Fosi Audio V3 Mono Amplifier Review

[Sokel]

Sokel mentions - better thermals, yes - heat dissipation is easy to achieve but hardly any commercial or even DIY amps ever really deal effectively with what is a very important aspect. I understand Commercial resistance to dealing with this because it would drastically lengthen the life of components.

Internal PSU - why on earth would you want to put this inside the same chassis and risk interference with the circuit components?

Layout, component quality with ample operating headroom and good thermal dissipation negate the need for a longer warranty. Same reasons re. return and repair.

As someone who has always modded a lot of gear, especially caps and resistors in the signal path, some manufacturers make this 'possibly' deliberately difficult.

The fact that these monos have no volume control is a good thing. How often do you see manufacturers boasting about using an Alps Blue, as standard it seriously sits upon the sound, shunted with the right resistors it mostly disappears which is good thing.

Just a note,in the specific Hypex I gave as example has the PSU integrated with the amp (same module) so I believe (hope) has been taken care of the usual caveats.
Agreed upon all the rest.

 

[MrOtto]

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

 

[PlasticDoc]

@PlasticDoc

1. Are these "beat tones" present in all Class D mono-blocks?

2. Is the audibility of these beat tones theoretical or empirically verified?

3. If audible, what coloration would be introduced (if a generalization is possible)?

Thanks.

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.

 

[SMen]

Am I right that the Topping PA7 Plus is internally bridged with two TPA3255 chips and one power supply?

 

[MCH]

Am I right that the Topping PA7 Plus is internally bridged with two TPA3255 chips and one power supply?

I don't know about the topping pa7 (have not seen pictures without heatsink), but other amps with more than one TPA32xx chips (like the aiyima boards or the Denon Heros avr) have the chips wired in master/slave mode, that avoids these issues.

 

[SMen]

I don't know about the topping pa7 (have not seen pictures without heatsink), but other amps with more than one TPA32xx chips (like the aiyima boards or the Denon Heros avr) have the chips wired in master/slave mode, that avoids these issues.

Interesting, Okay, so the issue with the two monoblocks might be this master slave mode being unavailable - or two difficult to implement? I am wondering if this is not really 'edge case' stuff - the realm of "extremely improbable and rare temporary event"! None of the testers have reported anything when listening. Fosi have an FAQ answer on this and they refer to a "margin of error". At the end of the day - there are going to be lots of inexpensive, stereo PFFB units that measure extremely well coming down stream, I would hazard a guess.

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

 

[Roland68]

I don't know about the topping pa7 (have not seen pictures without heatsink), but other amps with more than one TPA32xx chips (like the aiyima boards or the Denon Heros avr) have the chips wired in master/slave mode, that avoids these issues.

Interesting, Okay, so the issue with the two monoblocks might be this master slave mode being unavailable - or two difficult to implement? I am wondering if this is not really 'edge case' stuff - the realm of "extremely improbable and rare temporary event"! None of the testers have reported anything when listening. Fosi have an FAQ answer on this and they refer to a "margin of error". At the end of the day - there are going to be lots of inexpensive, stereo PFFB units that measure extremely well coming down stream, I would hazard a guess.

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

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.

Let's be honest, people, anyone who buys monoblocks and then saves on the power supply should take a look and think about the usefulness of their plan.
Monoblocks are built precisely because of the separate power supply and spatial separation, what else makes them different from stereo and multi-channel power amplifiers?

 

[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?)?