Fosi v3 Mono - User Impressions | Owner's Thread

[stigger]

@stigger
Did you run any measurement with the stock brick?
Or you didn't get any of them at all?

No, I didn't measure the brick, I was only measuring the consumption of the amp itself.

 

[antcollinet]

This one?

View attachment 389167

If that's the case the 0.21W or 0.3W consumption rule is even lower than the 0.5W rule.
It's not clear to me though if the "no load" condition means with the following device at off state or no device at all connected.
Cause even if off any device can present some load.

It shouldn't. I'd expect a physical power switch to be directly in line with the DC input.

In any case, altogether it is pretty damning. I can't see any interpretation of the regs that puts the Fosi amps (and probably many others) in compliance.

 

[martinus]

So I got my fosi monoblock at the beginning of this month (august). I did buy them with 20% discount. A great bargain I guess. I live in the Netherlands, there were no any problems in delivery from Fosi it self. The package was solid and undamaged. I have to try to build a small set up from equipement that I already owned;
-two monitor adio bronze bx2
-supra classic 4mm
-rca chris cables
-a raspberry pi 4 with an allo boss dac with an isolator v1.2. The dac is fueled by a liniear powersupply, the pi gets his juice with from an ifi ipower.
-picoreplayer
-a preamp from douk audio with tubes and a dac. The preamp is fueled by a liniear powersupply.
-an audioquest cat 700 forest is used for connecting the streamer with a switch
-netgear switch unmanaged
-48 v/10a powerspply
-fosi audio dc power noise filter
-fosi monoblocks
-belden powercables for the liniear powersupplys and the powerblock of fosi
-copper powerconnectors

The whole set up is parked on my desk where my computer is doing his work.
As I told this set up is build with equipement I alread possesed and some new stuff. My music I do get from picoreplayer with Qobuz, deezer, internetradio and spotify. My pc is connected with my pre-amp. For me this setup sounds great. It is punchy and fast. What I like is the stereo seperation. Iam not sure this is because of the use of two amps. Concerning is the temperature of the monoblock. I made them cool off with the help off a small fan. It does the trick. For the right volume I do use the 25 db gain for my rca connectors. For now Iam sattisfied with the overall resulted. Perhaps later on Iam looking for better biwired speakercables. Please tips and tricks are most welcome.

 

[Unbalanced]

So I got my fosi monoblock at the beginning of this month (august). I did buy them with 20% discount. A great bargain I guess. I live in the Netherlands, there were no any problems in delivery from Fosi it self. The package was solid and undamaged. I have to try to build a small set up from equipement that I already owned;
-two monitor adio bronze bx2
-supra classic 4mm
-rca chris cables
-a raspberry pi 4 with an allo boss dac with an isolator v1.2. The dac is fueled by a liniear powersupply, the pi gets his juice with from an ifi ipower.
-picoreplayer
-a preamp from douk audio with tubes and a dac. The preamp is fueled by a liniear powersupply.
-an audioquest cat 700 forest is used for connecting the streamer with a switch
-netgear switch unmanaged
-48 v/10a powerspply
-fosi audio dc power noise filter
-fosi monoblocks
-belden powercables for the liniear powersupplys and the powerblock of fosi
-copper powerconnectors

The whole set up is parked on my desk where my computer is doing his work.
As I told this set up is build with equipement I alread possesed and some new stuff. My music I do get from picoreplayer with Qobuz, deezer, internetradio and spotify. My pc is connected with my pre-amp. For me this setup sounds great. It is punchy and fast. What I like is the stereo seperation. Iam not sure this is because of the use of two amps. Concerning is the temperature of the monoblock. I made them cool off with the help off a small fan. It does the trick. For the right volume I do use the 25 db gain for my rca connectors. For now Iam sattisfied with the overall resulted. Perhaps later on Iam looking for better biwired speakercables. Please tips and tricks are most welcome.

Nice. I hadn't heard about picoreplayer, so you have given me a tip!
I plan to add some fans similar to what you have for the monos with a pwm fan speed controller

 

[Unbalanced]

I have a similar setup. Two V3 Monos fed from a WiiM Pro Plus using the RCA cable that came with the WiiM. Two separate 48V 5A power supplies. Gain on the Monos is set to 25db. All items received this past Sunday from Amazon Canada. Both units packaged in fancy printed box.

Everything works great and sounds great with the exception that one of the Monos does not enter standby. I tried reversing the RCA inputs. Same unit does not enter standby. I tried side by side placement and reverse stack order. Same unit does not enter standby.

I contacted Fosi. They asked me to disconnect the inputs and then power up the Monos to auto. They should enter standby after 20 seconds which they both do. Fosi told me to get better RCA cables.

Final test that I did was to play music and then disconnect the RCA input from the offending unit. The unit does not enter standby after 10 minutes, 20 minutes ...

I have ordered a replacement from Amazon and will be returning the offending unit.

Update:
With somewhat mixed feelings I am happy to report that the replacement unit enters standby as expected. I did not update my RCA cables.
Disappointed that I did not receive a response from Fosi on this issue for three days.

 

[Sokel]

I can't see any interpretation of the regs that puts the Fosi amps (and probably many others) in compliance.

I'm afraid it's not only about amps.
MiniDSP Flex for example officially states 2.5W in stand-by in it's product specs.
And so on...

 

[MCH]

I'm afraid it's not only about amps.
MiniDSP Flex for example officially states 2.5W in stand-by in it's product specs.
And so on...

Minidsp could probably qualify as networked devices. Apparently even Bluetooth capable devices can.

