, vinyl is garbage. Very enjoyable garbage, but garbage nonetheless. The AD conversion would have to be absolutely horrifically bad in order to make the situation worse.

I've seen several people describe how they used a cheap PC soundcard to make digitized backups of their collection, only to realize that it was impossible for them to tell the difference between the two. It's easy to capture the "magic", when it 100% stems from technical limitations. With a digital RIAA you still get the tactile goodness from fiddling with the vinyl and the turntable, but also much better control of the signal and it's post-processing. It's a win-win situation :D

Also, you'd have to go half a century or more back in time to find vinyl that most likely hasn't had its source material digitized at least once in the production process.

The whole idea of "analogue purity" is nothing but a happily ignorant dream. One I was enamoured with myself at some point, but luckily I've moved on.
 
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As promised before:
To get back to the thermal situation with the V3 monos: I had mine running all night (idle) after renewal of the thermal paste and the case temperature of that class D power amp seems to be at around 38,5°C (speaker connected), whilst room temperature (wall) this morning is about 21.7°C.
 
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To get back to the thermal situation with the V3 monos: I had mine running all night (idle) after renewal of the thermal paste and the case temperature of that class D power amp seems to be at around 38,5°C, whilst room temperature (wall) this morning is about 21.7°C.
You are measuring the wrong thing. I wouldn't really expect that doing anything with thermal paste, even removing it, would change the case temperatures.

Think of it like this, the chips are producing heat inside the case, the case temperature is going to rise until it dissipates the amount of heat produced by the chips at which point the temperature stabilises. The same amount of heat is being produced whether there is paste there or not so the case temperature is unaffected.

Inside the case it is a different matter of course. The poorer the thermal mating between chip and case the more the board and air inside will have to carry heat transfer to the case and so the internal components will be warmer. If you are concerned this is what you should be measuring.
 
You are measuring the wrong thing. I wouldn't really expect that doing anything with thermal paste, even removing it, would change the case temperatures.

Think of it like this, the chips are producing heat inside the case, the case temperature is going to rise until it dissipates the amount of heat produced by the chips at which point the temperature stabilises. The same amount of heat is being produced whether there is paste there or not so the case temperature is unaffected.

Inside the case it is a different matter of course. The poorer the thermal mating between chip and case the more the board and air inside will have to carry heat transfer to the case and so the internal components will be warmer. If you are concerned this is what you should be measuring.
Agree, no "single point" steady state measurement is going to give any meaningful information. Unless one measures a temperature gradient (i.e. at the chip and at the case simultaneously) or temperature Vs time (i.e. when the amp is switched on) or better a combination of the two, it will be impossible to asses how good or bad the thermal coupling is
 
Can someone confirm the value of the 2 carbon power resistors at the RCA output. Colour coding says they should be 8.2 ohms but mine measure 8.6 and 8.7. Was it a cost factor that Fosi chose carbon?
 
Agree, no "single point" steady state measurement is going to give any meaningful information. Unless one measures a temperature gradient (i.e. at the chip and at the case simultaneously) or temperature Vs time (i.e. when the amp is switched on) or better a combination of the two, it will be impossible to asses how good or bad the thermal coupling is
I think it's probably good enough to measure just at a single point in time when the amp has been on long enough for its temperature to stabilise. Personally I'm not at all interested in details of how quickly it reaches that temperature.

However to be useful that temperature measurement needs to be for the chip itself (and/or any other components of concern). All we can know from a case measurement is that the chips are going to be at some temperature hotter than the case.
 
Can someone confirm the value of the 2 carbon power resistors at the RCA output. Colour coding says they should be 8.2 ohms but mine measure 8.6 and 8.7. Was it a cost factor that Fosi chose carbon?
Get some nice mil spec Caddock MP930 and replace them if they are critical and have to endure heat (they cost a bit but they deserve it,they are bomb-proof)
 
Is there a reason I need to turn the preamp volume up higher for the v3 monos to get the same loudness as a single ZA3?

For Heresy IV speakers, the V3 monos require about 10% to 15% more preamp volume vs the single ZA3. I expected the opposite to be true.

Using an Eversolo DMP-A6 as the preamp. It is the same streaming or playing CDs through the optical port.

I don't hear a sound quality difference between the V3 monos vs the ZA3. Haven't done any measurements other than temperature. The ZA3 stays a lot cooler without a fan blowing across them.

I don't really know what the PFFB is supposed to do in the V3s. Would that account for the different required preamp volume levels?
 
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