Fosi Audio V3 Mono Amplifier Review

[cprogrammer]

One of my Fosi v3 Mono suddenly started making some sizzling sound inside like how you fry eggs on a pan. Wispy white smoke started coming from the right vent. I was not playing anything. I had just switched it on and was making a playlist to be played. Jumped and quickly turned off the power. Waited for few minutes, disconnected my speaker and connected a cheap speaker to the output and switched it back on. The unit turns on. I also hear the sound of relay or relays clicking. But no sound when I play something. Have written to Fosi support. Let me see how fast they respond. The amp is just around 5 months old. Should I open the unit and see what is burnt inside? I have to open 2 screws at the bottom and two screws at the back right?

 

[Doodski]

One of my Fosi v3 Mono suddenly started making some sizzling sound inside like how you fry eggs on a pan. Wispy white smoke started coming from the right vent. I was not playing anything. I had just switched it on and was making a playlist to be played. Jumped and quickly turned off the power. Waited for few minutes, disconnected my speaker and connected a cheap speaker to the output and switched it back on. The unit turns on. I also hear the sound of relay or relays clicking. But no sound when I play something. Have written to Fosi support. Let me see how fast they respond. The amp is just around 5 months old. Should I open the unit and see what is burnt inside? I have to open 2 screws at the bottom and two screws at the back right?

If you feel like opening it take some pics for us.

 

[Bleib]

One of my Fosi v3 Mono suddenly started making some sizzling sound inside like how you fry eggs on a pan. Wispy white smoke started coming from the right vent. I was not playing anything. I had just switched it on and was making a playlist to be played. Jumped and quickly turned off the power. Waited for few minutes, disconnected my speaker and connected a cheap speaker to the output and switched it back on. The unit turns on. I also hear the sound of relay or relays clicking. But no sound when I play something. Have written to Fosi support. Let me see how fast they respond. The amp is just around 5 months old. Should I open the unit and see what is burnt inside? I have to open 2 screws at the bottom and two screws at the back right?

The screws on the backside are enough

 

[cprogrammer]

If you feel like opening it take some pics for us.

Here are the images
One of the capacitor looks strange. Is that Cap just next to some 3 legged chip OK? It is just in front of the 2200 uF capacitor. Also the smell is strongest in that region.

Here are other images

Image of the backside. Doesn't look anything burnt here

 

[cprogrammer]

I figured out what got burnt. I had to use a magnifying glass and see it outside in sunlight to see the burnt material. There is a regulator LM 2576H and a diode SS310. The diode is burnt and the legs around LM2576 has burn marks on the PCB around the 1st and 2nd legs. Most probably the diode got burnt and material got sprayed around. Fosi support is going to send me a new board. SS310 is a Schottky Diode with 3A current rating. What would cause this to burn?

EDIT added a photo. You have to enlarge to see the diode. It is at the bottom on the PCB just in front of the 4 pin LM2576H regulator

 

[Jimster480]

Just ordered 2 of these to test out with Klipsch RP-8060's

 

[telemike]

Can’t believe how good these little amps are. I can’t quantify or measure it, but I feel there’s more punch with these. So funny, these little boxes are powering my huge Klipsch Forte 4s

 

[Old_School_Brad]

Can’t believe how good these little amps are. I can’t quantify or measure it, but I feel there’s more punch with these. So funny, these little boxes are powering my huge Klipsch Forte 4s

Nothing incredible about it.

• Sensitivity: 99dB/2.83V/m. (more like 95)

However, you may notice some audible colorations due to the Forte IV’s complex load characteristics and the Fosi V3’s sensitivity to load variations. This makes it plausible that you could perceive a difference with the Fosi compared to your previous amplifier.

 

[Blew]

Nothing incredible about it.

• Sensitivity: 99dB/2.83V/m. (more like 95)

However, you may notice some audible colorations due to the Forte IV’s complex load characteristics and the Fosi V3’s sensitivity to load variations. This makes it plausible that you could perceive a difference with the Fosi compared to your previous amplifier.

Are you confusing the V3 with the V3 Mono? The V3 Mono has hardly any sensitivity to load variations.

