Fosi v3 Mono - User Impressions | Owner's Thread

[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.

 

[jvdburgt]

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.

That’s the thing that confuses me about the V3M’s. I noticed that they very steadily use 10W per amp in on/active mode, no matter the type of content (or volume) I’m playing.

With 90% efficiency, you’d expect the actual power usage to be much more volatile.

 

[jvdburgt]

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 .

Except for the V3M’s it’s 5W per amp

 

[Sokel]

That’s the thing that confuses me about the V3M’s. I noticed that they very steadily use 10W per amp in on/active mode, no matter the type of content (or volume) I’m playing.

With 90% efficiency, you’d expect the actual power usage to be much more volatile.

This reputation (rightfully so) comes from Purifi probably which has this numbers from fairly low usage.

TPA3255 on the other hand looks like this:

So between 40-70% for sane use cases.

Except for the V3M’s it’s 5W per amp

That can't be,it wouldn't allow it for import in Europe in such state,it's illegal.
Except if this state is something called ampDisable in pro audio and it makes some sense with it's detached PSU.

Edit:If it's confirmed about that 10W staying On and doing nothing the above curve starts right there,at 10W instead of the 30mW TI's ideal system state.
So efficiency is WAY lower if that's true and measured at the right conditions.

 

[stigger]

That can't be,it wouldn't allow it for import in Europe in such state,it's illegal.

Yep, that's what I said earlier in this thread. From what I see, this amp does not meet EU regulations.

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.

 

[Down South]

Using fans inside an amp is not a good idea or having it driven from the amps electrical supply, that's why the papst supply comes from the dis. block. There is no acoustic noise as I stated, it's important to use a quality fan. Placing it below the amps and using the monos vertically with the pretty orange slats removed means the fan is operating at optimum efficiency.

Mistake here - I should have written powered by a PC

 

[Down South]

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.

The life of all equipment that experiences current inrush is shortened. It's always been recommended to leave CDPs on and it's something I've always done with the 3 CDP's i've used since 1990. We bought a Sony Brava TV which has been left 'on' since 2009 - works just fine and uses so little energy, I think it's less than 1 W.

 

[Down South]

I think Fosi should take a good look at the rational comments made by many of us on this thread. Indeed this thread is a very good example of how a forum should operate - no trolls, just people inputting sensible suggestions and sharing useful info. which in turn generates more of the same.

Fosi could redesign the enclosures to operate vertically, include a soft start module in the PSUs and look at idle current use.

 

[antcollinet]

So efficiency is WAY lower if that's true and measured at the right conditions.

You're missing the fact that the graph is for the chip amp on it's own. The 10W (or 5W) or whatever it turns out to be is all the PSU losses, plus the losses of whatever circuitry is built around the chip amp.

 

[Guddu]

Fosi could redesign the enclosures to operate vertically, include a soft start module in the PSUs and look at idle current use.

I have 10 tpa3255 amps, and feel like Fosi should have made v3 mono case bigger more like at least ZA3.
My Marantz nr1711 (with about 80-85% volume) runs cooler than v3 mono pair, and without pop noises and relay sounds.
I am sure another kickstarter would come in with an improved version, sooner or later

 

[Guddu]

That’s the thing that confuses me about the V3M’s. I noticed that they very steadily use 10W per amp in on/active mode, no matter the type of content (or volume) I’m playing.

With 90% efficiency, you’d expect the actual power usage to be much more volatile.

Another way to look at this could be that the amplifier isn’t efficient until first 5 or 10 watts which is the case with every tpa3255 amplifier I have tested so far (and I have almost all of them).
But then when you use it, those 10 watts end up giving you decent start, in fact you might not even need anymore power if you are using background low volume listening and you will see it stays on that utilization only.
And this is the case with all tpa3255 finished amps from aiyima, fosi, and others I have got.
Just giving another prospective.

