Fosi Audio V3 Mono Amplifier Review

[sikahr]

From the datasheet, in BTL stereo, at 48V, THD+N 1%,
@ 4 ohm Max power is 2 x 230w, equals 2 X 7,5 Ampers = 15A
@ 8 ohm Max power is 2 x 130w, equals 2 x 4 Ampers = 8A
48V PSU 10A looks much better then 5A.

 

[Guddu]

From the datasheet, in BTL stereo
48V PSU 10A looks much better then 5A.

Correct - for stereo - as per datasheet, and practically as well.

But one must consider the thermal requirements, actual implementation, and limitations of that specific implementation & topology.
And hence the tests & measurements of the finished product are important than specifications of the chip.

 

[Guddu]

For 8 Ohms load there are no data for PBTL mono mode in datasheet and i can't find measurement at 48V online.
If we presume half Max power of 4 Ohm PBTL, 260/2, 130W, equals cca 4A current, so 5A PSU is enough in this case.

Only for reference - BTL Stereo vs PBTL Mono:

 

[ryanboyle918]

I wouldn't want to be a seller of Hypex or Purifi at this point. Fosi and Aiyima are iterating so quickly that they're already highly competitive with Hypex and Purifi at, what, close to one fifth the price for comparable units at retail?

I wouldn't want to be a seller of Hypex or Purifi at this point. Fosi and Aiyima are iterating so quickly that they're already highly competitive with Hypex and Purifi at, what, close to one fifth the price for comparable units at retail?

We are going to expand more local distributor and official dealer to come with us for better customer service.
We prefer to built-up a longterm and win-win cooperation partnership.
Just contact me, if you were interested to join with us.

 

[Fosi Audio]

As someone who isn’t an engineer, I will do my best to analyze the issue of power supply and output power.
The V3 Mono utilizes the TI TPA3255 amp chip configured in PBTL mode. We can refer to TI’s datasheet to discuss the output power of the TPA3255 at different input voltages.

As we can see, with the 48V supply voltage, the rated power at a 4Ω load is about 260W, and at a 2Ω load, it is 450W. This is very close to the power we measured on our AP analyzer when using a 48V/5A power supply. Therefore, if we need to further increase the output power, increasing the current of the power supply is not very effective; instead, we should consider increasing the input voltage.

Our team measured with a 48V/10A power supply and found that the output power of a single V3 Mono does not significantly increase compared to using a 48V/5A power supply. We also measured powering two V3 Monos with a single 48V/10A power supply and found that, compared to powering one V3 Mono with a 48V/5A power supply, the output power was exactly the same. Therefore, we are offering a one-to-two power configuration option for more flexible system building. And, by using one less power supply unit, you can save some space and achieve a neater system setup.

 

[DavidM1]

We also measured powering two V3 Monos with a single 48V/10A power supply and found that, compared to powering one V3 Mono with a 48V/5A power supply, the output power was exactly the same.

Thanks for the information. Was there any difference in other measurements? Was there a difference with noise or distortion, for example? Even if the difference is inaudible I'm curious to know if there was any other effect of sharing the power supply.

 

[Fosi Audio]

Thanks for the information. Was there any difference in other measurements? Was there a difference with noise or distortion, for example? Even if the difference is inaudible I'm curious to know if there was any other effect of sharing the power supply.

We measured both PSUs that we provide, and compared all the other parameters and found there is almost no difference.

 

[GabrielPhoto]

We measured both PSUs that we provide, and compared all the other parameters and found there is almost no difference.

While testing the v3 stereo mode with the 48v 5amp running dual Dayton BST-300ex shakers the amp is unable to handle it and the sound keeps cutting out.
Is this maybe a case where the 48v 10a can help or something else going on?

 

[sikahr]

Fosi,
48V 5A PSU is 250W PSU.
2 Ohm PBTL load power is 450W, equals to 15 A current.

250W-450W
5A-15A

 

[sikahr]

While testing the v3 stereo mode with the 48v 5amp running dual Dayton BST-300ex shakers the amp is unable to handle it and the sound keeps cutting out.
Is this maybe a case where the 48v 10a can help or something else going on?

