Fosi v3 Mono - User Impressions | Owner's Thread

[Negatywny]

This mistake is so easy for us to make I wish overload protection was one of the essential requirements of all modern kit ...

Until yesterday, I lived in blissful ignorance, completely convinced that since there are 50 sizes of plugs in these power supplies, the diameter of the plug increases with the power of the power supply, and there is simply no physical possibility of connecting a too large power supply - and because it is simple and cost-free, an idiot-proof solution that completely solves the problem, there is no need to use any fancy protection circuits...

Just think of how best to spoil yourself with a new state of the art $200 DAC ...

it was just a few months old Topping E50 - it perfectly suited my needs - XLR outputs for the V3M and RCA outputs for the integrated amplifier that could work simultaneously - in addition, a beautiful orange display that perfectly matched the orange LEDs of the V3M.

So I ordered another one, the same

I will add here that, similarly, the V3M functionality with a choice of XLR and RCA inputs fits perfectly into a system with a stereo and a home theater receiver.
V3M allows you to eliminate the amplifier switch, which significantly reduces the number of cables.

And while we're at it, I'm very pleased with the sound of the V3M - not only is the bass more powerful than in my audiophile-grade integrated hybrid amplifier, but the highs are clearer too. It seems that the V3Ms get more out of my floor speakers than any amplifier I have tried before.
Great job FOSI. The only thing I'm missing at the moment is a V3M in exactly the same housing as the Topping E50 and in a blue color version

 

[MCH]

I hope all devices with medium/low power consumption use USB-PD asap.

 

[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)

 

[Stoutblock]

I’ve been enjoying the V3 monos for a few weeks now. What can I say, they work and they seem to drive my Soliloquy 5.0 speakers just fine. A little concerning about how hot the case gets. Maybe it’s OK but for a few dollars I was able to add some finned heat sinks on top using some thermo tape. Amps were running 109 deg F as measured at a vent now they are at 104 deg F.

 

[jvdburgt]

Just love how we’re Mad-Maxing these things

 

[Zek]

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.

 

[Stoutblock]

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.

I was thinking the same thing. I plan on having these out of sight and use the signal sensor for power so having them upside down is no issue to me. I also want to check for thermo paste inside as I guess most are saying Fosi did not use it on the production run. I will give it a try and do some temperature measurements.

 

[reubenno]

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.

 

[Sokel]

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.

Ok,I'll post it one more,last time.
Do you have a way to measure them this way?

Cause if you do you might see this:


without fan


with fan

And that's not on the same grid.ie USB powered by side for example.

It may be minor in the face of catching fire so I don't judge,but if someone picked this amp by SINAD alone something like this MAY flush it down the drain.

 

[reubenno]

Ok,I'll post it one more,last time.
Do you have a way to measure them this way?

Cause if you do you might see this:

View attachment 382618
without fan

View attachment 382619
with fan

And that's not on the same grid.ie USB powered by side for example.

It may be minor in the face of catching fire so I don't judge,but if someone picked this amp by SINAD alone something like this MAY flush it down the drain.

Nope, I have no way of testing, to be honest I don't much care if it hurts the SINAD as long as the amps run cool.
I'm largely using the Monos to take strain off of my Denon X4800H for my front channels, and I'm using the RCA input so I'm definitely not getting the best SINAD possible anyways.

I'm by no means an expert on SINAD and electronics in general, but the fan is connected to my Nvidia shield's USB port, and the shield is powered by the same circuit as the Fosi's and my AVR, so I doubt I've got an optimal low noise power setup anyways.

My Kef R3s still sound great to me and much more dynamic and clean than via my Denon AVR.

 

[SMen]

Ok,I'll post it one more,last time.
Do you have a way to measure them this way?

Cause if you do you might see this:

View attachment 382618
without fan

View attachment 382619
with fan

And that's not on the same grid.ie USB powered by side for example.

It may be minor in the face of catching fire so I don't judge,but if someone picked this amp by SINAD alone something like this MAY flush it down the drain.

Okay so to be clear you are saying that adding fans wrecks the SINAD?

 

[MCH]

Ok,I'll post it one more,last time.
Do you have a way to measure them this way?

Cause if you do you might see this:

View attachment 382618
without fan

View attachment 382619
with fan

And that's not on the same grid.ie USB powered by side for example.

It may be minor in the face of catching fire so I don't judge,but if someone picked this amp by SINAD alone something like this MAY flush it down the drain.

but that 300something and harmonics and low frequency stuff are at -120/-130dB, or are we looking at H3 that jumps from -104 to -94? because the rest of the harmonics get completely chopped by the fan - pretty good job!
on a serious note, how were those measurements taken? i am curious

 

[Sokel]

Okay so to be clear you are saying that adding fans wrecks the SINAD?