 

[Jon L]

I have 10 tpa3255 amps, and feel like Fosi should have made v3 mono case bigger more like at least ZA3.
My Marantz nr1711 (with about 80-85% volume) runs cooler than v3 mono pair, and without pop noises and relay sounds.
I am sure another kickstarter would come in with an improved version, sooner or later

I really don't want monoblocks and two large power supplies taking more room than needed on my desktop.
I will wait for an improved stereo version of Fosi V3, with roomier back panel with improved connector spacing and an actual ON/OFF switch (PLEASE!) to compete with the new Aiyima A70.

I would get the Aiyima A70, but Aiyima unfortunately forgot to add a separate ON/OFF switch, added useless subwoofer output, and came up with the dumb double-decker internal board layout, which doesn't let certain vertical discrete op-amps fit.

 

[Guddu]

I would get the Aiyima A70, but Aiyima unfortunately forgot to add a separate ON/OFF switch,

Triggered in works for me, but ON/OFF switch is the way to do.

added useless subwoofer output,

Most users will need 150 Hz for powered sub only, rest subwoofer will take care of anyway.

and came up with the dumb double-decker internal board layout,

In fact, I would consider it as upgradable design and more easier to troubleshoot and fix. It solves many things if you consider design wise.

which doesn't let certain vertical discrete op-amps fit.

it is true for others as well. Clearance for opamp is more or less similar to v3 mono.

It’s your choice to wait for another product, but A70 is a good PFFB stereo amplifier specially with its xlr performance.
I hope Fosi’s stereo PFFB should be around the corner as well…..

 

[rgpit]

I received my order yesterday - two V3 monos and two 48v/5a power supplies. They sent only one XLR cable and one opamp. Have others received pairs of cables and opamps with their order of two V3 Monos?

They only sent me 1 MUSE02 and I purchased 2 V3s. I tried to explain this to their customer service in multiple emails and all I could get was an explanation that I only needed 1 in my amp. Very frustrating. They did tell me I could buy an additional one if I wanted.

 

[early rejecter]

They only sent me 1 MUSE02 and I purchased 2 V3s. I tried to explain this to their customer service in multiple emails and all I could get was an explanation that I only needed 1 in my amp. Very frustrating. They did tell me I could buy an additional one if I wanted.

The reward was a single MUSE02. You had the option to get a second one instead of the hex driver and cable(s), but you had to specify that option.

 

[rhing]

Just as a follow-up, I am enjoying the V3 Monos in my system. I am using two 48V/10A power supplies and I installed a pair of MUSES02 op amps in each amplifier.



I finally got hold of a Fluke 568 digital thermometer to measure the temperature of the enclosures after playing music for hours.

• 4 hours...................Amp 1: 110°F (43.3°C) top and 116°F (46.7°C) bottom....................Amp 2: 108°F (42.2°C) top and 114°F (45.6°C) bottom
• 8 hours...................Amp 1: 112°F (44.4°C) top and 116°F (46.7°C) bottom....................Amp 2: 109°F (42.8°C) top and 114°F (45.6°C) bottom

It's also getting slightly warmer in my room just because it's a warm day (92°F outdoors and 79°F indoors) and the afternoon sun is shining into my listening room. I would consider my measurements to indicate that the amps have been operating in a stable thermal condition for the last eight hours.

If anyone is concerned about the heat of the enclosure, I would check to ensure there is thermal conducting compound on the heat sink plate has been properly applied to the heat sink plate used to thermally couple the TPA3255 IC to the Aluminum enclosure for proper heat dissipation. When I unboxed my amps, I noticed there wasn't complete coverage on the heat sink plate to better couple the heat sink to the enclosure, so I evenly applied Arctic MX-6 compound as a thin film on the entire heat sink plates.



I also elevated the enclosures using some inexpensive foamed elastomer pads used in HVAC applications for vibration isolation. I use these under my equipment to improve air flow underneath the amps and for vibration isolation.

