Fosi v3 Mono - User Impressions | Owner's Thread

[Negatywny]

Maybe it’s OK but for a few dollars I was able to add some finned heat sinks on top using some thermo tape.

Haha, looks predatorily, like mohawk gremlin. Fosi should add some leds to it and sell as gamers edition

 

[MCH]

I exaggerated it a little so we can see the effect better and I included all values for better visuals.
So,at 1030Hz:

View attachment 382626
No fan


View attachment 382627

with fan

It's a little horror show.

What happens with the harmonics at the other charts are probably canceling,same as we do it deliberately combining the amplitude with the opposite phase.
It's random really,and that's the worst part of it.


It can be electrical noise too but yes,location changes the effect to the point of being insignificant if it's far enough.
Right on top or the bottom of the amp,is NOT far enough.

thanks!. But see, the THD doesn't change now

 

[reubenno]

I exaggerated it a little so we can see the effect better and I included all values for better visuals.
So,at 1030Hz:

View attachment 382626
No fan


View attachment 382627

with fan

It's a little horror show.

What happens with the harmonics at the other charts are probably canceling,same as we do it deliberately combining the amplitude with the opposite phase.
It's random really,and that's the worst part of it.


It can be electrical noise too but yes,location changes the effect to the point of being insignificant if it's far enough.
Right on top or the bottom of the amp,is NOT far enough.

Thanks, I'll aim for around 10cm of distance between the fan and the amps.
Hopefully that'll strike a good balance between cooling and low SINAD impact.

 

[Sokel]

thanks!. But see, the THD doesn't change now

Yes,it's completely random.
If you could see the test running,the harmonics were jumping up and down,what's shown is just a small average.
Also,have a look at what happens inside the notch,at the sides of the skirt.

To cut the story short,it does not seem like a good idea.

 

[Toroid]

Got my monos set up with dual 10A power supplies. This is replacing a noisy Behringer EP2500 (fans and power supply noise). The rest of the chain is: Turntable with Schiit Skoll phono and a Kara preamp. On the digital side I have a chromecast audio and a Schiit modi 3 (Wiim pro and an SMSL D6S on the way) all balanced connections. Speakers are Vandersteen 2Cs from the late 80s. The first thing I noticed was a super deep, black background, no noise whatsoever. The next thing I noticed was more bass as compared to the Behringer, but the sound was on the quieter side. Since I'm using XLR and am only getting 20db gain (Behringer was 34db gain) I realized I needed to tweak my gain settings on the preamps. Upon tweaking settings for a bit, I settled on Kara full gain mode and increased the Skoll gain from 40db to 47db. Now, this made everything more lively and woke up the V3 monos. I'm really enjoying the sound, but if I'm going to knit pick, the treble does seem more recessed and perhaps not as dynamic (darker overall) as the Behringer pro amp. (That thing rocked pretty good even if big, heavy and noisy). I'm attributing this to that the monos may be more neutral than the Behringer thus accounting for the difference. I have the Wiim pro coming soon so may play around with the EQ to get it to my flavor, as well. Anyone have any tips for getting more dynamics out of the V3s? Opamp swap possibly? (Also, I realize that the Vandersteens are pretty inefficient so may not synergize the best)

I may have to take back all my knit picks. I just installed my new Wiim pro and connected to Amazon music now the treble is back and dynamics are pushing the Vandersteens around like school yard bullies! And my God...the bass, the bass man. This is with no eq. Btw...I think there is some magic/synergy at work with the wiim and v3 monos (even more gain perhaps?). Gotta go listen to more tunes...

 

[EddNog]

Ah, well then… SO much cleaner without all those fans cluttering the deck!

-Ed

 

[Down South]

Here's my cooling solution, I'll get a 3d printed stand eventually, but a 200mm Noctua fan underneath the amps has done absolute wonders for the temps.

The amps went from being uncomfortable to touch to damn near stone cold. I'd highly recommend this setup if you want to keep the amps running cool.

15 years ago along with a Dutch friend we used computer fans to cool the mosfets and power resistors in hybrid amps there, were no issues with either mechanical vibration or electrical interference for 3 reasons:

(1) we used ebm-papst 4412 FGL -12V. 1.3W fans

(2) it is mounted on pieces of rubber type material 2mm/ cylindrical pieces of softwood (25mm) then felt pads, held in place with screws on all 4 corners. I'm not even sure that this arrangement needs screws - whatever I intend to replace the the lot. I'm lucky I can use the slate enclosure I had made when I lived in Spain. I just have to make a top plate slotted to allow air flow to the 2 monos.

(3) by using an adjustable ac/dc PSU 12V powered via the dis. block NOT USB there will be no electrical interference. The PSU we used had adjustable voltages 3-4.5-6-7-9-12V. I tried the ebm-papst fan and PSU on the desk without any enclosure, using 4.5V @ 30cm only a bat would hear a 'suggestion' of hum, of course no one is going to be sitting this close These papst fans were the best available for our purposes 15 years ago. I've checked online and I can't see anything to touch them. They aren't cheap but will seriously lengthen the life of the monos.

Now here comes the bummer - for those that don't live in the USA - Mouser has them @ US$33.83/€31 BUT they are only available to OEM.design customers AND they are not available to EU/UK customers.

Can EU members check where we can buy them at the best price I have seen some outrageous price gouging - anywhere in the EU we don't get shafted for import duties.

After I have satisfied myself that the Fosi's are keepers, I'd like to buy a second fan so that I'm covered for the future.

 

[MCH]

Well, there are not one but two fans inside Audio Precision APx555, so I am sure there is a way to do it right.

They don't even look very fancy

 

[Sokel]

Well, there are not one but two fans inside Audio Precision APx555, so I am sure there is a way to do it right.