Shakers are 4 ohm,
From the datasheet, in BTL stereo, at 48V, THD+N 1%,
@ 4 ohm Max power is 2 x 230w, equals 2 X 7,5 Ampers = 15A

 

[GabrielPhoto]

Shakers are 4 ohm,
From the datasheet, in BTL stereo, at 48V, THD+N 1%,
@ 4 ohm Max power is 2 x 230w, equals 2 X 7,5 Ampers = 15A

And to clarify the same happens to the aiyima 07 max so I have to run each shaker with a single 07 max in bridge mode and then it works brilliant

 

[gwing]

And to clarify the same happens to the aiyima 07 max so I have to run each shaker with a single 07 max in bridge mode and then it works brilliant

If the above calculations are correct you would need, for maximum power output , 15A @ 48V which would mean one 07 amp for each shaker *each* with a 10A power supply. That said if the amp is normally supplied with a 5A supply I wouldn't assume it a done deal that you can overdrive it with higher capacity supplies (it would seem unlikely that Fosi have actually tested these amps so far beyond their design parameters).

I don't know anything about your shakers, but do they have a volume control you can turn down so they work within the limits of the amp(s) powering them?

 

[Talisman]

Shakers are 4 ohm,
From the datasheet, in BTL stereo, at 48V, THD+N 1%,
@ 4 ohm Max power is 2 x 230w, equals 2 X 7,5 Ampers = 15A

Just out of curiosity, why use such an advanced and high-performance power amplifier for shakers? I think we need something very powerful and less sophisticated instead.
A professional Behringer amplifier for example or simply a Sabaj A20A 2022 which puts out 350watts when bridged. Any old Yamaha p1500/3500 power amplifier would do the job much better and can be found used for less than 150 euros

 

[Sokel]

Just out of curiosity, why use such an advanced and high-performance power amplifier for shakers? I think we need something very powerful and less sophisticated instead.
A professional Behringer amplifier for example or simply a Sabaj A20A 2022 which puts out 350watts when bridged. Any old Yamaha p1500/3500 power amplifier would do the job much better and can be found used for less than 150 euros

Same curiosity here,why struggle with it and don't get a used pro-audio nice and light little beast who can throw you out of your chair?
Sound has nothing to do with it.

 

[Fosi Audio]

Fosi,
48V 5A PSU is 250W PSU.
2 Ohm PBTL load power is 450W, equals to 15 A current.

250W-450W
5A-15A

Generally speaking, a 48V/5A power supply should suffice for normal use, and the one we provide actually includes a certain margin.

Using a 48V/10A power supply compared to a 48V/5A power supply can provide a higher current capacity and greater safety margin for the amplifier. This increased current capacity effectively reduces voltage drops in power lines and internal circuits under high loads, improving the response of the amplifier when handling dynamically complex audio signals. Moreover, the higher current output means that the system is less likely to overheat or shut down due to current overload when facing peak loads, thereby enhancing the overall reliability and stability of the system. Additionally, opting for a more robust power supply can alleviate the operational stress on various components of the amplifier, prolong the lifespan of the equipment, and offer more flexibility for potential system upgrades in the future.

 

[somebodyelse]

While testing the v3 stereo mode with the 48v 5amp running dual Dayton BST-300ex shakers the amp is unable to handle it and the sound keeps cutting out.
Is this maybe a case where the 48v 10a can help or something else going on?

My guess is something's getting too hot with sustained high output, and protection is kicking in. Whether that's the amp or the PSU I couldn't say. @pma noted the A07 shut down after a few minutes sustaining a lower power output (~50W IIRC). That had a smallish internal heatsink and no ventilation, while Fosi use the case as a heatsink so should do somewhat better. The tests here are short term, not like the FTC spec power tests that include long term preconditioning at a good proportion of rated output. Pointing a fan at the amp and/or psu may help keep the temperature under control.

 

[sikahr]

Just out of curiosity, why use such an advanced and high-performance power amplifier for shakers? I think we need something very powerful and less sophisticated instead.
A professional Behringer amplifier for example or simply a Sabaj A20A 2022 which puts out 350watts when bridged. Any old Yamaha p1500/3500 power amplifier would do the job much better and can be found used for less than 150 euros

@Talisman @Sokel
@GabrielPhoto using Shakers, not me

I'll use my amps for light pro audio (Behringer PK 108, Power rating: 320 W peak, Impedance: 8 Ohm)
Plan is using 2 amps in mono PBTL mode with 48V 5A PSU each.
Target Max continuous power is 122-126W @1%THD (Amir measurement), which equals to cca 4A current, so 5A PSU (per amp) is enough in this case.

 

[Trasam Audio]

Does the V3 MONO adopt flat copper inductor?

 

[Trasam Audio]

View attachment 360792

Looks like the GAIN switcher only works for RCA input, the XLR has fixed gain.

 

[Deleted member 72219]

Looks like the GAIN switcher only works for RCA input, the XLR has fixed gain.

Accurate.

I actually like that the XLR has lower gain than either RCA setting; allows me more room to play with source gain, preamp buffer mode selection (I have a Schiit Freya+) and volume adjustment granularity.

-Ed