Fosi Audio V3 Mono Amplifier Review

[seaninbrisbane]

Not necessarily.

#1 are you using balanced or single-ended connections?
#2 do you know what your AVR and sub do to the signal polarity

It seems to depend

My understanding is that the Fosi's maintain signal polarity when you use balanced connections (there is a little debate about that actually, hopefully someone can clarify) whereas the signal polarity is reversed when using single-ended connections.

So: IF you are using balanced connections AND your AVR/Sub also maintain signal polarity THEN connect everything up as normal.
Otherwise you need to work out what's going on and connect accordingly.

You can just wire it all up and listen to it too

Thanks very much for taking the time to reply. I'm using single-ended connections with a Denon X3700H AVR. This is my first time setting up a home theatre.

 

[seaninbrisbane]

Well, you have to measure things with the mic anyway right, and if it's a Denon it should check the phase anyway..

That's good to know, thanks.

 

[korgua]

I am happy with my V3Ms and still not got round to testing the MUSE02 op amps yet. I saw this mod on the Fosi Audio Global Community Facebook and was curious on what others thought of adding / replacing some of the capacitors? https://www.facebook.com/share/p/TUTkPGtb8weheSke/

 

[antcollinet]

I am happy with my V3Ms and still not got round to testing the MUSE02 op amps yet. I saw this mod on the Fosi Audio Global Community Facebook and was curious on what others thought of adding / replacing some of the capacitors? https://www.facebook.com/share/p/TUTkPGtb8weheSke/

No-one can see that unless they join the group. I'm certainly not going to.

However this type of mod is exceptionally unlikely to make any improvement. Far more likely to mess something up.

 

[EddNog]

No-one can see that unless they join the group. I'm certainly not going to.

However this type of mod is exceptionally unlikely to make any improvement. Far more likely to mess something up.

I must admit that I have requested to join that group just purely out of morbid curiosity

-Ed

 

[DavidM1]

The modding fad makes no sense to me. The appeal of the V3m amps is how well they compete with others for test results and price. Mine sound tremendous.

What’s to be gained by second guessing the design just because some paid YouTube influencers puff up their impressions? Show me the data.

 

[Chrispy]

FWIW

 

[antcollinet]

FWIW

Please can people posting youtube videos include a summary of what it is saying. They are a very inefficient way of transferring information, and people shouldn't have to watch the damn thing to find out if it has any interest to them at all.

It would also be useful to know why the poster is posting it. What point (if any) are they trying to make. Do they agree with the content, or not? What are their own thoughts on it. Etc.

 

[Basilderat]

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?

 

[korgua]

No-one can see that unless they join the group. I'm certainly not going to.

However this type of mod is exceptionally unlikely to make any improvement. Far more likely to mess something up.

This is what was posted and I was interested in understanding other peoples experience & expertise with similar modifications, are they with merit?

Now here is the area of improvement for the power in the V3 monos and why:
Electrolytic capacitors are not fast enough to deliver enough energy for the high frequencies. Ok, some smaller value faster capacitors are found on the board, but my finding was - by adding a superfast 1 uF X2 capacitor parallel to each of the two big capacitors it significantly improved the sound - significantly! It was a wow moment! It is the yellow capacitors in the picture of the above view of the board and a closeup picture.
How could this be that it made such a big improvement?
It is feeding a class D amplifier, a pulse switching amplifier. Because the output is very fast switching pulses and not just switching according to the music, it is imperative to have enough big superfast capacitors for the TDA3255 to create exact, fast and powerful pulses. That power chip switches up to 100.000 times per second! The pulses are longer or shorter, depending on the music, and then filtered to smoothen out the pulses to become music (or whatever signal you input.)
On the other power rails having lower voltages I put a small ceramic capacitor parallel to each electrolytic capacitor, intended to give the circuits enough fast energy to reproduce the micro details in the music. They are small enough to easily be soldered on the bottom of the board to the pins of these capacitors (the blue ones in the bottom view picture).
Then I inspected the signal path. As I only use the balanced input, being the best input on the V3 monos, I only upgraded the balanced signal path.
There are used good quality electrolytic capacitors. These are good, but not the best. I decided to change each electrolytic capacitor to Wima red film capacitors. Yes, they are more expensive and would raise the cost of the unit, but soundwise still worth it. The electrolytic value is 10 uF and what I could barely fit in was 4.7 uF Wima film capacitors. Doing so could risk to make the bass become less strong. But after testing I found no reduction to notice at all, and my speakers play all the way down...
I changed 4 but not the 3 ones for RCA input only. They should preferably also be upgraded. The ones I changed are the red squared ones on the top view picture.
Now testing and comparing my modified V3 monos with my big class A/B amps was giving me shivers! Wow, now we're talking high end! Now the Fosi Audio V3 monos are better than my big mono blocks!!

