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Fosi Audio V3 Mono Amplifier Review

Rate this amplifier:

  • 1. Poor (headless panther)

    Votes: 14 2.2%
  • 2. Not terrible (postman panther)

    Votes: 20 3.1%
  • 3. Fine (happy panther)

    Votes: 123 19.2%
  • 4. Great (golfing panther)

    Votes: 485 75.5%

  • Total voters
    642
I will surrender :) now, because I seem to be "wrong".
Good luck to the one who asked...
 
I will surrender :) now, because I seem to be "wrong".
Good luck to the one who asked...
Look, i know where my problem is and you are partially right. But is not true that Fosi is not responsible for logistics... If you sell something to somebody and send it by mail, if the customer doesn´t receive the product, you are free from responsabilities ?
 
Look, i know where my problem is and you are partially right. But is not true that Fosi is not responsible for logistics... If you sell something to somebody and send it by mail, if the customer doesn´t receive the product, you are free from responsabilities ?
I agree, Fosi is ultimately responsible.

However, are you sure that the items are with Spanish customs? I would enquire there.

I would also enquire with the logistics company.

You have the tracking number and the name and address of the destination.

They are either still in transit with no evidence of final delivery or they are lost or stolen. Depending on where they are you may have to take what you’ve found out back to Fosi. Good luck with it.
 
I agree, Fosi is ultimately responsible.

However, are you sure that the items are with Spanish customs? I would enquire there.

I would also enquire with the logistics company.

You have the tracking number and the name and address of the destination.

They are either still in transit with no evidence of final delivery or they are lost or stolen. Depending on where they are you may have to take what you’ve found out back to Fosi. Good luck with it.
Fosi told me the monos are stuck in Spanish customs, and on the tracking it stop on Spain customs. Fosi ask me for evidences fromk kickstarter and credit card bill , and to send them . They told me to wait , and they assure the all duties. Last news was about 20 days ago...
 
Look, i know where my problem is and you are partially right. But is not true that Fosi is not responsible for logistics... If you sell something to somebody and send it by mail, if the customer doesn´t receive the product, you are free from responsabilities ?
I am not familiar with the kickstarter procedure and its obligations for the seller, thus I will keep my mouth shut now :)
 
By any chance, have you checked if the Amazon units currently shipping in the US are "phase corrected" or "original" ? Just curious.
I asked Fosi how to distinguish units with/out reversed phase and they sent this. Note extra QC label for units without inverted phase. My units from Amazon received Aug 20 were inverted phase.

Fosi V3 Mono Phase Inversion Comparison.png
 
Well, isn’t that what they are stating? 2 stickers = not inverted phase?
 
Btw, ordered my pair on July 16th direct from Fosi, departed from their Chinese facilities on Aug 8th, arrived in my mailbox on Aug 20th. They both have two QC-stickers.
 
Well, isn’t that what they are stating? 2 stickers = not inverted phase?
My fault. I didn't read ist correctly. I removed my posting already...
My units, allthough delivered after August 8th from the German Fosi Audio warehouse, still have only one QC sticker on their bottom. So it looks as if I have to do the conversion - one way or the other - myself...
 
Even WITH the DC filter in place, when using single-ended/RCA inputs, he still gets the noise with a single power supply feeding both amps. With balanced/XLR inputs, no noise. Probably the best path to take when implementing these amps is either don't share power supplies or only do so if using balanced inputs, and not when using single-end inputs.

-Ed
 
Tested these briefly in my home setup with the 48/10 power supply and DC filter, simply swapped out the Nord (see signature) using XLR connections. Dead quiet. Have to put ear within 2-3 inches of tweeter, at 0dB volume, to catch any traces of hiss.
 
Package 2x Fosi V3 Mono from the official Alistore... A crumpled (traditionally for Fosi) small free cardboard box without identification marks. It's horrible.
Not only are the boxes no branding, but the size of the seat is 5 cm longer and 1 cm wider... The device is hanging out there when traveling. They could at least seal it with a piece of Styrofoam ...
Complete disregard for customers. Even cheap non-branded devices are not send like this.
Shame!
IMG_20240826_174720.jpg
 
Even WITH the DC filter in place, when using single-ended/RCA inputs, he still gets the noise with a single power supply feeding both amps. With balanced/XLR inputs, no noise. Probably the best path to take when implementing these amps is either don't share power supplies or only do so if using balanced inputs, and not when using single-end inputs.