View attachment 382707

They don't even look very fancy

There's a good article about it:

While DC fans might appear to be electrically noiseless, they do produce acoustic and electrical noise. The different types of fans will incur produce their own types of EMI, creating difficulty in passing EMC tests. Even a DC-driven motor will produce EMI thanks to the spinning magnet used to attract and repel the rotor, producing strong switching noise during commutation. EMI generated from DC fans is normally limited to conducted EMI in the fan power leads (for 2 wire DC fans). This fan electrical noise is normally injected into the common ground, where it reappears at the output of any amplifier that drives the fan.
This is not to say that a DC fan does not produce radiated EMI, but the radiated EMI will be at the same frequency as the rotation rate due to uncontained magnetic fields (UMF) from the permanent magnet and stator windings. UMF exists in virtually all fans to some degree, but the first step in dealing with UMF is the responsibility of the manufacturer. Some manufacturers will place a thin steel enclosure in their fans to suppress UMF in at least two mounting planes. This means that radiated EMI is strongly dependent on the orientation of the fan.


Radiated EMI from UMF can induce a low frequency ripple current in a nearby high inductance circuit. Larger fans generally require stronger magnetic field for driving, thus they will exhibit stronger EMI at a given rotation rate. However, even at thousands of RPM rotation rates, the frequency of this radiated EMI will only be in the range of hundreds of Hz.

More,here:

Cooling Fan Electrical Noise Reduction in Your PCB

Who hasn’t opened up their PC or laptop and taken a long look at its fans and heatsinks? If you’re working with high speed components, high frequency components, or power components, then you’ll need to devise some sort of cooling strategy to remove heat from these components.

resources.altium.com

 

[gwing]

Can EU members check where we can buy them at the best price I have seen some outrageous price gouging - anywhere in the EU we don't get shafted for import duties.

I have run a silent fanless PC for years and get components in the UK from https://www.quietpc.com/components

They do good fans and flexible silicon mounting struts that work well.

 

[jvdburgt]

It would be better if the additional cooler was glued to the bottom of the amplifier where the temperature is highest and turned completely upside down...
The housing and cooling of the chip are poorly designed, the cooler on the chip should have been on the upper side of the housing because it would have better removal of warm air.

That was my initial intuition as well. However, as Fosi explicitly wants to use the entire case as a heatsink, it might actually make sense to do it this way (as it ensures maximum heat spreading over the entire case).

 

[Sokel]

That was my initial intuition as well. However, as Fosi explicitly wants to use the entire case as a heatsink, it might actually make sense to do it this way (as it ensures maximum heat spreading over the entire case).

Common sense would suggest that it would be better bolted at the bottom (with some longer screws,same with the ones used) and put to the side with the heatshink's fins looking straight up (as it intended to be the proper orientation) .
That way it would help a little with the cap's (now) cooking apart from the chip.

 

[Sokel]

Also,for the ones who want to use a fan (and again,I can understand why) a nice trick is to use a simple thermal bimetal contact switch at a desired temp.
This will make the fan stay inactive until the desired temp (you can choose it) will trigger it.
Is dead simple to install,just connect in series with the power line of the fan and attach it to the case.




Edit:You'll need to take the N.O. (Normally Open) variation.

 

[gwing]

Received my power conditioner to 'fix' the split power supply problem today, thank you Fosi.

• It seems nicely made and kind of cute. Looks much better than the earlier published pictures.
• Kudos to Fosi for also supplying an extra Y cable with it rather than just a gender changer so that we don't introduce yet another connection in the power chain.
• No audible difference though, not unexpected as I had no audible problem in the first place with 1x10A driving two monos As I understand it this would only manifest if you drive the amps hard anyway, which is something I'm not going to subject my ears to.

P.S. the power conditioner does do *something* as it now takes an extra second or so for the amp relays to click in when activating from standby. Maybe a capacitor in there that has to charge up.

 

[Pelagic]

My V3 Mono x2 + 48v/10a Power Supply x1 were delivered yesterday afternoon. I connected them to my stereo-only system (using two 48v/5a's I already have) and let them play at medium-low volume overnight. The cases were very warm this morning but not hot. I don't have audiophile ears, but they sound very good through my Wharfedale Lintons. Today I'll switch them to my home-theater system (Onkyo TX-RZ50 to Polk R700's) and use the 48v/10a PS (no filter yet).

The Phase Check track from Bunker Analog on Tidal confirms that they're in phase with each other. I'll check again when they're in the 5.1.2 HT system, but I guess it's been confirmed that they all have reverse polarity.

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.

 

[EddNog]

or 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.

You've apparently experienced a temporal anomaly!

-Ed

Sorry...bad Star Trekkie dad joke.

 

[gwing]

Was it a round flat van and a dodgy looking driver?

 

[Stoutblock]

Ah, well then… SO much cleaner without all those fans cluttering the deck!

View attachment 382645

-Ed

Combined with the SVS sub and metas that is a very well thought out system! You might consider a DSP to take it over the top?

 

[EddNog]

Combined with the SVS sub and metas that is a very well thought out system! You might consider a DSP to take it over the top?

Thank you; I have full 10-band PEQ plus various plugins like Balamce control in the DAP that I use as my streamer for room correction in conjunction with the DSP in the subwoofer.

-Ed

 

[Down South]

There's a good article about it:


More,here:

Cooling Fan Electrical Noise Reduction in Your PCB

Who hasn’t opened up their PC or laptop and taken a long look at its fans and heatsinks? If you’re working with high speed components, high frequency components, or power components, then you’ll need to devise some sort of cooling strategy to remove heat from these components.

resources.altium.com

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.