Fosi v3 Mono - User Impressions | Owner's Thread

[avdoc]

I'm extremely happy with my 2x V3 monos with 2x 5A power supplies! With the 5A power supplies, I have no turn-on pops through the speakers (I think it may a 10A PS problem). I'm using the V3 monos with RCA pre-outs from my Pioneer Elite SC-LX901 receiver (for those of you unaware, the Pioneer was the premier receiver a few years ago and uses class D ICE amplifiers) into my Magnepan 2.5R speakers using DH Labs silver sonic cabling (RCAs and speaker cables) in an extremely large open concept living area with 20 foot cathedral ceilings. Magnepans are extremely revealing and inefficient 4 ohm speakers which require quality amplification and high current. Regarding sound quality, the Pioneer has a hard edge to the sound which is unpleasant compared to the natural sounding V3s. Also, the sonic background of the V3 monos is completely silent whereas the Pioneer has low level noise. I blind A/B compared the V3 monos vs. the Pioneer with my wife who is not an audiophile and she corroborated my observations (I used an SPL meter to level match the Pioneer). The V3 monos do get hot, but no hotter than my Pioneer. It's not burn-your hand hot, but it's more than just warm. The V3 monos are currently being powered by a 15 amp line on the same circuit as all my other equipment (receiver, TV, blu-ray player, lights), so I'm particularly impressed with their performance on the sub-par electrical connection I currently have available (I'm planning to install a dedicated 20 amp outlet for them soon). Despite the large size of my room and the inefficiency of my Magnepans, the V3 monos are able to drive the speakers to room-filling levels with both music and movies. Regarding the output level of the V3 monos, I am running them at 25dB gain as I liked the sound vs the 31dB. Compared to the Pioneer, I had to turn the volume up 3.5dB to match the output. However, since the sound quality is better I was able to turn the volume down compared to how I normally listen so I'm very happy with the output. I have owned many high-end amplifiers in the past costing many, many times the price of the V3 monos and weighing exponentially more. I'm thrilled that sound like this can come out of such a small, light, and inexpensive component. Once they're available on Amazon, I'm planning to purchase enough to power my 7.2.4 system and a processor with balanced outputs, but given how good the V3 monos sound as is I'm more than content for now.

 

[timiambeing]

I'm extremely happy with my 2x V3 monos with 2x 5A power supplies! With the 5A power supplies, I have no turn-on pops through the speakers (I think it may a 10A PS problem). I'm using the V3 monos with RCA pre-outs from my Pioneer Elite SC-LX901 receiver (for those of you unaware, the Pioneer was the premier receiver a few years ago and uses class D ICE amplifiers) into my Magnepan 2.5R speakers using DH Labs silver sonic cabling (RCAs and speaker cables) in an extremely large open concept living area with 20 foot cathedral ceilings. Magnepans are extremely revealing and inefficient 4 ohm speakers which require quality amplification and high current. Regarding sound quality, the Pioneer has a hard edge to the sound which is unpleasant compared to the natural sounding V3s. Also, the sonic background of the V3 monos is completely silent whereas the Pioneer has low level noise. I blind A/B compared the V3 monos vs. the Pioneer with my wife who is not an audiophile and she corroborated my observations (I used an SPL meter to level match the Pioneer). The V3 monos do get hot, but no hotter than my Pioneer. It's not burn-your hand hot, but it's more than just warm. The V3 monos are currently being powered by a 15 amp line on the same circuit as all my other equipment (receiver, TV, blu-ray player, lights), so I'm particularly impressed with their performance on the sub-par electrical connection I currently have available (I'm planning to install a dedicated 20 amp outlet for them soon). Despite the large size of my room and the inefficiency of my Magnepans, the V3 monos are able to drive the speakers to room-filling levels with both music and movies. Regarding the output level of the V3 monos, I am running them at 25dB gain as I liked the sound vs the 31dB. Compared to the Pioneer, I had to turn the volume up 3.5dB to match the output. However, since the sound quality is better I was able to turn the volume down compared to how I normally listen so I'm very happy with the output. I have owned many high-end amplifiers in the past costing many, many times the price of the V3 monos and weighing exponentially more. I'm thrilled that sound like this can come out of such a small, light, and inexpensive component. Once they're available on Amazon, I'm planning to purchase enough to power my 7.2.4 system and a processor with balanced outputs, but given how good the V3 monos sound as is I'm more than content for now.

