Fosi Audio V3 Mono Amplifier Review

[vuittion]

What is the general consensus, buy the fosi v3 mono's with the 10 amp power supply or buy two 5 amp supplies.

 

[ninetylol]

What is the general consensus, buy the fosi v3 mono's with the 10 amp power supply or buy two 5 amp supplies.

2x5a or 2x10a

 

[burkm]

The general consensus seems to be, that 2x 48VDC / 5A is to prefer, because the 1x 10A with a filter and splitter seems to generate some interactions between both mono amps (distortion, noise etc.) plus it produces some additional hum/noise, if only on amp is active. The 2x 48VDC / 5A version uses two power bricks and has therefor no additional intermodulation distortion (=> true mono). Space requirements are almost the same, although the 10A power brick is larger by itself, and an additional filter is provided / needed, on its output side which at least seems to reduce some interactions through the splitter (filter) between both amps.
The 10A power brick does not provide any additonal (output-)advantages as stated by Fosi Audio themself.

Note: Both 48VDC power supplies lead to a "hotter" amp (higher output voltage and power), reaching about 43°C or its equivalent in Fahrenheit in its idle state and about 50°C or 122°F during full use. Higher temperatures shorten the life expectancy of electrolytic capacitors and resistors.

 

[burkm]

I wasn't too concerned about the phase being off, but did a "test" for fun (non measured, and not blind).

Moved the Fosi LC30 amp/speaker switch to my office. Same speakers (Sony SSC-S5), but two amps. The older Fosi V3 stereo vs the V3 monos.

The V3 stereo was louder at the same preamp level on the Wiim Ultra. The V3 stereo seemed to have a tiny bit more treble, but the subwoofer bass sounded better.

I changed the phase switch on the subwoofer and now the bass sounds better with the V3 monos, so I guess I did receive a set with the reversed phase. Expected as each only has one QC sticker.

It doesn't seem right to me for the V3 stereo to be louder than the V3 monos since they have more power on paper, but it is. Other than the slightly increased treble, I do not hear any difference in sound quality. I guess the V3 stereo was actually better than I thought it was.

I recommend the LC30 to anyone that wants to do a simple, quick comparison of amps or speakers or have two setups like my main system (stereo and atmos).

Had to compare the V3 monos vs the ZA3 with the LC30. Again the ZA3 is louder as previously determined. The subwoofer sounded wrong with the ZA3 as expected since I changed the phase for the monos. Switching the phase back corrected that for the ZA3.

Did a compare between the V3 stereo vs the ZA3. ZA3 slightly louder at same preamp level. Not as much difference vs the V3 monos. V3 stereo still seemed to have more treble. Both sounded great. Subwoofer phase needs to be the same for the ZA3 and the V3 stereo. Needs to be switched for the V3 monos.

Knowing what I do now, it doesn't seem like there is really any advantage in my two setups to having the V3 monos vs the ZA3 Stereo or maybe even the V3 stereo. All of them sound great.

I've also "tested" all of them driving my new Klipsch Heresy IV speakers. All sounded equally great as did the Loxjie A40 which seems to have the most power of any of them. Still noticed a slight treble boost with the V3 stereo vs all the others.

It is simple: the gain structure is different. The V3 monos need more voltage at the TRS/XLR input, the RCA/Cinch input might be somewhat adapted, because of that switchable gain (back plate): +21 db is fixed for TRS/XLR and +25db or +31db is for RCA/Cinch input. My impression: The V3 monos are much better sounding (SQ) all around...
But Your personal preferences naturally are determining the final outcome...

 

[imral3]

Email received from Fosi support, regarding V3's phase identification (not sure if already mentioned):

"Here I have enclosed a photo to show the placement of the QC and QR code labels on units where the phase is NOT inverted."

 

[Lux_ury]

Why don't you guys wait for a solution from Fosi, they said they would develop a better DC filter so hopefully one PSU one DC filter, problem solved?
I've got plan B which involves one PSU and two standard DC filters. Not tested it out, as I don't want to buy another filter for the sake of waiting for Fosi to supply me a new improved one, all for waiting an extra half of a month or so.
Either way the argument Fosi gave me was the one 48v 10amp brick is more efficient?
I just need to wait I see they have bundled fans for the heat sayers (LOL emoji) Quick sketch I know it's not tidy, but you hopefully get the idea? Not tested just an idea, don't come back say it doesn't work.

 

[Deleted member 72219]

Why don't you guys wait for a solution from Fosi, they said they would develop a better DC filter so hopefully one PSU one DC filter, problem solved?
I've got plan B which involves one PSU and two standard DC filters. Not tested it out, as I don't want to buy another filter for the sake of waiting for Fosi to supply me a new improved one, all for waiting an extra half of a month or so.
Either way the argument Fosi gave me was the one 48v 10amp brick is more efficient?
I just need to wait I see they have bundled fans for the heat sayers (LOL emoji) Quick sketch I know it's not tidy, but you hopefully get the idea? Not tested just an idea, don't come back say it doesn't work.

