Fosi Audio V3 Mono Amplifier Review

[MCH]

For stereo power amplifiers with 2 TPA3255 in mono operation, you should avoid using the master slave mode and implement a sufficient power supply.

The master slave mode was actually intended for multi-channel power amplifiers or AVR amplifiers, where the power supply is usually very limited for cost reasons.

Source for either statement?

 

[antcollinet]

Source for either statement?

Plus a stereo amp is just a particular cases of a multi channel amp - but with only two channels.

 

[iLoveCats]

You're not 'saving' by buying a single power supply with double the amperage. And Fosi already said a 10a on a single unit has no benefit.

 

[Roland68]

Source for either statement?

That murder argument again.
- Read the developer forums
- Deal with where the actual area of operation of the Chps is (small tip, low bodget)
- Look at the circuit suggestions in the data sheet and evaluation board -> Low Budget (this is also what the cheap designs are based on, e.g. A7)
- Don't you think it would be a good idea to have two separate amplifiers, each amplifying one side of a stereo signal, working independently of each other without affecting each other?
Of course, background knowledge and understanding of these chips, circuits and power supplies also help.

One should also not forget that companies like Topping, Sylph Audio, 3E Audio and XRK Audio have only shown what these TPA325x chips can actually do,
Or does anyone really believe that these further developments and also the Fosi monoblock with these measured values would even exist without these companies?

Which is why Fosi moved first with the monoblocks. They seem to have done quite well ...

3E Audio and Sylph Audio have had monoblocks with such performance and measurements for a few years, but unfortunately they are not ready with cases and are more expensive.

 

[amix]

And Fosi already said a 10a on a single unit has no benefit.

That's not what they said. Read here.

 

[kelesh]

Enough talk, ship the pre-orders out already!

 

[antcollinet]

That's not what they said. Read here.

No, it pretty much is what they said on this forum, here.

 

[SMen]

3E Audio and Sylph Audio have had monoblocks with such performance and measurements for a few years, but unfortunately they are not ready with cases and are more expensive.

I agree. They are DIY orientated and it is indeed a shame that they could not 'package' or 'source' things like the cases.

For stereo power amplifiers with 2 TPA3255 in mono operation, you should avoid using the master slave mode and implement a sufficient power supply.
The master slave mode was actually intended for multi-channel power amplifiers or AVR amplifiers, where the power supply is usually very limited for cost reasons. This mode really makes sense.
The mode is also not intended for use across devices.

This is good to know. It will be interesting to see the final version of the power supply provided by fosi.

In fact, it would be good to be able to compare the distributed version in a week or so with the V3 mono pre-production model reviewed here by Amir.

I was looking at this http://archimago.blogspot.com/2023/10/part-ii-topping-pa5-mk-ii-plus-pa5ii.html having looked up the Hypex mentioned by @Sokel which I think is this one: https://www.audiophonics.fr/en/power-amplifiers/audiophonics-mpa-s250nc-xlr-power-amplifier-class-d-stereo-ncore-nc252mp-2x250w-4-ohm-p-14185.html?search_query=hypex s250&fast_search=fs

I suspect many here will know this blog but I have only just found it. This review seems on point for Hypex vs 3251 vs 3255 models above.

It seems very good blog. And a good reference point, at some point, for where these Fosi v3 mono's slot into the scheme of things.

 

[Fosi Audio]

@Fosi Audio When can we buy Fosi V3 Mono at fosiaudio.com?

It'll be available on fosiaudio.com and Amazon marketplaces in July.

 

[rvsixer]

No, it pretty much is what they said on this forum, here.

What @amix posted is indeed something Fosi stated, as is the post you referenced. Basically they are contradicting themselves in an apples vs. oranges kind of way. They should clarify which is correct (and backup the FAQ claims of better current handling/lower voltage drops with complex audio on the 10A supply with data imo).

 

[amix]

No, it pretty much is what they said on this forum, here.

Did you even read the FAQ entry? There is more to an amplifier than just power output...

Also, here in the forum they stated: https://audiosciencereview.com/foru...o-v3-mono-amplifier-review.53474/post-1949671

 

[antcollinet]

Did you even read the FAQ entry? There is more to an amplifier than just power output...

Also, here in the forum they stated: https://audiosciencereview.com/foru...o-v3-mono-amplifier-review.53474/post-1949671

Yes I did - and if I remember correctly it is the same statment at your forum link.

It is nonsense. I don't think it was written by an engineer - more likely a marketing guy trying to justify the 10A supply.

 

[rvsixer]

Yes I did - and if I remember correctly it is the same statment at your forum link.

It is nonsense. I don't think it was written by an engineer - more likely a marketing guy trying to justify the 10A supply.

I agree it is nonsense (that the same Fosi Audio account posted two differing comparisons of the 10A supply). And also agree the FAQ is nonsense and contains marketing speak, what exactly is complex audio (as compared to what, simple audio?)?

 

[Negatywny]

And also agree the FAQ is nonsense and contains marketing speak, what exactly is complex audio (as compared to what, simple audio?)?

simple audio - one tone, complex audio - multiple tones...?

 

[Cal_Cobra]

The V3M Kickstarter launch has an optional upgrade package that includes their new, unreleased and [apparently] still in development SP601 "DYNAUDIO EMIT20" killer speakers. As evident by their lack of updates, and variety of user based tuning demos, along their recent "Your Voice Matters: Help Shape the Sound of the SP601!" post which shows three different [crossover?] designs and their "SPL vs FREQ" test results, it would apper that speaker design is new territory for Fosi.

