Fosi Audio V3 Mono Amplifier Review

[Negatywny]

i really hope they don't cause i paid for completed product not for do it yourself kit, or even apply your thermal paste onto your power amplifier kit without thermal paste in it.

 

[fredreadrick]

Did you get an email upon Fosi sending your package, or did it just arrive without further notice? I am curious since I have two Monos on the way from the original Kickstarter, but have heard nothing since confirming my shipping address and reward.

Got notification email on shipping details on June 17, was tracking it online at given link.

 

[fredreadrick]

Those are the 10a power supplies? I see 4 amps and 2 supplies

Ordered with 5a psu...

 

[fredreadrick]

I suspect that the shipments are being organized by the options that were chosen. I work for a HW company and if we had to ship thousands of shipments containing a dozen different combinations, we would organize them in those combination groups to make it more efficient.

It will be interesting to see what the earlier shipments were comprised of. I'm backer ~#157 and haven't received any shipment notification, but I'm getting two amps, the 10A power supply and op amps. Not sure if I have seen where anyone else with that combination was notified.

In any event, they probably should provide an update, but I trust Fosi as a company until given a reason not to trust them. I'm looking forward to getting my amps but have plenty of other summer chores to keep me busy

Backer #530 here - 4monos with 2- 5a PSUs

 

[Megaken]

But is it getting hot when you use it?

 

[fredreadrick]

But is it getting hot when you use it?

By feel, it's hotter than ZA3....

 

[Bleib]

Let in some air underneath?

 

[fredreadrick]

Let in some air underneath?

Yes. I put a 20mm rubber feet. It helps, still warm to the touch but tolerable.

Am from Philippines, not air-conditioned room, room temp is +-30°C..,

 

[jvdburgt]

Soooo, if they’re getting hot then the heatsink seems to be doing it’s job, right?

 

[Bleib]

Yes. I put a 20mm rubber feet. It helps, still warm to the touch but tolerable.

Am from Philippines, not air-conditioned room, room temp is +-30°C..,View attachment 377225

Ah ok, obviously room temperature plays a role as well. If I had bought these I might have modded it with heatsinks on top.

 

[fredreadrick]

Soooo, if they’re getting hot then the heatsink seems to be doing it’s job, right?

Yes even without thermal paste.

 

[jvdburgt]

Btw, I just came across this picture from a review that seems to show thermal paste on this test version.

Raises the quesiton if Fosi decided the V3 Mono can do without, or if the absense of thermal paste on your specimen is a mistake ...

 

[jvdburgt]

And, with a closer look, two other differences between the test model and the production version (see red circles). I'm not an electrician, so I have no clue how to interpret this, but undoubtedly some other people here will have educated guesses about this

 

[GGroch]

Btw, I just came across this picture from a review that seems to show thermal paste on this test version.

I believe it shows paste between the plate and the circuit board. The paste in question is between the plate and the chassis.

 

[EddNog]

I believe it shows paste between the plate and the circuit board. The paste in question is between the plate and the chassis.

No, it’s the same. What has changed is that the heat sink in the test sample was anodized black. The production heatsink is silver/bare metal.

-Ed

 

[GGroch]

No, it’s the same. What has changed is that the heat sink in the test sample was anodized black..

Thanks, my mistake. Fosi posted a YouTube video earlier on V3 Mono heat dissipation. I am not worried with or without goop.

 

[MCH]

And, with a closer look, two other differences between the test model and the production version (see red circles). I'm not an electrician, so I have no clue how to interpret this, but undoubtedly some other people here will have educated guesses about this View attachment 377260

I believe, but can't confirm, those are the capacitor/resistor of the zobel network. Seems they changed from SMD to those bigger throw holes.
I think I remember reading, and would love others to confirm, that as a result of the PFFB implementation those resistors could get pretty hot (I am not talking about this amplifier specifically but TPA32xx in general) so could be Fosi saw a higher wattage resistor was needed. It will be a good thing.
I believe for instance 3E audio just uses 3 SMD resistors in parallel, probably to achieve the same. Would like to see how aiyima handles this (probably they don't).

 

[EddNog]

i really hope they don't cause i paid for completed product not for do it yourself kit, or even apply your thermal paste onto your power amplifier kit without thermal paste in it.

Just guessing won’t get any of us anywhere anyway.

Unfortunately, simply feeling or even scanning the temperature of the enclosure doesn’t tell us the complete story. If the heatsink isn’t well-coupled to the chip and/or the enclosure isn’t well-coupled to the heatsink then thermal transfer is inefficient and as a result the amplification chip/circuit may be very, very hot despite the enclosure being fairly cool on the outside. Arguably, you would want the enclosure to show lots of heat because that means it is doing the job of taking heat from the chip/circuit and dissipating it to the surrounding air.

The best solution is either some sort of diagnostic readout from the chip itself (probably not an option in this scenario) or to find an extremely fine thermal sensor/thermistor and place it as close as possible to the amplification chip/circuit core without affecting mechanical contact to the heatsink and/or enclosure to get a proper, accurate gauge of operating temperature of the amplification chip/circuit.

On the bright side, Texas Instruments’ specifications indicate this chip is rated for thermal operating range up to a massive 150° Celsius!

-Ed

 

[PJ_Schmidt]

And, with a closer look, two other differences between the test model and the production version (see red circles). I'm not an electrician, so I have no clue how to interpret this, but undoubtedly some other people here will have educated guesses about this View attachment 377260

Those two large resistors are designed to protect from current inrush when applying power. It appears they previously used SMD resistors which (to my eye) are obviously undersized given the bulk capacitance used in this design.

 

[MCH]

Those two large resistors are designed to protect from current inrush when applying power. It appears they previously used SMD resistors which (to my eye) are obviously undersized given the bulk capacitance used in this design.

the thermistor you are referring to is this: