Fosi v3 Mono - User Impressions | Owner's Thread

[antcollinet]

I posted this query on the review thread but it got hijacked by the capacitor dude. Hoping someone here will take the time to reply:

So I have a Topping L70 preamp connected to both a Topping PA7 amp via XLR driving one pair of speakers, and also to two Fosi V3 Monos via RCA driving another pair of speakers. I assume after reading this thread that I should swap red for black speaker wires output from the Fosi?

Only if you are playing both amps at the same time to be heard in the same place.

There is no problem with the phase reversal if you are not using different amps with different phases at the same time (for example an amp driving speakers, and another driving a sub - or with home theatre multiple speakers)

 

[ichonderoga]

Wait a minute. Unless the Fosi Mono's sound better than your very old TacT, wasn't it money wasted? I suppose you could now sell your TacT..

Yeah you have a point, one which I also considered. But I really wanted to see what 15+ years of innovation would get me. Running around continuously recommending equipment I haven't tried becomes boring. So I took the plunge, one that was significantly cheaper than the TacT in its day and got at least similar performance (if not better) - That's a win I my book

I'm sure I'll find a suitable place for the TacT, but I won't sell it, it's to dear to me.

 

[Basilderat]

Only if you are playing both amps at the same time to be heard in the same place.

There is no problem with the phase reversal if you are not using different amps with different phases at the same time (for example an amp driving speakers, and another driving a sub - or with home theatre multiple speakers)

I am definitely playing them both at the same time in the same place. Have we determined that the Fosi's are 180 deg from absolute phase?

 

[antcollinet]

I am definitely playing them both at the same time in the same place. Have we determined that the Fosi's are 180 deg from absolute phase?

I don't think we yet have an absolutely clear statement if it is one input that is inverted, or both.

It would be really good to get a definitive statement from @Fosi Audio here. (Apologies if you've given one and I've just missed it)

 

[Rafaille]

I don't think we yet have an absolutely clear statement if it is one input that is inverted, or both.

It would be really good to get a definitive statement from @Fosi Audio here. (Apologies if you've given one and I've just missed it)

If they did I missed it too. Last I read from them was some marketing bs where they admitted that polarity was reverse but did not say if it was only on RCA or XLR or both inputs... Would definitely be nice to know for sure, or at the very least to know whether all amps produced to date behave the same or not so we could rely on trusty measurements from other owners.

 

[Basilderat]

I don't think we yet have an absolutely clear statement if it is one input that is inverted, or both.

It would be really good to get a definitive statement from @Fosi Audio here. (Apologies if you've given one and I've just missed it)

We need someone with a V3M and a two channel scope. Play a fixed tone, look at input vs output ...

 

[antcollinet]

We need someone with a V3M and a two channel scope. Play a fixed tone, look at input vs output ...

Yes, that would be a start, but we shouldn't have to.

@Fosi Audio should be properly informing their customers.

1 - Which of the inputs is inverted
2 - Advice on when this matters and what to do
3 - What are the plans - if any - to fix (in detail, including how fixed units will be identified)

 

[jkw23]

As a data point, I did a quick test of the rca and balanced inputs using the following setups:

RCA: Yamaha AVR pre outs -> v3mono

XLR: Yamaha AVR pre outs -> WiiM ultra -> Topping d90 -> v3mono

I then ran YPAO (Yamahas version of Audyssey), and under both situations, they were in phase when I switched the speaker polarity. Alternately, they both showed as out of phase when I matched the output polarity. So it appears both inputs are inverted (at least with my v3 monos which I purchased as part of the kickstarter campaign).

 

[jooc]

You asked for examples of better, and you were given examples. Now you are saying it doesn't fit your definition of better. Very trollish.

Here's the eternal issue:

In this crowd, when everyone has the necessary background, it's obvious looking at those charts that the Purify/etc amplifiers will not be able to provide any audible difference over the Fosi that a human being could detect with any modern speaker playing music at any listenable volume.

However, I've seen people like Andrew Johnson and other youttube-level 'experts' use charts like that to 'prove' that you need to spend $600+ on a purify-like amps, because - well, look at the charts, see that huge spike starting at 10K? OMG that .5 DB at 20K is going to destroy the sound of your system!!! Subscribe below!