Prior to all this, they've posted several YouTube videos with various crossover settings, and compared against a pair of Dynaudio EMIT20's, with the audio differences for users to comment on. The Dynaudio EMIT20 SQ appears to be their goal for the SP601.

I love companies that are interactive with their customer base, and have good marketing folks that take customer feedback to product management/engineering to build what consumers want, but in this case, it appears that Fosi may be a bit lost when it comes to making audiophile grade speakers?

Now they've updated their Kickstarter V3M page that the optional SP601 speakers in the campaign will be delayed until August, which means we probably won't see the speakers land until Christmas [2024 ??].

As a pledge backer of the V3M+SP601 package, I personally do not mind the delay if it means they're building audiophile grade crossovers, or whatever they need to do in order to engineer the speakers to truly be Dynaudio EMIT20 killers, which seems to be their goal.

Still I wonder what is the cause of the SP601 speaker delay? @Fosi Audio ?

On a positive note, if this is your thing, Fosi Audio is very generously offering an additional opamp as compensation for the delay - "**Additionally, as a token of our apology, we would like to offer you an additional MUSES02 chip with your order.*"

Sort of a silver lining for those who ordered the speakers AND have the desire for the opamp upgrade. Fosi stated that just changing one per amp had a positive audible outcome. I wonder if the extra opamp with the speaker packages will sequester additional Kickstarter pledges? Perhaps they will reach their new $500K goal, it's getting close as the coundown on the final few days plays out.

Any speculation as to the SP601 delay?

 

[DavidM1]

Fosi stated that just changing one per amp had a positive audible outcome.

I couldn’t find the quote but my memory is that their wording was more along the lines of users might find a sound they like more. It would be a stretch to suggest they said changing chips would give an objective improvement.

 

[Cal_Cobra]

I couldn’t find the quote but my memory is that their wording was more along the lines of users might find a sound they like more. It would be a stretch to suggest they said changing chips would give an objective improvement.

Right, that makes sense and that's effectively what they claim here in their post from the KS V3M FAQ:

• The V3 Mono has three op-amps. What does each one do? And if I want to get a better sound, which one should I change?
  
  The V3 Mono's mainboard houses a total of three op-amps. One is located near the RCA input and is used to convert the RCA signal into a balanced signal. The other two are situated close to the amplifier chip. By replacing just one of the two, we can achieve the effect of sound signature tuning. Of course, if we were to replace both op-amps, the adjustment would be even more pronounced.
  Last updated: Mon, April 22 2024 7:50 AM PDT

 

[Sokel]

Right, that makes sense and that's effectively what they claim here in their post from the KS V3M FAQ:

• The V3 Mono has three op-amps. What does each one do? And if I want to get a better sound, which one should I change?
  
  The V3 Mono's mainboard houses a total of three op-amps. One is located near the RCA input and is used to convert the RCA signal into a balanced signal. The other two are situated close to the amplifier chip. By replacing just one of the two, we can achieve the effect of sound signature tuning. Of course, if we were to replace both op-amps, the adjustment would be even more pronounced.
  Last updated: Mon, April 22 2024 7:50 AM PDT

I don't know how to say it mildly but I'll say it anyway.
Such statements are either marketing or ignorance.

Fosi will maybe prove good at implementing stuff down the road,but given the fact that we had to explain to them what an electronic crossover is at another thread I wouldn't know for which of the two to blame them.

Please forget the op-amp stuff,people test them for years,no one proved any benefit and if things go south changing them you end up with a door-stopper.

 

[Great Sun Jester]

@AdamG Multiple Off topic posts deleted and 2 week thread bans issued as promised in post 1156 above.

 

[echt]

1. "All" and "None" are usually too radical expressions when applied to audio equipment, but as a general rule:

"issues can arise if multiple Class-D amplifiers switch simultaneously, but are not synchronized and managed.

Issues include:
• Power Supply Overloading resulting from all amplifiers switching on the same edge, causing the supply to droop or sag below the regulated voltage.
• Beat Interference or Beat Tones are audible tones that occur when slightly misaligned switching frequencies interact to create another frequency."

2. Yes and yes. In the case of the Fosi 3 Mono's TPA3255 chip, there is a TI note that better addresses this issue, see: Multi-Device Configuration for TPA32xx Amplifiers

3. It could be more than just coloration it could be "audible tones that occur when slightly misaligned switching frequencies interact to create another frequency".

In addition:

4. Power Supply Overloading is one reason why it might be a bad idea to run two Fosi 3 monoblocks from a single Fosi power supply. Admittedly, there may be better (and probably more expensive) power supplies that are less prone to this problem.

5. In comparison to the aforementioned Fosi monoblocks, the Fosi 3 PFFB STEREO represents a superior value proposition for the average home audio consumer, particularly in the context of power supply overloading and beat interference.

@PlasticDoc
Not sure whether to thank you or curse you for opening a can of worms I did not know existed. Guess I'll go with thanks!

@amirm
The only issues that concerns me on the V3 monos are the beat tone (significant concern) and power delivery contention (minor concern) mentioned by PlasticDoc above.

1. When you test monoblocks do you test only one channel or both driven simultaneously?

2. Would your tests pick up:
a) spurious beat tones
b) power supply overloading when both monoblocks accessing the wave edge simultaneously?

3. If the switching frequencies don't match exactly would we be expecting a frequency mismatch in a fraction of a hertz? single digits? What frequency band of spurious tone(s) do we expect to receive?

4. Overall, do you consider beat tones significant issue for switching frequency (Class D only?) amps.

Thanks.