Fosi Audio V3 Mono Amplifier Review

[mike70]

I'm not going to argue with TI, it's their chip . However in practice this isn't an issue for complete amps or amps using typical modules. Take two Fosi V3 monoblocks, it doesn't matter if they share a DC power supply (shared 10A) or an AC power supply (2x5A). Each amp has its own internal power supply (PVDD) reservoir caps. The TI app note is more relevant for amps with common supply _after_ the PVDD caps. Which may be an issue for you in your compact DIY build but not for these Fosi amps or any others using modules with separate reservoir caps for each chip.

Power supply pumping is a concern but usually handled by wiring each module in alternate senses at input and output, so module A has inputs and outputs wired as normal, while module B has input signals inverted, and speaker outputs also inverted, for the same result but opposite power draw. Once that is dealt with the clock sync question is mostly moot I think, especially for music signals.

Back to the main point though, there is no downside to having a shared 10A supply instead of two 5A supplies for the Fosi amps.

And if your main speakers have a HPF (generally 80hz or something like that) ... the power current requirements are ridiculous, I mean, the PSUs will be laughing all the time.

 

[wyup]

Okay, but the question everybody wants to know is: Does a single V3 mono perform better with the 10A supply instead of the 5A?
Meaning more juice to the bone?
Or the caps feeding the chip can't release over 5A?

 

[Guddu]

Back to the main point though, there is no downside to having a shared 10A supply instead of two 5A supplies for the Fosi amps.

You are right.
and just to add, there is nothing wrong (or even probably a good idea) is getting to separate PSU's if **money isn't an issue** and
- you have a bit demanding power requirements
- want to distribute power between 2 different power outlets, because of any reason
- asymmetric placement of speakers w.r.t. distance
- using with AVR or room correction (or anything) resulting in asymmetric power drawn
- using speakers that go low enough requiring a bit of more power

 

[YesChickenNuggets]

Has Fosi confirmed yet if we get more power output using 2x 48v-10amp powersupplies?

 

[Guddu]

Okay, but the question everybody wants to know is: Does a single V3 mono perform better with the 10A supply instead of the 5A?
Meaning more juice to the bone?
Or the caps feeding the chip can't release over 5A?

TPA3255 PBTL Mono won't gain anything (significant or useful) from 48v 5a to 10a, no benefit.

@Fosi Audio Its a good idea to add a table or chart on your Fosi v3 mono product page with output power on different PSU options.

 

[312elements]

TPA3255 PBTL Mono won't gain anything (significant or useful) from 48v 5a to 10a, no benefit.

@Fosi Audio Its a good idea to add a table or chart on your Fosi v3 mono product page with output power on different PSU options.

Maybe you’re the right person to ask this question… there were recently reports that the power ratings aren’t sustainable or are more like short bursts. Would the larger power supply mitigate that? Would an unregulated power supply mitigate that?

 

[Ze Frog]

Has Fosi confirmed yet if we get more power output using 2x 48v-10amp powersupplies?

They responded a few days ago, remains the same, no benefit beyond the supplied power supply which is good, shows the power supply wasn't an afterthought and these are designed to reach peak performance regardless of separate 5 or 10 amp single supplies or one 10 amp shared.

 

[Guddu]

Maybe you’re the right person to ask this question… there were recently reports that the power ratings aren’t sustainable or are more like short bursts. Would the larger power supply mitigate that? Would an unregulated power supply mitigate that?

Right person for this question- me, probably not.
But I would like to use regulated power supply for everything if I can afford for the use and if my mains has voltage drops.
But for these amps, I personally won’t.
In the context of this amplifier or TPA3255 PBTL, 48v is giving more power. If voltage drops then that is a potential issue.

 

[Ze Frog]

Maybe you’re the right person to ask this question… there were recently reports that the power ratings aren’t sustainable or are more like short bursts. Would the larger power supply mitigate that? Would an unregulated power supply mitigate that?

Where did you hear the output is not sustainable please?

Should imagine these provide specified ratings beyond a single tone. Hopefully Erin will review it at some point as he includes that and found the WIIM amp performed a little under. No offence to the WIIM though, but that was their very first amplifier so really not too much of a negative really. Especially when an 85dB speaker will put out 100dB at 16 watts equating to 91dB at a listening position of 3 meters.

 

[312elements]

Where did you hear the output is not sustainable please?

