Fosi Audio V3 Mono Amplifier Review

[Killingbeans]

Astley or Rubin?

 

[MCH]

I certainly don't have a vast knowledge of heat conduction, but I don't think that a room temperature difference between 22- 26C translate into same figure for the device when working at much higher temperature than ambient.

within such small ranges, it certainly does, roughly.

 

[Lux_ury]

Ok after 4 hours of non stop playing I recorded a temperature of 41C when I first powered it up.
The second picture is the maximum temperature of 35.5C
Ambient 22.C-22.5C
lower temp of 5.5C after the passive radiator and thermal pad costing me U$6.00 dollars per 1C drop (Laugh emoji)

 

[antcollinet]

I certainly don't have a vast knowledge of heat conduction, but I don't think that a room temperature difference between 22- 26C translate into same figure for the device when working at much higher temperature than ambient.

It certainly does.

When you dump power into the enclosure of any device, that power (in the form of heat), must dissipate to the environment (room temperature air). It does this through the thermal resistance of the device to air interface.

This is the same for heatsinks, (or any device trying to get heat out of it into the air) Their key -performance specification is thermal resistance to air rated as degrees C per watt. That means the heatsink temperature is (Thermal resistance) X (power) above the heatsink ambient air temperature. This means that as the ambient temperature rises, so does the surface temperature of the heatsink/device - by the same amount - assuming power is constant.

 

[kelesh]

Whoah! I’m guessing this post is from someone who heats and cools their house a lot. 26C is not at all uncommon in most of Australia nor in Shenzhen where Fosi is based. I still don’t understand the fuss about amplifiers being quite warm to touch. It is to be expected, especially because the case is the heat sink.

"The American Heritage Dictionary of the English Language identifies room temperature as around 20–22 °C (68–72 °F),[1] while the Oxford English Dictionary states that it is "conventionally taken as about 20 °C (68 °F)".[2]"

That's a general consensus, from Wiki. I generally aim for 72-74 °F but, like I said, preferences vary. The point is that, these variations can and do affect the equipment temperature, and vice versa. If I turn on a just a few computers, my room temperature can rise by a few degrees. Class A amps, well, they are like heaters! So I don't think there is anything wrong with the OP's amps, it's all just physics (heat transfer).

 

[gwing]

"The American Heritage Dictionary of the English Language identifies room temperature as around 20–22 °C (68–72 °F),[1] while the Oxford English Dictionary states that it is "conventionally taken as about 20 °C (68 °F)".[2]"

That's a general consensus, from Wiki. I generally aim for 72-74 °F but, like I said, preferences vary. The point is that, these variations can and do affect the equipment temperature, and vice versa. If I turn on a just a few computers, my room temperature can rise by a few degrees. Class A amps, well, they are like heaters! So I don't think there is anything wrong with the OP's amps, it's all just physics (heat transfer).

The issue isn't really how much the amps heat up the room, that might an issue when playing my big class A valve amps in the summer but for any normal amp and in particular these little class D amps you can effectively ignore any contribution they make to room heating. Neither does the heat the case itself reaches matter unless it is dangerously hot to the touch.

The real heat issue is instead how hot the components inside the case get and how much that shortens their life. They are going to be mostly running at a higher temperature than the case itself and so need to be specified accordingly, or to have more effective cooling provided for them

 

[kelesh]

The real heat issue is instead how hot the components inside the case get and how much that shortens their life. They are going to be mostly running at a higher temperature than the case itself and so need to be specified accordingly, or to have more effective cooling provided for them

Longevity is always a valid point, hopefully Fosi have done their homework on this. More effective cooling would mean either a bigger heatsink/case for passive or forced air (fan) for active; and it is specifically the lack of these that's part of the appeal of these little amps IMO, so let's hope they last as they are. Owners are, of course, free to modify at will if they feel something needs to be added or changed. That said, I think I may have some peltiers lying around from the PC overclocking days ...

 

[A.wayne]

Its a Hot deal , The price sounds about right ....

 

[Nopiano]

Ok after 4 hours of non stop playing I recorded a temperature of 41C when I first powered it up.
The second picture is the maximum temperature of 35.5C
Ambient 22.C-22.5C
lower temp of 5.5C after the passive radiator and thermal pad costing me U$6.00 dollars per 1C drop (Laugh emoji)

Very similar findings here. Our room is usually between 20 and 22C ambient and I’ve checked the amps each day since last weekend when I first started using them. My highest reading is 39.1C.

I’m using a medical thermometer that has an object setting too. You can see a little kettle symbol in the window.

As much space as I can give the Monos, they are on an old Quadraspire bamboo turntable platform, and that’s sitting on my Pass Labs XA25 protected from inadvertent scratches by a rectangle of leather-cloth.

 

[kelesh]

Amazon is going to have a replacement for the bad one here Monday as well as having UPS pick up my return item the same day. Good customer service.

By any chance, have you checked if the Amazon units currently shipping in the US are "phase corrected" or "original" ? Just curious.

 

[Brian Hall]

By any chance, have you checked if the Amazon units currently shipping in the US are "phase corrected" or "original" ? Just curious.

I didn't check. Just hooked them up and they sounded good.

