Fosi Audio V3 Mono Amplifier Review

[antcollinet]

The more I understand, the bigger c**k up this seems by Fosi

Yes, I'd hoped they could swap the balanced connection with wires - but it looks like the balanced input is soldered directly to the PCB - so that is not possible either.

So it looks like the only proper solution will be PCB tracking change. I wonder if that is what they are planning.

 

[Bleib]

Hmm, I wonder how normal polarity issues are with other products as well. Topping PA5 was only XLR and PA5 II introduced RCA for instance..

 

[antcollinet]

Hmm, I wonder how normal polarity issues are with other products as well. Topping PA5 was only XLR and PA5 II introduced RCA for instance..

The fact we've not heard anything means they are probably fine.

It's not very hard - you just need to make sure that if you have multiple inputs, they all deliver the same phase (as each other) to the power section of the amp, and then however the outputs are connected, colour and label them so that output phase = input phase.

 

[Bleib]

The fact we've not heard anything means they are probably fine.

It's not very hard - you just need to make sure that if you have multiple inputs, they all deliver the same phase to the power section of the amp, and then however the outputs are connected, colour and label them so that output phase = input phase.

Well, we had well over a hundred pages before someone tried out the RCA input through their Denon AVR pre-out.
How many will try out XLR?

 

[Sokel]

Well, we had well over a hundred pages before someone tried out the RCA input through their Denon AVR pre-out.
How many will try out XLR?

Most of the thread is about waiting so the lots of pages is not an indicator.

However,the issue was found because someone got the safe practice of actually measuring something that got into the chain.
Not so common,I wish more people do that.

 

[antcollinet]

Well, we had well over a hundred pages before someone tried out the RCA input through their Denon AVR pre-out.
How many will try out XLR?

OK - but most of those pages were before anyone had a device. It was only a couple of weeks after the first shipments before we found out.

 

[vuittion]

Does this amp accept trs balanced cables.

 

[EddNog]

Does this amp accept trs balanced cables.

Yes.

-Ed

 

[vuittion]

Thank you

 

[vuittion]

I am going to order two of these amps via Amazon UK. I dont have a massive budget and will also need a Dac with balanced trs outputs to use as a preamp. Any ideas on the cheapest solution.

 

[antcollinet]

I am going to order two of these amps via Amazon UK. I dont have a massive budget and will also need a Dac with balanced trs outputs to use as a preamp. Any ideas on the cheapest solution.

SMSL D0100 or D6 or Topping E50 are amongst the lowest cost balanced output DACs

At a little more there's also the Schiit modius - but with XLR outputs rather than TRS

 

[EddNog]

SMSL D6 or Topping E50 are amongst the lowest cost balanced output DACs

Do their volume controls work well? I had an SMSL DO100 a while back and the volume control wasn’t usable because of the insanely loud clicking/popping noises between tracks whenever sample rate changed if I tried using a straight power amp or setting volume to max on a power amp with adjustable volume/gain.

-Ed

 

[antcollinet]

Do their volume controls work well? I had an SMSL DO100 a while back and the volume control wasn’t usable because of the insanely loud clicking/popping noises between tracks whenever sample rate changed if I tried using a straight power amp or setting volume to max on a power amp with adjustable volume/gain.

-Ed

No idea - I don't have any of them. @vuittion should probably find some owners to ask.

 

[vuittion]

SMSL D0100 or D6 or Topping E50 are amongst the lowest cost balanced output DACs

At a little more there's also the Schiit modius - but with XLR outputs rather than TRS

Thank you

 

[EddNog]

Thank you

I recommend against DO100 due to the clicking/popping noises when changing sample rates. First hand ownership experience.

-Ed

 

[Miley_B]

My pair of Fosi V3 Mono were delivered just over a week ago. Sadly I haven't had much time to listen to them however when I measured them within my system, using the XLR input showed an inverted polarity.
I contacted Fosi and they asked me to check my wiring and the RCA input so I did a few mores tests (My RCA and XLR inputs have the same phase and polarity) and sent them some measurement data after which they sent me the same confusing reply that some other members on this forum received stating that the amplifier doesn't have positive or negative phases.
I'm very impressed with Fosi responsiveness to email but less impressed by the actual content of the replies as they clearly aren't resolving the confusion.
For me the inversion is not a big deal although I see no reason for the product to have been released with it this way when it's such a simple fix. But IMO if it is to be inverting then it must be stated somewhere in the literature or on the unit.
Someone earlier asked about some Topping units and I have measured the PA7 plus and the original PA5 both on XLR and found the polarity to be normal (positive).

No doubt my input will add to the confusion so I shall look forward to the next 100 pages of this review thread.

 

[DavidM1]

It seems the issue, if I’m following it correctly, is that by incorporating PFFB Fosi’s design has made balanced and single ended inputs opposite in polarity at the binding posts. Not a concern for anyone using only either balanced or single ended for stereo put possibly an issue with multiple amps, say, in home theatre.

It seems the solution is straightforward and easy to implement. Fosi should include a statement in the manual to say that in multi amp systems they recommend using either balanced or RCA connectors for all amps in the system to avoid the possibility of speakers being out of phase.

Warning customers that the polarity is reversed between the different inputs is pretty much all that’s needed.

 

[early rejecter]

Fosi should include a statement in the manual to say that in multi amp systems they recommend using either balanced or RCA connectors for all amps in the system to avoid the possibility of speakers being out of phase.

That advice only addresses the issue if all of the amps in the system are V3 Monos; it doesn’t account for common scenarios like a system that includes a subwoofer amplifier, or an AVR powering surrounds.

 

[Sokel]

Now wait,because @Miley_B reports that both XLR and RCA are the same and reversed.
That changes things and differs from other users experience.

Someone must measure this thing properly,on lab conditions.

 

[antcollinet]

Now wait,because @Miley_B reports that both XLR and RCA are the same and reversed.
That changes things and differs from other users experience.

Someone must measure this thing properly,on lab conditions.

Agreed (Perhaps not lab conditions - but at least with an oscilloscope looking at input compared with output for both inputs) . Confusion abounds.