Fosi Audio V3 Amplifier Review

[gasolin75]

The amp play 2x160 watt 4 ohm at 1% thd peak 190 ish pr channel with a 48 5 a power supply

if your worried about not having power either get zu audio or tekton audio speakers or 2 of these amps in bridged mode https://www.audiophonics.fr/en/hifi...-ma5332m-bluetooth-50-350w-4-ohm-p-17037.html

 

[peng]

Hello Gasolin75
I thought that if the Power supply is 48V on let's say an load of 6 ohms, U/R = 48V /6 Ohms 8 Amps is requested per Loudspeaker
But Fosi is limited to 5A in total so 2.5A per channel
So per channel P=U*I =48*2.5= 120W per channel

Same with 42V , 7A requested ; but 8.5A in total, thus 4.25A per channel
So per channel 42*4.25 =178W

But effectively I didn't think about Max gain (I remember i have read 20x on Fosi V3 so yes 26dB
Can you elaborate?
Just trying to learn and understand

The more expensive Audiophonics 48 V 7.3 A is obviously better than the Fosi 48 V 5 A, all else being equal (meaning the specs are verifiable and are measured under the same conditions and according to the same applicable standards).

As far as your calculations go, you may or may not benefit from the 7.3 A vs the 5 A because it depends on your speaker's impedance characteristics, and the contents you are listening to, though given the choice, I would always take the one rated for higher current, when the rated voltages are the same.

 

[TurtlePaul]

Amir is being coy when describing the Fosi 48V supply. To be clear - the test shows it outputting closer to 7 amps. I don’t think you get anything going with the Audiophonics supply unless it is similarly very conservative in the rating.

 

[antcollinet]

What would be the best match for getting best power from
Fosi 48V 5A or Audiophonics 42V 8.5A power supplies?

Is this correct to expect max 48v*2.5A =120W per channel if Fosi
and 42*4.25A = 178.5W with Audiophonics whatever the load between 4 and 8 Ohms?

It depends on your speaker impdeance.

8ohm speakers will need more voltage.
4ohm speakers will need more current.

For your speaker impedance Rs

It will current limit at IxI * R
It will voltage limit at VxV / R

Take the lowest of the two limits as the power that PSU can deliver to your speakers (for both channels driven use half the PSU power)

You also need to account for the fact that the chip amp needs about 5V of headroom - so for power calculations take 5V off the PSU voltage. And that voltage represents the maximum peak of a sine wave, so you need to then divide by sqrt(2) to get an RMS voltage.

So Maximum speaker voltage (for power calc) = (Vpsu-5)/1.41
48V PSU gives 30.4V RMS
42V PSU gives 26.1V RMS


This however is complicated by the fact that in Amirs measurements, the FOSI had very good short term current headroom over the rated current, so can deliver a lot more power than the calculations would suggest.

 

[peng]

Amir is being coy when describing the Fosi 48V supply. To be clear - the test shows it outputting closer to 7 amps. I don’t think you get anything going with the Audiophonics supply unless it is similarly very conservative in the rating.

Unless there is current limiting incorporated, most if not all power supplies have short term overcurrent capability. So, if the 5 A, or 7.3 A (Audiophonic's) are the "continuous" ratings, they of course can output more, even much more on short term basis, such as demands from music listening.

I asked Amir about "continuous" measurements and he said "I don't measure anything as continuous. I show sweeps and such but don't say they are continuous ratings."

 

[peng]

It depends on your speaker impdeance.

8ohm speakers will need more voltage.
4ohm speakers will need more current.

For your speaker impedance Rs

It will current limit at IxI * R
It will voltage limit at VxV / R

Take the lowest of the two limits as the power that PSU can deliver to your speakers (for both channels driven use half the PSU power)

You also need to account for the fact that the chip amp needs about 5V of headroom - so for power calculations take 5V off the PSU voltage. And that voltage represents the maximum peak of a sine wave, so you need to then divide by sqrt(2) to get an RMS voltage.

So Maximum speaker voltage (for power calc) = (Vpsu-5)/1.41
48V PSU gives 30.4V RMS
42V PSU gives 26.1V RMS


This however is complicated by the fact that in Amirs measurements, the FOSI had very good short term current headroom over the rated current, so can deliver a lot more power than the calculations would suggest.

lol.. it would have saved me one post if I had read yours first. By the way, where did you get the info about the 5 V headroom requirement for the Fosi amp?

