Fosi Audio V3 Mono Amplifier Review

[DavidM1]

I’m not sure you understand the issue. The same thing could happen on an incorrectly implemented RCA/XLR source input switch on a stereo amp as well.

It’s not hard to understand. Fosi says xlr and rca are the same. Some people here doubt it, which is why I asked if anyone had tried a listening test. When they bring out their next stereo integrated amp it’s unlikely to have any issues with polarity.

 

[Sokel]

Video posted at #3096 post shows that polarity is the same for both RCA and XLR.
Assuming that all that fosi changed are the speaker wires they should both have the same and correct polarity in the revised version.

Older version requires opposite connection for speaker wires by the user.
This soldering may be beginner "my first soldering iron" level but at least shows that is all they have changed so the older amps are too have RCA and XLR same polarity,only reversed.

Ok,one could curse to the heavens for such a mess but there is a small excuse such half-baked products have,after all is a kickstart item,child diseases is the norm to it.

 

[DavidM1]

Ok, I’ve just done the mod. Even though I’m listening in stereo to 2 x V3m and it makes no difference, I’ve reversed my speaker connections. Now the signal is correct polarity and all is right with the world. Cheaper than buying a high end power cable for my DAC.

 

[burkm]

It looks to me, if those soldering connections have been done by someone, who is new to the soldering technique.
But if thats all there has to be done and it's valid for both inputs, then someone shouldn't have to sent his amps back to China just for that....
Even a simple exchange of the plugin positions (polarity inverted) of the speaker cables would be OK (some sticker for this is required, if some one else or You lateron is doing this).
Note: There are simple (and cheap) professional instruments available, which show the phase/polarity of each unit, Some even might have it already at home....

 

[burkm]

Ok, I’ve just done the mod. Even though I’m listening in stereo to 2 x V3m and it makes no difference, I’ve reversed my speaker connections. Now the signal is correct polarity and all is right with the world. Cheaper than buying a high end power cable for my DAC.

It only makes a difference, if You are mixing it with some other (non-inverting) amps or an active subwoofer, because than phase inversion (polarity change) does some "strange" things...
The combination might not even been hearable tp someone, if an automated room-measuring software, i.e Audyssey/YPAO/MCACC (?) etc. is taking care of any polarity/phase errors already (the distances might change).

 

[Killingbeans]

It looks to me, if those soldering connections have been done by someone, who is new to the soldering technique.

It's hard to make a modification like that look good. At least the joints don't look cold.

A thick wire soldered to a big lump of metal takes a lot of heat, and the insulation on the wires won't be happy about going through a second big thermal cycle, no matter that you do.

They should probably have replaced the wires with fresh ones, and smothered the terminal ends with gel flux before reflowing. But... time and money.

 

[burkm]

It - too - looks, as if done in a hurry.
I don't know, if Fosi Audio ordered an external company doing this "conversion", but to me this modification still looks rather "badly" done.
Delivering this to someone who bought those amps a few days ago is a rather "ugly"... I would redo it with a shrink tubing at least to cover that "misshape".
I will have to open mine (several new units), just to see, what I got...

 

[Sokel]

At least the joints don't look cold.

I'm not so sure about the red wire,if not cold it's definitely not in contact with the post's metal,it's only the solder in between that keeps them together.
I would return that.

Some heatshrink would also make the wire not looking like it was in some kind of flame-thrower conflict.

Edit:also the plastic of the posts have seen better days,magnifying them show signs of prolonged heat (probably by the absence of the gel you mentioned that would make a nice quick job if used)

 

[iLoveCats]

It's not been a terribly productive evening so far.
I've already posted a screenshot of measurements which is a clearer indication than this video IMO but learning how to make this video was a very effective way of avoiding paperwork duties.
As I've previously said, I backed the kickstarter and received my two units a few weeks ago before Fosi would have made any modifications. RCA and XLR are matched and inverted in my units.

This ends the argument. Both inputs result in reversed polarity. Thank you.

 

[vuittion]

After seeing the soldering my two Fosi Audio V3 Mono's are going back to Amazon UK for a refund.

Im not sold on the sound quality and now seeing this it's the excuse I needed. I've had a few Class d amps and each and everyone makes my ears bleed.

 

[Killingbeans]

It - too - looks, as if done in a hurry.

I will almost guarantee you it was done in a hurry. We're talking about a product with a $140 retail price. Fosi's own margin goes into the red really fast if they don't do these modifications at blistering speed.

 

[Killingbeans]

I've had a few Class d amps and each and everyone makes my ears bleed.

I'm guessing all of them was the kind with no post filter feedback, and you used them to drive speakers with high impedance in the treble region. Or maybe they were underpowered for your use case and were clipping like crazy.

Either that or the countless scary bedtime stories being told about Class D have taken root in your brain and won't let go

 

[Ohlsdorfer]

It is also unclear why not desolder the wires from the printed circuit board, instead of mixing them up with colors near the terminals

 

[Killingbeans]

Probably because you can do it without removing the PCB from the chassis. Again, time is money.

 

[vuittion]

I'm guessing all of them was the kind with no post filter feedback, and you used them to drive speakers with high impedance in the treble region. Or maybe they were underpowered for your use case and were clipping like crazy.

Either that or the countless scary bedtime stories being told about Class D have taken root in your brain and won't let go

Could be, but I never seem to get the same symptoms when im listening to a class a/b

 

[rvsixer]

It’s not hard to understand. Fosi says xlr and rca are the same. Some people here doubt it, which is why I asked if anyone had tried a listening test. When they bring out their next stereo integrated amp it’s unlikely to have any issues with polarity.

I guess I disagree. They got polarity wrong at launch, the blurb they released with the revised version still doesn’t say both rca and xlr inputs result in the same output polarity, and their support refuses to answer the question for me.

So I don’t see how that will resolve itself on an upcoming unannounced future stereo amp, and a sub listening test just doesn’t cut it you need to measure for it.

 

[DavidM1]

I guess I disagree. They got polarity wrong at launch, the blurb they released with the revised version still doesn’t say both rca and xlr inputs result in the same output polarity, and their support refuses to answer the question for me.

So I don’t see how that will resolve itself on an upcoming unannounced future stereo amp, and a sub listening test just doesn’t cut it you need to measure for it.

Hang on. Fosi has said rca and xlr are the same and there was a post earlier where someone tested it and agreed. I don’t understand all the negativity. It was the same when there was a thread panic about heat.

Phase issues with speakers are typically easy to hear by a/b comparison. If it isn’t audible at all to the listener because one speaker is a sub then perhaps the polarity difference isn’t all that important.

 

[iLoveCats]

There's literally a video demonstration by a member in this thread showing the phase is exactly the same on XLR and RCA inputs.

 

[Fosi Audio]

Sorry to have made many friends confused. We can confirm the phase is the same for both RCA and XLR input based on the measurement using an AP analyzer.

Our engineer connected two V3 Monos, one with RCA input and the other with XLR input. We can find that the phases are the same based on the AP test result.

 

[Fosi Audio]

BTW, we found some users may use an RCA-to-XLR cable to connect V3 Mono. If the convertor cable's XLR configuration is different from the standard as follows, the phase may be inverted.