In reality, a TPA3255-based system with adequate components around it is going to pass any blind ABX listening test any human would be able to take.

 

[antcollinet]

Here's the eternal issue:

In this crowd, when everyone has the necessary background, it's obvious looking at those charts that the Purify/etc amplifiers will not be able to provide any audible difference over the Fosi that a human being could detect with any modern speaker playing music at any listenable volume.

However, I've seen people like Andrew Johnson and other youttube-level 'experts' use charts like that to 'prove' that you need to spend $600+ on a purify-like amps, because - well, look at the charts, see that huge spike starting at 10K? OMG that .5 DB at 20K is going to destroy the sound of your system!!! Subscribe below!

In reality, a TPA3255-based system with adequate components around it is going to pass any blind ABX listening test any human would be able to take.

Hmm - what about the significant FR variation you get with load variance with those TPA3255 amps which have not implemented PFFB (most of them). I don't think it is possible to claim that is inaudible.

 

[Deleted member 72219]

Here's the eternal issue:

In this crowd, when everyone has the necessary background, it's obvious looking at those charts that the Purify/etc amplifiers will not be able to provide any audible difference over the Fosi that a human being could detect with any modern speaker playing music at any listenable volume.

However, I've seen people like Andrew Johnson and other youttube-level 'experts' use charts like that to 'prove' that you need to spend $600+ on a purify-like amps, because - well, look at the charts, see that huge spike starting at 10K? OMG that .5 DB at 20K is going to destroy the sound of your system!!! Subscribe below!

In reality, a TPA3255-based system with adequate components around it is going to pass any blind ABX listening test any human would be able to take.

Right, that was not my initial interpretation of the question. Better is better (regardless of our ability to actually hear it with our own ears/brains).

-Ed

 

[jooc]

Hmm - what about the significant FR variation you get with load variance with those TPA3255 amps which have not implemented PFFB (most of them). I don't think it is possible to claim that is inaudible.

I meant to say pffb-based 3255 systems like this Fosi v3 mono, but I'd bet that 100 blind ABX tests against a Purify for example vs non-PFFB 3255 like A07 Max - same speakers, same everything else, typical modern speakers - abx test would bring something close to 50-50, random plot, for preference or even discernability.

I'm sure I could find a speaker pair that would tax both to the point where that comparison could get iffy, but I won't be using speakers like that IRL anytime soon.

I could be proven wrong re blind abx tests, I just don't think I will be. Would love to see more professionally done abx testing frankly.

Edit: This sub-discussion was spun off from a comment that manufacturers should stop using the 'old' tpa3255 in amplifiers, and I an others were curious what newer amplifier chip should be used instead to build systems around. With the adapation of pffb now with the tpa3255, how is the tpa3255 'old', and if it is, what should replace it?

 

[SMen]

Here's the eternal issue:

In this crowd, when everyone has the necessary background, it's obvious looking at those charts that the Purify/etc amplifiers will not be able to provide any audible difference over the Fosi that a human being could detect with any modern speaker playing music at any listenable volume.

However, I've seen people like Andrew Johnson and other youttube-level 'experts' use charts like that to 'prove' that you need to spend $600+ on a purify-like amps, because - well, look at the charts, see that huge spike starting at 10K? OMG that .5 DB at 20K is going to destroy the sound of your system!!! Subscribe below!

In reality, a TPA3255-based system with adequate components around it is going to pass any blind ABX listening test any human would be able to take.

I agree. At what point to we reach such diminishing technical returns that it becomes questionable spending more.

I came to ASR because I read the Aiyima A07 review after getting one and thinking it sounds good. The Fosi's sound much more powerful, transparent ... and I am getting altogether a much larger scale / presence from the speakers. I can look at the measurements and say, okay, 80db SINAD vs 100 ... that would appear to be audible, along with I am presuming performance with different loads, distortion etc.

But at what point 110 db SINAD vs 100? Manufacturers reducing gain to the minimum to improve figures (not just amps but dacs etc)

This is why I am hoping for more user impressions here vs other amps users here actually own and have used.

