Fosi v3 Mono - User Impressions | Owner's Thread

[Raxumit]

For those interested in such things, here's the shipment tracking info. When I got the notification that they'd been delivered I checked the front porch: nothing there. Checked all around the house, checked the neighbor's houses: nothing. As I was walking back up my driveway, a USPS van drove by. I flagged down the driver and showed him the delivery notification on my phone. He looked puzzled, then rummaged around in the back of his van and came up with my package. Don't know what that was about.

Often times delivery drivers will do strange seeming things like mark a delivery as attempted when they have not in fact attempted. This is to goose their personal metrics, which may be so unforgiving that the drivers feel they have no choice to keep their schedules and stay employed.

Marking your delivery as delivered when he's intending to get to it later, but wanting credit for delivering it early / already, might be what's going on here.

Just a guess.

 

[jbaumann]

Thank you for the suggestion, will try something similar: put the mono's for front speakers on one smart plug, and the mono's for the surrounds on another (and the center without smart plug); with a one second delay between powering them on. Let's see of that does the trick.

I also found a inrush current limiter plug (H-Tronic 1114730) that should do the trick, but that would be another $35-40 down the drain

Fosi just told me that they have an NTC with 20R to limit the inrush current. If this is placed on the primary side, then with 240V mains this would lead to 12A max inrush current per amp. This would nicely explain the problem, and would suggest the solution of turning on one of the two amps with a slight delay is the correct way to go.

Cheers, Joe

 

[Down South]

Fosi just told me that they have an NTC with 20R to limit the inrush current. If this is placed on the primary side, then with 240V mains this would lead to 12A max inrush current per amp. This would nicely explain the problem, and would suggest the solution of turning on one of the two amps with a slight delay is the correct way to go.

Cheers, Joe

It would be nice if all audio gear had a soft start module fitted as standard - they are dirt cheap. In the old valve radios there was always a valve fitted that did just that - you could watch the radio gradually come to life

 

[Down South]

Apparently Farnell in the UK and France have the specific ebmpapst 4412 FGL fan in stock, even though it is no longer produced. My mate Harry was an IT man and checked out the best fan for us to use. It has a 35000 life. It uses 1.3W. it requires a 500ma PSU with adjustable voltage.

 

[Slowloris]

waiting on my preorder. Has anyone stacked these to against a vidar? I’ve been looking for a used one but am going to wait for these. I just dropped 300$ on a new turntable pre amp and cart so saving money is nice

 

[ChrisJM]

Thought my correspondence with fosi tech support may be of interest to some. Like others, I've been concerned about the heat issue, when my two amps run hot, not warm. In particular, what did fosi think about prospective reliability. I asked them about this. Their first response didn't answer, so tried again:
"

Thanks for your reply. You haven't, however, answered my point about reliability. If the amp operates normally under 85C, what is reliability expected to be like. My other class D amps do not run anywhere near as hot.as.the fosi and one that does run hot, a topping pa5 had early reliability issues. I am really surprised at the fosi for this reason.

Fosi Audio Very about the bad experience. Due to the compact design, the heat of the machine will be unbearable for human skins. Applying an air cooling system under the machine is recommended.However, the working temperature of the machine is always normal under 85 Celsius." The thought of the amp operating 'normally' at under 85C came as a surprise. Like others I'm using fans to cool and this seems effective. Could I ask others, should class D run hot? Does it also imply the fosi is less efficient in operation? I have a Sudden a21 amp and didn't expect the fosi to give it a run for the money (slight exaggeration ;-)). My other class D amps (topping pa5 aside) all run cool. Btw heat issue aside the amps sound very good so far.

 

[Guddu]

Thought my correspondence with fosi tech support may be of interest to some. Like others, I've been concerned about the heat issue, when my two amps run hot, not warm. In particular, what did fosi think about prospective reliability. I asked them about this. Their first response didn't answer, so tried again:
"

​ Thanks for your reply. You haven't, however, answered my point about reliability. If the amp operates normally under 85C, what is reliability expected to be like. My other class D amps do not run anywhere near as hot.as.the fosi and one that does run hot, a topping pa5 had early reliability issues. I am really surprised at the fosi for this reason.

Fosi Audio Very about the bad experience. Due to the compact design, the heat of the machine will be unbearable for human skins. Applying an air cooling system under the machine is recommended.However, the working temperature of the machine is always normal under 85 Celsius." The thought of the amp operating 'normally' at under 85C came as a surprise. Like others I'm using fans to cool and this seems effective. Could I ask others, should class D run hot? Does it also imply the fosi is less efficient in operation? I have a Sudden a21 amp and didn't expect the fosi to give it a run for the money (slight exaggeration ;-)). My other class D amps (topping pa5 aside) all run cool. Btw heat issue aside the amps sound very good so far.