 

[Rafaille]

This is what was posted and I was interested in understanding other peoples experience & expertise with similar modifications, are they with merit?

Now here is the area of improvement for the power in the V3 monos and why:
Electrolytic capacitors are not fast enough to deliver enough energy for the high frequencies. Ok, some smaller value faster capacitors are found on the board, but my finding was - by adding a superfast 1 uF X2 capacitor parallel to each of the two big capacitors it significantly improved the sound - significantly! It was a wow moment! It is the yellow capacitors in the picture of the above view of the board and a closeup picture.
How could this be that it made such a big improvement?
It is feeding a class D amplifier, a pulse switching amplifier. Because the output is very fast switching pulses and not just switching according to the music, it is imperative to have enough big superfast capacitors for the TDA3255 to create exact, fast and powerful pulses. That power chip switches up to 100.000 times per second! The pulses are longer or shorter, depending on the music, and then filtered to smoothen out the pulses to become music (or whatever signal you input.)
On the other power rails having lower voltages I put a small ceramic capacitor parallel to each electrolytic capacitor, intended to give the circuits enough fast energy to reproduce the micro details in the music. They are small enough to easily be soldered on the bottom of the board to the pins of these capacitors (the blue ones in the bottom view picture).
Then I inspected the signal path. As I only use the balanced input, being the best input on the V3 monos, I only upgraded the balanced signal path.
There are used good quality electrolytic capacitors. These are good, but not the best. I decided to change each electrolytic capacitor to Wima red film capacitors. Yes, they are more expensive and would raise the cost of the unit, but soundwise still worth it. The electrolytic value is 10 uF and what I could barely fit in was 4.7 uF Wima film capacitors. Doing so could risk to make the bass become less strong. But after testing I found no reduction to notice at all, and my speakers play all the way down...
I changed 4 but not the 3 ones for RCA input only. They should preferably also be upgraded. The ones I changed are the red squared ones on the top view picture.
Now testing and comparing my modified V3 monos with my big class A/B amps was giving me shivers! Wow, now we're talking high end! Now the Fosi Audio V3 monos are better than my big mono blocks!!

Sure, why not... I mean this goes way beyond my (poor) understanding of audio electronics but is there any measurements to back up this "wow moment"?

 

[Ordin Aryguy]

In all my 40 years of electronics design I’ve never once read a data sheet for a capacitor that had a parameter for “speed.”

I’ll say it again, capacitors have become the new cables. People are convincing themselves, through no science or measurements at all, that “cap rolling” makes a difference.

 

[Down South]

In all my 40 years of electronics design I’ve never once read a data sheet for a capacitor that had a parameter for “speed.”

I’ll say it again, capacitors have become the new cables. People are convincing themselves, through no science or measurements at all, that “cap rolling” makes a difference.

Coupling caps - changing them can make a big difference. I've only once bought into the expensive audiophile thing and regretted it almost immediately - silver foil caps. They were good but the next week bought some cheap as chips Russian K73-16 PEPT ones, slagged off by some old American 'gurus'.

There's a big thread from some years ago on diyaudio 'pept capacitors-One Of The Best.

In a word 'transparent', Like a lot of others on that thread, didn't want to accept what the OP wrote but he was right. He had spent a lot of money on audiophile/fool caps - well worth reading what he wrote.

Of course the real 'true believers' came steaming in with insults as they always do - had never used them, didn't need to - they were right and everyone else was wrong/deluded/stupid. The audiofools believe that to be good caps must be big -the K73-16 aren't. There other PEPT caps that are said to be as good. I've used 10 and 22uF caps in speaker x/overs. One American speaker maker daren't tell his American clients he uses them, they would go crazy - everything COMMIE is bad LOL.

I don't know if I have values that would work in this amp or if it would benefit.

The word transparent is maybe insufficient to describe these caps, it's that other caps colour the sound, these don't. I can only think of one other component that has the same effect - Z foil resistors.

O/A if you can't hear a difference in sound from different caps I think you have a real hearing problem.

