Fosi Audio V3 Mono Amplifier Review

[GiBo61]

I have the Sabaj a30a. Do you think that two of this Fosi v3 monos could be a better option with a good dac?

I also have a Sabaj A30a and I'm really happy about it. I guess the performance will be similar but with more boxes and cables around. Furthermore the Sabaj has a sub out with high pass and low pass filters plus tone controls.

 

[DavidM1]

Yeah, but to be fair Fosi aren't exactly too far off. Some nicer cases and inbuilt power supply as you say and they are pretty much there.

As for the toggle switches, kind of like them myself, like a switch to have an old school kind of quality. Best switchgear ever that I have experienced is the Denon PMA 110. That thing is so mechanically satisfying. I'll probably purchase one at some point on that fact alone.

I know knob feel is a big thing in hifi (yes, I wrote that) but it hadn’t crossed my mind that these switches were a problem. Kinda old-school now that I think about it.

 

[Billy Budapest]

Not unless the rest of the package changes. Meaning integrated PSU and replacing those cheap stick-switches on the front with some nicely machined buttons.

I think those switches look classy.

 

[GabrielPhoto]

Guys, based on the load variance of all these amps with this same chip, I was wondering....
Using them strictly as an amp for transducers like the Dayton BST-300EX or Buttkickers LFE...it would seem this model or the V3 have the least drop below 20hz followed by the aiyima 07max .
The za3 seem to be the worst in that regard.
Is that a fair assessment?

 

[Fosi Audio]

I am curious about the standby power consumption. Has It been measured jet bij @amirm?

Within the EU there are regulations telling manufacturers to minimize power consumption of the devices they are producing.

A wide range of equipment – audio and video equipment, microwave ovens and electric toys – can have standby and off modes.

since 2009 these devices are required to switch to a low-power mode (such as standby) after a reasonable amount of time
since 2013, they must not consume more than 0.5 Watts in standby or in off mode, or 1 Watt if they are on standby while displaying their status or information
EU Ecodesign requirements are mandatory for all manufacturers and suppliers wishing to sell products consuming electric power in standby and off mode in the EU.

Standby, networked standby and Off mode

Off mode, standby and networked standby mode. Energy efficiency of products.

energy-efficient-products.ec.europa.eu

Does Fosi meet these requirements?

The v3 mono will cost no more than 0.5W in stand mode.

 

[Fosi Audio]

Hi, you write that it is possible to connect 2 amps to 1 48v power block. Is this degrades the power of the amps? To get full power should I use 2?

Our team has confirmed through testing that when two V3 Monos are connected to a single 48V/10A power supply via the Y splitter cable, the output power of each is the same as a single V3 Mono connected to a 48V/5A power supply.

 

[JyPay]

And what about one 10A power supply on one amp ?

 

[MCH]

Our team has confirmed through testing that when two V3 Monos are connected to a single 48V/10A power supply via the Y splitter cable, the output power of each is the same as a single V3 Mono connected to a 48V/5A power supply.

What about noise over a period of time (until the oscillators drift one cycle)? Can you share some measurements?

 

[Fosi Audio]

Yah, ZD3 will be same form factor as ZA3

So the upcoming preamp (ZD3) will be same form factor/width as ZA3 and not V3 variants?

 

[Fosi Audio]

47kOhm for the RCA input.

Sorry, we need to make a revision that the input impedance for RCA is 25kΩ, and for XLR, it is 5kΩ.

 

[wilbur1]

The only SLIGHT problem I might have in buying a couple of these is this. On their webpage for this new unit there is the following: "With a power supply splitter cable, a single PSU can supply power to two amps, saving space and maintaining tidiness, offering you more flexible combination solutions.", which suggests you could potentially buy two of the amps, but just one power supply unit. I asked Fosi directly about this, and - to their credit - got a reply reasonably quickly: "It will launch on Kickstarter on April 20th, there isn't the option to purchase two units but with just one power supply". It seems just a fraction disingenuous, therefore, to tout the benefits of a single power supply for two amps but then say that option is not available.

 

[georgehifi]

Sorry, we need to make a revision that the input impedance for RCA is 25kΩ, and for XLR, it is 5kΩ.

