Fosi v3 Mono - User Impressions | Owner's Thread

[Freshman1966]

I intentionally posted in this "Impressions" thread because I am quite fed up with the bickering that occurs in literally any ASR topic - as soon as someone dares to write one of the trigger words, someone else goes off... While I really enjoy and appreciate the technical information I can get here at no cost provided by a few experts, I also get more and more bored by these useless discussions (see above).

Anyway, since I stated in my last post that I could not hear a difference between the Monos and my Atoll IN 300, I have to apologize and correct my inital assessment. Yesterday and today I did quite a bit of comparing (note, I do not use the word "test"). Not being a professional reviewer or sound specialist makes it difficult for me to put the differences into words. I give it a very unscientific shot, anyway.

First of all, I turned off all DSP settings, including Dirac. The Monos were set to a gain of 25 dB. I listened to one track at a time and changed the cables (or maybe you would call them "interconnects") which takes about 30 seconds.
The levels between the amps was actually pretty equal - at least I could not tell if one of them was louder. One thing was very notable, though - one of the Minis had minus 3.5 db gain, which I adjusted in the MiniDsp.
I used tracks which I know well, a bit of big band with male voices, and otherwise mostly female jazz singers (sorry, I am a sucker for those)

This is what I got without putting it into any prose:

• Stock op amp.
  • Fosi has a smaller stage (does not reach outside the speakers)
  • The lower bass is not as a well defined (the Dynaudio go to 43 hz, -6db)
  • The voices are somehow not as present or forward
  • Voices sound good with the Mono but the Atoll can give them more timbre (any Seinfeld fans around?)
  • Instruments seem to "wander" a bit more than with the Atoll
  • I guess that everything above somehow is interconnected (there's the "interconnect")
• Swapped one of the op amps for Sparkos
  • The difference in the voices gets smaller (a tad warmer)
  • To be honest, I would have expected a bigger difference - but everything else is more or less the same as before. But of course, I can't do a fast comparison between before and after the op amp switch.

BTW: It was my first op amp switch and Youtube was my teacher. For those who have not done it before - be very very careful when you remove the stock op amps. Their legs are so thin and sensitive, it's almost impossible to get them out without bending them. My first one got quite butchered.

Not sure if should bother installing the second pair of Sparkos - I cannot imagine that it would improve drastically.

As my Farewell words I want to say: The Monos are absolutely fantastic for the money! I don't know if I had bothered looking for something else if I hadn't already had this Atoll here to compare.

So, now you can stone me... bias, bias, bias!!!
Cheers, Stefan

 

[SMen]

I intentionally posted in this "Impressions" thread because I am quite fed up with the bickering that occurs in literally any ASR topic - as soon as someone dares to write one of the trigger words, someone else goes off... While I really enjoy and appreciate the technical information I can get here at no cost provided by a few experts, I also get more and more bored by these useless discussions (see above).

Anyway, since I stated in my last post that I could not hear a difference between the Monos and my Atoll IN 300, I have to apologize and correct my inital assessment. Yesterday and today I did quite a bit of comparing (note, I do not use the word "test"). Not being a professional reviewer or sound specialist makes it difficult for me to put the differences into words. I give it a very unscientific shot, anyway.

First of all, I turned off all DSP settings, including Dirac. The Monos were set to a gain of 25 dB. I listened to one track at a time and changed the cables (or maybe you would call them "interconnects") which takes about 30 seconds.
The levels between the amps was actually pretty equal - at least I could not tell if one of them was louder. One thing was very notable, though - one of the Minis had minus 3.5 db gain, which I adjusted in the MiniDsp.
I used tracks which I know well, a bit of big band with male voices, and otherwise mostly female jazz singers (sorry, I am a sucker for those)

This is what I got without putting it into any prose:

• Stock op amp.
  • Fosi has a smaller stage (does not reach outside the speakers)
  • The lower bass is not as a well defined (the Dynaudio go to 43 hz, -6db)
  • The voices are somehow not as present or forward
  • Voices sound good with the Mono but the Atoll can give them more timbre (any Seinfeld fans around?)
  • Instruments seem to "wander" a bit more than with the Atoll
  • I guess that everything above somehow is interconnected (there's the "interconnect")
• Swapped one of the op amps for Sparkos
  • The difference in the voices gets smaller (a tad warmer)
  • To be honest, I would have expected a bigger difference - but everything else is more or less the same as before. But of course, I can't do a fast comparison between before and after the op amp switch.

BTW: It was my first op amp switch and Youtube was my teacher. For those who have not done it before - be very very careful when you remove the stock op amps. Their legs are so thin and sensitive, it's almost impossible to get them out without bending them. My first one got quite butchered.