The charts (and not me) are showing the device having an about 100dB SINAD without the fan and about 90dB SINAD with the fan.
I'll say it straight away,that's probably inaudible (as I think it would be even at 80dB if it was about distortion alone and not noise) .

But if anyone's targets high SINAD it's maybe a good idea to forget about fans,along with led lights,other motors,etc so to get close to the isolated lab results.

Nope, I have no way of testing, to be honest I don't much care if it hurts the SINAD as long as the amps run cool.
I'm largely using the Monos to take strain off of my Denon X4800H for my front channels, and I'm using the RCA input so I'm definitely not getting the best SINAD possible anyways.

I'm by no means an expert on SINAD and electronics in general, but the fan is connected to my Nvidia shield's USB port, and the shield is powered by the same circuit as the Fosi's and my AVR, so I doubt I've got an optimal low noise power setup anyways.

My Kef R3s still sound great to me and much more dynamic and clean than via my Denon AVR.

Yep,that's as honest as it gets,if it sounds nice to you the rest of us is just theories.

 

[Sokel]

on a serious note, how were those measurements taken? i am curious

As described,one with the DUT as-is and the other with a 120mm fan placed on top of it,powered by a 12V charger away from the gear.
It's easy to replicate with other measurements too,tell me if you like to see more (other that THD+N vs Power) .
It may need another thread for stuff like this though.

 

[reubenno]

As described,one with the DUT as-is and the other with a 120mm fan placed on top of it,powered by a 12V charger away from the gear.
It's easy to replicate with other measurements too,tell me if you like to see more (other that THD+N vs Power) .
It may need another thread for stuff like this though.

Thanks, so if I wanted to add a fan would I need to ensure that it's on a different electrical circuit?

I'm pretty content just living with the potentially reduced performance but I'm curious as to if you know why having a fan plugged into the same circuitry would cause such a spike in noise.

Just for reference, the fan I'm using is 5v, not sure if that makes a difference to the potential SINAD performance drop.

Thanks again.

 

[MCH]

As described,one with the DUT as-is and the other with a 120mm fan placed on top of it,powered by a 12V charger away from the gear.
It's easy to replicate with other measurements too,tell me if you like to see more (other that THD+N vs Power) .
It may need another thread for stuff like this though.

I get the impression (attention, noob alert), that the third harmonic just happens to sit right on the crest of one of those broad non random noise peaks, whatever they are. That crest happens to be ca. 10 db above the noise floor so the third harmonic seems to be 10 db higher. Can anyone explain if that is what we are seeing here?
If you had the measurement with a 1030 Hz tone instead of 1 kHz, i would be curious to see if the third harmonic also appears higher or stays as it was without fan.
(Sorry for the potential nonsense).
Was the DUT an amplifier?

 

[jvdburgt]

Just so to understand, but the effect of the fan is mechanical, as in vibrations when they are mounted (almost) directly on the amp, or are they electrical or magnetic or something?

 

[Sokel]

Thanks, so if I wanted to add a fan would I need to ensure that it's on a different electrical circuit?

I'm pretty content just living with the potentially reduced performance but I'm curious as to if you know why having a fan plugged into the same circuitry would cause such a spike in noise.

Just for reference, the fan I'm using is 5v, not sure if that makes a difference to the potential SINAD performance drop.

Thanks again.

What you see is on different circuit.
What greatly matters thought is the proximity of the fan,a few cm away can have a greatly reduced effect.

If you had the measurement with a 1030 Hz tone instead of 1 kHz, i would be curious to see if the third harmonic also appears higher or stays as it was without fan.
(Sorry for the potential nonsense).
Was the DUT an amplifier?

That's easy to see,wait a few minutes (headphone amp)

 

[reubenno]

Ah thanks!!
I was under the impression it was electrical noise not the actual physical location of the fan being close to the amps, that is causing the issues.

My fan isn't touching the amps, it's around 5cm below, but I can definitely raise the amps up further so that there's a larger gap to reduce the impact.

Thanks again, I appreciate I'm a major noob and that you're providing me with your time and expertise.

 

[Sokel]

If you had the measurement with a 1030 Hz tone

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


No fan




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.

Ah thanks!!
I was under the impression it was electrical noise not the actual physical location of the fan being close to the amps, that is causing the issues.

My fan isn't touching the amps, it's around 5cm below, but I can definitely raise the amps up further so that there's a larger gap to reduce the impact.

Thanks again, I appreciate I'm a major noob and that you're providing me with your time and expertise.

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.