# Fosi Audio V3 Mono Amplifier Review

## Rate this amplifier:

• ### 4. Great (golfing panther)

• Total voters
504

#### Zuiko

##### Member
How are you getting those calculations? You can't just assume that all the PSU power can be output to speakers.

My goal was 'simplified' power from the power supplies, not actual power to the speakers.
I get even that's theoretical. The comparison may still be useful in relative terms...

#### antcollinet

##### Master Contributor
Forum Donor
not actual power to the speakers.
Then you shouldn't state per channel power, and should clearly state you are only talking about PSU power output.

The comparison may still be useful in relative terms...
It isn't - it is misleading.

#### dr_mick51

##### Active Member
intersting.
Top: this ebay listing https://www.ebay.co.uk/itm/275540643117
Bottom: Guddu's review here in ASR:
most (all?) huntkey models, the three figures after the letters denote power in watts

View attachment 366964

have seen worse made though :
View attachment 366969
Both are the same power supply. The Model number (HKA30048063-7D which means 300W, 48V 6.3A) is the same, the input current is the same. The actual output power is the same. I think it's a little dishonest/misleading to state that the second PS provides 10A(max), people may believe this is a 480W power supply.
The real question is , do we really need all that power? With the 4Vrms input signal we provide at -12dBFS or even -14dBFS attenuation(x0.2 to x0.25) , and the total amplifier gain of 20.5dB or x10.6, the output voltage the amp can produce is 4V x0.20 x10.5= 8.4V, at 4Ohm we have 8.4^2 / 4= 17.64W

This means that a 8.4V DC/0.707 = 12V DC Power supply with 2A is more than capable of providing power for this particular use case. This is in "theory" because we know the TPA3255 needs at least 18V and 10.8V for the other digital circuitry:

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#### gwing

##### Active Member
Forum Donor
I think it's a little dishonest/misleading to state that the second PS provides 10A(max), people may believe this is a 480W power supply.
Am I missing something here? Fosi have kindly shown on this forum that their supply is indeed capable of the claimed 48V 10A output, have you not read those posts or are you suggesting the supplied evidence and results are false/faked?

#### Talisman

##### Major Contributor
Forum Donor
Both are the same power supply. The Model number (HKA30048063-7D which means 300W, 48V 6.3A) is the same, the input current is the same. The actual output power is the same. I think it's a little dishonest/misleading to state that the second PS provides 10A(max), people may believe this is a 480W power supply.
The real question is , do we really need all that power? With the 4Vrms input signal we provide at -12dBFS or even -14dBFS attenuation(x0.2 to x0.25) , and the total amplifier gain of 20.5dB or x10.6, the output voltage the amp can produce is 4V x0.20 x10.5= 8.4V, at 4Ohm we have 8.4^2 / 4= 17.64W

This means that a 8.4V DC/0.707 = 12V DC Power supply with 2A is more than capable of providing power for this particular use case. This is in "theory" because we know the TPA3255 needs at least 18V and 10.8V for the other digital circuitry:
View attachment 369480
Before drawing this kind of conclusion it would be useful to continue reading....

#### amix

##### Member
ps. looks like 250 people or so are getting the 2x 48V 10A ... If you're here, what speakers are you driving or what are your reasons for 480W/channel?
Here!

Though it's not about the 480W/channel, especially since Fosi doubts, the 10A will give much more output power.

I did so, since I suffer from bad synergy of my speakers and my amplifier (QUAD 66 Pre + QUAD 306 PA) for far too long. The speakers are Dynaudio Contour 1.3 SE. It is generally believed, all across the forums I visited so far, that Dynaudios want not so much power as they want current. I still don't understand the technical aspects behind it, but I had enough and took the chance to get the higher current supplies.

Dynaudio's customer support recommended an amp with high reserves.

#### Fosi Audio

##### Senior Member
Audio Company
Forum Donor
Both are the same power supply. The Model number (HKA30048063-7D which means 300W, 48V 6.3A) is the same, the input current is the same. The actual output power is the same. I think it's a little dishonest/misleading to state that the second PS provides 10A(max), people may believe this is a 480W power supply.
The real question is , do we really need all that power? With the 4Vrms input signal we provide at -12dBFS or even -14dBFS attenuation(x0.2 to x0.25) , and the total amplifier gain of 20.5dB or x10.6, the output voltage the amp can produce is 4V x0.20 x10.5= 8.4V, at 4Ohm we have 8.4^2 / 4= 17.64W

This means that a 8.4V DC/0.707 = 12V DC Power supply with 2A is more than capable of providing power for this particular use case. This is in "theory" because we know the TPA3255 needs at least 18V and 10.8V for the other digital circuitry:
View attachment 369480
Hello there, please ignore the model number on the power supply. This 48V/10A power supply is custom-made with Huntkey, and we will correct the model name. We have previously released the relevant test report and test video for this power supply. For details, please refer to here.

#### jvdburgt

##### Member
Fosi posted details about their SP601 speaker, asking users’ inout on which calibration they prefer.

Thoughts?

#### Talisman

##### Major Contributor
Forum Donor
View attachment 369955Fosi posted details about their SP601 speaker, asking users’ inout on which calibration they prefer.

Thoughts?
I think it's a frequency response recorded in the room, so I don't really understand what we're supposed to infer

#### Jeromeof

##### Addicted to Fun and Learning
Forum Donor
I think it's a frequency response recorded in the room, so I don't really understand what we're supposed to infer
Exactly - they should have provided some quasi-anechoic measurements at least

#### Sokel

##### Master Contributor
I see they use an LMS analyzer though.
Results should be comparable between measurements.

#### ovi

##### Member

Rated power depends on the load impedance and power supply.