Not sure if should bother installing the second pair of Sparkos - I cannot imagine that it would improve drastically.

As my Farewell words I want to say: The Monos are absolutely fantastic for the money! I don't know if I had bothered looking for something else if I hadn't already had this Atoll here to compare.

So, now you can stone me... bias, bias, bias!!!
Cheers, Stefan

Oh thank heavens, a user impression on a user impressions thread! I think you should install all, and make sure you are not mixing and matching any op amps and then compare with your Atoll.


I genuinely don't think that swapping one is going to be viable (make much of a difference ... I do not understand any benefit to mixing op amp types in a parallel circuit but anyone please correct me if I am wrong) But it is very good that you have the Atolls as a yardstick.

On a serious note, if you have a 3db variation between your monos, then this is serious and Fosi need to replace that.

Please would you verify this? 3db is clearly audible as a balance shift and would shift where instruments and voices might appear in the soundstage.

Many people will be using these without Dsp

Post edit: balance variation db with all same op amps

 

[antcollinet]

3db is clearly audible as a balance shift and would shift where instruments and voices might appear in the soundstage.

Certainly is - 3dB represents half power, and an approx 30% reduction in perceived volume.

 

[T&T]

So ...I just started rolling op amps...Opa1656 are good choice also Muses02 and one muses02 and one bb scarce dual cans woooh the layers on vocals and some instruments amazing, the stock opamps are good but too harsh on top.
Using sparkos ss3602 on the jesheli akm4499

 

[SMen]

So ...I just started rolling op amps...Opa1656 are good choice also Muses02 and 1 muses02 with my scarce bb dual cans woooh the layers on vocals and some instruments amazing, the stock opamps are good but too harsh on top.
Using sparkos ss3602 on the jesheli akm4499

Well, all I can say is I am delighted your v3 monos did not blow up with either the Opa1656 or Muses01's !

Certainly is - 3dB represents half power, and an approx 30% reduction in perceived volume.

This is great @antcollinet ... seriously - if we can have amp comparisons with as "close" as possible level matching that is a good thing. I will be doing my best with mine.
Maybe if @Freshman1966 remeasures that would be good.

and if I may just add, Monsieur Freshman ... I think that 1966 was a very good year ;-)!

 

[T&T]

Well, all I can say is I am delighted your v3 monos did not blow up with either the Opa1656 or Muses01's !


This is great @antcollinet ... seriously - if we can have amp comparisons with as "close" as possible level matching that is a good thing. I will be doing my best with mine.
Maybe if @Freshman1966 remeasures that would be good.

and if I may just add, Monsieur Freshman ... I think that 1966 was a very good year ;-)!

I been rolling opamps for years in all my tpa3255 amp never have a problem, Fosi v3, Aiyima07, Aiyima07 Pro and 07 Max, just check twice that the opamp is in the right position if not boom.

 

[stigger]

Regarding off mode, the remaining losses will be in the power supply - in which nothing is done to reduce power, because there is no off switch for that

My amp arrived a couple of days ago, so I tried powering it through a lab supply. On - 5.2W, Auto - 3W, Off - 0W. So indeed, when it's off, it's off, and the rest is the PSU idle consumption. The amp's auto mode still consumes way too much, though. So my point stands: the "idling" module in the amp has no excuse for consuming 3 watts, that's bad design. That's almost 8 euros per year in some countries, if I'm not mistaken.

 

[Basilderat]

May sound reasonable to the uninitiated, but in reality it is proven to be unreliable.

The Dishonesty of Sighted Listening Tests

An ongoing controversy within the high-end audio community is the efficacy of blind versus sighted audio product listening tests. In a blind...

seanolive.blogspot.com

Unreliable does not equate to useless. Let's say you connect one amplifier to the left channel and a second, different amplifier to the right channel. You then match SPLs using a fixed reference tone. You then play your favorite audiophile track/s and sweep from left to right and back with a balance control. You do this over several sessions. You happen to far prefer the sound of one channel over the other. Lets say one channel sounds compressed and muddy and the other sounds perfect. The difference is huge. Yes, I know it's sighted and I'm conscious of bias effects and psycho-acoustics. I know it fails the ASR standard. I still think it's a reasonable test that I would be comfortable with. However, if the difference between channels is slight then unsighted testing and measured performance becomes necessary.

 

[AaronJ]

Unreliable does not equate to useless. Let's say you connect one amplifier to the left channel and a second, different amplifier to the right channel. You then match SPLs using a fixed reference tone. You then play your favorite audiophile track/s and sweep from left to right and back with a balance control. You do this over several sessions. You happen to far prefer the sound of one channel over the other. Lets say one channel sounds compressed and muddy and the other sounds perfect. The difference is huge. Yes, I know it's sighted and I'm conscious of bias effects and psycho-acoustics. I know it fails the ASR standard. I still think it's a reasonable test that I would be comfortable with. However, if the difference between channels is slight then unsighted testing and measured performance becomes necessary.

