Fosi Audio V3 Mono Amplifier Review

[Rotel75]

Is there a simple explanation why the XLR input measures better that the RCA? one more op amp, different gain, ..?
I'm using a RCA to XLR cable since a few days, so SINAD 100 now?
Couldn't they just remove the RCA input and add an adapter instead?

 

[antcollinet]

Is there a simple explanation why the XLR input measures better that the RCA? one more op amp, different gain, ..?
I'm using a RCA to XLR cable since a few days, so SINAD 100 now?
Couldn't they just remove the RCA input and add an adapter instead?

XLR typically has better results because (again typically) the input voltage is 2x the RCA input voltage (4v instead of 2V). This means the gain can be 6dB lower, so the noise is amplified 6dB less. This typically results in a 6dB better SNR.

You can see this in the input voltage for the two input in the review. (0.41V XLR vs 0.23V RCA). So no, just using an adapter doesn't help.

 

[Lasy]

XLR typically has better results because (again typically) the input voltage is 2x the RCA input voltage (4v instead of 2V). This means the gain can be 6dB lower, so the noise is amplified 6dB less. This typically results in a 6dB better SNR.

You can see this in the input voltage for the two input in the review. (0.41V XLR vs 0.23V RCA). So no, just using an adapter doesn't help.

Wouldn’t one need the same 0,41V to reach 5W output using an rca-xlr adapter on the xlr inputs? If the xlr input accepts a typical grounded cold adapter that is…

 

[gwing]

Wouldn’t one need the same 0,41V to reach 5W output using an rca-xlr adapter on the xlr inputs? If the xlr input accepts a typical grounded cold adapter that is…

Yes, whether your source is RCA or XLR you need, for a given gain, the same input voltage to produce the same 5W output. The rca-xlr adapter isn't going to increase the voltage so you need extra gain in the V3 to reach the same output level, hence you get more amplification of the noise as well.

However, that extra doubling of the pre-amp output voltage to reach the XLR levels does need more gain in the pre-amp which is going to offset the advantages you get from less gain in the power amp. The advantage though is that with XLR the pre-amp isn't amplifying any noise picked up in the pre/power amp interconnects or the power amp itself with extra gain so that is where you come out ahead.

 

[antcollinet]

Yes, whether your source is RCA or XLR you need, for a given gain, the same input voltage to produce the same 5W output. The rca-xlr adapter isn't going to increase the voltage so you need extra gain in the V3 to reach the same output level, hence you get more amplification of the noise as well.

Correct

However, that extra doubling of the pre-amp output voltage to reach the XLR levels does need more gain in the pre-amp which is going to offset the advantages you get from less gain in the power amp.

To an extent - There is no benefit for the quantisation noise in the digital signal - the lower amp gain is offset by the increased DAC gain. However the full benefit exists for the amp "self noise", which is no longer amplified as much.

 

[C0mbat]

I own different Hypex-Modules based amps including. Nilai500 and at least I think Fosi Mono's are even par

Thanks. This is exactly the feedback I was looking for. I don't need more power so there doesn't seem to be any potential benefit.

 

[petch]

Is the 48V/10A PSU with the power filter okay? Or should I just get 2 48V/5A PSUs?

 

[Rotel75]

Is the 48V/10A PSU with the power filter okay? Or should I just get 2 48V/5A PSUs?

I had the 10A brick first, but I prefer two PS... no filter needed, independent power and short speaker cables.
Using two Aiyima 36V 6A, limiting the max. wattage and (hopefully) reducing the chip heat.
Really surprised how detailed and dynamic these amps are.

 

[C0mbat]

Unfortunately not. I've have only NC400, NCx500 and UCD2K beside the Nilai500 here. In summary to my ears Nilai500 is most musical (but a bit to cold for my ears although driven by tube preamp). more fun is Fosi V3 Mono and even better 3E Audio modules that I built two mono amps on.
Looking forward these days to receive the new 3E Audio finished mono amps.