You can calculate input sensitivity with
`sqrt(Rated power [W] * load impedance [Ω]) * 10 ^ (gain [dB] * -1 / 20)`

So for 240W at 4Ω, XLR input you need sqrt(240*4)*10^(-20.5/20)=2.93Vrms

With RCA in, it's sqrt(240*4)*10^(-25.5/20)=1.64Vrms

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#### staticV3

##### Master Contributor
Check this out, may be useful:

ovi

#### amix

##### Member
Does anybody know the V3 Mono's damping factor? And does it change with the 10A PSU? @Fosi Audio

#### Rover

##### Active Member
Hello there, please ignore the model number on the power supply. This 48V/10A power supply is custom-made with Huntkey, and we will correct the model name. We have previously released the relevant test report and test video for this power supply. For details, please refer to here.
Hi.When will the Fosi Audio M3 Mono be available?

#### antcollinet

##### Master Contributor
Forum Donor
Hi.When will the Fosi Audio M3 Mono be available?
Kickstarter has June as an estimate.

#### Atryx10

##### New Member
I'm new here, so IDK if this should be in its own thread or not, but how would you connect these up in a 2.1 surround setup? I was considering getting a DAC and headphone amp (that could be used as pre-amp), so I'd have something that I could use for both headphones and speakers, but I don't understand how it'd be possible to connect that with three Fosi V3 Mono for a 2.1 setup, since as far as I can tell, headphone amps don't seem to have the capability for more than 2.0. I was thinking of getting a FiiO K19, but maybe I should just give up on trying to get this to work...

Edit: Thanks for the answers! That has made me get some additional questions, but as it's going to stray from the main topic of this thread, it's better for me to wait with replying until this gets moved to its own thread
Though, from what I gather so far, it's going to be for the best if I get a separate DAC and headphone amp, with the headphone amp having pre-amp capabilities and a sub out. If my understanding is correct, I should be able to make do with my FiiO Q15 as the DAC, and just try to find a headphone amp with a sub out. Perchance
Now, I wonder how cursed it would be if I were to use a FiiO K19 plugged into a Denon AVC-X3800H, that then plugs into the Fosi V3 Mono amps. This stack would after all have the ability for IEM and headphone driving, alongside the ability to do surround up to 7.4.4

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#### antcollinet

##### Master Contributor
Forum Donor
Options:

1 - You need a Dac or other device with a built in crossover, and output for a sub. One example would be a mini DSP flex.
2 - You split the 2.0 output, and send it both to the main amps, and to the sub. Then use the low pass filter on the sub to perform the crossover. No high pass for the main speakers this way though.

#### DTTOM37

##### Active Member
I'm new here, so IDK if this should be in its own thread or not, but how would you connect these up in a 2.1 surround setup? I was considering getting a DAC and headphone amp (that could be used as pre-amp), so I'd have something that I could use for both headphones and speakers, but I don't understand how it'd be possible to connect that with three Fosi V3 Mono for a 2.1 setup, since as far as I can tell, headphone amps don't seem to have the capability for more than 2.0. I was thinking of getting a FiiO K19, but maybe I should just give up on trying to get this to work...
Hi, Bienvenue ;-)
1rst: Usually the .1 may be an active subwoofer, which means it already has integrated amplifaction. You would only need a third amplifier in case you use a third passive speaker/sub (unamplified)

2nd: In case you use an active sub, you could get a DAC (like the SMSL D6/6s) that allows dual full range signal output via a) balanced/TRS and b) unbalanced/RCA outputs, which could feed a) you speakers with the Mono V3 and b) the active sub. Imho, one of the cheaper options, and quite doable if your sub does low pass filtering.

3rd: Alternatively you could look at the WIIM range, which may - with the all new WIIM Ultra - may allow pre-amp functionality & 2.1 output.
Afaik, it's still assumed that its parametric EQ will receive high pass / low pass functionality quite soon. (pehaps it already has and I am not up to date ?)

Means: HP: Signal above selected frequency will be outpt to the speaker amp, LP: Signal below selected frequency will be sent to subwoofer only.

As often, the more you invest the better are your options for your specific use case. AFAIK

#### rvsixer

##### Addicted to Fun and Learning
I'm new here, so IDK if this should be in its own thread or not, but how would you connect these up in a 2.1 surround setup? I was considering getting a DAC and headphone amp (that could be used as pre-amp), so I'd have something that I could use for both headphones and speakers, but I don't understand how it'd be possible to connect that with three Fosi V3 Mono for a 2.1 setup, since as far as I can tell, headphone amps don't seem to have the capability for more than 2.0. I was thinking of getting a FiiO K19, but maybe I should just give up on trying to get this to work...
IMO should be in its own generic thread, but onwards:
1) 2.x, by definition, is not a surround setup (you need surround speakers for that, 2.x is just front/left/x subs)
2) Headphones (generally) only support 2.0 (no sub input or output). Of the few that do support a "sub" inside of them, the crossover is internal to them so still only need 2.0 input.
3) Many ways to skin this cat, what I would setup:
- miniDSP Flex Eight as already mentioned (assuming all your sources are digital).
- Fosi mono blocs for the 2.x output to speakers (make sure your passive sub(s) are okay with the Fosi output limits, otherwise just use a different amp for the sub(s)). If your subs are active that negates the need for external amp(s).
- Would make for a very compact and versatile base setup, easy to change up amps/speakers etc. in the future
- Always use more than one sub but that's a whole other discussion

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