I did clearly notified in my 1st post itself that these amps ran pretty hot (not warm), and I specifically compare this with many other tpa3255 amps keeping the comment relevant.
If Fosi are saying that it’s normal for these amps then a customer can only accept and use it as it is, or add some active cooling like a fan or something.

 

[Jon L]

Fosi Audio Very about the bad experience. Due to the compact design, the heat of the machine will be unbearable for human skins. Applying an air cooling system under the machine is recommended.However, the working temperature of the machine is always normal under 85 Celsius." The thought of the amp operating 'normally' at under 85C came as a surprise. Like others I'm using fans to cool and this seems effective.

Is Sudgen A21 fuller/warmer sounding but maybe with less apparent clarity/detail than Fosi V3 monos?

Fosi point is technically correct, but I'd be more worried about bullet 2 below:

1. "Operating range: The TPA3255's operating junction temperature range is specified as 0°C to 150°C. However, operating at or near the maximum temperature for extended periods will likely reduce the device's lifespan.
2. Thermal cycling: Repeated heating and cooling cycles can also contribute to reduced lifespan, particularly if the temperature fluctuations are large and frequent."

 

[antcollinet]

It would be nice if all audio gear had a soft start module fitted as standard - they are dirt cheap. In the old valve radios there was always a valve fitted that did just that - you could watch the radio gradually come to life

That was because, with valves, if you didn't' soft start them the thermal shock of inrush into the cold low resistance heater elements would dramatically shorten their life.

 

[antcollinet]

Is Sudgen A21 fuller/warmer sounding but maybe with less apparent clarity/detail than Fosi V3 monos?

Fosi point is technically correct, but I'd be more worried about bullet 2 below:

1. "Operating range: The TPA3255's operating junction temperature range is specified as 0°C to 150°C. However, operating at or near the maximum temperature for extended periods will likely reduce the device's lifespan.
2. Thermal cycling: Repeated heating and cooling cycles can also contribute to reduced lifespan, particularly if the temperature fluctuations are large and frequent."

That means just don't turn them on and off every 5 minutes. Any normal cycling will be fine.

 

[Sokel]

That means just don't turn them on and off every 5 minutes. Any normal cycling will be fine.

Auto-on does exactly that during the day though,at least at all the amps I know,if you frequently listen to music.
The broad temperature fluctuations on the other hand is more likely to shorten life and has little to do with the amps being on or off as just being on and without working hard should be at a comfortable thermal steady state.

 

[Deleted member 72219]

Auto-on does exactly that during the day though,at least at all the amps I know,if you frequently listen to music.
The broad temperature fluctuations on the other hand is more likely to shorten life and has little to do with the amps being on or off as just being on and without working hard should be at a comfortable thermal steady state.

Uh…there’s a very loud audible relay sound when they kick on. My home office is 4 feet over from my listening spot for my system. If they were kicking on and off automatically every 5 minutes, I would expect to hear that relay ticking off at least every 10 minutes. I NEVER hear them ticking on except when I actually start playing music—doesn’t matter if I have my preamp muted or not, either. Given my home office is right there, I spend hours upon hours upon hours every day sitting just several feet away from those amps. The auto-on is not nearly as sensitive as you might think there, my friend.

-Ed

 

[Sokel]

Uh…there’s a very loud audible relay sound when they kick on. My home office is 4 feet over from my listening spot for my system. If they were kicking on and off automatically every 5 minutes, I would expect to hear that relay ticking off at least every 10 minutes. I NEVER hear them ticking on except when I actually start playing music—doesn’t matter if I have my preamp muted or not, either. Given my home office is right there, I spend hours upon hours upon hours every day sitting just several feet away from those amps. The auto-on is not nearly as sensitive as you might think there, my friend.

-Ed

Ok,let me understand how it works.
Normally sense make an amp kick in with signal (music),you SHOULD hear the relay click and when music stops and some given minutes pass the amp goes to stand-by (there's some indicator showing it usually) .
You shouldn't hear a realy click when it goes to stand-by (it's silent when it opens)

Is that how it works?Cause if it is it's fine.

 

[MCH]

Is Sudgen A21 fuller/warmer sounding but maybe with less apparent clarity/detail than Fosi V3 monos?

Fosi point is technically correct, but I'd be more worried about bullet 2 below:

1. "Operating range: The TPA3255's operating junction temperature range is specified as 0°C to 150°C. However, operating at or near the maximum temperature for extended periods will likely reduce the device's lifespan.

what does this mean? the recommended range is 0 to 125°C, the warning kicks in at 120°C. At 150°C the chip will switch off, you cannot operate it at this temperature.