 

[tades]

I don't take into account the capability of PS to exceed rated power
Audiophonics 42V 8.5A
If 4 ohms 42/4 = 10.5A per channel requested if 8 ohms 5.25A per channel requested
In both cases max current is 8.5/2 = 4.25A is the limitation => 42*4.25W per channel =178W

Fosi 48 5A
4 ohms 48/4 = 7 per channel requested if 8 ohms 6A per channel
in both cases max current is 5/2 =2.5A in both cases this is the limitation 48*2.5 per channel = 120 W

 

[peng]

I don't take into account the capability of PS to exceed rated power
Audiophonics 42V 8.5A
If 4 ohms 42/4 = 10.5A per channel requested if 8 ohms 5.25A per channel requested
In both cases max current is 8.5/2 = 4.25A is the limitation => 42*4.25W per channel =178W

Fosi 48 5A
4 ohms 48/4 = 7 per channel requested if 8 ohms 6A per channel
in both cases max current is 5/2 =2.5A in both cases this is the limitation 48*2.5 per channel = 120 W

I used Gasoline's link and it showed 48 V 7.3A so the 42 V 8.5 A must be a different PS.

I know you are not taking into account of the PS overcurrent capabilities, but I mentioned it because you asked the question which one is better, right?

If you are only referring to the rated output, then as also mentioned already, it depends on your speaker's impedance characteristics. Post#1885 covers it with a couple of numerical examples. I would just add that looking at single point impedance won't tell the whole story. If you look at the actual impedance vs frequency range curve, then you will know better whether the 42 V 8.5 A power supply is better, or worse.

Based on W only is not as good as considering both voltage and current. Again, see the examples in ancollinet's post1885. Then post back if you have questions.

 

[tades]

Adaptateur Secteur Alimentation 100-240VAC vers 42V DC 8.5A - Audiophonics

Cet adaptateur secteur prend en entrée une tension de 100-240VAC et permet de disposer en sortie d'une tension de 42V DC pour un courant de 8.5A. Son connecteur de sortie est au format Jack DC 5.5/2.5mm, compatible 5.5/2.1mm.

www.audiophonics.fr

Adaptateur Secteur Alimentation 100-240V AC vers 48V 7A DC - Audiophonics

Cet adaptateur secteur prend en entrée une tension de 100-240VAC pour sortir du 48VDC 7.3A (350W). Les composants sont intégrés dans un châssis en Aluminium robuste dissipant parfaitement la chaleur dégagée par les composants.

www.audiophonics.fr

I don't understand the 1.41 as these are DC's PS

 

[peng]

Adaptateur Secteur Alimentation 100-240VAC vers 42V DC 8.5A - Audiophonics

Cet adaptateur secteur prend en entrée une tension de 100-240VAC et permet de disposer en sortie d'une tension de 42V DC pour un courant de 8.5A. Son connecteur de sortie est au format Jack DC 5.5/2.5mm, compatible 5.5/2.1mm.

www.audiophonics.fr

Adaptateur Secteur Alimentation 100-240V AC vers 48V 7A DC - Audiophonics

Cet adaptateur secteur prend en entrée une tension de 100-240VAC pour sortir du 48VDC 7.3A (350W). Les composants sont intégrés dans un châssis en Aluminium robuste dissipant parfaitement la chaleur dégagée par les composants.

www.audiophonics.fr

I don't understand the 1.41 as these are DC's PS

Between the two, without seeing the speaker's specs I would take the 48 V 7A, but that's just based on educated guess. The thing to consider is that if the power supply is rated for 48 V then you will get just 48 V, but the current rating of 7 A, or 8.5 A, are not limited to those values as I mentioned earlier, because they can supply more current, in some cases significantly more, on short term basis (even for SMPS such as these bricks).

 

[tades]

Thanks Peng, Gasoline Antcollinet and Turtlepaul

These are exactly the kind of insights I expected !
The speaker is a four loudspeaker having a complex load "nominal 8 ohms/ minimal 4 ohms)

Final question : 42V-8.5A and Fosi 48v 5A are in similar price tag (the 48v 7A is 3 times the price)
Which one would you use ?
the 178W per channel calculated for 42-8.5 in #1888 is well above the 120W calculatedand close to peak power measured for Fosi in #1882

 

[antcollinet]

lol.. it would have saved me one post if I had read yours first. By the way, where did you get the info about the 5 V headroom requirement for the Fosi amp?

Read it somewhere (TI Chip stuff). Can't find it now in the datasheet.

But it is reasonable that the amp cannot put out the same output voltage as input. There must be voltage drops.

 

[antcollinet]

I don't take into account the capability of PS to exceed rated power
Audiophonics 42V 8.5A
If 4 ohms 42/4 = 10.5A per channel requested if 8 ohms 5.25A per channel requested
In both cases max current is 8.5/2 = 4.25A is the limitation => 42*4.25W per channel =178W

Fosi 48 5A
4 ohms 48/4 = 7 per channel requested if 8 ohms 6A per channel
in both cases max current is 5/2 =2.5A in both cases this is the limitation 48*2.5 per channel = 120 W

But you won't get max voltage and max current together unless the speaker impdeance exactly matches that requirement.

