Fosi Audio V3 Mono Amplifier Review

[Inertiaman]

There is (and can be) almost no vertical air flow in this design. The entire area is blocked by the PCB - where are you expecting air entering the bottom of the case to go?. The thermal design relies almost entirely on conducting heat to the chassis. There will be some small trickle of air out of the side vents, fed though the small gap between the edges of the PCB and the housing.

Good point, I hadn't reviewed the photos of the enclosure. Having now done so, I still see simple opportunities for improvement. Maximizing airflow on all surfaces of the chassis (both interior and exterior) would benefit heat dissipation. So offsetting the holes on the side panels (left side high, right side low, for example) would improve the passive convective airflow through the unit. I can't quantify the scale of the benefit, but certainly it would improve, no?

Frankly I wonder if, given the orientation of the TPA3255/heatsink/chassis, would the unit run cooler if placed upside down??

 

[Deleted member 72219]

…Frankly I wonder if, given the orientation of the TPA3255/heatsink/chassis, would the unit run cooler if placed upside down??

You would not be the first person to guess this.

-Ed

 

[Inertiaman]

You would not be the first person to guess this.

-Ed

Yeah, I'm coming in about 180 pages late here!

Probably even better to place it on edge: you get top and bottom holes + the largest surfaces (chassis top & bottom) have constant convective airflow.

Waiting now for you to point me at some post 100 pages earlier where someone 3D printed some clips/feet to hold a pair of these side by side

 

[Deleted member 72219]

Yeah, I'm coming in about 180 pages late here!

Probably even better to place it on edge: you get top and bottom holes + the largest surfaces (chassis top & bottom) have constant convective airflow.

Waiting now for you to point me at some post 100 pages earlier where someone 3D printed some clips/feet to hold a pair of these side by side

Hah…yes, someone did actually do that. Unfortunately, it is so far back that I don’t have enough time to find it for you!

-Ed

 

[antcollinet]

I can't quantify the scale of the benefit, but certainly it would improve, no?

I very much doubt it - not nearly enough vertical difference in hight to create airflow.

 

[Endibol]

I have two splitter cables thanks to Fosi ... But if I understand you correctly, we could junk the DC filter and just have a better splitter cable.
So the problem was with the splitter cable? Thank heavens they sound good despite all this (the V3 monos)!

If I remember correctly Fosi sent a second splitter cable with the filter. This was necessary because a splitter cable with a different configuration male/female connectors was needed to insert the filter.

 

[Endibol]

I'm planning on using both the RCA and XLR inputs (for two different sources) - RCA being driven from the preouts on my Arcam AVR360 (quite curious to see how the v3 monos compare to a reasonably high end AVR which claims 90wpc...). This will cover Film, TV and streamed music use through the AVR. How do people find the manual switches on the front? Robust? Any audible pops or clicks when switching? Should I worry about the RCA noise issue with the single 10a supply? How do people find the auto power switching? Is it useful/works as intended?

The switches are robust. You can switch from XLR to RCA and back without any clicks or plops. Upon switching the amp there is silence for a few tenths of a second and than switches to the selected mode. The Fosi feels very robust and solid anyway. They sound great with the fairly insensitive Ascend Sierre -1 v2 speakers.

 

[badie]

There is (and can be) almost no vertical air flow in this design. The entire area is blocked by the PCB - where are you expecting air entering the bottom of the case to go?. The thermal design relies almost entirely on conducting heat to the chassis. There will be some small trickle of air out of the side vents, fed though the small gap between the edges of the PCB and the housing.

V3 Stereo seems to have an evenly big PCB (didn´t make any measeurements) and there is significant airflow through the unit (bottom to top).
You can feel it and make it visible with a little smoke.

But I do agree - V3 mono relies almost entirely on conducting heat to the chassis.


This is the marketing image for V3 stereo taken from FOSI website for the V3 stereo:

Result: maximizing conductive cooling by heatsinking the IC to the chassis (I believe this to be a good choice) and benefiting from airflow.