In case you need the spec, the cable connectors are DC 5.5mm external/2.5mm internal diameter.

-Ed

 

[totti1965]

Thank Amir so much for the measurement! The V3 Mono is another amplifier co-created with members, following the V3 stereo amp. We would particularly like to thank @Toku, @ModDIY , @mike70 , @cyclo, and all the other members who have provided us with invaluable suggestions.

The V3 Mono is our first amp with PFFB implementation. During the period we sent the set to Amir for testing, our R&D team did not stop optimizing the V3 Mono, and we have now further improved its frequency response curve. Below is the chart for your reference.
View attachment 360736


The V3 Mono is currently in production, and it will be launched on Kickstarter on the 20th of this month. There will be very attractive discounts available then, and we hope you'll stay tuned!

@amirm: I would like to ask you whether there will be a re-evaluation one day: Would you like to take another look at the Fosi V3 Mono in the current version, with the further improved linearity and the correct-phase cabling?

You did a re-evaluation with the Benchmark AHB-2 also - and I found it very interesting! Product consistency etc....

A propos consistency: It would be great if it were possible to "work through" a strict, numbered checklist in future amplifier tests. This would prevent certain interesting tests from being forgotten for one device or another and only running for certain devices. For example, it would be great if the 19 kHz/20 kHz intermodulation test was carried out for every device and, for comparability with stereophile, their special test was also always run (even if it is not that informative). It would also be great to always see the broadband up to, say, 200 kHz plotted, as well as the high frequency behavior up to 1 MHz for switching amplifiers - after all, you want to know where the switching frequency is, etc. A fixed checklist would help you not to forget anything.... I am not talking about the test of the Fosi V3 monoblocks here, but generally about some earlier tests.
As an example: You don´t run the stabilitiy "cube" test for each and every amp, but it would be nice to see it on a regular base.

I know, that this all would be extra work and at this time your tests for e. g. amps is by far the best that one can find at the whole internet.
Thank you so much for everything you have done for us music aficionados, even if you found my suggestions inappropriate!

Yours,

thorsten

 

[burkm]

Why don't you guys wait for a solution from Fosi, they said they would develop a better DC filter so hopefully one PSU one DC filter, problem solved?
I've got plan B which involves one PSU and two standard DC filters. Not tested it out, as I don't want to buy another filter for the sake of waiting for Fosi to supply me a new improved one, all for waiting an extra half of a month or so.
Either way the argument Fosi gave me was the one 48v 10amp brick is more efficient?
I just need to wait I see they have bundled fans for the heat sayers (LOL emoji) Quick sketch I know it's not tidy, but you hopefully get the idea? Not tested just an idea, don't come back say it doesn't work.

Are You sure they would supply a 2nd (improved) filter at no further cost ?
You might have to pay for it...

 

[mike70]

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?

You don't have any loses in the process with a decent ADC ... and many things to win in the digital domain with DSP.

I use my vinyl with a MiniDSP Flex and I can't find any difference with the pure analog path.

In other aspect, let me say that I have many (many) records that sounds better than the CD digital version. CD is a better format, yes, and CAN sound better, yes, but ... the awful truth is in the mastering / recording. If the digital version is compressed to death ... that's no way better.

 

[totti1965]

You don't have any loses in the process with a decent ADC ... and many things to win in the digital domain with DSP.

I use my vinyl with a MiniDSP Flex and I can't find any difference with the pure analog path.

In other aspect, let me say that I have many (many) records that sounds better than the CD digital version. CD is a better format, yes, and CAN sound better, yes, but ... the awful truth is in the mastering / recording. If the digital version is compressed to death ... that's no way better.

You are right by 1.000.000%! Today there is often more compression in the CD Format - without any need!
And: Linn did a lot of research in digitize or don’t digitize the LP 12 analogue music signal.
They decided to digitize the signal in their most expensive chains years ago! It simply sounds better with 192 kHz 24 bit and a bit of equalizing.

 

[Bernard23]

The general consensus seems to be, that 2x 48VDC / 5A is to prefer, because the 1x 10A with a filter and splitter seems to generate some interactions between both mono amps (distortion, noise etc.) plus it produces some additional hum/noise, if only on amp is active. The 2x 48VDC / 5A version uses two power bricks and has therefor no additional intermodulation distortion (=> true mono). Space requirements are almost the same, although the 10A power brick is larger by itself, and an additional filter is provided / needed, on its output side which at least seems to reduce some interactions through the splitter (filter) between both amps.
The 10A power brick does not provide any additonal (output-)advantages as stated by Fosi Audio themself.

Note: Both 48VDC power supplies lead to a "hotter" amp (higher output voltage and power), reaching about 43°C or its equivalent in Fahrenheit in its idle state and about 50°C or 122°F during full use. Higher temperatures shorten the life expectancy of electrolytic capacitors and resistors.