 

[JeremyFife]

I'm happy that Purifi / Hypex NCx500 based amplifiers are technically better than the wee Fosi v3 mono under review.

I'm unlikely to buy one because they are more expensive and there are cheaper alternatives (like the Fosi v3 mono) that are more than good enough for me.
In some senses then the Fosi v3 mono is, for me, "better".

Different uses of the word: technical or engineering quality vs utility.

Actually, I probably won't get the Fosi v3 when I finally need a new amp. Not bothered by the phase inversion although I wish Fosi would clarity. Following the conversation about heat, although I live in Scotland so cooling is not a problem.

By the time I need one I fully expect that something else will come along

 

[Giro413]

I did this for a couple of days and it does seem that unplugging my turntable removes the problem. Hopefully grounding the turntable (which the WiiM Ultra will allow) will fix it.

I have now received my Wiim Ultra, which I have hooked up to the V3 Monos. Even without the turntable hooked up at all the V3's keep clicking on and off. Reason why turnable is not hooked up is that my SUPPHON050: SUPRA PHONO cables won't fit in the ULTRA. A bit surprising to me as the Wiim Pro Plus had no issue with those same cables. Guess I have some tweaking of settings and searching for rca adapters to do.

 

[Sokel]

I agree. At what point to we reach such diminishing technical returns that it becomes questionable spending more.

I came to ASR because I read the Aiyima A07 review after getting one and thinking it sounds good. The Fosi's sound much more powerful, transparent ... and I am getting altogether a much larger scale / presence from the speakers. I can look at the measurements and say, okay, 80db SINAD vs 100 ... that would appear to be audible, along with I am presuming performance with different loads, distortion etc.

But at what point 110 db SINAD vs 100? Manufacturers reducing gain to the minimum to improve figures (not just amps but dacs etc)

This is why I am hoping for more user impressions here vs other amps users here actually own and have used.

There's more technical aspects than measurements only under the hood.

What I consider better doesn't burn your speakers/upstream devices,most importantly your ears and of course your house.

So how one takes care to get less of the above? (there's no zero chance,all devices can fail)
Two things,thoughtful engineering and third party western certifications.

Ok,it would be even nicer to be ENEC,but that's hard to find.
But,proper stress tests (heat,vibration,long-time testing at all possible climate variations,etc ) and certifications need both time and money,sometimes we read about the new Purifi module for example expected in a year (hint,it's not the design that takes so long,it's all the above along with the R&D)

So,"better" is not an abstract term we use without thought.

 

[Miley_B]

My impressions of Fosi V3 Mono
Since there seems to continued interest in how these perform I'm posting my, somewhat limited experience with them so far.

Background info
I backed the kickstarter project and went for two units with one 10a PSU and opted to wait until the power filter was ready before they shipped anything which meant I received the amplifiers later than many backers despite being an early backer.
I was drawn to the project because of the PFFB implementation, the remarkable value proposition shown from the testing conducted by Amir and of course mono blocks are audiophile cool! At this price I was happy to take a punt on them and even if they were to end up not being in my main system they would surely find service somewhere given their excellent measurement results.
My listening hasn’t been extensive as I have been very busy with work however I’ve heard enough now to form a firm opinion.

Initial impression
Very positive. They look good, feel solid and are nicely finished in my opinion. I like that they come with a combi XLR 1/4" jack socket. If I didn’t know how much they cost and just had a guess I would certainly have guessed that they cost more than I paid.

Lets get the computer out and see what's going on
At the first opportunity I had I plugged them into my basic 2ch stereo home system using the balanced XLR connection and ran some in room REW tests comparing against the Topping PA7 plus which was in there previously. They were unsurprisingly remarkably similar in frequency, phase and impulse response. Referencing back to the Topping PA7 plus frequency response measured in Amirs test dated April 18th 2023 showed that the V3 mono has a frequency response matching Fosi revised design as posted in post #14 of the review thread.
What does separate the PA7 and the V3M in my measurement is the V3 mono has a slightly elevated harmonic distortion between 5kHz and 18kHz particularly at 12kHz where it was briefly as much as a 5dB increase. All of my measurements for this test, both amps, show elevated odd harmonics within my system centred on 12.4kHz which will no doubt be exaggerating anything in this area.
The other thing which was immediately obvious was of course the polarity inversion, this isn’t a problem for my situation, however I did reach out to Fosi to ask for clarification and their reason for doing this, I received the same responses as others on this forum and wasn’t quite sure what to make of their replies.

