Fosi Audio V3 Mono Amplifier Review

[Guddu]

Probably something that measures just as high but has more functionality (bass management, tone control, equalization, etc.).

-Ed

I hear you….
But comparison always loose its meaning if we compare a power amplifier with an integrated amplifier.

Back to the topic of the thread,
Amir measured the amplifier as it comes from the store, who can tell what change opamp rolling may bring without a repeat measurement.
And whatever data is available so far (with other amps), it shows no benefits, not at least measured one.

 

[Guddu]

How much?


I think I am being "miss-quoted" a bit here ... I quoted the term "nicer" which is why I put it in inverted commas "" ...

My bad then

@Guddu I think you have an owners thread started over here ... https://www.audiosciencereview.com/...v3-mono-user-impressions-owners-thread.54043/

Let's have fun over there when the rest of us get some of these ourselves!

Yes please

 

[SMen]

Probably something that measures just as high but has more functionality (bass management, tone control, equalization, etc.).

-Ed

Or power output dials!

 

[Sokel]

I think the reason why we are interested in these 3255 based amps, is because of how much more you have to spend to get a 'nicer amp' (not getting into what qualifies as 'nicer').

I'm not going to write what I consider as nicer but in general and close to price something like this:

vs

vs

(link)

That's two of the most meaningful measurements.
Add better thermals,on board PSU,western certifications,longer warranty,ease of return/repair,etc.

 

[SMen]

My bad then

Your owners thread I keep referencing here is excellent! I'm looking forward to posting my own highly subjective impressions

 

[Guddu]

Your owners thread I keep referencing here is excellent! I'm looking forward to posting my own highly subjective impressions

Please do, I am looking forward to have participation there.

 

[SMen]

I'm not going to write what I consider as nicer but in general and close to price something like this:

View attachment 371116 vs View attachment 371115

View attachment 371117 vs View attachment 371118

That's two of the most meaningful measurements.
Add better thermals,on board PSU,western certifications,longer warranty,ease of return/repair,etc.

Yes okay. But again these 325* class D's are what have "upended" the market in my view. Really challenging how much we need to pay more to hear better.

And yes I am looking forward to participating.

 

[Sokel]

Yes okay. But again these 325* class D's are what have "upended" the market in my view. Really challenging how much we need to pay more to hear better.

And yes I am looking forward to participating.

The one I posted (Hypex) costs $444.
I hope is now clear why one should not reach close or exceed this price.

 

[SMen]

The one I posted (Hypex) costs $444.
I hope is now clear why one should not reach close or exceed this price.

Yes - I understand your point of view and kind of agree. The game changing element is that the "price cap" for improved performance is getting lower - I wonder if we don't need to go better than the hypex you mention for a "really audible" improvement.

Even with measurements, I'd still like to listen to a Hypex. You see, my journey to this web forum, ASR was AFTER buying and listening to the little Aiyima A07, and deciding to look up why it might sound pretty good (which it did). And so I found Amir's review in my lookup.

From my point of view, even going to monos (for my efficient speakers) is overkill. I reckon that a higher performance balanced stereo unit for less, must surely be just around the corner. So audibly as good in most use case scenarios for $150. I don't like all the opamps in the Fosi ZA3. Nearly went down the DIY route with a Sylph.

I will see (listen / hear} in a couple of weeks!

Yes looking at your charts again referencing AUDIOPHONICS MPA-S250NC - keeping perspective on these add ons with things like opamps needed. I like the fact that the frequency response rolls off above 10khz too (from the review link)... and a single box! Need a balanced version because I'm using balanced phono pre... Cool!

 

[Sokel]

I like the fact that the frequency response rolls off above 10khz too (from the review link)

Yes,that's another one,Hypex rolls off 0.5dB (most class D amps do,even Purifi) at 20Khz,Fosi has the opposite,a peak of 0.5 dB.

The most important thing though is as seen at the chart Hypex is completely load independent and Fosi has some dependency out of the audible range.
Fosi stated that improved that after the review but only measurements will tell us.

Measurements about op-amps was done here with the best conditions possible,a Purifi.
Even the slightest improvement would show if it was there.But it wasn't,it's so faint as much we can consider it measurement variation.
So...

 

[antcollinet]

I suppose internally balanced design is a good thing, but this means full potential is realized when feeding the amp true balanced signal. If using RCA input, one needs to upgrade THREE op-amps per mono. Six discrete op-amps, we are looking at around $500-600!

Just to try and rebalance this thread a little.

No, you don't need to replace (not upgrade) three op amps per mono.

Because you don't need to replace ANY opamps. As has been said many times here - especially on the op amp rolling thread, it is a pointless exercise offering nothing of any value for audio quality - almost certainly nothing even audible for anyone.

 

[echt]

This is indeed a well done FAQ.

The answer to: "How are you synchronizing the TPA3255 oscillator between the monoblocks in order to avoid Class D "Beat Tones" ? " ,
should have been a simple and honest: "We don't.".

This is another reason why the Fosi V3 Stereo PFFB will be a superior value proposition for the average consumer in comparison to the Fosi V3 Mono.

@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.

 

[Down South]

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.

 

[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?