Fosi Audio V3 Mono Amplifier Review

[Deleted member 72219]

I assume Fosi just switches the wires from the PCB to the output connectors? That's fine with me as its something I can easily DIY myself to make my current amps the same as the corrected ones from Fosi. Also easy to tell which configuration you have by having a peek inside.

View attachment 384091

Uh is that an antistatic cloth under there?

-Ed

 

[Stoutblock]

Uh is that an antistatic cloth under there?

-Ed

The best kitchen towel money can buy...

 

[DannyBoyNYC]

Is anyone else experiencing odd behavior with the auto setting? My monos seems to wake for no apparent reason. This happens every couple of hours randomly on one of the amps (not at the same time so far). There's a click and the LED goes bright. They go back to low power again after a while. Been going on since I powered them up 2-3 weeks ago. Mine are connected to a single 10a power supply with a filter and splitter. IIRC the issue was there and possibly worse before I received and hooked up the filter.

 

[antcollinet]

Is anyone else experiencing odd behavior with the auto setting? My monos seems to wake for no apparent reason. This happens every couple of hours randomly on one of the amps (not at the same time so far). There's a click and the LED goes bright. They go back to low power again after a while. Been going on since I powered them up 2-3 weeks ago. Mine are connected to a single 10a power supply with a filter and splitter. IIRC the issue was there and possibly worse before I received and hooked up the filter.

Most likely noise on the inputs to your amp. Does it happen if the inputs are disconnected?

 

[iLoveCats]

Is anyone else experiencing odd behavior with the auto setting? My monos seems to wake for no apparent reason. This happens every couple of hours randomly on one of the amps (not at the same time so far). There's a click and the LED goes bright. They go back to low power again after a while. Been going on since I powered them up 2-3 weeks ago. Mine are connected to a single 10a power supply with a filter and splitter. IIRC the issue was there and possibly worse before I received and hooked up the filter.

I can wake mine up by flipping on the light switch for the floor lamp in the living room.

 

[MCH]

I can wake mine up by flipping on the light switch for the floor lamp in the living room.

That's an unexpected feature

 

[JimFarrell29]

Just received mine yesterday and have noticeable hum from both midrange drivers at idle which does not increase with volume. I am using the preamp output from my Allnic 300b tube amp.
I have four different amps in my system and have no hum from any of them, so the Fosi does seem to be the culprit. I did swap the polarity of the speaker cables, being aware of the phase issues. This removed the hum from one channel but not the other.
I do have a Fosi P3 preamp and a vintage Sansui with a preamp out so will try it with those and see if the issue remains.
I bought the Fosi out of curiosity to see if it can retain the character of the 300b amp while giving it more oomf when driving my Wharfedale Elysian-4s.
Any thoughts or similar experiences?

 

[Deleted member 72219]

Just received mine yesterday and have noticeable hum from both midrange drivers at idle which does not increase with volume. I am using the preamp output from my Allnic 300b tube amp.
I have four different amps in my system and have no hum from any of them, so the Fosi does seem to be the culprit. I did swap the polarity of the speaker cables, being aware of the phase issues. This removed the hum from one channel but not the other.
I do have a Fosi P3 preamp and a vintage Sansui with a preamp out so will try it with those and see if the issue remains.
I bought the Fosi out of curiosity to see if it can retain the character of the 300b amp while giving it more oomf when driving my Wharfedale Elysian-4s.
Any thoughts or similar experiences?

My dad got a very faint (from his listening position) hum from his Magnepan LRS+ with both, the ZA3s and the original, stereo V3. Haven’t tested with V3 Monos yet as I am only shipping them out to him today, so he won’t have them until probably next week. His preamp is an Audio Research SP16, and I have reason to suspect potentially an input/output impedance mismatch or perhaps something else between his preamp and these Fosi amps. Sometimes mixing old with new yields strange results.

I can only hear the faintest of hiss when playing my head inches from my KEF LS50 Metas when driven by any of the Fosi amps. Preamp is Schiit Freya+ and it seems to pair beautifully well with them.