 

[nitpicker1]

Did a new test, still seems right to me... The PSA said "might" be wrong...

Input signal taken from RCA before it enters V3:


Polarity measuring shown both straight and reversed on purpose:


PCB dates:


Live measurement compared to Audacity playing the file.

 

[Sokel]

Did a new test, still seems right to me... The PSA said "might" be wrong...

Input signal taken from RCA before it enters V3:
View attachment 389413

Polarity measuring shown both straight and reversed on purpose:
View attachment 389412View attachment 389411

PCB dates:
View attachment 389415

Live measurement compared to Audacity playing the file.

That's the first version with RCA input,right?
Can you do the same for XLR?

 

[nitpicker1]

That's the first version with RCA input,right?
Can you do the same for XLR?

Sorry, I have no XLR cables or equipment laying around. Not sure if it's the first. I was pledge 1602 early bird, kinda late on the wagon I guess.

 

[JLB321GO]

Has anyone tried the Mono v3 with an aftermarket 48V/5A power supply?

Also, I wonder if placing a 10000 uF capacitor in parallel with the stock power supply output will improve general amplifier dynamics.

 

[burkm]

Placing a large capacitor at the output of a power supply might lead to all sorts of problems, because it depends on the design of the PS output circuitry if it "tolerates" this without causing any problems (oszillations etc). If you try it, be prepared, that the PS might crash and be "destroyed" irrepairably..
Note: The PS schematics provided by the manufacturer might be of help...

 

[antcollinet]

Placing a large capacitor at the output of a power supply might lead to all sorts of problems, because it depends on the design of the PS output circuitry if it "tolerates" this without causing any problems (oszillations etc). If you try it, be prepared, that the PS might crash and be "destroyed" irrepairably..
The PS schematics provided by the manufacturer might be of help...

And even if it works - it won't improve the dynamics. The amp can already deliver all the dynamics needed, by virtue of being able to deliver full power 20kHz.

 

[DCinATX]

One way to judge the Mono V3s is- did anyone hook them up, dislike them, and put them away/ sell/ return? For me, they beat out an AVR amp, but perhaps that isn’t a huge challenge…

For me, the F3M beat out a Rega Brio-R. Again, not a terribly high bar. But it might be an interesting data point for someone.

In my case, the Brio struggled driving a pair of Buchardt S400 MKII speakers I bought used. At first, I thought the extended bass range of the Buchardts (relative to a pair of Wharfedale Diamond 225s) was exciting some room node in the bass region. After swapping in a pair of F3M, it’s pretty clear that the Brio simply didn’t have enough power into a 4-ohm load.

In other words, all the bass bloat is gone with the F3M in the system. Moreover, I can easily integrate my SVS sub with the Buchardts. The latter was impossible with the Brio.

Signal path:

Upgraded Project Debut Carbon —> Tavish Design Vintage 6SL7 phono stage —> Schiit Kara (balanced output) —> Fosi v3 mono —> Buchardt S400 MK2

 

[kelesh]

I'm hereby reporting the following user impression: I've now taken my pair out of the box and done a general physical examination. Next month, I hope to power them on. By the end of the year, I hope to have the phase issue resolved and possibly even connect speakers and do some listening. I still have no plans or use for the Muses chip, I don't even know why I received it, as I didn't ask for it.

 

[Unbalanced]

I plan to add some fans similar to what you have for the monos with a pwm fan speed controller

The fan controller hasn't arrived yet, but I did hookup one fan without the controller. The fan blows the air across the units and through the side vents. I am impressed at the difference that a constant air stream makes.
I have my two monos stacked. Both units are now cool.

I think that there is a good aftermarket opportunity for someone to sell a proper cooling solution for the V3 monos. As nice as the form factor is, it is poor from a cooling point of view as it just traps the heat inside the case. As good as the electrolytic caps inside the monos may be, the heat will significantly shorten their lifespan.

 

[kelesh]

I think that there is a good aftermarket opportunity for someone to sell a proper cooling solution for the V3 monos. As nice as the form factor is, it is poor from a cooling point of view as it just traps the heat inside the case. As good as the electrolytic caps inside the monos may be, the heat will significantly shorten their lifespan.

Or - another aftermarket opportunity - produce a super fancy aluminium enclosure with adequate cooling, sized to fit a pair of V3 monos inside, extend the power, controls, inputs and outputs to the outside enclosure - then seal the whole thing permanently with something like epoxy and sell it for $40K as an "esoteric, no-compromise super amp" to those with money to burn. A couple of dumbbells can be added for proper weight.

 

[burkm]

Contrary to some opinions here, I still think, that the cooling solution for those V3 mono amps is "sub-optimal", as no cool air has the opportunity to enter (and escape) the case from below and the sideways ventilation strips are not enough to have the components inside kept cool for a sustained period of time.
Forced air by some fans (front or sideways) might be a "solution" to that problem, which shortens the life expectancy of thise components inside.
A combination ot the original V3 stereo cooling concept and its current implementation of the V3 mono might also be a solution then...

 

[Bleib]

Although it doesn't run very cool, I bet many of us have had AVRs that runs a lot hotter.

 

[nitpicker1]

Forced air by some fans (front or sideways) might be a "solution" to that problem, which shortens the life expectancy of thise components inside.

That's just nonsense, no way airflow would ever shorten life span of any electrical components, unless it was salty/humid air.

I'd cool the surface below if anything, as that's the main surface they decided to use for heat dissipation.

But unless it's reaching 60c+ I won't worry about it at all.