Unreliable is in fact useless. Nothing more than “cool story bro” in the scientific community. There are many issues with your proposed testing methodology. L and R channels produce different content. Is this accounted for? How is SPL being measured? I sure hope it isn’t a phone mic. The test also needs to be repeatable.

Amplification has been solved technology for 50 years. I’m sure the Fosi’s sound great paired with literally any great speakers that don’t push them beyond their capabilities.

 

[keith_h]

Just a reminder this is the user's impressions thread, not a conversation about psycho acoustics, engineering methodologies, listening test techniques or the like. Its the impression of the user no matter how it was derived. Discussions about scientific methodologies and the need to use calibrated test equipment, dyno testing amplifiers and triple blind tests are cool, but this is not the point here. Thanks.

All I'm really interested in, and maybe others as well, is whether the post author thought there was some improvement. What did they perceive or even thought they perceived. Any other useful information like the audio chain, the room size, anything unusual they may have done like op amp swaps and so forth. Unconcerned whether they were wearing a lab coat or not at the time since this is absolutely not science which is the point.

The listening is where the rubber hits the road. The science of measurement only suggests potential and this device has been measure properly and thoroughly discussed in that context elsewhere. Here in this thread the non science of an end user enjoying your favourite tune in the listening chair is the end goal. Surely how it sounds to the owner is the thing that truly matters in any case.

 

[NTK]

A user's impression in sighted listening only matter to that user. Starting at about 56:35, Here were what Dr Toole said:

... and you're forming opinions. And the only way we can get those consistent opinions out of you is not let you know what you are listening to. Do it blind. But if you know what you're listening to, I don't care what you're thinking, it doesn't matter ...​

 

[keith_h]

In this thread we are not designing equipment or scientifically testing or evaluating it. The only thing that matters at this part of the process is how it sounds to the person who owns it. That's what I am interested here in this thread. Floyd, a very credentialed, experienced and distinguished fellow is talking about something else entirely. He would be no use in this thread at all.

 

[DavidMcRoy]

For what it's worth, I received notice on July 12 that I should receive my order of four (4) V3 Monoblocks, two (2) 48VDC 10A power supplies and associated filters in 1 to 2 weeks. My kickstarter order is number 1992. I am in the State of Washington, USA.

 

[antcollinet]

Unreliable does not equate to useless. Let's say you connect one amplifier to the left channel and a second, different amplifier to the right channel. You then match SPLs using a fixed reference tone. You then play your favorite audiophile track/s and sweep from left to right and back with a balance control. You do this over several sessions. You happen to far prefer the sound of one channel over the other. Lets say one channel sounds compressed and muddy and the other sounds perfect. The difference is huge. Yes, I know it's sighted and I'm conscious of bias effects and psycho-acoustics. I know it fails the ASR standard. I still think it's a reasonable test that I would be comfortable with. However, if the difference between channels is slight then unsighted testing and measured performance becomes necessary.

Which is the same mistake people keep making.

Cognitive biases can create perceived differences in sound that are "huge". Hearing such a significant sound difference is not a justification to say a blind test is not needed.

There is a caveat on that. If you are hearing differences that come from obvious measurable changes that are known to create audible impacts then you can trust more, that what you are hearing is real. Like in the example above of one channel out of phase - or if you are changing tone controls, or using equalisation. In other words where what is changing will always result in audible effects, it is reasonable to assume what you are hearing is from those changes.

However, if you are hearing differences where there is no rational explanation for that change coming from the engineering, or measurements - such as for rolling op amps, or comparing equally well measuring gear - then you literally cannot trust sighted listening impressions. And no matter how huge the perceived difference is, only blind testing can confirm if it is real or not.

In fact, hearing a huge difference where there is expected to be none, is more an indication that it comes from bias. You won't hear a huge difference if the performance of the gear is identical, or near identical.

 

[SMen]

In fact, hearing a huge difference where there is expected to be none, is more an indication that it comes from bias. You won't hear a huge difference if the performance of the gear is identical, or near identical.

'Huge' is the word here. Using hyperbole to describe perceived changes really does not help anyone.

But users' impressions on this thread generally have not been like that, and hopefully things will stay that way.

I'm not at all sure about that panning technique especially using stereo, with different amplifiers - too much in the mix literally, and literally changing volume levels while assessing? This seems the worst of techniques - how to really confuse the brain!

 

[Sokel]

Ok,let's get serious about thermals now.

