Fosi Audio V3 Mono Amplifier Review

[memphiskat]

This was posted on FB by Fosi. Looks like the same statement posted here with the addition of the news that they will modify the polarity markings on the next production batch.


"Fosi Audio
3h ·
Official Statement Regarding the Inverted Phase of the V3 Mono
Dear V3 Mono Users,
Due to the implementation of the PFFB architecture, the phase inside the V3 Mono is inverted when the input signal is processed, which can help enhance the audio quality. The polarity markings on the V3 Mono's back panel align with the chip’s output and not the inverted phase. Normally, using two V3 Monos together won't cause any phase issues. However, if you integrate the V3 Mono with other equipment, please note that the phase might be inverted.
We apologize for any inconvenience this may have caused. This is indeed a shortcoming in our work, as we failed to clearly inform everyone about this design in advance. We will modify the V3 Mono and make the polarity markings match the phase in the next batch of production.
If you have any other questions or feedback regarding this statement or the V3 Mono, please feel free to contact [email protected]. Thank you for your attention and understanding.
Best Regards,
Fosi Audio Team"

 

[EddNog]

This was posted on FB by Fosi. Looks like the same statement posted here with the addition of the news that they will modify the polarity markings on the next production batch.


"Fosi Audio
3h ·
Official Statement Regarding the Inverted Phase of the V3 Mono
Dear V3 Mono Users,
Due to the implementation of the PFFB architecture, the phase inside the V3 Mono is inverted when the input signal is processed, which can help enhance the audio quality. The polarity markings on the V3 Mono's back panel align with the chip’s output and not the inverted phase. Normally, using two V3 Monos together won't cause any phase issues. However, if you integrate the V3 Mono with other equipment, please note that the phase might be inverted.
We apologize for any inconvenience this may have caused. This is indeed a shortcoming in our work, as we failed to clearly inform everyone about this design in advance. We will modify the V3 Mono and make the polarity markings match the phase in the next batch of production.
If you have any other questions or feedback regarding this statement or the V3 Mono, please feel free to contact [email protected]. Thank you for your attention and understanding.
Best Regards,
Fosi Audio Team"

Yes, so fix for single-ended users and break for balanced input users. Outstanding!

-Ed

 

[antcollinet]

Yes, so fix for single-ended users and break for balanced input users. Outstanding!

-Ed

That's what I was thinking. I guess they could swap the polarity of the balanced input at the same time.

@Fosi Audio can you clarify?

 

[SMen]

Is this not handled where the op amp converts the RCA unbalanced input to balanced? Surely this is where Fosi need to make the necessary changes?

 

[antcollinet]

Is this not handled where the op amp converts the RCA unbalanced input to balanced? Surely this is where Fosi need to make the necessary changes?

Possibly - but that would require a PCB layout change. Far more likely they are going to just swap the colours of the speaker terminals and any +/- markings - which is what they said they were doing.

 

[SMen]

Possibly - but that wold require a PCB layout change. Far more likely they are going to just swap the colours of the speaker terminals and any +/- markings - which is what they said they were doing.

Or even just how the RCA connects to the board?

Or am I completely missing something and being v. dumb!

 

[somebodyelse]

Or am I completely missing something and being v. dumb!

You even liked the post where I explained what you were missing last time you asked.

 

[antcollinet]

Or even just how the RCA connects to the board?



View attachment 383621

Or am I completely missing something and being v. dumb!

You can't swap the RCA wires, since one of them is connected to ground. You don't want to connect the signal wire to ground.


EDIT : or what @somebodyelse said.

 

[SMen]

You even liked the post where I explained what you were missing last time you asked.

You can't swap the RCA wires, since one of them is connected to ground. You don't want to connect the signal wire to ground.


EDIT : or what @somebodyelse said.

Thank you. That was what I needed to understand better (because where I was coming from was swapping wires rather than having to modify the board). And yes thank you @somebodyelse as I re-reread and you did explain about the RCA - but generally with likes I'm either appreciating someone for actually taking the trouble to technically explain (yours, and you both), or for making me laugh...

The more I understand, the bigger c**k up this seems by Fosi ... so I spread a couple more likes for the cynical remarks too !

 

[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