 

[EddNog]

I posed a similar question in the ZA3 thread, but…

Just wanted to report back with something odd. My pair of ZA3s that I gifted to my father after upgrading my chain to V3 Monos, he said the left ZA3 failed first and then the other one eventually went, after he attempted to hook his REL subwoofer up to them via high (speaker) level connection. He is returning the two seemingly dead amplifiers to me to check them out, but they don’t arrive until Monday. For now, he has begun rearranging his chain to utilize the low/line-level input for his subwoofer instead by hooking it up to the second output on his preamp.

Has anyone had an opportunity to or succeed with hooking up a subwoofer via high level connection to a pair of V3 Monos? If so, which wires did you run to which speaker jacks on which channel/amp?

Or is there a technical reason why this is a massive no-no, maybe due to how monoblocs are laid out in general?

-Ed

 

[MCH]

I posed a similar question in the ZA3 thread, but…

Just wanted to report back with something odd. My pair of ZA3s that I gifted to my father after upgrading my chain to V3 Monos, he said the left ZA3 failed first and then the other one eventually went, after he attempted to hook his REL subwoofer up to them via high (speaker) level connection. He is returning the two seemingly dead amplifiers to me to check them out, but they don’t arrive until Monday. For now, he has begun rearranging his chain to utilize the low/line-level input for his subwoofer instead by hooking it up to the second output on his preamp.

Has anyone had an opportunity to or succeed with hooking up a subwoofer via high level connection to a pair of V3 Monos? If so, which wires did you run to which speaker jacks on which channel/amp?

Or is there a technical reason why this is a massive no-no, maybe due to how monoblocs are laid out in general?

-Ed

The speakers signal in these amps is not referenced to ground (=all speaker terminals are above ground even when there is nothing playing). You need to check if your subs high level input is. If yes, you might be shorting the Fosis to ground, even before you start playing music.
If this was the case, could even be that the over current protection kicked in and maybe the amps are not actually broken??

 

[antcollinet]

I posed a similar question in the ZA3 thread, but…

Just wanted to report back with something odd. My pair of ZA3s that I gifted to my father after upgrading my chain to V3 Monos, he said the left ZA3 failed first and then the other one eventually went, after he attempted to hook his REL subwoofer up to them via high (speaker) level connection. He is returning the two seemingly dead amplifiers to me to check them out, but they don’t arrive until Monday. For now, he has begun rearranging his chain to utilize the low/line-level input for his subwoofer instead by hooking it up to the second output on his preamp.

Has anyone had an opportunity to or succeed with hooking up a subwoofer via high level connection to a pair of V3 Monos? If so, which wires did you run to which speaker jacks on which channel/amp?

Or is there a technical reason why this is a massive no-no, maybe due to how monoblocs are laid out in general?

-Ed

As @MCH said. Traditional amps have the black speaker terminal connected to ground. Chip amps are run in BTL (Bridge tied load) mode which means both speaker terminals are driven with voltage. One termain goes + while the other goes - and vice versa.

Your father's sub black terminal is almost certainly connected to ground which means when connected with high level, the black amp output is short circuited. This is not specific to mono-blocks, but to all amps operating in BTL.

It is possible to connect via high level signals by connecting only the red amp terminal to a red sub terminal, and then connecting the black SUB terminal back to a ground point on the amp. However I've not tried this and it would be a good idea to check with both FOSI and the sub manufacturer that it is OK.

Probably better to use a splitter cable between the source and the input to the amp and use low level connection that way from the source.


There needs to be much more publicity from amp and sub manufacturers about this. Or sub manufacturers need to stop connecting one of the inputs to ground, and use a diff amp on the high level connections.


EDIT: I've just checked an up to date manual for my sub. This note is added. It is possible your sub manufacture may have a similar isoltator option - or you can probably use the one from BK electronics.

 

[jbaumann]

Slightly off-topic: How do I ask whether anyone wants to exchange/swap my Muse op amp with his/her XLR cable (Germany - Frankfurt or Karlsruhe area)? I‘m absolutely happy with the Mono‘s built-in op amps’ performance.