Where is this general concensus and based on what data?

Seems to generate some interactions - either it does or doesn't.

It definitely produces an annoying hum in the live channel when the other amp is switched off, both on = silent (using the internationally recognised standard method of ear against the tweeter at 0db volume setting on your system). Though no one is ever going to listen to just one channel, right?

The temperature issue could be solved by using a lower voltage PSU. You might get as much output but that's unlikely to be a problem for most buyers of these amps ie a second / bed room system

 

[ninetylol]

Im still deciding between 2x monos with 48V5A or a Fosi V3 Stereo with 48V10A.

Seems to result in same power for half the price without pffb.

Any impressions?

 

[Bleib]

Im still deciding between 2x monos with 48V5A or a Fosi V3 Stereo with 48V10A.

Seems to result in same power for half the price without pffb.

Any impressions?

If one unit is important then I'd wait for a stereo release for the mono.

 

[burkm]

@Bernhard23
Just read through different threads on the Fosi Audio V3 mono and You will find the "general consensus"
All "phenomenons" have been described in detail, and even that problem, that not all "disturbances" have been cured by filtering the DC power input and then some are still left - more or less - probably because of interactions between both amps through the filter. This results in those recommendations, that two 5A power supplies are better then one 10A power brick plus filter...

Fosi Audio did provide at the beginning of its delivery (kickstarter) NO filter, but then decided due to unfavorable experiences by users to develop and deliver its own filter for the 10A power supply. But even then some left over problems did still exist, which caused Fosi Audio to rethink its filter design and decide to improve on it in the "near future", meaning after its 1st batch had been sold out. How this will come out is still "open" not even decided, if the current filter will be exchanged for "no cost". Even then there seems something to be left on the table, because no "true mono design" with all its desirable effects like - theoretically - "complete isolation" and "infinite channel separation" still remain unresolved by one 10A power supply and filter + splitter.

 

[totti1965]

Im still deciding between 2x monos with 48V5A or a Fosi V3 Stereo with 48V10A.

Seems to result in same power for half the price without pffb.

Any impressions?

If your speakers are flat 6 Ohms in the range between - lets say - 7 kHz and 20 kHz - then the Fosi V3 is a good choice.
No need for the 10 A Power Switch. As you can see in some posts here, 48 Volt 5 A results in practically the same power (within a 5 to 10 % range).
That is so for the Monos and there is no reason to think it is different for the stereo.
If your set up tends to be a bit bright and your speakers are more about 4 Ohms in the 7 kHz to 20 kHz range:
The V3 stereo will sound a bit milder in the heights than a PFFT amp. Perhaps that is what you are searching for.
If your speaker has not enough "kick" in high frequencies but is more on the 8 Ohm side - it will sound brighter and perhaps more pleasant than any PFFT amp.
So the V3 Stereo can be a winner in some situations.

 

[burkm]

Responsible for the power output of the V3 mono is mostly the 48VDC voltage, not the 10A. Fosi Audio itself wrote, that power output would be "approximately" the same with both power supplies. Space requirements are - almost - equal because of that needed additional DC filter plus splitter cabling, thus "space savings" will not happen. I therefore still favor the 2x 48VDC/5A power supply due to all the other arguments provided

 

[ninetylol]

I think Fosi is not lieing when they say theres almost no profit with 48v10a over 5a with the V3 Mono . But their own specs say, that a V3 Stereo with a 48v10a gives the same output per channel than a Mono with 48V5A.

 

[antcollinet]

That is so for the Monos and there is no reason to think it is different for the stereo.

Except with the monos you have 5A available for each channel. For the same power capability in a stereo amp 10A is needed.

 

[Down South]

So in the 70s we had golden ears that could hear things we couldn't measure? Really? What exactly is "shite" as a measure of a device? Surely what you mean is that at that time, they were not measuring the important characteristics that influenced SQ; so what is measured today that is, but wasn't back then?

No, but then people listened to music instead of thinking about it, so a crap sound was easy to distinguish from good sounding equipment. There are a lot of people making negative psychological comments about 'others' who don't realise they are exposing their own irrational mentality.

Of course measurements are very important but to hear what 'sound' a piece of equipment is producing you have to actually listen. If you are thinking, then you are projecting ie. putting filters in front of the sound., why because thought can only operate in space-time, which of course is the past. To really hear music without filtering it you have to stop thinking and operate on input only. Sadly many cannot do that so they never really hear music. To describe others as delusional or 'influenced by price' is a defence system. To project onto others that you have never met or listened to a piece of music with is irrational.

Long ago I got really bored by true believers always using the hoary old excuse that hearing is influenced by price. I've heard very expensive gear that I and others thought sounded like crap. There are plenty that are impressed by bling, more fool them. I don't care what physical image a piece of gear has but I know there are plenty who will buy simply by how 'good' something looks.

All music equipment should be constructed with only two objectives - to maximise sound quality and longevity of use. The visual aspect should be of secondary importance.