Fosi Audio V3 Mono Amplifier Review

[Lux_ury]

Just used two 48v power bricks sorted out the Hum and popping when on and off.
That YouTube chap who said to use two bricks was right (Laugh emjoi) No DC filter inline. The auto functionality works flawless on mine no delays signal triggers the relay fine.

 

[Guddu]

 

[rvsixer]

Perhaps something like this...

Tangent PreAmp II (Black)

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Good find.
I'm not the one who was looking, but looking at the datasheet/user manual specs there are none for the sub out. So I kind of doubt the original requestors configurable subout criteria is met (most lower cost devices I have seen/used simply have a full range mono signal for "sub out"). And like the miniDSP suggestion I had put forth, there's the superfluous preamp section the requestor did not need.

 

[Stoutblock]

So none of the Fosi information releases specify different polarity between SE (RCA) and Balanced (XLR)? So were both originally incorrect and now fixed? Or is one or the other originally incorrect and now corrected? Anyone in possession of the new revised version? Curious if they just reversed the output wires to the speaker terminals? If so, we should be able to assume both SE and Balanced were originally incorrect?

Here is a photo from the Fosi FB group that shows new vs old.

 

[Bleib]

View attachment 386594

Seems they should specify in more detail which are fixed and if it's both XLR and RCA. Serialnumbers usually are a good way as purchase dates will be quickly forgotten by most.

 

[Sokel]

fosi has to urgently make sure that PR has some short of connection and understanding with the engineer guy they have there.
I mean...

When someone doesn't know which is which (as the above),how can people expect to get out of this polarity mess?

 

[antcollinet]

Also who is running two bricks and are you running two DC filters

The filter is only needed if you run two amps from one PSU.

 

[antcollinet]

So were both originally incorrect and now fixed? Or is one or the other originally incorrect and now corrected?

We still don't know. because @Fosi Audio IS CONSISTENTLY FAILING TO PROVIDE CLEAR INFORMATION. (Sorry for shouting, but this is getting ridiculous now.

I simply don't understand why.

My recommendation to anyone thinking about purchasing to hold off until this is rectified.

 

[rvsixer]

Pre purchase decision here:
Between the larger 10A brick AND the filter, I am just not seeing the touted more compact/cleaner installation vs. two of the smaller 5A supplies. Is it just me?

I also just sent their support staff the following polarity question, will not purchase before answered satisfactorily:

I would like to purchase your Fosi Mono V3 amps before the 20% off discount code expires. Please advise on the new Fosi Mono V3 units produced after 8/2/2024 (with polarity fix), that switching between RCA and XLR inputs WILL NOT switch speaker output polarity.

In my specific use case of a 2.1 system with a subwoofer (with built-in plate amp):
1) User has a 2.1 system
2) Right and left main speakers are driven by Fosi Mono V3 amps
3) Subwoofer is driven by its own internal amp
4) User selects RCA input on Fosi Mono V3 amps
5) Fosi Mono V3 amps and subwoofer amp are setup to have correctly matched relative polarity (i.e. no severe dip at crossover frequency etc.)
6) User selects XLR input on Fosi Mono V3 amps
7) Fosi Mono V3 and subwoofer amp CONTINUE to have correctly matched relative polarities (i.e. phase between mains and sub are NOT reversed from Fosi RCA input configuration)

 

[antcollinet]

Is it just me?

No, its not - just get two 5A supplies and have done.

 

[Lux_ury]

We still don't know. because @Fosi Audio IS CONSISTENTLY FAILING TO PROVIDE CLEAR INFORMATION. (Sorry for shouting, but this is getting ridiculous now.

I simply don't understand why.

My recommendation to anyone thinking about purchasing to hold off until this is rectified.

Just like a kick starter in the balls.
Just being clear I'm using one 48v 5amp from v3 and the other sent with my kit 48v 10Amp brick.
Maybe if they used Delivery Dates it would help, as I pre ordered mine in early July and got it delivered 14th Aug.

It begs the questions
Testing is done on single test frequency feeds, not speakers right so polarity doesn't matter?
I love the single fact the tests were done on a single unit with one unit from a product that should be tested in pairs off one PSU? This might have highlighted the dual psu problems?
Don't get me wrong I love the monos just testing from Fosi and independent testers could have corrected stuff earlier because that DC filter didn't work for me, it hummed if one unit was off and popped everytime it was on or off.

 

[Brian Hall]

Sorry if I missed it, but what do you do for a sub out when the channels are separated to two boxes like this and I only use one active subwoofer?

Ignore this. I was thinking these had a sub out.

 

[Fosi Audio]

We still don't know. because @Fosi Audio IS CONSISTENTLY FAILING TO PROVIDE CLEAR INFORMATION. (Sorry for shouting, but this is getting ridiculous now.