This is the marketing image taken from FOSI website for the V3 Mono:

Result: Nicer looking unit same conductive design BUT no more (significant) airflow.
I did believe in the advancement, thinking the hole on the sides were additional and not the only ones)

The measurements I made upuntil now (Post #3339 in this thread) show clearly that the V3 stereo thermal design is way more effective. I think FOSI made a visual design choice without testing the thermal performance and called it "Advanced Cooling Design".

I would really like to see how the V3 mono would perform thermally if you were to put holes in bottom and top. But I am too scared to drill holes in anodized aluminium. (maybe chipping of black color) - did anybody tried this?

@Fosi Audio Maybe it would be possible for FOSI to offer/send out a replacement for just the middle part of the case with holes in it. So that users could replace it on their V3 monos and hopefully get the same thermal performance as with V3 stereo. I wonder how much the middle part of the case does cost in production. Probably the mono one with the orange side-holes was more expensive, than the original (V3 Stereo) one.

And I myself really do like the design of these holes. If I were afraid of dust i would just glue a black net underneath - same as my computers do protect themselves against dust.

 

[antcollinet]

The measurements I made upuntil now (Post #3339 in this thread) show clearly that the V3 stereo thermal design is way more effective. I think FOSI made a visual design choice without testing the thermal performance and called it "Advanced Cooling Design".

But you don’t actually know, because you are only measuring case temperature, not how effectively the internal components are being cooled. (But kudos for doing the measurements - far more than I have ever done post retirement )

Obviously if you are optimising heat transfer by letting hot air out of the enclosure, then the case will not get as hot. However it is possible the build up of heat in the air inside the case (because all the power losses must first be transferred to the internal air) may be much worse.

If you are optimising heat transfer through direct coupling to the chassis, then obvously the chassis will get hotter. But the internal air may well be cooler since you are not putting all the power losses into it.

The only way you can know for sure is by measuring the temperature of internal components - and the only way of doing that effectively is by glueing thermocouples or other temperature sensors directly to the components.

In my former life we even had capacitors specially made by the manufacturer with thermocouples inside them, so we could measure the internal capacitor temperature.

 

[badie]

But you don’t actually know, because you are only measuring case temperature ...
The only way you can know for sure is by measuring the temperature of internal components - and the only way of doing that effectively is by glueing thermocouples or other temperature sensors directly to the components.

you are right. Best I can measure is case temp at heatsink position. Might not be right in absolute temp of the IC itself - maybe good enough for comparing V3 stereo vs V3 mono thermal design.

But good point we have no idea how hot all other components are ...
Maybe we can assume, that without airflow (convective heat transfer) other components might even be hotter ...
Because conductive heat transfer is mostly-only happening for the IC.

And we do seem to be more worried about the life expectancy of the capacitators?

 

[antcollinet]

you are right. Best I can measure is case temp at heatsink position. Might not be right in absolute temp of the IC itself - maybe good enough for comparing V3 stereo vs V3 mono thermal design.

But good point we have no idea how hot all other components are ...
Maybe we can assume, that without airflow (convective heat transfer) other components might even be hotter ...
Because conductive heat transfer is mostly-only happening for the IC.

And we do seem to be more worried about the life expectancy of the capacitators?

If measuring heatsink temperature then you’d need to measure both heatsinks a similar distance from the IC.


The internal air temp assumption won’t work because it depends on both airflow, AND losses into the internal air - and we don’t know either.

But as you say, capacitor temperature is probably most critical - measuring some of the capacitor temps would be best.

An approximation would be measuring the air temperature close to the capacitors which would give an idea regarding which design has the coolest internal air temperature. In that case you’d need to measure air temp sufficiently far from the cap that the cap is not directly heating it (perhaps about 1cm away, and to the side - so not in any rising air from the cap)

 

[amix]

There is (and can be) almost no vertical air flow in this design. The entire area is blocked by the PCB

They could have used the side vents for intake and have an outlet on top.

 

[boblingted]

Hah…yes, someone did actually do that. Unfortunately, it is so far back that I don’t have enough time to find it for you!

-Ed

In the V3 mono owners thread on June 28th here
There was another thread where somebody measured temperature with the amp placed vertically. Made a small difference of about 5°C they reckoned.

 

[Mort]

I feel like we will watch this product mature.

Instead of the usual gimmick of packaging features around a crappy core , Fosi built a solid clean core with crappy or, maybe more fairly, non-existent features.