Not too good for passive preamps, tube preamps or tube output dacs with digital domain volume then.

Cheers George

 

[Ze Frog]

The only SLIGHT problem I might have in buying a couple of these is this. On their webpage for this new unit there is the following: "With a power supply splitter cable, a single PSU can supply power to two amps, saving space and maintaining tidiness, offering you more flexible combination solutions.", which suggests you could potentially buy two of the amps, but just one power supply unit. I asked Fosi directly about this, and - to their credit - got a reply reasonably quickly: "It will launch on Kickstarter on April 20th, there isn't the option to purchase two units but with just one power supply". It seems just a fraction disingenuous, therefore, to tout the benefits of a single power supply for two amps but then say that option is not available.

They have tested and it makes no difference. Plus you can purchase their or some other power supplies on Amazon or their website to go that route. Let's not forget the cost of these things and the fact this is using high quality components that stuff costing far more don't use.

 

[mcdn]

The power supply sharing is something interesting to me. Actually, various TPA3255 can be operated in master/slave mode so that they delay the switching between each other, apparently to "minimize noise coupling between audio channels through the power supply." and "Inter-channel delay is needed to optimize audio performance and to get better operating conditions for the power supply" according to the datasheet (below).
Given the fact that most probably two fosi sharing PSU with one of these Y cables are in fact directly connected in between, but not in master/slave mode, i would be curious to understand what this means for the performance of the amps and the power supply.

View attachment 361807

Unless you have an AM radio in the same cabinet it’s irrelevant. I have 4 modules in a diy amp without using the clock slaving and it’s fine.

 

[wilbur1]

They have tested and it makes no difference. Plus you can purchase their or some other power supplies on Amazon or their website to go that route. Let's not forget the cost of these things and the fact this is using high quality components that stuff costing far more don't use.

I don't see how this comment is relevant to the issue raised. Yes, they say the 10A power supply performs the same powering two amps as the 'normal' 5A one does with a single amp, but the point I raised is the fact that they have no plans to offer buyers the opportunity to buy 2 amps plus the single 10A power supply. The availability or otherwise of 3rd-party power suplies is irrelevant.

 

[mcdn]

What about noise over a period of time (until the oscillators drift one cycle)? Can you share some measurements?

That… doesn’t make much sense? The power supplies are DC

 

[Fosi Audio]

The only SLIGHT problem I might have in buying a couple of these is this. On their webpage for this new unit there is the following: "With a power supply splitter cable, a single PSU can supply power to two amps, saving space and maintaining tidiness, offering you more flexible combination solutions.", which suggests you could potentially buy two of the amps, but just one power supply unit. I asked Fosi directly about this, and - to their credit - got a reply reasonably quickly: "It will launch on Kickstarter on April 20th, there isn't the option to purchase two units but with just one power supply". It seems just a fraction disingenuous, therefore, to tout the benefits of a single power supply for two amps but then say that option is not available.

Sorry for the inconvenience. We'll provide the option of one 48V/10A PSU+Two V3 Monos on Kickstarter.

 

[wilbur1]

Sorry for the inconvenience. We'll provide the option of one 48V/10A+ Two V3 Monos on Kickstarter.

Can't say fairer than that. This is why folks like us are interested in Fosi's products. The company is responsive to user feedback, and flexible enough to adjust accordingly. That is the way you build a loyal customer base! Kudos to you!

 

[MCH]

That… doesn’t make much sense? The power supplies are DC

See the extract from TIs datasheet you quoted a few posts above

 

[Ze Frog]

I don't see how this comment is relevant to the issue raised. Yes, they say the 10A power supply performs the same powering two amps as the 'normal' 5A one does with a single amp, but the point I raised is the fact that they have no plans to offer buyers the opportunity to buy 2 amps plus the single 10A power supply. The availability or otherwise of 3rd-party power suplies is irrelevant.

They offer the power supplies, but individual ones are desperate items. Don't forget that the majority of their customer base won't even think about power supplies and just use the one provided. I get what you are saying, but it's a simple fix by purchasing the required power supplies you desire.