Fosi Audio V3 Amplifier Review

[TurtlePaul]

Thank you for clarifying! I am not very familiar with the terminology. I guess I am a bit confused. Given the speakers are the same, would not more power into them translate to more gain/loudness?

Power is a measure of energy.

Gain is a ratio of increasing voltage.

If you set both amps to the same volume with the same speakers, then they are both sending the same amount of power. Power only matters if you run out of it (which will sound absolutely awful).

THX specifies that most amps have 29 dB of gain. Some manufacturers of receives can run their gain a little "hotter" than than this and can be 30 dB or more at max volume. This Fosi amp had 26 dB of gain. So if this Fosi amp and a receive are both at max volume, this amp is likely to be at least 3 dB quieter. That doesn't mean it is out of power - if you can turn up the input signal you can get more volume out of it.

What are you using as a source?

 

[GXAlan]

Power is a measure of energy.

Gain is a ratio of increasing voltage.

If you set both amps to the same volume with the same speakers, then they are both sending the same amount of power. Power only matters if you run out of it (which will sound absolutely awful).

THX specifies that most amps have 29 dB of gain. Some manufacturers of receives can run their gain a little "hotter" than than this and can be 30 dB or more at max volume. This Fosi amp had 26 dB of gain. So if this Fosi amp and a receive are both at max volume, this amp is likely to be at least 3 dB quieter. That doesn't mean it is out of power - if you can turn up the input signal you can get more volume out of it.

The other analogy is to imagine two amplifiers

Amplifier1 = 50X, up to 1000
Amplifier2 = 100X, up to 800

If your preamp outputs 2, amp1 boosts it to 100 while amp2 boosts it to 200. You actually have to turn down the volume to match the levels.

But when your amplifier outputs 9, the first amplifier hits 450 cleanly, but second unit clips.

If you want it really loud, you can only turn up your preamp to 8 for amp2 to get 800 but you can turn up your preamp to 20 and get to 1000.

But some preamps can only reach a value of 5, etc.

Gain is the multiplier, and maximum power is how much it can put out given sufficient input.

dB Gain Calculator

Determine dB gain by entering initial and final power levels into the dB gain calculator.

www.omnicalculator.com

This is a nice way to look at voltage and dB gain. Remember watts is volts squared divided by resistance.

 

[gasolin75]

 

[gasolin75]

Hi all!

Quick review of V3

First i tried with 48V PSU and amp is clearly overheating!! About 50-60 degrees around whole enclosure. Could be something wrong with PSU (looks like original, but without Fosi inscription)? Then i hooked 32V and temperature dropped almost on ambient temperature around 25 degrees, but sound degraded- much of low listening volume bass was gone, amp lost grip. Boxes are Wharfedale Denton 80, 6 ohm, 86db eff.
So for 100 EUR good amp without sterile class d sound but overheating is clearly issue here. I had similar class d amp Nuforce Icon which is much better sounding and also stone cold in operation.

Almost every amp will overheat if you play loud, for shure more likely to do it with a 48 volt psu then a 32 volt psu

 

[stoyansbg]

Power is a measure of energy.

Gain is a ratio of increasing voltage.

If you set both amps to the same volume with the same speakers, then they are both sending the same amount of power. Power only matters if you run out of it (which will sound absolutely awful).

THX specifies that most amps have 29 dB of gain. Some manufacturers of receives can run their gain a little "hotter" than than this and can be 30 dB or more at max volume. This Fosi amp had 26 dB of gain. So if this Fosi amp and a receive are both at max volume, this amp is likely to be at least 3 dB quieter. That doesn't mean it is out of power - if you can turn up the input signal you can get more volume out of it.

What are you using as a source?

That makes sense. I was testing with a cheap Mii Bluetooth receiver that has no Vrms output specs. My plan was to use an iPhone with a ligtning to 3.5 dongle as a source. It's supposed to put out 1 Vrms with higher than 300 Ohns loads, which I guess any amp input is a lot higher than that. I'll see how this plays out and look for a proper DAC if not satisfied.