Should imagine these provide specified ratings beyond a single tone. Hopefully Erin will review it at some point as he includes that and found the WIIM amp performed a little under. No offence to the WIIM though, but that was their very first amplifier so really not too much of a negative really. Especially when an 85dB speaker will put out 100dB at 16 watts equating to 91dB at a listening position of 3 meters.

I think it stemmed from Erin’s ZA3 video, or V3? Whichever he reviewed.

 

[GabrielPhoto]

Maybe you’re the right person to ask this question… there were recently reports that the power ratings aren’t sustainable or are more like short bursts. Would the larger power supply mitigate that? Would an unregulated power supply mitigate that?

Maybe that explains my issues trying to use stereo mode with a v3 or aiyima 07 max and both unable to do it without audio cutting out for my Dayton BST-300ex shakers.
They can handle one single but not when both channels are in use. That was with the 48v 5a

 

[staticV3]

TPA3255 PBTL Mono won't gain anything (significant or useful) from 48v 5a to 10a, no benefit.

The 2Ω output that Amir measured is 100W short of the TPA3255's specs:

New Fosi Audio V3 Mono vs Topping PA5 II vs Topping PA7 (inc. 'Plus' versions)...and Aiyima A70

I am curious which voltage regulator will be inside the Fosi V3 Mono. I noticed that the late Michael Beeny had suggested that some of the earlier TPA3255 burn pile might have been generated from not using something capable. His example of capable is...

www.audiosciencereview.com

Isn't it likely that a 10A supply would get the V3 Mono closer to spec?

 

[Ze Frog]

I think it stemmed from Erin’s ZA3 video, or V3? Whichever he reviewed.

Ah, haven't seen that one, I'll look it up.

I'm hoping these do reach at least very near to specifications, Fosi likely saw that review or got feedback and implemented a fix going forward, they seem genuinely on the ball in that regard.

 

[Sig.Rossi]

Too bad that it does 't have a volume control. I thought I could use that to balance my right and left channel, which would be necessary. I am not able to do this on the front end. It would have been an easy buy.

Any ideas which one would be the best solution for:

RCA connections
and being able to balance left and right?

Could I use two stereo amps with volume control as mono amps?

Which one of those small class D amps could do that and would have the best measurements for RCA connections?

I know Douk/Nobosound had a stereo amp with two volume controls. But its not on par with the best sinad amps.

 

[SMen]

Too bad that it does 't have a volume control. I thought I could use that to balance my right and left channel, which would be necessary. I am not able to do this on the front end. It would have been an easy buy.

Any ideas which one would be the best solution for:

RCA connections
and being able to balance left and right?

Could I use two stereo amps with volume control as mono amps?

Which one of those small class D amps could do that and would have the best measurements for RCA connections?

I know Douk/Nobosound had a stereo amp with two volume controls. But its not on par with the best sinad amps.

I find one of these useful: https://www.ebay.com/itm/353414949618 - it's a passive dual balanced / RCA and if you don't mind the dual volume it will do balance control obviously.

 

[LightninBoy]

Seriously considering running up to 5 of these in my HT room, maybe even replacing the bryston 4B sst for the mains. At the very least these will be perfect for the surround channels.

 

[musicforcities]

I have had poor luck relying on protection circuitry with bridged amps.

Ah of course sorry I missed that fact.

Still, the speaker screw downs are insulated and dc plug is insulated. and while I can’t tell from the photos on this one but on some devices the female jack is slightly recessed so that plug insulation extends into the chassis a mm or two such that it’s pretty hard for even a stray strand of speaker wire to get in there.

Stick with insulated banana plugs on the speaker wires for this thing and all should be ok.
I’d use bfa style banana plugs as they seem to grip better than the typical ones on these small posts. Though they stick out a bit because the smalls jacks are usually too short. but do can normal banana plugs.

Big picture is that we are doomed to the sub-optimal 5 way speaker posts as the default standard. If only the world used speakon connectors. But no way they would fit in this device imagine. the plugs are just too wide. And I don’t see companies using spring or screw terminals. And please no phoenix terminals (the absolute worst imho…because the plugs and sockets rely solely on the very weak friction of the electoral contacts to hold them in.)

For these tiny amps, the otherwise annoying speaker terminals that nad amps used in the 90s and early 2000s would make a lot of sense. They had a plastic sleeve around the screw post that allowed bare wire or small thin spades to be inserted only from the top into a slot that of course also kept them from rotating over time or tightening. (or bananas at the back as usual). This eliminated the problem of stray wire strands or uninsulated spades shorting. They were not very cable “jewelry” friendly either lol. But economics of manufacturing seem to dictate the use of already available options. Though lots of AVRs seem to have something similar do maybe there are ones available.