Sometimes I think we hifi aficionados have to rethink what used to be the standard criteria for great sound, I’m loving mine after a few days playing. Obviously my ear/brain learning has played a part now I am more used to the sound, a little EQ for my speakers and the room specifically measured with the V3 Mono’s helped as well.

I’m wondering whether to try the Muse02 op amps I chose as a free gift in them at some point, I think I did read on here that someone reckoned it was a poor idea as the Muse 02 was unstable, but that might have been in the V3?

In a few weeks when I have moved I will get my valve amp out of its box (recently repaired and up and running) and do a comparison! When I went to pick it up from the guy who repaired it (well who discovered it was a dodgy rectifier valve and replaced it!) that’s Malvern Audio Research, he had it playing through £20k custom built speakers and it blew me away… utterly mind blowing, renewed my love of audio reproduction

 

[gwing]

Have gone for the single 10A power supply with two V3 Monos and just today got a message from Fosi asking if I wanted them to send everything except the power filter today. It seems there is a delay in production with the filters and they will ship that out separately after 15 July. Great news. I think I can do without the filter to start with, so I opted for that solution.

Exactly he same on all counts for me. I'm #1400 and live in the UK.

 

[Guddu]

Based on the various user reports, it seems that there is a (perceived) difference in how hot these things run, ranging from “warm” to “very hot”.

I’m curious if these differences are merely subjective or might be due to technical causes.

Some users reported that there is no cooling paste between heatsink and case. Has that been the case for everyone so far or do some users have received units with cooling paste?

Cooling paste or thermal paste isn't going to cool down the chip or amplifier, it simply helps with heat transfer between sandwitched objects.
In general, amplifier case getting hot simply means heat transfer is happening.
However, I read in a few user posts that the bottom (where the metal heatsink is directly sandwiched) runs cooler than the case top which seems a bit odd. I can’t say for sure but if it is because of the heat generated by other components or heat accumulation inside the case by anything then it’s not a good sign for me.
Anyways, I already reported heat situation way before others and I guess it’s acceptable by most if not all.
It makes me think why a manufacturer not use slightly bigger case to deal with the major devil to start with, it’s more important to function properly with longevity than looking smaller for an amplifier.

 

[Petrushka]

Chips are safe up to 70c or so, which is too hot to hold.

 

[Guddu]

Chips are safe up to 70c or so, which is too hot to hold.

Chip temperature would be way higher than the case temperature, if the case is running around 45 than chip might reach it’s limits with a bit harder running.

 

[gwing]

Cooling paste or thermal paste isn't going to cool down the chip or amplifier, it simply helps with heat transfer between sandwitched objects.

That doesn't entirely make sense. If you get better heat transfer to the (metal) case the chip will be cooler and the case will be hotter so you get more heat loss from the case so the amp as a whole should be cooler.

 

[Guddu]

That doesn't entirely make sense. If you get better heat transfer to the (metal) case the chip will be cooler and the case will be hotter so you get more heat loss from the case so the amp as a whole should be cooler.

The case has significant more area for heat dissipation and air flow exposure than the bottom part where chip heatsink is directly attached.
Anyways, if you think it’s normal than all good.

 

[gwing]

The case has significant more area for heat dissipation and air flow exposure than the bottom part where chip heatsink is directly attached.
Anyways, if you think it’s normal than all good.

No, I don't think that it is either normal or good for the chip not to have thermal paste and/or some form of ensuring heat transfer from the chip. That said, maybe heat dissipation is sufficient without it and it can get away without the paste - I assume Fosi have done their homework here but, still, mine will have thermal paste.

 

[EddNog]

No, I don't think that it is either normal or good for the chip not to have thermal paste and/or some form of ensuring heat transfer from the chip. That said, maybe heat dissipation is sufficient without it and it can get away without the paste - I assume Fosi have done their homework here but, still, mine will have thermal paste.

Yup, I am the one that found they didn’t put any at the factory, and I applied a thin, even layer before closing the amps back up.

-Ed

 

[Guddu]

Yup, I am the one that found they didn’t put any at the factory, and I applied a thin, even layer before closing the amps back up.