 

[Jimster480]

Are you confusing the V3 with the V3 Mono? The V3 Mono has hardly any sensitivity to load variations.
View attachment 439070

I certainly didn't detect any in my use of them over this past week.

 

[hoovey]

Nothing incredible about it.

• Sensitivity: 99dB/2.83V/m. (more like 95)

However, you may notice some audible colorations due to the Forte IV’s complex load characteristics and the Fosi V3’s sensitivity to load variations. This makes it plausible that you could perceive a difference with the Fosi compared to your previous amplifier.

I can safely say that the V3 Monos sound far better than my AVR-1312 did. I used to prefer class AB to class D (for car audio mostly, just preference) but this is my first experience with modern class D amps and they're great.

I'll take some measurements once a couple pieces of equipment I ordered get here.

 

[Old_School_Brad]

I can safely say that the V3 Monos sound far better than my AVR-1312 did. I used to prefer class AB to class D (for car audio mostly, just preference) but this is my first experience with modern class D amps and they're great.

I'll take some measurements once a couple pieces of equipment I ordered get here.

Your comment is unrelated to the comment of mine that you quoted.

In any case.
Not all Class D amplifiers are great -just as not all Class A/B amplifiers are. Take the Denon AVR-1312, for example -a budget AVR that claims to deliver 75W of low-distortion power. However, the specifications are not very detailed, and the actual numbers could be worse off.

That said, there is no technical reason why it should sound better or worse than your V3 Monos. The only way to determine this objectively is through an A/B blind test. You've already noted a perceived difference, but this is likely due to bias-influenced perception. To counteract this, you need to eliminate visual cues -your eyes, in particular, can play a big role in shaping expectations.

If you proceed with testing, ensure volume matching by using a digital multimeter (DMM) on the outputs with a test signal. If one component is even slightly louder, you’ll likely prefer that one.

 

[kleankord]

LONG time lurker. I'm running the 2 mono blocks using the 48v10a with splitter. Is there perceivable benefit to splitting these out to their own 48v 5a blocks? Will it result in more power to each speaker? TIA

 

[Audionaut]

Is there perceivable benefit to splitting these out to their own 48v 5a blocks? Will it result in more power to each speaker? TIA

If you are happy with the splitter and it is the version without noise, you can leave everything as it is.
Two power supply units with 48V and 5 amps have the same output as one with 10 amps.
In this case, two power supply units will not increase performance.

 

[Jimster480]

LONG time lurker. I'm running the 2 mono blocks using the 48v10a with splitter. Is there perceivable benefit to splitting these out to their own 48v 5a blocks? Will it result in more power to each speaker? TIA

There is no sonic improvement as the power output is the same.

 

[Jeff29]

What about using 1 x 48 v 10 block per V3 mono amp ?

Will it increase or double the power output ?

 

[Brian Hall]

What about using 1 x 48 v 10 block per V3 mono amp ?

Will it increase or double the power output ?

Try it and report back.

 

[Bleib]

What about using 1 x 48 v 10 block per V3 mono amp ?

Will it increase or double the power output ?

Likely only warmer units

 

[Jimster480]

What about using 1 x 48 v 10 block per V3 mono amp ?

Will it increase or double the power output ?

Duno what you would need double the power for... These things are crazy loud even with big floor standing speakers... On my DAC I only reach 65% volume and my house is very loud to say the least.
They are driving Klipsch RP-8000F Gen II... 20-25 Is a normal listening volume....

 

[Old_School_Brad]

Duno what you would need double the power for... These things are crazy loud even wit but floor standing speakers... On my DAC I only reach 65% volume and my house is very loud to say the least.
They are driving Klipsch RP-8000F Gen II... 20-25 Is a normal listening volume....

There are many variables that influence how much amplifier power someone might truly need -often more than people initially expect.

Factors like;
listening distance,
typical volume levels,
and whether a person listens to bass-heavy music all play significant roles.
On top of that, using room correction, EQ, or DSP can drastically increase power demands.

Another key aspect is speaker sensitivity, and not just the rated spec -real-world sensitivity across the full frequency range can vary a lot.

So ultimately, without knowing these specifics, it’s not really possible to make definitive statements about how much power someone else needs. Context is everything.