Other stuff
I have not used the auto power switch functionality other than briefly to confirm it switches on and off as expected.

They do run quite hot but so do other TPA3255 based amplifiers that I’ve tried so I’m not overly worried, I shall leave that up to others on this forum to concern themselves with. Probably best not to wrap them up in a cosy jumper on a hot summers day though. To touch there doesn’t seem to be much difference between the temperature when the V3m is working moderately hard and when it is on but at idle.
The PSU certainly is quite large but I haven’t noticed it get so much as warm thus far.
It’s unlikely I will be pushing them to their output limits in my modestly sized house, maybe at their limit heat may become more of an issue.

Listening
This is the interesting bit right?! As I previously mentioned the other amplifier that I have in the system currently is the Topping PA7 plus.
They do not sound identical. I felt I could hear the slightly elevated HF distortion from the moment I plugged them in (before I’d uncoiled my microphone XLR), then I thought I was imagining it because it seemed inconsistent but the more I listened the more convinced I was that I could hear something, it’s minor but it's certainly present. I find it to be noticeable in tracks which are on the brighter side and content that is hard panned as it increases the apparent width whilst also smearing the HF detail ever so slightly. Encouraged by the data and being somewhat unconvinced that I wasn’t kidding myself I utilised a very disgruntled wife and daughter for blind testing and confirmed that after level matching I could hear the difference, however it really is very slight and I had to create short loops of a couple of tracks that I thought brought it to prominence to get consistent results. Not terribly representative of the real world! FWIW all blind testing was using a single speaker (and therefore a single amp on the PSU) to eliminate the possibility of L/R comb filtering skewing my perception.
I effectively hear no background noise with either amplifier.
I have heard no other sonic difference. For me it is quite incredible how well these amplifiers perform for the money.

Stuff I’ve used to assess performance
DAC :
RME ADI-2 Pro FS R Black edition
Focusrite Red8Pre
Software:
Smaart V8
REW V5.x
Roon
Qlab V5
J river Media Center 32
Micropohone:
Earthworks M23R
Speakers:
Focal 906

One other thing, the little orange power light on one unit appears to have failed!

 

[antcollinet]

80db SINAD vs 100 ... that would appear to be audible

Whatever you are hearing (if anything) is very unlikely to be the SINAD difference.

Possibilities are:

Load dependent frequency response on the A07 (No PFFB)
More available power (A07 overloaded and clipping)
Nothing at all (sighted listening impacted by perceptive bias). This is IMO the most likely.

 

[SMen]

My impressions of Fosi V3 Mono
Since there seems to continued interest in how these perform I'm posting my, somewhat limited experience with them so far.

Background info
I backed the kickstarter project and went for two units with one 10a PSU and opted to wait until the power filter was ready before they shipped anything which meant I received the amplifiers later than many backers despite being an early backer.
I was drawn to the project because of the PFFB implementation, the remarkable value proposition shown from the testing conducted by Amir and of course mono blocks are audiophile cool! At this price I was happy to take a punt on them and even if they were to end up not being in my main system they would surely find service somewhere given their excellent measurement results.
My listening hasn’t been extensive as I have been very busy with work however I’ve heard enough now to form a firm opinion.

Initial impression
Very positive. They look good, feel solid and are nicely finished in my opinion. I like that they come with a combi XLR 1/4" jack socket. If I didn’t know how much they cost and just had a guess I would certainly have guessed that they cost more than I paid.