I simply don't understand why.

My recommendation to anyone thinking about purchasing to hold off until this is rectified.

Hi there, let me explain it.

For V3 MONO units purchased on or after August 2nd, 2024: The output polarity of V3 MONO has been revised. You can connect your speaker terminals normally without reversing the polarity.
-For V3 MONO units purchased before August 2nd, 2024: Using two V3 Monos together won't cause any phase issues. However, if you integrate one V3 Mono with other equipment, please note that the phase might be inverted(both RCA and XLR). To achieve optimal sound quality, please connect the speaker terminals reversely when connecting to your V3 MONO amplifier.
* If you purchase the V3 Mono from the Fosi Audio website after August 2nd, 2024, it will be the updated version. For purchases from platforms like Amazon, eBay, or AliExpress, please contact our customer service to confirm which version you are receiving.
We apologize for any inconvenience caused by this and appreciate your patience as we work diligently to rectify the problem.

 

[burkm]

But how to differentiate between both versions if they haven't been bought directly from Fosi Audio in China ?

I checked with mine (several) V3 Mono units bought through German Ebay/Fosi Audio and delivered from a German warehouse a few days ago and none seems to carry a serial-number or production-date sticker.
The only way to know if they have the speakers phase reversed on the RCA input (or both: XLR and RCA inpust ?) would be to measure them individually !
They all carry the same production-ID - at least on my units - on a bottom sticker...

 

[Bleib]

Looks like we need to compare before and after pics by ourselves. Le sigh

 

[antcollinet]

Hi there, let me explain it.

For V3 MONO units purchased on or after August 2nd, 2024: The output polarity of V3 MONO has been revised. You can connect your speaker terminals normally without reversing the polarity.
-For V3 MONO units purchased before August 2nd, 2024: Using two V3 Monos together won't cause any phase issues. However, if you integrate one V3 Mono with other equipment, please note that the phase might be inverted(both RCA and XLR). To achieve optimal sound quality, please connect the speaker terminals reversely when connecting to your V3 MONO amplifier.
* If you purchase the V3 Mono from the Fosi Audio website after August 2nd, 2024, it will be the updated version. For purchases from platforms like Amazon, eBay, or AliExpress, please contact our customer service to confirm which version you are receiving.
We apologize for any inconvenience caused by this and appreciate your patience as we work diligently to rectify the problem.

Hi

Thanks for the reply - perhaps you can expand a little

Prior to the fix:

You say "might" be inverted. Is it? or Is it not? There is no "might" - unless you have shipped different designs at different times.
Is it definitely BOTH the RCA input and the XLR input that are inverted? Because some here have done some tests that indicated only one of them is inverted.

AFTER the fix - are both inputs the same and non - inverted?

HOW have you implemented the fix? Assuming both inputs were inverted presumably it was only necessary to swap the wires to the speaker terminals internally? (Knowing this might enable people to check if they have a fixed unit or not)

Thanks.

 

[burkm]

The problem is, that for the 1st delivery the German "Widerufsfrist" has been depleted by the delivery of the "gift" (July 26), because ebay Germany had been signaled the delivery of the amps, although the "real" delivery of the V3 Mono units happened quite a bit later on; their delivery has been around August 8th. The second delivery happened lateron, where "gift" and amp delivery happened on consecutive days. Here I am still in the German "Widerrufsperiode" of 14 days, ebay stated even October 13th for the return. What a mess...

The statement of Fosi Audio concerning the polarity of the V3 Mono speaker ouputs confuses me too, because now the signal to the speakers of both, XLR and RCA input, are inverted (?), although, following by the comments of several buyers who seem to have tested it, this should have happened only be for the RCA inputs... Strange !

What is the real situation now ???

Note: That "official" statement I am referring to has not been sent to me, but seems to have been published on the Fosi Audio web site, but where ??? I can't find it...

 

[Zek]

HOW have you implemented the fix?

Here is a photo from the Fosi FB group that shows new vs old.

They just reversed the output wires to the speaker terminals.

 

[Sokel]

@Fosi Audio ,a simple question:

Does XLR and RCA input result in the same polarity at the output?
Have you tested that?

Because some reports said otherwise,that they are different.That's the important test.

 

[MCH]

Maybe the evidence of RCA and XRL having opposite phases are weaker than it seems?

I have been following this thread and I only remember one report of different polarity of RCA vs XRL, and that was based on a room measurement with sub integration iirc.

On the other side, there was another member that made more in depth measurements showing RCA and XRL had the same phase. To the best of my knowledge Fosi never said the phase of both inputs was different.

My apologies if I have missed something.

PS: I have the feeling that Fosi should have done nothing but perhaps adding a caution sticker, now there are amps out there with opposite polarity, and being monoblocks…. Just my opinion