Fosi Audio V3 Mono Amplifier Review

[antcollinet]

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.

 

[Killingbeans]

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

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.

 

[burkm]

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.

 

[gwing]

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.

 

[MCH]

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

 

[Down South]

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?

 

[gwing]

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.

 

[Sokel]

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)

 

[Angeloasi]

could I possibly drive the old b&w 800N’s with these?

 

[Brian Hall]

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?

 

[Zek]

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?

V3 mono has less gain and therefore requires a higher input voltage.

 

[burkm]

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?

The volume position of the preamp is not really relevant, because it depends on the individual sensitivity of the amp (and preamp), the established over-all gain structure (preamp => amp) and the layout (type) of the specific volume control, which is been used.
As long as You reach the required loudness from Your speakers everything is supposed to be "fine"...

 

[Brian Hall]

As long as You reach the required loudness from Your speakers everything is supposed to be "fine"...

No issues there.

 

[burkm]

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.

Should be quite "hard" to get hold of the individual components temperature within the closed cabinet for a "private" user

My intention: I just gather the temperature on the surface of the cabinet and try to get it => hotter (!), so the temperature transfer between the case (and its components, especially the heat "generator" TPA3255) is improved. That'all, but some are misinterpreting what I'm doing Applying new thermal past is needed anyways, as soon as I remove the PCB from the cabinet, which i have to do to get a climps of the speaker connections soldering.

If it helps in doing what I did is at least "doubtful" because I don't know, if the heat transfer as a whole has been really improved by my actions. Both cases (I just changed two of those amps I got) showed signs of slipping in the PCB whilst thermal paste had already been applied, so i think, the one, who inserted the PCB into the casing originally, was facing the same problems I had. They just applied the thermal paste in between the 2 screws, while this might have been the place with max. even pressure. At least both amps appeard to be the same in this respect, so it's probably done by purpose and cost considerations (labor, time and amount of themal paste used).

 

[MCH]

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.

How quickly it reaches that temperature is telling you how good is the thermal coupling between chip and heatsink, and indirectly, how "cold" the chip will be. Faster case warmup <- better thermal coupling -> cooler chip

All we can know from a case measurement is that the chips are going to be at some temperature hotter than the case.

And that's why the single point measurement at the case is useless.

What I was addressing is the people aiming to have an idea of how good the thermal coupling is, like the discussions about thermal paste Vs no thermal paste etc. I agree that at the end the important thing is the temperature of the chip and other components, but that is going to be a result of how efficient the heat sink is.

 

[SMen]

Thanks...that I can clearly understand, but I wonder about others.

I differ ...

Why would you want to digitize ... well possibly for convenience (for adding to a play list or for use with portable player). ...

Many recordings were not so well transferred to the digital format. Analogue to digital converters have improved ... so compare an 80s CD of 60s Jazz by Stan Getz or Paul Desmond / Dave Brubeck to a good modern transfer made with better ADC's , and hopefully it will sound as good or better than the original recording on vinyl.

A lot of digital remasters were simply not a patch on the originals. The vinyl revival did not just happen because of artwork, or 'tactile' play back. For many people, myself included, I just said ... hold on a minute ... if I just listen to some of these recordings on vinyl the digital version does not compare.

In 2024 however, digital playback is greatly improved.

There are also issues about 'loudness' ... recordings are 'jacked up' or 'peek limited' to such a degree that the vinyl can sound more natural ... ironically because mechanically the loudness can't work on the inner grooves of the record! Look up the saga regarding Michael Jackson's "Bad" ... the producer Quincy Jones successfully sued because the record company added so much peak limiting to his production in later production runs of the record ... 'the loudness wars' ...

For whatever reason though ... I still just prefer listening to the records rather than a digital transfer, even if A/B ing them shows little perceptable (if any) difference with a pretty good ADC I have. It's a whole different way of listening - you listen to the album.

 

[SMen]

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.

Just come across this after replying to @courtesy ... at what date in the development of ADC's do you think that they became 100% audibly identical?

80s, 90s, 2000's, 2010's, 2020's

or have they been perfect since the 1980's in your view / measured performance?

 

[Bernard23]

I differ ...

Why would you want to digitize ... well possibly for convenience (for adding to a play list or for use with portable player). ...

Many recordings were not so well transferred to the digital format. Analogue to digital converters have improved ... so compare an 80s CD of 60s Jazz by Stan Getz or Paul Desmond / Dave Brubeck to a good modern transfer made with better ADC's , and hopefully it will sound as good or better than the original recording on vinyl.

A lot of digital remasters were simply not a patch on the originals. The vinyl revival did not just happen because of artwork, or 'tactile' play back. For many people, myself included, I just said ... hold on a minute ... if I just listen to some of these recordings on vinyl the digital version does not compare.

In 2024 however, digital playback is greatly improved.

There are also issues about 'loudness' ... recordings are 'jacked up' or 'peek limited' to such a degree that the vinyl can sound more natural ... ironically because mechanically the loudness can't work on the inner grooves of the record! Look up the saga regarding Michael Jackson's "Bad" ... the producer Quincy Jones successfully sued because the record company added so much peak limiting to his production in later production runs of the record ... 'the loudness wars' ...

For whatever reason though ... I still just prefer listening to the records rather than a digital transfer, even if A/B ing them shows little perceptable (if any) difference with a pretty good ADC I have. It's a whole different way of listening - you listen to the album.

I use a £30 mic from Dayton that has an ADC built into it that's perfectly capable digitalising analogue sound waves as a reference instrument. I think the device in the Ultra is inherently better than the majority of analogue phono preamps. Preserving the sound of an LP is a non issue, anything else is likely placebo.

 

[burkm]

Notwithstanding the ongoing arguments

It's about 14:00 hours now over here (mids of Germany) and both units have reached average surface temperatures of 42°C - 43°C on top (room temperature - nearest wall - reached about 24.3°C).
I measured about 10 places each on top of the V3 mono cabinets (still idle) and it seems, depending on the rising room temperature, that they have stabilized right now at that appr. surface temperatures. The temperatures show a deviation of around 1°C, depending on where I measured. Fans have not been used and both amps have been placed side-by -side horizontally within a distance of appr. 1 inch (2,54 cm). Lateron I will do a "stress" test and measure again with source material playing - endlessly (loop) - at an average loudness of ???. In combination with other user measurements it should give an appr. impression, how the amps behave temperaturewise during "normal" use.

 

[tkst3llar]

I have the opportunity to get some 48V PSUs from work that are plenty big, Meanwell lighting switching power supplies, dimmable power supplies, industrial power supplies etc. Is there something special about the PSUs that Fosi provides or will any reasonable one suffice, even laptop PSUs?