Lets get the computer out and see what's going on
At the first opportunity I had I plugged them into my basic 2ch stereo home system using the balanced XLR connection and ran some in room REW tests comparing against the Topping PA7 plus which was in there previously. They were unsurprisingly remarkably similar in frequency, phase and impulse response. Referencing back to the Topping PA7 plus frequency response measured in Amirs test dated April 18th 2023 showed that the V3 mono has a frequency response matching Fosi revised design as posted in post #14 of the review thread.
What does separate the PA7 and the V3M in my measurement is the V3 mono has a slightly elevated harmonic distortion between 5kHz and 18kHz particularly at 12kHz where it was briefly as much as a 5dB increase. All of my measurements for this test, both amps, show elevated odd harmonics within my system centred on 12.4kHz which will no doubt be exaggerating anything in this area.
The other thing which was immediately obvious was of course the polarity inversion, this isn’t a problem for my situation, however I did reach out to Fosi to ask for clarification and their reason for doing this, I received the same responses as others on this forum and wasn’t quite sure what to make of their replies.

Other stuff
I have not used the auto power switch functionality other than briefly to confirm it switches on and off as expected.

They do run quite hot but so do other TPA3255 based amplifiers that I’ve tried so I’m not overly worried, I shall leave that up to others on this forum to concern themselves with. Probably best not to wrap them up in a cosy jumper on a hot summers day though. To touch there doesn’t seem to be much difference between the temperature when the V3m is working moderately hard and when it is on but at idle.
The PSU certainly is quite large but I haven’t noticed it get so much as warm thus far.
It’s unlikely I will be pushing them to their output limits in my modestly sized house, maybe at their limit heat may become more of an issue.

Listening
This is the interesting bit right?! As I previously mentioned the other amplifier that I have in the system currently is the Topping PA7 plus.
They do not sound identical. I felt I could hear the slightly elevated HF distortion from the moment I plugged them in (before I’d uncoiled my microphone XLR), then I thought I was imagining it because it seemed inconsistent but the more I listened the more convinced I was that I could hear something, it’s minor but it's certainly present. I find it to be noticeable in tracks which are on the brighter side and content that is hard panned as it increases the apparent width whilst also smearing the HF detail ever so slightly. Encouraged by the data and being somewhat unconvinced that I wasn’t kidding myself I utilised a very disgruntled wife and daughter for blind testing and confirmed that after level matching I could hear the difference, however it really is very slight and I had to create short loops of a couple of tracks that I thought brought it to prominence to get consistent results. Not terribly representative of the real world! FWIW all blind testing was using a single speaker (and therefore a single amp on the PSU) to eliminate the possibility of L/R comb filtering skewing my perception.
I effectively hear no background noise with either amplifier.
I have heard no other sonic difference. For me it is quite incredible how well these amplifiers perform for the money.

Stuff I’ve used to assess performance
DAC :
RME ADI-2 Pro FS R Black edition
Focusrite Red8Pre
Software:
Smaart V8
REW V5.x
Roon
Qlab V5
J river Media Center 32
Micropohone:
Earthworks M23R
Speakers:
Focal 906

One other thing, the little orange power light on one unit appears to have failed!

Excellent! I do hope the HF distortion bit is bias! Great review. I'm probably going to rope in a couple of kids over the next couple of weeks - and use one speaker and then another for proving the op amps don't make a difference

 

[SMen]

Whatever you are hearing (if anything) is very unlikely to be the SINAD difference.

Possibilities are:

Load dependent frequency response on the A07 (No PFFB)
More available power (A07 overloaded and clipping)
Nothing at all (sighted listening impacted by perceptive bias). This is IMO the most likely.

Yes, I think power would be an obvious one, and PFFB on 8ohm speakers too. I have certain 60s albums that are painful if there is high frequency response 'uplift'.
The completely different volume control would be another factor - balanced relay vs unbalanced basic volume pot in the Aiyima.
Unless my perception of improvement regarding the balanced relay is perceptive bias?

But as with diminishing returns in terms of how much we spend, or diminishing returns as advances are made in measured technical excellence, there are diminishing returns on certain arguments. There comes a point when two pieces of equipment do, in fact, sound different to each other when level matched and so forth, and the perceptive bias opinion becomes a form of bias .

You can't stir a volume pot! Surely?! I think you probably can, (and it is all good fun).




I'll be self-arming myself with the perceptive bias argument for the op amps...