Fosi Audio V3 Mono Amplifier Review

[antcollinet]

Where did you get the input sensitivity value from?

From the 20dB gain, and calculating the volts you need for 120W output at 8ohm. (120W being the power you get at 1%THD)

 

[edgar-bcn]

From the 20dB gain, and calculating the volts you need for 120W output at 8ohm. (120W being the power you get at 1%THD)

Ok, I see, you're considering 20dB instead of the max. 31db gain value (RCA input) because the input source is around 10-12dB less, I'm right?

 

[somebodyelse]

I would. Once I've made a digital copy of my LPs and CDs on a small PC using SSD storage it is essential to keep it on charge, otherwise you can lose electrons and the music is lost - 5 watts is nothing to leave on 24/7.

Either you've misunderstood what someone told you, or they were teasing you, or they didn't know what they were talking about. The flash storage in SSDs doesn't need power to keep data for months, often years. It's similar to that in a USB drive or microSD card. The bit that needs power to retain data is RAM, but it's extremely unlikely any of your files are stored there, other than as a temporary copy.

https://www.anandtech.com/show/9248/the-truth-about-ssd-data-retention has more details, prompted by a fuss in media and forums some years back. A consumer SSD kept at 30 C has to retain data for at least a year without power. At lower temperatures it will last longer.

 

[antcollinet]

Ok, I see, you're considering 20dB instead of the max. 31db gain value (RCA input) because the input source is around 10-12dB less, I'm right?

Because the person I was replying to was using XLR. Which is 20dB

On the RCA input/31dB (x35.5) gain, then you have an input sensitivity of 0.87V (8 ohm for 120W)
On the 25dB setting (x18) then input sensitivity is 1.7V

 

[BrooklynNick]

I would. Once I've made a digital copy of my LPs and CDs on a small PC using SSD storage it is essential to keep it on charge, otherwise you can lose electrons and the music is lost - 5 watts is nothing to leave on 24/7.

Even if that were true (it is not), what does leaving your amplifier on 24/7 have to do with the SSD in your computer? (Answer: Nothing at all.)

Edit: BTW, You may be recalling from a really long time ago. In the very early days of solid state storage, this was true.

 

[edgar-bcn]

Because the person I was replying to was using XLR. Which is 20dB

On the RCA input/31dB (x35.5) gain, then you have an input sensitivity of 0.87V (8 ohm for 120W)
On the 25dB setting (x18) then input sensitivity is 1.7V

I was trying to figure out why I have the same "problem" as others with Fosi and my DAC (miniDSP Flex HT) which delivers up to 2 Vrms using RCA.

With my old Marantz SR6009 (110W/8 Ohm) I have no problems driving my B&W 685 S2 (87dB/8 Ohm), but with the miniDSP and the Fosi the lack of power is clearly noticeable.

 

[Kayshot]

Even if that were true (it is not), what does leaving your amplifier on 24/7 have to do with the SSD in your computer? (Answer: Nothing at all.)

Edit: BTW, You may be recalling from a really long time ago. In the very early days of solid state storage, this was true.

I think the point he is making is that leaving his SSD running used around 5 watts, and he left it on 24/7.

He felt that the ~5 watts from that was negligible, so feels the same about the amp using that amount of power 24/7.

 

[Nuigurumi]

You would make a big favor to the friends here if you opened it and take some pictures up close at both sides.

Nothing looks out of the ordinary.

 

[Sokel]

Nothing looks out of the ordinary.

View attachment 380044View attachment 380045View attachment 380046

Did you try swapping PSU?
(if you use the 2 5A ones)

It could be that too.

 

[Nuigurumi]

Did you try swapping PSU?
(if you use the 2 5A ones)

It could be that too.

Yes.
It still turns on and 'clicks'.
Just no sound output.

 

[Zek]

With my old Marantz SR6009 (110W/8 Ohm) I have no problems driving my B&W 685 S2 (87dB/8 Ohm)

Because Marantz has ten times lower input sensitivity compared to Fosi.

 

[Talisman]

I was trying to figure out why I have the same "problem" as others with Fosi and my DAC (miniDSP Flex HT) which delivers up to 2 Vrms using RCA.

With my old Marantz SR6009 (110W/8 Ohm) I have no problems driving my B&W 685 S2 (87dB/8 Ohm), but with the miniDSP and the Fosi the lack of power is clearly noticeable.

Once again, please try to read and understand the comments of those who help you, there is no lack of power.

 

[edgar-bcn]

Because Marantz has ten times lower input sensitivity compared to Fosi.

View attachment 380048

Uhmm, but this only applies when I use the Marantz solely as an amplifier (which I tried connecting the miniDSP to its 7.1 CH IN inputs), but when I used only the AV receiver?

Do you mean I need a more powerful amplifier because of the higher input sensitivity?

 

[edgar-bcn]

Once again, please try to read and understand the comments of those who help you, there is no lack of power.

Sorry for bothering! I'm struggling trying to understand why I haven't gotten the results I was looking for.

 

[Keauval]

Are you trying to replace a Sansui AU-9500 with the Fosi's? How much do you want for it?

I Can make you an offer of 230$ for the 2 V3 Mono with 48V 5A PSUs

 

[Keauval]

I like the schiit kara with 12db extra gain in xlr mode

But if the Fosi V3 Mono Can reach 2x120W with 5V inside, why shoule I put 100V inside ?

 

[Talisman]

Sorry for bothering! I'm struggling trying to understand why I haven't gotten the results I was looking for.

In the previous pages you will find excellent explanations of @antcollinet , you cannot expect him to explain everything again every time a new user makes this observation.
There is no power problem, it is just a question of the gain of the amplifier which needs a higher voltage input signal to reach its maximum power.
Turn that volume knob, the trend of listening volume at 9 o'clock is over

 

[SMen]

Turn that volume knob, the trend of listening volume at 9 o'clock is over

This is a good thing and good advice and I hope so...

Sorry for bothering! I'm struggling trying to understand why I haven't gotten the results I was looking for.

Too often manufacturers would try and give the impression of "power" by having "loud" at 9 o'clock. And I still read people equating power with where they get to on the volume dial... It also becomes much harder to make subtle changes to volume when it max's out so early in the dial rotation.

 

[antcollinet]

Uhmm, but this only applies when I use the Marantz solely as an amplifier (which I tried connecting the miniDSP to its 7.1 CH IN inputs), but when I used only the AV receiver?

Do you mean I need a more powerful amplifier because of the higher input sensitivity?

Your Maranz only needs 0.2V input for full power.

The FOSI needs nearly 2V (in 25dB gain) or nearly 1V in 31dB gain.

Your Mini DSP can output 2V (I assume you have the RCA Version) so you just need to turn the volume up. Near full volume on the DSP will take you to near full power

IF your program material (the music) is close to full level.

You might be more comfortable with the higher gain (31dB) setting on the amp.

 

[mike70]

People try to justify their preconceived concepts ... thinking over scientific and right arguments is much more harder. The brain is programmed to maintain us alive and happy.. and that includes not changing the status quo.

Then you see that "but, did you read what was posted?" moments.