My guess is we see steady, regular new versions of this over the next few years. Let's hope they don't mess with the core.

 

[audioaudio]

Hi. I'm new here. My V3 Monos are still in the mail from China, to Canada. I ordered directly from the Fosi website.

Question: As far as I have read the Fosi V3 Monos are pretty bleeding edge when it comes to power and size for audio amplification. Is it possible that the tech has existed in other applications for some time and "hot" enclosures are a normal thing for these kinds of amps?

I have experience with a cellphone booster. It's amp is about the size of the V3 and completely enclosed with no holes. When it was deployed it was very hot to touch. I was confident there was an issue. After looking into it, the amps normal operational temperature is 115 degrees celsius!!! That thing has been running for months, 24/7, at that temperature. I can't speak to long term reliability but the company is reputable with a great warranty plan (which they wouldn't have if the products were prone to failure).

When they get here, my setup will be Tidal > Wiim Ultra > Fosi V3s > Magnepan 0.7

I'll be sure to maintain a presence here on the form but my expectation is that with my setup the Fosi's will run HOT and I'm okay with that. Just my 2 cents.

 

[Piotr]

Hey!

So I've been holding out for ages to upgrade my main system, and I finally bit the bullet! I've got pretty high hopes for this V3 mono - I'm thinking it'll be on par with the Yamaha AS-701. It's replacing my old Marantz MCR-601, which is a decent budget Class D setup, but getting on a bit now.

I'm pairing it with the ZD3 DAC. To be honest, the main selling point for me wasn't even the audiophile stuff - it was the idea of having one remote to rule them all in the living room. How cool is that? One TV remote for everything in the house, thanks to these new DACs with eARC.

I know there's a chance I might not love the look of it, or the external power supplies and small components, but if it sounds good, I dare to forgive. For 300 bucks whole package? It's a steal.

I'm really digging the whole monoblock concept - the design and philosophy just make sense to me. I'm hoping it'll sort out any crosstalk issues and widen the soundstage. Whenever I visit friends with fancy setups, I always get a bit jealous of their stereo effect. My current setup sounds alright, but it's kind of flat - almost like it's in mono.

So Fosi, take my 300 bucks and widen this stage up!

 

[Inertiaman]

I would really like to see how the V3 mono would perform thermally if you were to put holes in bottom and top. But I am too scared to drill holes in anodized aluminium. (maybe chipping of black color) - did anybody tried this?

If the case is definitely anodized and not powder coated, there should be zero risk of any chipping. However, the interior edges of the hole will definitely be silver rather than black, so you'd need to be OK with that cosmetic appearance. Although careful use of black Sharpie would go a long way to concealing the silver edges

The bigger challenge in my opinion is successfully drilling so many holes in a consistent geometric pattern that doesn't end up looking like a hack job. Without a CNC or a small mill, its going to be difficult. Maybe if you printed a pattern on paper, and adhered it to the case, and were very careful with a handheld drill, you could get it done.

 

[DavidM1]

But I was really surprised when I unpacked the V3 monos and found out that the ventilation holes on top and bottom got cancelled.

Did you buy something online without looking at a picture of it? Why did you do that?

This line of conversation serves solely to disparage a product that has moved the goal posts for amps. I’m sure there are some people who would rather it hadn’t.

 

[Sokel]

If the case is definitely anodized and not powder coated, there should be zero risk of any chipping. However, the interior edges of the hole will definitely be silver rather than black, so you'd need to be OK with that cosmetic appearance. Although careful use of black Sharpie would go a long way to concealing the silver edges

The bigger challenge in my opinion is successfully drilling so many holes in a consistent geometric pattern that doesn't end up looking like a hack job. Without a CNC or a small mill, its going to be difficult. Maybe if you printed a pattern on paper, and adhered it to the case, and were very careful with a handheld drill, you could get it done.

The solid way of drilling without any slips is pre-nailing the points to be drilled.
It's doesn't need to be a crater a steel nail or the appropriate tool can do the job just fine so the drill will never slip.

 

[ninetylol]

My V3 monos ordered from amazon.de end of september still have phase inverted (1qc sticker only)