Fosi Audio V3 Mono Amplifier Review

[burkm]

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...

 

[avdoc]

Archimago has part one of his review up. FYI

Link please?

 

[burkm]

Part I: Fosi Audio V3 Mono Amp; Class D + PFFB, TI TPA3255 - Retail box with single 48V/10A power supply and filter. [With initial measurements.]

A blog for audiophiles about more objective topics. Measurements of audio gear. Reasonable, realistic, no snakeoil assessment of sound, and equipment.

archimago.blogspot.com

 

[EddNog]

Part I: Fosi Audio V3 Mono Amp; Class D + PFFB, TI TPA3255 - Retail box with single 48V/10A power supply and filter. [With initial measurements.]

A blog for audiophiles about more objective topics. Measurements of audio gear. Reasonable, realistic, no snakeoil assessment of sound, and equipment.

archimago.blogspot.com

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

 

[mags65]

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.

 

[Progronom]

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!

 

[SMen]

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

 

[Lux_ury]

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?

 

[burkm]

@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 ! 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 ?

 

[renoxd]

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?

 

[burkm]

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...

 

[WillBrink]

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

Are you not at least partially defeating the benefits of the two amps by having them share a PS?

 

[antcollinet]

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

Because most modern sources can provide more than the 1.75V needed (typically 2V for RCA sources).

 

[EddNog]

Are you not at least partially defeating the benefits of the two amps by having them share a PS?

That’s how I feel about it, but apparently a decent number of people don’t care except to save money by only having to pay for one power supply and/or actually do care about the meager difference in space utilization of having a second unit.

-Ed

 

[kelesh]

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.

View attachment 388556

I wonder, how long before they correct all the units already produced and then eliminate this extra step and sticker.

 

[multichannel_guy]

It looks like 2 fosi monos with two 48V 5Amp power adapters is $280
2 fosi monos with two 48V 10 Amp power adapters is $420

Are the 10 Amp adapters worth the extra $140, if running Magnepan LRS? Thanks guys.

 

[thunderchicken]

I’m getting popping from mine on power off and during volume changes. I’m using the hypex preamp, and the problem was enough to warranty the unit. Hypex replaced a board and sent it back to me. The pops have lessened but are still an issue. This still points to the preamp, but it seems to be an issue with the fosi monos as well if they do it at power off. DC is getting through but it’s not apparent from where.

 

[EddNog]

It looks like 2 fosi monos with two 48V 5Amp power adapters is $280
2 fosi monos with two 48V 10 Amp power adapters is $420

Are the 10 Amp adapters worth the extra $140, if running Magnepan LRS? Thanks guys.

My dad is using V3 Monos with his LRS+ in a decent sized room, sitting around 12’/3meters away with smaller power supplies than even 48V and is happy with it. I think you’re fine with separate 48V 5A supplies.

-Ed

 

[multichannel_guy]

My dad is using V3 Monos with his LRS+ in a decent sized room, sitting around 12’/3meters away with smaller power supplies than even 48V and is happy with it. I think you’re fine with separate 48V 5A supplies.

-Ed

What is the approximate SPL levels he is listening at the 12 feet distance?

 

[EddNog]

What is the approximate SPL levels he is listening at the 12 feet distance?

He’s pretty old school and wouldn’t know how to measure that for me. I can take a measurement next time I go up to New York, but it may be weeks away.

I can say this much: he listens louder than I do, and I’m normally around 65-70dB at my listening position only 9 feet away from my LS50 Metas.

If I had to guesstimate, 70-75dB for the old man.

-Ed