Thanks for bringing my attention to 3E Audio. Another one to look at What do you think the advantages of the new finished mono amps are vs the Fosi Audio V3 Mono?

https://www.aliexpress.com/item/1005007964184254.html

I've got my concerns about the company to be honest. Their website doesn't load and why have they called it a mono stereo amplifier?

 

[Rotel75]

Thanks for bringing my attention to 3E Audio. Another one to look at What do you think the advantages of the new finished mono amps are vs the Fosi Audio V3 Mono?
I've got my concerns about the company to be honest. Their website doesn't load and why have they called it a mono stereo amplifier?

I think 3E's naming ideas are poor... see 260-2-29A and 480-1-29A
But technically I trust them (industry experience, parts used) much more than Fosi (defect reports, wire issues, filter).
If I didn't have the V3M already, I'd get one of the a A5/7.

 

[uktweaker]

Is the 48V/10A PSU with the power filter okay? Or should I just get 2 48V/5A PSUs?

I bought the config with 48v/10a and dc filter and was not at all happy. Amps cross triggering and bad hash noise if one amp was off. I bought two aiyima 48v 10A GaaN power bricks on amazon (uk) and couldn't be happier now.

 

[cfwotzka]

Thanks for bringing my attention to 3E Audio. Another one to look at What do you think the advantages of the new finished mono amps are vs the Fosi Audio V3 Mono?

https://www.aliexpress.com/item/1005007964184254.html

I've got my concerns about the company to be honest. Their website doesn't load and why have they called it a mono stereo amplifier?

Fully understand your point. 3E Audio, as far as I know, is mainly OEM supplier and that might be a reason that have not invested very much in their B2C interface yet. their are many users out there very happy with 3E Audio modules (used for DIY projects) that couldn't await them to provide finished amps. website perhaps just overloaded right now I guess. if you find a minute search on this forum for 3E Audio and be surprised

 

[cfwotzka]

Thanks. This is exactly the feedback I was looking for. I don't need more power so there doesn't seem to be any potential benefit.

exactly my point of view as well

 

[Vlvvv]

Hello! My current system is - fosi zd3 + aiyima a70. The sound is fine, but I got the idea of replacing the aiyima a70 with two fosi v3 mono. Please tell me if it's worth doing or not? Maybe there is someone who owned them and compared them? Thanks)

 

[antcollinet]

Hello! My current system is - fosi zd3 + aiyima a70. The sound is fine, but I got the idea of replacing the aiyima a70 with two fosi v3 mono. Please tell me if it's worth doing or not? Maybe there is someone who owned them and compared them? Thanks)

The onlly thing the V3 will bring you is a little more power.

But it is only 1.3dB more power resulting in an approx 13% increase in perceived volume.

Personally I would not bother.

 

[JW001]

The onlly thing the V3 will bring you is a little more power.

But it is only 1.3dB more power resulting in an approx 13% increase in perceived volume.

Personally I would not bother.

13% - is it an increase of the perceived volume or rather the ratio of powers? The perceived increase of volume will be next to none.

 

[Vlvvv]

The onlly thing the V3 will bring you is a little more power.

But it is only 1.3dB more power resulting in an approx 13% increase in perceived volume.

Personally I would not bother.

Thank you very much for your answer! And happy new year!

 

[antcollinet]

13% - is it an increase of the perceived volume or rather the ratio of powers? The perceived increase of volume will be next to none.

Percieved volume. Which is why I said "perceived volume" . And yes, a 13% perceived volume change not very noticeable - certainly not worth paying a few hundred £$ for. But it is noticeable.


1.3dB as a percentage of power is about 35%

 

[antcollinet]

And happy new year!

Same back.

 

[JW001]

Percieved volume. Which is why I said "perceived volume" . And yes, a 13% perceived volume change not very noticeable - certainly not worth paying a few hundred £$ for. But it is noticeable.


1.3dB as a percentage of power is about 35%

Right, right... 10 lg (power_ratio) = 1.3dB ==> power_ratio = 10 ** 0.13 = 1.35 ==> power_increase_percent = 35%

I guess, my question is how you arrived at the perceived volume (loudness?) increase.