-Ed
It's Okay when both are on, I am pretty sure in his article. Also in my experience. I quite like my dinky little filter even though they were both fine without it :D :D
 
Anyone run a female Y spliter to both amps on single PSU without the DC filter?
Will Fosi send another new DC filter improved or will they send two separate DC filters to each amp?
Anyone run two DC filters LOL!
Can someone run one amp with xlr the other rca then see what noises it makes?
I might make a new Y cable with better shielding?
So many questions?
 
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@Progronom
Probably one of the last Kickstarter units sent. They might not have had the right packaging anymore because of this. They seem to have gotten more units ordered/sold, then they were prepared to. Surprise ! Surprise ! :cool: As far as I know they were overwhelmed by their own success...
As long as there is no "real" damage done to the amp it should be OK.

I opened one of my units bought at different times from Fosi Audio through their German warehouse. It was in a new slim black cardboard box with tweh amos outline at the outside. That was one of the newer charges sent. It had been ordererd by me after August 8th 2024... It still had the inverted phase (1 QC sticker and cable colors were still "original") and only the middle part of the heatsink (between the screws) had been pasted (thermal paste). I didn't want to touch the original soldering, so I put a sticker with the phase reversal shown (now correct phase) on the back plate.
Note: Some of the components soldered had quite "long legs" on the backside almost touching the cabinet's bottom, which I shortened a bit just for safety reasons.

I cleaned the heatsink plus the opposing cabinet inerts and renewed the thermal paste on the heatsink. I pasted it this time the full heatsink length to improve the thermal coupling, which might lead now to higher cabinet temperatures :) but should lower the temperature somehow on the inside. A short test: it was still working.
I will report its idling temperature lateron.

Anything I missed ?
 
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Even WITH the DC filter in place, when using single-ended/RCA inputs, he still gets the noise with a single power supply feeding both amps. With balanced/XLR inputs, no noise. Probably the best path to take when implementing these amps is either don't share power supplies or only do so if using balanced inputs, and not when using single-end inputs.

-Ed
I also have that noise. Fosi answered that without this filter, the noise would be louder.

From the archimago.blogspot:
"With the rated 240W into 4Ω 1%, we're looking at maximal we're looking at maximal 31Vrms so if using the +25dB gain setting, the source should be able to provide up to 1.75Vrms. With the +31dB gain setting, at least up to 0.9Vrms. ... Most modern source devices (DAC, preamp, streamers...) should have no problem providing at least 1.75Vrms output"

Sorry if this is a stupid question, but why "at least"?

If in my Wiim Ultra I can set: 500 mVrms, 800 mVrms, 1 Vrms, 2 Vrms output voltage manually - are any of these settings beneficial for sound quality, or completely forbidden? On the Wiim forum it's recommended to set such output voltage to conveniently control the volume. Can any of these settings can negatively affect the sound or the v3 mono units itself?
 
I also have that noise. Fosi answered that without this filter, the noise would be louder.

From the archimago.blogspot:
"With the rated 240W into 4Ω 1%, we're looking at maximal we're looking at maximal 31Vrms so if using the +25dB gain setting, the source should be able to provide up to 1.75Vrms. With the +31dB gain setting, at least up to 0.9Vrms. ... Most modern source devices (DAC, preamp, streamers...) should have no problem providing at least 1.75Vrms output"

Sorry if this is a stupid question, but why "at least"?

If in my Wiim Ultra I can set: 500 mVrms, 800 mVrms, 1 Vrms, 2 Vrms output voltage manually - are any of these settings beneficial for sound quality, or completely forbidden? On the Wiim forum it's recommended to set such output voltage to conveniently control the volume. Can any of these settings can negatively affect the sound or the v3 mono units itself?
One of the reasons, why I chose a separate 48VDC/5A power supply for each of those amps.
To get the full power of the Fosi Audio V3 mono amp you should switch to the 2Vrms output of Your Wiim Ultra. "at least" means, that the output voltage of the preamp should reach minimal 1.75Vrms, which is less then the 2Vrms Your unit is capable of. Otherwise, if Your speakers are highly efficient, You could chose one of lesser output voltages...
 
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