Fosi Audio V3 Mono Amplifier Review

[antcollinet]

Excactly. It is the TA3255 chips "internal" temperature I like to lower and this needs a medium called "thermal paste" That's all there is to it.
It helps to "cool" the inerts of that amp with the help of thermal paste and the heat sink (casing)...
That's, what every manufacturer is after, in't ist ?

Good - but the point I was making is that a high case temperature is not an indication that themal paste is not applied or insufficiently applied. That seems to be a mistake a lot of people are making.

"Wow - this amp feels hot - I'd better take it apart and apply more paste"

 

[renoxd]

I received the 2 units a couple of weeks ago and the mains filter somewhat later. The top covers reach a temperature of about 40 degrees C even if there is no music playing.

Mine reach over 45C when turned ON, without speakers connected. 38 in standby mode. I have asked few questions to Fosi Team and waiting for clarification. If the answers wont be satisfying, I will send them back

 

[Killingbeans]

2. The listener was used to something that wasn’t as even in its response.

I'm again reminded of how my grandmother used to switch off her hearing aids most of the time because of how being deaf had become the new normal. When she could actually hear the sounds from her surroundings, she descibed it as "infernal noise"

 

[totti1965]

YouTube Video from Christian Schwarzbeck in German Language to discuss the polarity problem:

 

[DavidM1]

Mine reach over 45C when turned ON, without speakers connected. 38 in standby mode. I have asked few questions to Fosi Team and waiting for clarification. If the answers wont be satisfying, I will send them back

Others might be able to clarify but I always thought that having an amp on without speakers connected risks damage.

 

[Doodski]

I always thought that having an amp on without speakers connected risks damage.

No damage can happen. It's safe to do. Just remember to shut the unit down upon reconnecting the speakers.

 

[Young Moon]

V3 모노를 분해하고 방열판 전체에 열전도 페이스트를 다시 도포했습니다.

이전에는 방열이 중앙에서만 원형으로 적용되었습니다.

지금은 뜨겁지 않고, 그냥 따뜻할 뿐입니다.

 

[Doodski]

V3 모노를 분해하고 방열판 전체에 열전도 페이스트를 다시 도포했습니다.

이전에는 방열이 중앙에서만 원형으로 적용되었습니다.

지금은 뜨겁지 않고, 그냥 따뜻할 뿐입니다.

Good to hear the temperature is down.

 

[NTK]

Good to hear the temperature is down.

If it is the chassis temperature that goes down, and assuming that the amp chip is generating the same amount of heat, a cooler chassis means that the heat conduction from the amp chip to the chassis is reduced.

 

[Doodski]

If it is the chassis temperature that goes down, and assuming that the amp chip is generating the same amount of heat, a cooler chassis means that the heat conduction from the amp chip to the chassis is reduced.

True or it might be spread over a larger surface area of the sheet metal?

 

[NTK]

If we consider the average temperature of the chassis, a higher average chassis temperature will mean that more heat will be dissipated by the chassis to the environment. Since that heat has to come from the amp, a higher average chassis temperature means that there is more heat conduction from the amp to the chassis.

 

[Jukka]

WoW! Can you give examples so I can see the stuff they are offering with 10% distortion?

Fosi Audio V3

Using a minimalist design language, focusing more on enhancing the sound quality and performance of the product, making it the best-sounding power amplifier of Fosi Audio to date.

fosiaudio.com

 

[antcollinet]

If it is the chassis temperature that goes down, and assuming that the amp chip is generating the same amount of heat, a cooler chassis means that the heat conduction from the amp chip to the chassis is reduced.

This is my expectation also - and must consequently mean the power not going to the chassis is now causing other components in the design to get hotter - starting with the chip, then conducting to the PCB and then to the internal air.

which goes alongside my view that people messing about with thermal paste are just as likely to make things worse, as better. It is not simply a case of slapping it on and hoping for the best. The paste needs to be as thin as the design allows, with the pressure as high as the design allows.

High pressure doesn't just mean tightening the screws until the veins pop in the hapless modders forehead - this is likely to cause mechanical damage. It is about tightening the screws to the designed torque - which none of us know.

In a former life one of our most expensive design/manufacturing failures was incorrect application of thermal paste. And we got it wrong more than once.

True or it might be spread over a larger surface area of the sheet metal?

But that would only be the case where contact is made with the case - which might reduce a local hotspot there (I think on the underside where the chip makes contact - but this is not what people are touching). After that, a larger surface area of contact will result in better heat transfer to the case which will make it warmer.

 

[antcollinet]

Others might be able to clarify but I always thought that having an amp on without speakers connected risks damage.

That's another myth harking back to the days of tube amps - which could be damaged by running without load.

 

[MCH]

Others might be able to clarify but I always thought that having an amp on without speakers connected risks damage.

Actually, this has been discussed in TI audio forum.

IIRC (I can’t find the exact link), TI claimed it was safe to run their TPA3255 eval board without load, but also recommended to use, if in doubt, catch diodes to VDD and ground to avoid any potential issues. I noticed the Fosi V3 mono and the latest 3E boards have said diodes, so I would said it should be safe.

This other link to TI audio forum explains what the diodes do:
“In order to run a class-D amp open load, you will need to place some diodes from the outputs to power and ground to keep the voltage generated by the LC filter resonance from causing an over-voltage event on the output pins. These diodes are only needed if you plan to run the filter un-loaded.”

https://e2e.ti.com/support/audio-group/audio/f/audio-forum/368873/tas5630b-working-without-heatsink-and-load/1297169?tisearch=e2e-sitesearch&keymatch=unloaded%25252525252520catch%25252525252520diodes#1297169

 

[DavidM1]

That's another myth harking back to the days of tube amps - which could be damaged by running without load.

Thanks. I’m a guitarist who owns a tube amp so that would probably be why I’ve heard it.

 

[burkm]

Good - but the point I was making is that a high case temperature is not an indication that themal paste is not applied or insufficiently applied. That seems to be a mistake a lot of people are making.

"Wow - this amp feels hot - I'd better take it apart and apply more paste"

I am not inclined to judge, if high temperatures are common for this amp or not. I'm just looking, if any thermal paste has been applied to the chip's heatsink as is quite normal. That's it... => quite simple.
The other thing is, that due to that "split time" delivery a few days ago (difference now about > one week) and the situation, that I have to open the case anyway because of this, I would like to know, if any of those amps have been worked on, considering the stated "polarity" issue and the news released by Fosi Audio...
Depending on the outcome I might have to take some actions myself.

I'm just wondering, why this is named a "modification"...
For me it's just a "clarification" of what has actually been delivered...

 

[Doodski]

I'm just wondering, why this is named "modification"...

Anytime a stock piece of gear is modified by adding thermal paste, rolling OP amps etc it is referred to as a MOD and the action of it is called MODing.

 

[burkm]

I think of this rather as "omission during assembly", not a modification

 

[Lux_ury]

Weird if the monos were to be realised in winter would the threads of heat be less?
Weird it was around July they released the first batch correct? (Rub chin emoji)