Thank you, @GXAlan!

 

[peng]

I just got my V3 with 48V PSU and I like how it sounds very much. It did feel a bit weak though at max volume with a pair of 6 Ohm speakers so I plugged in an old Sony TA-F535R amp, which is rated at 110W/4Ohm and 90W/8Ohm, to the same speakers. Without any measuring equipment, and using the same audio source, the Sony drove the speakers a lot harder. I did not expect this amp to give out 300W but am kind of disappointed it did not match the lower wattage rated amp from last century. Also bummed what causes the apparent difference. According to the review, V3 should be able to put out 100W. Could the Sony be rated less than what it's capable of?

Edit: On a second thought my audio source sound level may be too low and I guess Sony's integrated preamp probably does a better job lifting it up before passing it down to the amp. Could that be it?

As you alluded to in the end, the input level to the V3 amp is important when comparing it with an avr, integrated, or even a power amp. For such an apples to apples comparison, the V3's volume should be set to maximum. Even then, the gains of the amps being compared may not be equal, the ones with higher gain than the V3 will give you the impression that it can drivr your apeakers harder.

 

[wpo7]

I just got my V3 with 48V PSU and I like how it sounds very much. It did feel a bit weak though at max volume with a pair of 6 Ohm speakers so I plugged in an old Sony TA-F535R amp, which is rated at 110W/4Ohm and 90W/8Ohm, to the same speakers. Without any measuring equipment, and using the same audio source, the Sony drove the speakers a lot harder. I did not expect this amp to give out 300W but am kind of disappointed it did not match the lower wattage rated amp from last century. Also bummed what causes the apparent difference. According to the review, V3 should be able to put out 100W. Could the Sony be rated less than what it's capable of?

Edit: On a second thought my audio source sound level may be too low and I guess Sony's integrated preamp probably does a better job lifting it up before passing it down to the amp. Could that be it?

yes I suspect your source level is too low for v3

 

[gasolin75]

I ordered last night with the 48V PSU on the Fosi site. A shame that it ships from China. Lets see if this will take one week or one month. I would have preferred to order on Amazon but didn’t need the price or waste of two power bricks.

with the 48 v psu 103 euros + what ever shipping costs depending on what you choose and vat https://www.audiophonics.fr/en/inte...d-amplifier-tpa3255-2x225w-4-ohm-p-17954.html

 

[gasolin75]

Capacity: 60 watts(PROGRAM), 120 watts(MAX) Nominal Impedance: 8 ohms

They say if the amp too weak tweeters will eventually fail, if too strong it will just easily blow them up at slight accident.

Because Yamaha NS10 Studios can handle 60 watt rms and 120 watt peak doesn't mean you should use,have a 60 watt or 120 watt amp


Wrong, they don't fail, they will just distort or sound agressive (turn the volume down), too much power and you blow them up, IF YOU NEED TO PLAY THAT LOUD YOU NEED SPEAKERS THAT CAN PLAY MUCH LOUDER, pa speakers or klipsch,zu audio or tekton speakers

 

[GGroch]

RE: Fosi 6th Anniversary Video

Cool. It shows the V3 being made.... Careful what you ask for, they are noting everything we say!
Very detailed, it even covers the fake fake TI chip controversy.

 

[gasolin75]

89w at 8 ohm, 140w at 4 ohms.., yeah this thing is a power house

Peaks at 190 is watt in 4 ohm 1% thd but is it 20hz-20khz or 1khz and for how long can it play that loud spoiler alert, not for a long time, certainly not for a party with normal sensitive speakers (2-4 hours)

 

[antcollinet]

Peaks at 190 is watt in 4 ohm 1% thd but is it 20hz-20khz or 1khz and for how long can it play that loud spoiler alert, not for a long time, certainly not for a party with normal sensitive speakers (2-4 hours)

But that is Ok. With real music, as long as it is not clipping then even with peaks at 190W, average power will be 10dB or more below that. So 19dB average or lower.

