Fosi Audio V3 Mono Amplifier Review

[georgehifi]

Anyone know how high input impedance have Fosi V3 mono RCA inputs?

I'd love to know this also. anyone out there know???

Cheers George

 

[georgehifi]

Reserved for @AdamG to kindly post the specs.


View attachment 360740
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Can't find them anywhere, any chance you got to measure the input impedance on the rca or the xlr inputs @amirm ??

Cheers George

 

[DC4582]

Curious if anyone would recommend upgrading to dual mono block v3's from my current stereo v3? It's a 2.1 system used strictly for music with emotiva T0 towers rated at 4ohm / 87db, an RSL 12s sub and a wiim pro+ for dac/streaming. This is my first setup ever and i already love it. I don't feel like i need additional power as i can already hurt my ears with it. Any other reasons to upgrade? Is PFFB that big a deal?

 

[SMen]

Curious if anyone would recommend upgrading to dual mono block v3's from my current stereo v3? It's a 2.1 system used strictly for music with emotiva T0 towers rated at 4ohm / 87db, an RSL 12s sub and a wiim pro+ for dac/streaming. This is my first setup ever and i already love it. I don't feel like i need additional power as i can already hurt my ears with it. Any other reasons to upgrade? Is PFFB that big a deal?

Personally, I am only thinking of the PFFB because I have 8ohm Triangle speakers ... if your towers are a stable 4ohm the v3 stereo is probably fine ... though I am sure others will chip in. If the emotiva dip below 4 ohm then maybe not...

 

[surroundman]

Curious if anyone would recommend upgrading to dual mono block v3's from my current stereo v3? It's a 2.1 system used strictly for music with emotiva T0 towers rated at 4ohm / 87db, an RSL 12s sub and a wiim pro+ for dac/streaming. This is my first setup ever and i already love it. I don't feel like i need additional power as i can already hurt my ears with it. Any other reasons to upgrade? Is PFFB that big a deal?

I am in a similar situation, and I will most likely switch to the monoblocks for two quite important to me reasons. From my DAC, I will use XLR for my monoblocks and RCA for my subwoofers, which is something that I cannot do with the old V3 with its only RCA inputs. Another reason is the auto on/off that the monoblocks have, which I too absolutely need.

 

[dpuopolo]

just try chucking a few of them in a drawer or on a shelf uncased to "hide them" and wait for them to move such that the PCB's are in contact.

It's not going to end well.

But I'm not doing that, so why even bring it up?

 

[antcollinet]

But I'm not doing that, so why even bring it up?

You need to read the post I was replying to from @olieb

 

[wyup]

if your towers are a stable 4ohm the v3 stereo is probably fine ...

I am afraid there is no such thing as a 'stable 4ohm speaker', all have a variable impedance curve across the frequency range that dips and peaks in a broad range of values. If a speaker is 4 ohm nominal, you can expect to dip down lower to have such an average value. It's those low impedance values usually at low frequencies that ask for high current to the amplifier. These V3 mono, V3 and ZA3 only have 5 amps to spare. In comparison, Hypex NC122MP, their lower powered amp (75W at 8ohm, 125W at 4ohm) has max. 12.5 amps per channel. (output voltage is +-20V symmetric -->40V, similar to Fosi 48V supply). So you may have higher power with V3 mono but be current limited for bass. I guess it depends on volumes you listen, though.

On the other hand, V3 and ZA3 seem to suffer from load (impedance) dependency: over 10KHz at 8 ohms highs are about 0.5db higher, and at 4 ohms about 0.5db lower. I think some users have reported that, though I'm not sure that it is noticeable in audible band. Your mileage may vary
However, this new V3 mono is PFFB enabled which is less than 0.5db on average for both loads.

 

[georgehifi]

I am afraid there is no such thing as a 'stable 4ohm speaker'

These come close

Cheers George

 

[georgehifi]

Can't find them anywhere, any chance you got to measure the input impedance on the rca or the xlr inputs @amirm ??

Can't believe this measurement that's important to some, is nowhere to be found, on either the V3 mono's or the V3 stereo!!

Cheers George

 

[YesChickenNuggets]

Question guys, if a speaker is rated 85db/watt and 80watts, does that mean I can crank it safely to ~97db 1 meter? Is there a fry the speaker number?