 

[Ordin Aryguy]

The word transparent is maybe insufficient to describe these caps, it's that other caps colour the sound, these don't. I can only think of one other component that has the same effect - Z foil resistors.

O/A if you can't hear a difference in sound from different caps I think you have a real hearing problem.

Colour and transparency are two other "technical terms" that I don't ever recall seeing parameters for on capacitor datasheets.

Capacitors are the new cables. No science. No measurements. Just flowery phooey.

 

[rvsixer]

All this caps and cables talk sheesh. Op amp swaps make the real difference, let's start discussing those ,

 

[Killingbeans]

O/A if you can't hear a difference in sound from different caps I think you have a real hearing problem.

If you did the comparison blind and it turned out you couldn't hear a difference either, none of us would have a relevant hearing problem. We'd just be human.

If there's a real audible difference, the most sensible next step would be to verify them with measurements. Chances are that the "odd man out" isn't actually more "transparent", but simply have electrical parameters ill-suited for the application. If it messes things up in an immediately intriguing way, it might be easily confusable with an improvement.

 

[somebodyelse]

Electrolytic capacitors are not fast enough to deliver enough energy for the high frequencies. Ok, some smaller value faster capacitors are found on the board, but my finding was - by adding a superfast 1 uF X2 capacitor parallel to each of the two big capacitors it significantly improved the sound - significantly! It was a wow moment! It is the yellow capacitors in the picture of the above view of the board and a closeup picture.
How could this be that it made such a big improvement?

Almost certainly because no controlled listening comparisons were used. If you look at the TPA3255 datasheet layout examples you will see:

Note T2: Close decoupling of PVDD with low impedance X7R ceramic capacitors is placed under the heat sink and
close to the pins.

It's almost certain that Fosi have followed this, or the measured performance would be worse. So there is already 'superfast' capacitance right next to the chip where it is more effective than the mod proposed. The mod probably made no difference, which would have been shown by before and after measurements, or recordings that could have been checked for changes.

On the other power rails having lower voltages I put a small ceramic capacitor parallel to each electrolytic capacitor, intended to give the circuits enough fast energy to reproduce the micro details in the music. They are small enough to easily be soldered on the bottom of the board to the pins of these capacitors (the blue ones in the bottom view picture).

Don't know where these are, but probably no difference - again no before and after measurements to demonstrate it's doing something useful. It's not impossible that there's a difference (IIRC it came up when opamp-rolling on the 3E integrated showed a difference, traced to a missing cap and the difference in PSRR between opamps) but with the PSRR of modern opamps it would be unusual.

Then I inspected the signal path. As I only use the balanced input, being the best input on the V3 monos, I only upgraded the balanced signal path.
There are used good quality electrolytic capacitors. These are good, but not the best. I decided to change each electrolytic capacitor to Wima red film capacitors. Yes, they are more expensive and would raise the cost of the unit, but soundwise still worth it. The electrolytic value is 10 uF and what I could barely fit in was 4.7 uF Wima film capacitors. Doing so could risk to make the bass become less strong. But after testing I found no reduction to notice at all, and my speakers play all the way down...

Again no before and after. I don't know the cap specs or the operating conditions - see the capacitor distortion thread for pointers on how this can effect performance.

 

[antcollinet]

Electrolytic capacitors are not fast enough to deliver enough energy for the high frequencies.

You can discount the whole article just from that line.

The tests show it has flat frequncy response up to 20KHz (and beyond) That is the fastest the amp has to operate - and if that is achieved, it shows all the components are fast enough - including the capacitors.

Their opening premise is faulty - the rest can be safely ignored.

 

[antcollinet]

All this caps and cables talk sheesh. Op amp swaps make the real difference, let's start discussing those ,

 

[DavidM1]

It’s fascinating to me that the world of hifi has so much phooey in it. If it was engine design there would be no hesitation in measuring results. Even if it was wine making then blind testing would be commonplace.

For some reason hifi has a history of opinions and puffery. Businesses have exploited the customer’s limited access to or understanding of information to milk the price/ quality relationship. The result is cables and other accessories that cost nothing to make and sell for thousands.

What’s weird is that even without products to buy hifi enthusiasts find ways to create the same illusions for themselves. We see otherwise sensible people placing weights on amps and DACs, lifting cables off the floor, swapping out insignificant parts in new gear, filling speaker stands with sand etc etc without the slightest inclination to objectively measure or test the results.

Fascinating.