Fosi Audio V3 Amplifier Review

[VientoB]

I'm pretty sure the knob controls volume, Matt.

 

[Matt1974]

I'm pretty sure the knob controls volume, Matt.

Does it do anything weird to the gain ratio is my question. But yes maybe I’m overthinking it!

 

[chomi]

Anyone buy a fosi V3 recently notice that they changed the case? (I opened it and same internal pcb) Almost exactly the same but the logos are more of a gray than white now. The left is one from a year ago and the right is one I bought recently.

 

[AnalogSteph]

Left logo is 100% silkscreen. Right could be lasered perhaps? A macro shot at an angle may tell more.

 

[Kagemusha]

I got yesterday the V3, and today is beeing returned, it was making like interference noises, coming from the 32V PSU. So nice components inside the amp but what components do they have in the PSU? . Luckily I bought it from Amazon.
My 1st and last Fosi device I will buy. I don want my house to burn down, if an amp make strange noises when I touch it I can not image what will happen in 1 or 2 years, if it manages to get that old.
I have and had smsl, topping and a loxje, all working fine, but this Fosi was a no for me. Maybe was just bad luck on this device.

 

[antcollinet]

I got yesterday the V3, and today is beeping returned, it was making like interference noises, coming from the 32V PSU. So nice components inside the amp but what components do they have in the PSU? . Luckily I bought it from Amazon.
My 1st and last Fosi device I will buy. I don want my house to burn down, if an amp make strange noises when I touch it I can not image what will happen in 1 or 2 years, if it manages to get that old.
I have and had smsl, topping and a loxje, all working fine, but this Fosi was a no for me. Maybe was just bad luck on this device.

Almost certainly nothing to do with the amp or power supply (Did you hear noise with no input connected?) and most likely to do with ground loops (or other ground issues) in your system.

 

[Kagemusha]

I have tested with 3 amps, and the electrical in the house is good. I have right now connected an Emotiva amp, and no issues.
Same for a loxje and an hypex.
Noises were there with only power connected, no speakers. The noises were not coming out from the speakers. If I touch the amp, only that, generate noise.

 

[bgravato]

I have tested with 3 amps, and the electrical in the house is good. I have right now connected an Emotiva amp, and no issues.
Same for a loxje and an hypex.
Noises were there with only power connected, no speakers. The noises were not coming out from the speakers. If I touch the amp, only that generate noise.

Was the noise coming from the amp or from the power supply? Could it be coil whine?

 

[damjov]

Hello friends,
I have b&w 683 (S1) attached to my tv in living room via old denon reciever avr2312. i use it for watching tv, movies, listening music on youtube ect. Before i have yamaha 1067 (now is broken) that sound much better than the denon that i use now. I have no experience with class d amps so i want to ask, is it possible to get good sound for my needs with a fosi v3, aiyima a07 or similar and connect with a smsl ps100 via hdmi arc with the tv? thanks

 

[antcollinet]

Noises were there with only power connected, no speakers. The noises were not coming out from the speakers. If I touch the amp, only that generate noise.

OK - fair enough. That is weird, and not right.

 

[Mikett]

Well I bought three of the FOSI V3 Stereo Amps and integrated them with a MiniDSP Dlex Eight DSP controller driven by a WIIM Pro.
This system was to update/renew/refinish a set of B&W 802F speakers I have had with me since 1981. Over 43 years old. The 802s had been stored away. I decided on the above project because 3 FOSI V3s with 48V were affordable to couple with the MiniDSP Flex 8. This was to test whether I should go active with some Satori Textreme drivers on my main rig.
Long story short. Incredible, when I first set them up roughly just by ear before using REW and measuring my friend who own some Magicos jaw dropped.
The rise in output at the extremes high frequencies might actually be a BENEFIT to older domes. I confirmed this with my measurements on the old 802 which still used the soft domes and not the aluminum, or diamond tweets. I have these tuned to 25Hz in my room, tuned out the room resonances and with the headroom with the 48V PS and low end DSP control I have there is no issue at all.
Thanks FOSI and Aiyima for this category of amps.

 

[Boozle00]

Hey Im looking for some help.

I have an audio technica lp7 turntable and a Cambridge audio phono pre-amp.

When using my sansui integrated this setup works fine.

When plugging this into the fosi V3 I get a high pitched ground hum. I believe its called a 120 sine or something like that.

I have tried extra grounding from the tt to the preamp and then to the fosi but am having little joy in solving this issue.

Any tips would be appreciated.

Many thanks

 

[Wolf11Man]

what input do you use at the Fosi?

 

[Old_School_Brad]

what input do you use at the Fosi?

Hey Im looking for some help.

I have an audio technica lp7 turntable and a Cambridge audio phono pre-amp.

When using my sansui integrated this setup works fine.

When plugging this into the fosi V3 I get a high pitched ground hum. I believe its called a 120 sine or something like that.

I have tried extra grounding from the tt to the preamp and then to the fosi but am having little joy in solving this issue.

Any tips would be appreciated.

Many thanks

How did you try grounding the Fosi?

 

[Wolf11Man]

The Aux output is not an alternative input for the small plug. That is why I ask. I had someone who thought this was just a second input.

Ah, yes, does it produce music through the speaker or only "hum". Hum usually is not high pitched, but a low frequency.

If there is normal music played with hum, unplug the phono-pre power supply. It should play on for a few seconds. Is the hum gone when the wall wart of the pre is plugged out?

 

[Boozle00]

View attachment 409035


How did you try grounding the Fosi?

Ground cable from ground terminal on tt to screw on fosi. Also tried from ground on phono pre to screw on fosi. Unless i need to do both?.

 

[Boozle00]

Rca in from from the phono pre-amp rca out

 

[Boozle00]

The Aux output is not an alternative input for the small plug. That is why I ask. I had someone who thought this was just a second input.

Ah, yes, does it produce music through the speaker or only "hum". Hum usually is not high pitched, but a low frequency.

If there is normal music played with hum, unplug the phono-pre power supply. It should play on for a few seconds. Is the hum gone when the wall wart of the pre is plugged out?

When playing the tt it produces music with the accompanying hum (this is more then a standard low frequency ground hum that im used to, its more high pitched).

Ill give the unplugging a go when im home next thans.

 

[Wolf11Man]

Also try to reverse the mains plug of tt, pre and Fosi PS one at a time and note differences.
You may have some power supply for a laptop, printer or whatever with the same power plug 5.5mm x 2.5mm, positive center pin. Anything from 18-48 Volt is fine. Worth a try, sometimes the PS is problematic with audio for unknown reason. I had some HP laptop supply that worked very well.
An expensive Mean Well SMPS produced some beeping sound from the speaker.

 

[antcollinet]

When playing the tt it produces music with the accompanying hum (this is more then a standard low frequency ground hum that im used to, its more high pitched).

Ill give the unplugging a go when im home next thans.

The problem might be that there is no actual earth ground to the system at all. I have a similar situation with my turntable, and have eliminated nearly all the noise by running a ground wire from the phono preamp ground terminal to a ground connection in an electrical socket.

If you do this take great care to ensure you are connecting to ground and not live or neutral. I removed the ground/neutral pins on the plug to be sure - we can do that in the UK.


EDIT - I've just looked up a couple of CA phono preamps, and they both have 3 pin power connectors which should mean this solution is not needed. Which Preamp is is you have? Does it have a 3 pin power connection, and is the earth terminal on the back connected to the earth terminal in the power connector? And do you have proper earthing in your mains supply?