 

[TurtlePaul]

The Fosi V3 has 26 dB of gain. This is a 20x voltage multiplier. If you feed it 1 V input that means 20 V output. It should be easy to see that even the 32 V power supply is not being pushed to max power in this case.

The industry standard for a 'line level' unbalanced signal from a CD player or DAC is 2 V. If your input had a 2V signal this would be 6 dB louder and be able to drive up to 40 V output to the speakers. Unfortunately, many phone dongles only output 1 V because they are driven off USB's 5 V power.

 

[antcollinet]

If you feed it 1 V input that means 20 V output. It should be easy to see that even the 32 V power supply is not being pushed to max power in this case.A

Actually it probably is. 1V input would be AC 1V RMS which is 1.41 peak. At the output that is 28V peak. The TI chip needs (spec) about 5V of headroom - so for that 28V peak on the output it would need 33V PSU - Though probably the 5V has a bit of headroom in it.

 

[TurtlePaul]

Actually it probably is. 1V input would be AC 1V RMS which is 1.41 peak. At the output that is 28V peak. The TI chip needs (spec) about 5V of headroom - so for that 28V peak on the output it would need 33V PSU - Though probably the 5V has a bit of headroom in it.

You are right. I thought the Apple dongle did 1 V peak-to-peak but it is RMS.

 

[gasolin75]

Thank you. Any other Fosi amp that can do clean 120W per channel at 8 Ohms?

No, if you need that much power for normal sensitive speakers, you need for sensitive speakers or a pa amp

If you need 2x120 watt in 8 ohm and use it, im shure the amp would shut down alot do to heat problems

 

[Juampa1989]

That makes sense. I was testing with a cheap Mii Bluetooth receiver that has no Vrms output specs. My plan was to use an iPhone with a ligtning to 3.5 dongle as a source. It's supposed to put out 1 Vrms with higher than 300 Ohns loads, which I guess any amp input is a lot higher than that. I'll see how this plays out and look for a proper DAC if not satisfied.

Thank you, @GXAlan!

Don't forget to look for a maximum of 2 vrms to avoid cuts. I have it with the fiio taishan d03k that gives 1.5 vrms. I bought and the smsl c100 quw gives 2 vrms which is the maximum of the fosi to use the entire volume of the fosi. I tested it with a fiio bta30 which is 3 vrms and trimmed with half a knob. It worked horrible, if I turned down the DAC, which can be adjusted with a knob, the audio was not of good quality. That's why I use the fiio taishan while the c100 arrives

 

[Juampa1989]

Hello, I take this opportunity to inform you that the c100 is discounted in case anyone is interested.
I just found this incredible item on AliExpress. Check it out! 50% DISCOUNT | SMSL C100 USB MQA DAC AK4493S XMOS

https://a.aliexpress.com/_mrefqXC

It is a dac that I consider to be a good companion for the fosi v3 given its specifications. The su1 was reviewed by amirm and it measured very well.
This one is quite similar to that one, the difference is that it has a remote control

 

[gasolin75]

Hello, I take this opportunity to inform you that the c100 is discounted in case anyone is interested.
I just found this incredible item on AliExpress. Check it out! 50% DISCOUNT | SMSL C100 USB MQA DAC AK4493S XMOS

https://a.aliexpress.com/_mrefqXC

It is a dac that I consider to be a good companion for the fosi v3 given its specifications. The su1 was reviewed by amirm and it measured very well.
This one is quite similar to that one, the difference is that it has a remote control

Not close to 50% off. Audiophonics just about the same price + what ever delivery you choose 2-3 days is fastest delivery for a european country

 

[Juampa1989]

Maybe it depends on the country or area