For example an 8 ohm speaker at 26.1V (RMS volts available from the 42V supply - will need 26.1/8 = only 3.2A, so you'll only get 85W per channel

 

[tades]

Thkx Antcollinet I was confused by the RMS volts !

 

[Juampa1989]

But you won't get max voltage and max current together unless the speaker impdeance exactly matches that requirement.

For example an 8 ohm speaker at 26.1V (RMS volts available from the 42V supply - will need 26.1/8 = only 3.2A, so you'll only get 85W per channel

Add that the source must emit 2 vrms on its analog output to reach that figure. If it emits less, those amplifier watts will not be reached. If more is used it will trim. Be it dac, tv, blueray, pc, etc.

 

[peng]

Thanks Peng, Gasoline Antcollinet and Turtlepaul

These are exactly the kind of insights I expected !
The speaker is a four loudspeaker having a complex load "nominal 8 ohms/ minimal 4 ohms)

Final question : 42V-8.5A and Fosi 48v 5A are in similar price tag (the 48v 7A is 3 times the price)
Which one would you use ?

To be more accurate, you need the impedance curve, not just 8 ohm nominal, 4 ohm minimum. Without that, we would have to assume something, for example, assuming there is no impedance peak significantly higher than 8 ohms in the current demanding low frequency range, and this is quite likely, then for 1/3 the price, I would take the 42 V 8.5 A power supply. On money no object basis, then the 48 V 7 A unit is the best.

Why not take the middle of the road approach and get the 48 V 5A one form Fosi?

The 178W per channel calculated for 42-8.5 in #1888 is well above the 120W calculated and close to peak power measured for Fosi in #1882

Let me repeat this, when you have both voltage and current specs, ignore the power specs and just focus on the voltage and current. For example, the 178 WPC (actually more like 157 W if antcollinet is right about the 5 V headroom reserve) is only valid if the load is 4 ohm, but about 85.6 W if the load is 8 ohm, down to 57 WPC if load is 12 ohm.

 

[tades]

Thanks for all Guy's : I'll have a lot to digest : I was focussed on Power and have to review all my mental processes
Thanks for all your clarifications.

As said : I was here to question and understand . I have now my part of job

 

[peng]

Thanks for all Guy's : I'll have a lot to digest : I was focussed on Power and have to review all my mental processes
Thanks for all your clarifications.

As said : I was here to question and understand . I have now my part of job

Maybe the following can help explain why I prefer to use voltage and current and the information are available.

First, consider the frequency response, using the 4-ohm rated KEF Reference 3:

SoundStageNetwork.com | SoundStage.com - NRC Measurements: KEF Reference 3 Loudspeakers

www.soundstagenetwork.com

Frequency response and sensitivity​

Sensitivity: 86.3dB (averaged 300Hz-3kHz on Listening Window, 2.83V/1m)

Chart A: 20Hz - 20kHz (measured @ 2m, plotted @ 1m)

You can see that if you apply 2.83 V to this speaker, it will give you roughly the specified 86.3 dB averaged 300-3000 Hz at 1 meter. You don't have to worry about impedance, as long as the power supply and output devices can handle the current demand. So far, no power "W" is mentioned, but obviously given the voltage and current, you can sort of calculate the "power" if you also know the phase angles (you can see it from the phase angle curve). Power is kind of not as meaningful, because the speaker's output is in SPL, and then is directly related to the applied voltage only (again as long as current is not limited).

In marginal cases, I consider voltage is more important because as I mentioned and repeated before, power supply cannot deliver high voltage than its rated maximum, not even on short term, but it can deliver higher short-term current above its rated maximum. That won't help if you listen to constant tones, but for music, the current demand by the speaker will not be constant, but vary with the music contents, and the speaker's impedance (based on the point on the frequency axis of the impedance curve.

Then look at the impedance curve:

See that the impedance varies with frequency, so in this case it actually dips to below 3 ohms, but also peak to about 18 ohms at about 3,000 Hz., but the important point is, who care, as long as you apply that same 2.83 V throughout the frequency range 20-20,000 Hz, and the amp can supply the current demand, you will get the 86 dB @ 1 meter, regardless of the calculated power delivered by the amplifier at that point.

Impedance magnitude variation​

 

[tades]

as long as you apply that same 2.83 V throughout the frequency range 20-20,000 Hz, you will get the 86 dB @ 1 meter,

This clarifies a lot
Many thanks

 

[Kunti]

I like reading and understanding.
I'm looking for the right music player information.
Difference between RCA 3.5 jack vs Bluetooth, is a DAC needed to play music?

if yes.
then I would choose one of the topping e30ii/ smsl
su-1.