First we take the power losses figures from TI's datasheet:



I think it's fair to consider a middle 40W value for an output of 200W at 4 Ohm at ideal conditions.

Now let's take the above value along with the provided heatshink to see where it stands.
We will use this calc:

Dimensions is the (unfolded) case,not sure about it's thickness though cause it matters,I gave it a generous 1 cm thickness,so if anyone has an accurate measure please provide it and I will correct the value.


As is:

It seems that it falls short.
For more W and lower impedance things are more dire of course.
Until we have a better measure of case thickness.that's how it looks like though and that's for near ideal conditions.

You can also use the calc to calculate more normal than 200W output conditions where power losses are closer to 10-20W which seems adequate to provide.

(disclaimer,that's for my given thickness,if less than 1 cm demands in size will be ever bigger,proportionately,same stands for all dimensions obviously )

 

[SMen]

Ok,let's get serious about thermals now.

First we take the power losses figures from TI's datasheet:

View attachment 380861

I think it's fair to consider a middle 40W value for an output of 200W at 4 Ohm at ideal conditions.

Now let's take the above value along with the provided heatshink to see where it stands.
We will use this calc:

Dimensions is the (unfolded) case,not sure about it's thickness though cause it matters,I gave it a generous 1 cm thickness,so if anyone has an accurate measure please provide it and I will correct the value.


As is:

View attachment 380862

It seems that it falls short.
For more W and lower impedance things are more dire of course.
Until we have a better measure of case thickness.that's how it looks like though and that's for near ideal conditions.

You can also use the calc to calculate more normal than 200W output conditions where power losses are closer to 10-20W which seems adequate to provide.

(disclaimer,that's for my given thickness,if less than 1 cm demands in size will be ever bigger,proportionately,same stands for all dimensions obviously )

Very interesting. I was wondering about holes in the top - this would have made sense - heat rising convection through the top would draw in cooler air from the sides.

Post edit - just seen this same suggestion on the v3-mono review thread.

 

[Sokel]

Very interesting. I was wondering about holes in the top - this would have made sense - heat rising convection through the top would draw in cooler air from the sides.

Post edit - just seen this same suggestion on the v3-mono review thread.

To make things more clear,the above calc considers a thermal budget of 43° C (that means the difference between the given ambient of 27° and the 70° max which the case will reach with the ideal heatshink).
If one wants it to operate cooler at the given conditions 200W@4 Ohm it means that the heatshink should be bigger (we're talking extremes here,no one in the right mind will drive it like that obviously) .

But that proportionately applies to all working conditions.And as I had a look my estimate for 1 cm thickness is overgenerous seems like even less than half of it,so double the ideal surface.
Holes on top and bottom could help I guess,for now a change in orientation could also help.

I would be cautious with it though.

 

[keith_h]

To make things more clear,the above calc considers a thermal budget of 43° C (that means the difference between the given ambient of 27° and the 70° max which the case will reach with the ideal heatshink).
If one wants it to operate cooler at the given conditions 200W@4 Ohm it means that the heatshink should be bigger (we're talking extremes here,no one in the right mind will drive it like that obviously) .

But that proportionately applies to all working conditions.And as I had a look my estimate for 1 cm thickness is overgenerous seems like even less than half of it,so double the ideal surface.
Holes on top and bottom could help I guess,for now a change in orientation could also help.

I would be cautious with it though.

Thanks for the detailed explanation. Mine operates between 30C when in standby and 40C when playing music. Its not powering a rock concert so that seems reasonable. The nCore amps in the M10 report 60C in operation.

TI's datasheet also showed the temp for thermal overload and thermal protection was way higher also. So while in theory a bigger heatsink might be desirable, it could also be argued the way in which the case has been used is a fair tradeoff for size considerations. For example a larger case to house a bigger board, dedicated heatsink and maybe a fan all leading to additional cost perhaps?

I've got them on their side now with a bit of space underneath to permit a bit more airflow.

 

[Sokel]

Thanks for the detailed explanation. Mine operates between 30C when in standby and 40C when playing music. Its not powering a rock concert so that seems reasonable. The nCore amps in the M10 report 60C in operation.

TI's datasheet also showed the temp for thermal overload and thermal protection was way higher also. So while in theory a bigger heatsink might be desirable, it could also be argued the way in which the case has been used is a fair tradeoff for size considerations. For example a larger case to house a bigger board, dedicated heatsink and maybe a fan all leading to additional cost perhaps?

I've got them on their side now with a bit of space underneath to permit a bit more airflow.

Thermal overload and thermal protection applies only to the TPA3255 chip,not to the rest of the components of the amp like caps,resistors,even cables and connectors (yes,these can fail too under temp).
When talking heat in such a constrained space that applies to every single component and affects them all.