 

[badie]

Ok after 4 hours of non stop playing I recorded a temperature of 41C when I first powered it up.
The second picture is the maximum temperature of 35.5C
Ambient 22.C-22.5C
lower temp of 5.5C after the passive radiator and thermal pad costing me U$6.00 dollars per 1C drop (Laugh emoji)

Have you thought about putting your temp probes inside the casing, e.g. on the board directly over the chip?
(i only have an infrared temp hand gun)

 

[Lux_ury]

Very similar findings here. Our room is usually between 20 and 22C ambient and I’ve checked the amps each day since last weekend when I first started using them. My highest reading is 39.1C.

I’m using a medical thermometer that has an object setting too. You can see a little kettle symbol in the window.

As much space as I can give the Monos, they are on an old Quadraspire bamboo turntable platform, and that’s sitting on my Pass Labs XA25 protected from inadvertent scratches by a rectangle of leather-cloth.

View attachment 388225

View attachment 388226

I did notice that the Oak underneath the amps got hot as wood is not conductive. I raised the airflow with some aluminium speaker isolator feet.
Yours looks great I was going to use bamboo raisers at one stage for the looks.

 

[Lux_ury]

Have you thought about putting your temp probes inside the casing, e.g. on the board directly over the chip?
(i only have an infrared temp hand gun)

Hi badie the probs are metal ends and conductive. Probably would short out something?
My logic has been opening the case and disturbing the TIM paste would be fruitless unless I absolutely needed to as any thermal paste needs to settle with heat and use.
Just like a PC Die.
It's important people understand the heat does not disappear all you are doing is moving it away from the place its generating from.
Hand held probs are useful, still shocked at the cost of new Flukes these days (Roll eyes emoji) May be we start taking temperatures directly underneath? (rub chin emoji )

 

[Nopiano]

I did notice that the Oak underneath the amps got hot as wood is not conductive. I raised the airflow with some aluminium speaker isolator feet.
Yours looks great I was going to use bamboo raisers at one stage for the looks.

Yes, I realise no conduction with the wood, but I think if I want to achieve more air flow I have all sorts of sundry feet, spacers, cones etc., accumulated over the years which could raise them a little. The bamboo cutout may help a little, and it adds to the visuals!

Prompted by your reply, I had a look in the spares (!) and found a set of 16mm diameter metal disks to protect flooring from speaker spikes that would be ideal. They go by various names like Skeets, or in my case Precision Geek speaker pads!

I agree the wood definitely enhances the look, something I hadn’t anticipated. Here it is from behind.

 

[badie]

May be we start taking temperatures directly underneath? (rub chin emoji )

Yeah - this sounds a better place for your probes then.
-------

I raised the airflow with some aluminium speaker isolator feet.

I did measure top, front, bottom (without taking any notes)
All readings made with a infrared hand gun thermometer type.
Same finding here: Raising the units just one cm resulted in up to -2°C on the underside/under the chip.
(Left them running side by side, one raised, one flat on the wood)
Now they are standing on 30yrs-old aluminium cones (my first speakers feet), which are a whopping 2,5cm high
--------

It's important people understand the heat does not disappear all you are doing is moving it away from the place its generating from.

+1 - the faster we take the heat away, the cooler the chip
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Max recorded temps here >41°C
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With my speakers 90db sensibility I am not drawing more than the idle 10W per unit (1x48V 10A PSU+Filter)

will write more on this ...

 

[Sokel]

Are we seriously talking about 5° ambient room differences here?
Seriously?

Amps suppose to work at all sane conditions,even in a cold or hot room.
Here's an example of one of the monos driving my lows (1200as) :

Had a look around at other,nicer class D than this one and the range is even broader.

 

[galego100]

So disapointed with @Fosi Audio , pledger Nº1256 ( May) both monos are stuck on Spain customs since 20 July , i´m at Portugal... @Fosi Audio don´t provide any solution , and the tracking stop since 20 July. Friends of mine bought from Amazon( Europe) and already receive it pretty fast ... No money , no monos, no answers, nothing...

 

[badie]

Amps suppose to work at all sane conditions,even in a cold or hot room.

+1
----,,

As I am running a two way active system ...

V3 Stereo driving Bass - cutoff 250Hz
PSU GaN 48V 5A (Fosi)
mean wattage draw 27W

2xV3 Mono driving FullRange
PSU ??? 48V 10A+Filter (Fosi)
mean wattage dram 22W -> 11W per unit

Meaning the V3 Stereo is dealing with 2,45 (27/11) times the power (drawn from the wall) running through its internals.
All units on cone feet 2,5cm high

Running this for the last 45 Minutes and fiddling a little with the numbers i got these temps and relations:

Meaning the V3 Monos are running ~14% cooler when on two fifths / 40% of the power running through the V3 Stereo (Measured on the bottom) (LOL).

Have to find a way to send more power through the monos without blowing my ears.
I am really interested in the thermal performance when in party mode, driving more power hungry speakers.
----..

More to come

 

[Lux_ury]

Are we seriously talking about 5° ambient room differences here?
Seriously?

Amps suppose to work at all sane conditions,even in a cold or hot room.
Here's an example of one of the monos driving my lows (1200as) :


View attachment 388295

Had a look around at other,nicer class D than this one and the range is even broader.

It's academic to me it's design is to take alot more heat before terminating. I'm doing the extra cooling for fun, but fancier D class usually have Internal heat spreaders that don't touch the chassis. My v3 audio has the same chip and the chassis doesn't get hot because its not using the chassis as a heatsink, but it has a few air holes at the top. I just spent over 24 odd dollars to yield 5C drop. I think someone posted a comments about one amp being cooler than the other and a member rightly said "I would be worried about the cooler one" (Wink emoji)