Fosi Audio V3 Mono Amplifier Review

[TurtlePaul]

I sure hope Fosi adds some sort of configuration ID between the inverted polarity and non-inverted polarity versions of the V3. If they don’t its going to be a huge opportunity to mess up a system if you have a mixture of both versions!

I think it will be clear - it sounds like they are going to switch which speaker terminal is labeled "+" and "-".

 

[Bleib]

I think it will be clear - it sounds like they are going to switch which speaker terminal is labeled "+" and "-".

Hope they clearly label version number on the amps so we know which are fixed.

 

[TurtlePaul]

Hope they clearly label version number on the amps so we know which are fixed.

The ones with the red binding post on the right will be new and the ones with the red binding post on the left will be the old version, if you get what I am saying they will do.

 

[Rafaille]

Still a very bad idea if RCA and XLR inputs give different polarity...
Would be nice to know for sure whether this is the case or not.

 

[mike70]

Wow - that's peak...errr.... something.

Audiophillia perhaps.

Well, you don't know that you get what you paid? 2k / foot interconnects will add more transparency ... like lifting a veil from the speaker.

Sorry, I forget the amps are 150 USD each

 

[DavidMcRoy]

My four amps arrived the other day and all have red on the left, and no + or - label. This is not a big deal for me since they're all going to be used to drive 12" woofers in my new 7-way DIY dipole speakers. I have to check for phase among all the drivers, anyway and everything's done in DSP, so I'll just flip polarity or not depending on what I see in the crossover region frequency response.

 

[SMen]

I've had a few Class D amps and have always found them harsh/clinical for my taste. How would you sum up the Fosi Audio V3 Mono sound.

My impression of the V3 Monos is that they do not 'add' anything that could be judged harsh or clinical to the sound.
I enjoy many analogue recordings from the 50's / 60s / 70s. Some of these are bright, but many more have what many of us view as a 'warm' sound. Guess what. They sound warm.

So it's all about the source in my view with the V3 Monos - which is what I was hoping for when I bought them.

 

[EddNog]

My impression of the V3 Monos is that they do not 'add' anything that could be judged harsh or clinical to the sound.
I enjoy many analogue recordings from the 50's / 60s / 70s. Some of these are bright, but many more have what many of us view as a 'warm' sound. Guess what. They sound warm.

So it's all about the source in my view with the V3 Monos - which is what I was hoping for when I bought them.

Accurate.

-Ed

 

[Stoutblock]

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.

 

[EddNog]

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?

 

[EddNog]

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.