The standard dc plug and jack ain’t all that great either in my mind for many reasons, especially once one is pumping 48v and a few amps through it. I’m sure it’s fine electrically but the plugs always seems like such a flimsy thing.

Still, the dc plug is insulated. Unless you are using spades or bare wire I think the chances of shorting are pretty minimal. And given the size of this entire unit and connection spacing, anything but relatively narrow, insulated banana plugs seems a bad idea.

 

[EddNog]

Ah of course sorry I missed that fact.

Big picture is that we are doomed to the sub-optimal 5 way speaker posts as the default standard. If only the world used speakon connectors. But no way they would fit in this device imagine. And I can’t see companies using spring or screw terminals. And please no phoenix terminals (the absolute worst imho…because the plugs and sockets rely solely on the very weak friction of the electoral contacts to hold them in.)

For these tiny amps, the otherwise annoying speaker terminals that nad amps used in the 90s and early 2000s would make a lot of sense. They had a plastic sleeve around the screw post that allowed bare wire or small thin spades to be inserted only from the top into a slot that of course also kept them from rotating over time or tightening. (or bananas at the back as usual). This eliminated the problem of stray wire strands or uninsulated spades shorting. They were not very cable “jewelry” friendly either lol.

The standard dc plug and jack ain’t all that great either in my mind for many reasons, especially once one is pumping 48v and a few amps through it. I’m sure it’s fine electrically but the plugs always seems like such a flimsy thing.

Still, the dc plug is insulated. Unless you are using spades or bare wire I think the chances of shorting are pretty minimal. And given the size of this entire unit and connection spacing, anything but relatively narrow, insulated banana plugs seems a bad idea.


I can’t tell from the photos on this one but on some devices the female jack is slightly recessed so that plug insulation extends into the chassis a mm or two such that it’s pretty hard for even a stray strand of speaker wire to get in there.

Just curious: why do some people appear to have some sort of severe adverse reaction to the mere thought of using banana plugs?

-Ed

 

[musicforcities]

Just curious: why do some people appear to have some sort of severe adverse reaction to the mere thought of using banana plugs?

-Ed

in theory (electrically and in terms of audio signal transmission) there is nothing inherently awful with them. Except for the risk of shorting live male plugs by careless users.

In practice the issue is that it’s not a really a proper a standard. The bannans plugs and jacks found in home audio have relatively large Variability /lack of precision in manufacturing, such that some plugs are too loose in some jacks, or vice versa. There is not really a standard beyond what in practice is a very nominal diameter (4mm).

And these tiny amps often have small and short terminals so you can’t insert the plug fully, which can exacerbate things.

I have found the “bfa” style plugs—with a tubular leaf spring type end—have much better grip and manage wider diameter sockets better. But they do stick out a bit and thus can bend if the wire is not supported. And they are not great for many repeated insertion/removal cycles.

The bfa style that have a full cylinder with a small spring wire are less susceptible to bending and better for many repeated cycles of connection. But are harder find. I think Sewell and gearit offer some.

The locking types usually have plugs too wide to use on these small amps…or many others these days. And are often insulated. Or are insulated but huge and/or silly expensive.

 

[EddNog]

The issue with the bannans plugs used in home audio is the variability/lack of precision in manufacturing, such that some plugs are too loose in some jacks, or vice versa. There is not really a standard beyond what in practice is a very nominal diameter (4mm).

And these tiny amps often have small and short terminals so you can’t insert the plug fully, which can exacerbate things.

I have found the “bfa” style plugs—with a tubular leaf spring type end—have much better grip and manage wider diameter sockets better. But they do stick out a bit and thus can bend if the wire is not supported. And they are not great for many repeated insertion/removal cycles.

The bfa style that have a full cylinder with a small spring wire are less susceptible to bending and better for many repeated cycles of connection. But are harder find. I think Sewell and gearit offer some.

The locking types usually have plugs too wide to use on these small amps…or many others these days. And are often insulated. Or are insulated but huge and/or silly expensive.

Honestly, I have never ever run into any of these problems running premade cables with swappable ends and just using the banana plug option. They’re tight enough, they go in fine, they don’t budge, and they sound fine.

-Ed