-Ed

Case doesn't have vents on the bottom part of case, so applying thermal paste or a thin pad should be easy but the sliding in/out might create a bit of mess.

 

[EddNog]

Case doesn't have vents on the bottom part of case, so applying thermal paste or a thin pad should be easy but the sliding in/out might create a bit of mess.

Yes, I push gently on the PCB as I slide it in to minimize contact until it is close to position. I did this many times with ZA3 and also the one time I opened my V3 Monos, and have not broken any of the amps.

-Ed

 

[PJ_Schmidt]

Have gone for the single 10A power supply with two V3 Monos and just today got a message from Fosi asking if I wanted them to send everything except the power filter today. It seems there is a delay in production with the filters and they will ship that out separately after 15 July. Great news. I think I can do without the filter to start with, so I opted for that solution.

fyi, As an experiment I tried running 2x monos on a single 10A power supply (my own high end 48v PS, not the one Fosi supplies), and the noise was surprisingly loud. Not speaker damaging loud, but certainly could not be ignored. Not a big deal for me as I have plenty of power supplies, but I wanted to see for myself how bad it would be. If I was you, I'd plan on getting a second PS from amazon until the filters from Fosi ship and you can use a single 10A.

 

[Toroid]

Are the power filters the same as the power supplies?

 

[Giro413]

fyi, As an experiment I tried running 2x monos on a single 10A power supply (my own high end 48v PS, not the one Fosi supplies), and the noise was surprisingly loud. Not speaker damaging loud, but certainly could not be ignored. Not a big deal for me as I have plenty of power supplies, but I wanted to see for myself how bad it would be. If I was you, I'd plan on getting a second PS from amazon until the filters from Fosi ship and you can use a single 10A.

Thank you for sharing your experience here. Appreciate it. I will probably just wait for the filter to arrive as I currently have no pre amp for it, anyway. Yes, I am one of the WiiM Ultra x Fosi V3 Monos audio-noobs Will be pairing the whole thing with a couple of Dali Oberon 5’s and an Argon S850 sub (which is currently the only parts of the setup I actually have in my home right now). Really looking forward to getting it set up though. So much that I am considering making some acoustic treatments to my living room in the meantime.

 

[Sokel]

I assume Fosi have done their homework here

Did they?
Lets leave aside the calc I have posted about heat dissipation and go to some serious implementation.
Let's use comparable (in power) amps in a no BS application:



(I think we all know what this is)

So,dimensions are 253 x 383 x 292 mm,so lets say 200 x 350 mm for the back plate?
It all acts as a heatshink but they didn't stop there as you see,they also added finned heatshink .

Is Neumann so generous wasting metal?I don't think so,they just did the calcs so they make sure their (pro) costumers won't waste time from stuff shutting down,etc.

 

[T&T]

Super Early backer #72 ...no news is bad news...wonder if they are short on Muses02 or my t-shirt size is not available.

 

[Giro413]

Super Early backer #72 ...no news is bad news...wonder if they are short on Muses02 or my t-shirt size is not available.

T-shirt is my guess. I ordered the Muses too and they didn’t mention them as a cause for delay. I would write them.

 

[EddNog]

T-shirt is my guess. I ordered the Muses too and they didn’t mention them as a cause for delay. I would write them.

But I received my t-shirt (size 5XL ROFL!!!).

-Ed

 

[SMen]

fyi, As an experiment I tried running 2x monos on a single 10A power supply (my own high end 48v PS, not the one Fosi supplies), and the noise was surprisingly loud. Not speaker damaging loud, but certainly could not be ignored. Not a big deal for me as I have plenty of power supplies, but I wanted to see for myself how bad it would be. If I was you, I'd plan on getting a second PS from amazon until the filters from Fosi ship and you can use a single 10A.

This is a strange one because one thing you would expect subjective reviewers (and there were a fair few who received early units) to hear and report on would be obvious noise, and they mostly received 48v 10A supplies. Noise did not seem to be a problem. Then there was a surge in 'concern' about synchronization and oscillation but this in the end seemed to be a bit of a storm in a teacup.

Does anyone know exactly where and why Fosi offered to include the filter?

I thought, when I found out, that it seemed to be a way to reassure more than anything else. I'm not expecting to hear noise with or without.

Has anyone received the Fosi10A supply out of interest with their monos?