1. Thermal cycling: Repeated heating and cooling cycles can also contribute to reduced lifespan, particularly if the temperature fluctuations are large and frequent."

what component does this refer to and where does this information comes from? (just curious)

 

[Deleted member 72219]

Ok,let me understand how it works.
Normally sense make an amp kick in with signal (music),you SHOULD hear the relay click and when music stops and some given minutes pass the amp goes to stand-by (there's some indicator showing it usually) .
You shouldn't hear a realy click when it goes to stand-by (it's silent when it opens)

Is that how it works?Cause if it is it's fine.

I’ve never noticed the relay click when it goes to auto-off, so I cannot verify if there is a sound or not—I have not specifically sat there and stared attentively for the 5-10 minutes minimum it takes for it to go auto-off. This is why I can only report/confirm relay sound upon auto-on.

Regardless, once it goes auto-off, there will be definitely be another relay click upon auto-on again.

Are we having a misunderstanding? Are you saying that there is some sort of third status, a Standby mode, where the amp is not Auto-off yet, but conserving some power because no music is playing? I am not aware of this third power state. On computers, yes. On these Fosi amps, not that I know of. But I am happy to be educated on it if there is. Otherwise I can state that none of my music has five minute silent gaps.

-Ed

 

[Sokel]

I’ve never noticed the relay click when it goes to auto-off, so I cannot verify if there is a sound or not—I have not specifically sat there and stared attentively for the 5-10 minutes minimum it takes for it to go auto-off. This is why I can only report/confirm relay sound upon auto-on.

Regardless, once it goes auto-off, there will be definitely be another relay click upon auto-on again.

Are we having a misunderstanding? Are you saying that there is some sort of third status, a Standby mode, where the amp is not Auto-off yet, but conserving some power because no music is playing? I am not aware of this third power state. On computers, yes. On these Fosi amps, not that I know of. But I am happy to be educated on it if there is. Otherwise I can state that none of my music has five minute silent gaps.

-Ed

The three states that exist are off,stand-by and on.
For an amp to use it's sense it can't be off,it can only do it in some short of stand-by state (you can tell as it's power demand by law should be under 0.5W in that state)

The fact that you hear the relay click when you start playing music means that it works as it should,wakes up from it's stand-by state to on.
It should have an indicator (like a different color led or something) to show it's two states when it's not off .

 

[Deleted member 72219]

The three states that exist are off,stand-by and on.
For an amp to use it's sense it can't be off,it can only do it in some short of stand-by state (you can tell as it's power demand by law should be under 0.5W in that state)

The fact that you hear the relay click when you start playing music means that it works as it should,wakes up from it's stand-by state to on.
It should have an indicator (like a different color led or something) to show it's two states when it's not off .

It does. The amber LED dims to a lower brightness when it is in auto but not fully on.

I think you and I are just calling one thing two different names. What you call standby is what I call auto-off state. We both agree what off is, which is manually switched off.

-Ed

 

[Sokel]

It does. The amber LED dims to a lower brightness when it is in auto but not fully on.

I think you and I are just calling one thing two different names. What you call standby is what I call auto-off state. We both agree what off is, which is manually switched off.

-Ed

It's about the naming I think.
I wouldn't call it auto-off simply because it doesn't go to off but to stand-by.
But yes,we're saying the same thing.

 

[Down South]

One of the stand out features of class D compared to valve/tube amps is their efficiency (90%+). Simply put, far more of the energy is converted into music, not wasted heat. At long last and for many reasons I should this year purchase land and build a house that whilst looking 'normal' will easy to build and very energy efficient due to materials used, design and intelligent use of energy. Part of this ethos is to have a sound system that uses as little energy as possible. This is where class D amps come in. My present speakers are 90dB, really efficient speakers can be at or near 100dB or above, needing only low powered amps even for big listening environments. I will not be using anywhere near the maximum power of the Fosis but having amps not working hard with ample power in reserve always means a better performance, I think we all know that.

Does Fosi or any other Chinese manufacturer anywhere state the efficiency of their amps? Being a rational person for me it is performance of gear that is important not how good or bad a piece of equipment looks. I realise that mine is a minority view - form should follow function, fashion trends are for consumer brainwashed junkies. The obsession with cramming everything into as small as possible flat square box is irrational and counter productive to electrical engineering logic. In comparison there was a time when Japanese companies produced gear that could easily fit into smaller enclosures but used 'conventional' sized units thinking that people would think they were being ripped off on price if the units were smaller.

Lots of audio gear could and should be built into vertical units and designed so that natural convection currents would be created with additional near silent PC type fans used in enclosures that enhanced the cooling effects. Of course this would mean extended life and 'hurt' future profits - they think.

 

[Rafaille]

I’ve never noticed the relay click when it goes to auto-off, so I cannot verify if there is a sound or not—I have not specifically sat there and stared attentively for the 5-10 minutes minimum it takes for it to go auto-off. This is why I can only report/confirm relay sound upon auto-on.

There is a relay click when it goes to auto-off/standby, although it is less loud than the auto-on one.