-Ed

 

[Stoutblock]

Just received mine yesterday and have noticeable hum from both midrange drivers at idle which does not increase with volume. I am using the preamp output from my Allnic 300b tube amp.
I have four different amps in my system and have no hum from any of them, so the Fosi does seem to be the culprit. I did swap the polarity of the speaker cables, being aware of the phase issues. This removed the hum from one channel but not the other.
I do have a Fosi P3 preamp and a vintage Sansui with a preamp out so will try it with those and see if the issue remains.
I bought the Fosi out of curiosity to see if it can retain the character of the 300b amp while giving it more oomf when driving my Wharfedale Elysian-4s.
Any thoughts or similar experiences?

Which power supplies do you have? Filters? XLR or RCA?

 

[Stoutblock]

Is anyone else experiencing odd behavior with the auto setting? My monos seems to wake for no apparent reason. This happens every couple of hours randomly on one of the amps (not at the same time so far). There's a click and the LED goes bright. They go back to low power again after a while. Been going on since I powered them up 2-3 weeks ago. Mine are connected to a single 10a power supply with a filter and splitter. IIRC the issue was there and possibly worse before I received and hooked up the filter.

RCA or XLR?

 

[antcollinet]

Just received mine yesterday and have noticeable hum from both midrange drivers at idle which does not increase with volume. I am using the preamp output from my Allnic 300b tube amp.
I have four different amps in my system and have no hum from any of them, so the Fosi does seem to be the culprit. I did swap the polarity of the speaker cables, being aware of the phase issues. This removed the hum from one channel but not the other.
I do have a Fosi P3 preamp and a vintage Sansui with a preamp out so will try it with those and see if the issue remains.
I bought the Fosi out of curiosity to see if it can retain the character of the 300b amp while giving it more oomf when driving my Wharfedale Elysian-4s.
Any thoughts or similar experiences?

Do you still get hum when you disconnect the tube amp? I am suspecting ground noise from the tube amp.

 

[Borland]

I had asked Fosi for a splitter cable to operate 2 V3 mono with a 10 A power supply. They sent me the cable but it's not the right one.
Does anyone have a photo of the splitter cable from Fosi?

THX !

 

[LarsF]

I had asked Fosi for a splitter cable to operate 2 V3 mono with a 10 A power supply. They sent me the cable but it's not the right one.
Does anyone have a photo of the splitter cable from Fosi?

THX !

I think that’s the right one, between the splitter cable and power supply is a filter with 2 female connections

 

[JimFarrell29]

Do you still get hum when you disconnect the tube amp? I am suspecting ground noise from the tube amp.

Nope. No hum with the tube amp disconnected. But then I don't get any hum using the tube amp as an integrated.
I'm using RCA connectors and have twin 48v/5A supplies. I do note that the hum is louder on the higher gain setting though it doesn't increase with volume

Thanks for your suggestions. I do have the V3 stereo but haven't used it in that system. Might give it a try and see if it hums.

 

[Borland]

I think that’s the right one, between the splitter cable and power supply is a filter with 2 female connections

Ah ok thank you!

 

[DannyBoyNYC]

RCA or XLR?

RCA being fed by a WiiM Ultra.

 

[JimFarrell29]

Do you still get hum when you disconnect the tube amp? I am suspecting ground noise from the tube amp.

So no hum when using the V3s with my vintage Sansui solid state as a preamp, but a loud thump when switching the Sansui on with the V3s attached. Don't like that at all. I think the V3s need to steer clear of vintage amps and vintage technology in modern amps.
Now we need Fosi to bring out a proper, actually useful preamp with multiple inputs and XLR balanced out.
Either that, or time to look again at the Topping Pre90.
I have the P3 but it really doesn't cut it as a proper pre.

 

[Jon L]

loud thump when switching the Sansui on with the V3s attached.

Are you saying you are turning on the Sansui (preamp) from off position while Fosi V3's are attached ALREADY powered on? Should never do that with any preamp+amp combinations.

 

[Zek]

a loud thump when switching the Sansui on with the V3s attached.

In the case of several devices connected in series, the switching on procedure should always be followed from the first in the series to the last, also when switching off, it should be done in the reverse order - from the end to the first one.

 

[JimFarrell29]

Are you saying you are turning on the Sansui (preamp) from off position while Fosi V3's are attached ALREADY powered on? Should never do that with any preamp+amp combinations.

Ahem... coughs and looks sheepish. Afraid so. Pretty sure the v3s were in the auto position. I'm an integrated amp kind of guy. Probably over 25 years since I had a prepower combo and I was trying a lot of different combinations. Switching on and off and messing with my inputs for other reasons.
Lesson learned. Hopefully not at the expense of my drivers.