 

[staticV3]

Question guys, if a speaker is rated 85db/watt and 80watts, does that mean I can crank it safely to ~97db 1 meter?

94dB based on those numbers ( 85+10*log10(80) ).

Is there a fry the speaker number?

"Rated power" and "Maximum power" used to be how manufacturers advertised long-term safe input power and absolute limit of instantaneous input power of their speakers.

Nowadays, you're more likely to find much more general specs like "Recommended Amplifier Power: 50-350 Watts RMS", because power handling can't really be condensed into a single Watts number.

It depends a lot on what kind of content you play and how long you play it.

Just back off the volume a bit once you hear your speakers complaining and you'll be fine.

 

[DC4582]

I am afraid there is no such thing as a 'stable 4ohm speaker', all have a variable impedance curve across the frequency range that dips and peaks in a broad range of values. If a speaker is 4 ohm nominal, you can expect to dip down lower to have such an average value. It's those low impedance values usually at low frequencies that ask for high current to the amplifier. These V3 mono, V3 and ZA3 only have 5 amps to spare. In comparison, Hypex NC122MP, their lower powered amp (75W at 8ohm, 125W at 4ohm) has max. 12.5 amps per channel. (output voltage is +-20V symmetric -->40V, similar to Fosi 48V supply). So you may have higher power with V3 mono but be current limited for bass. I guess it depends on volumes you listen, though.

On the other hand, V3 and ZA3 seem to suffer from load (impedance) dependency: over 10KHz at 8 ohms highs are about 0.5db higher, and at 4 ohms about 0.5db lower. I think some users have reported that, though I'm not sure that it is noticeable in audible band. Your mileage may vary
However, this new V3 mono is PFFB enabled which is less than 0.5db on average for both loads.

Yeah i couldn't find an impedance curve listed anywhere for the emotiva t0's so not sure how much lack of PFFB is affecting them? I have the Fosi v3 with a 48v power supply, but I also have the input signal to the Fosi high pass filtered at about 50hz. I am not super knowledgeable on amps watts and ohms and how they translate to spl at various frequencies. My current setup gets more than loud enough for comfortable listening.

 

[OpticonPrime]

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?

 

[TonyJZX]

i appreciate that kind of thought but it comes down to how their psu works and if the amp actually communicates back to the psu

and i reckon it does not do that... and worse, how does TWO amps do it?

its a dumb psu

the most if does it ramp up amperage if the fosi units calls for it

i have a suspicion many of the big power amps we have do not have much in the way of any power saving... except maybe the majors like yamaha etc.

 

[Calleberg]

Thanks @amirm. Especially for the Reactive Load tests and 19-20kHz IMD. Most of the newer TI3255 based Chipamps are getting pretty good by now. These additional test may reveal differences that the now Classic sinad spectrum does not. This one was not bothered much at all by the load, (While some others based on the same chip may shut down). The IMD shows there are still room for improvement, but at this price level its unfair to expect perfection.

 

[DavidM1]

So… what are the pros or cons of two 5amp power supplies vs one 10 amp supply with a splitter cable in terms performance and sound? For example, is there a greater risk of ground loops with either setup?

 

[wyup]

On Fosi Audio V3 mono announcing page it says:

Optional 48V/10A Power Supply​

Provides stable and robust power support, ensuring high-fidelity sound
quality to meet diverse audio playback demands.

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.

On specifications, power out is only specified with 48V/5A and 32V/5A. I wonder if the 48V/10A improves performance, or if it's for tidiness and simplicity sake with the two amps.

 

[dpuopolo]

These come close

Cheers George

Here's an idea to try: Take ONE of the outputs of your BTL output amplifier and put it through a 1000 uf 35 volt capacitor (With the + pointed towards the amplifier). Connect the + of your speaker to the - on the capacitor and the - of your speaker to ground (the - on your power supply input will do). By doing this you have done two things:

1. Lowered the amp's output voltage by 50% (and the power by 75%) and
2. Eliminated one output filter.

I'm curious as to how this improves the amp's high frequency response with only one output filter being used. I know this works successfully in the Loxjie A40 (It has a bipolar (+/-) power supply and it's - speaker terminals go to ground with only one filter in the + line).

 

[gvl]

How does one use the early bird discount? I got an email but the coupons don't lead to a page where I can place an order.