Fosi v3 Mono - User Impressions | Owner's Thread

[Keauval]

Well received my 2 V3 Mono with 5A 48V and 2 Muse02
Sounds good in RCA, some harsh in the voices (above 9khz)... New test to Come this Weekend with XLR and Kef 105.2

 

[PJ_Schmidt]

Got my pair installed today running each with its own power supply.

I designed and printed a cradle that holds both amps and my DAC in my media cabinet. I oriented them vertically to give a little more room for them to breath while fitting into the space I have for them.

So far they sound very good, but I need to listen more to really characterize their sound.

 

[EddNog]

Got my pair installed today running each with its own power supply.

I designed and printed a cradle that holds both amps and my DAC in my media cabinet. I oriented them vertically to give a little more room for them to breath while fitting into the space I have for them.

So far they sound very good, but I need to listen more to really characterize their sound.

That rack is awesome!

-Ed

 

[SMen]

So come on some of you who have received theirs. This is the user impressions thread! Do your worst!

 

[EddNog]

So come on some of you who have received theirs. This is the user impressions thread! Do your worst!

I mean they work, they sound great, there have been no reliability or operational issues. They are just monobloc power amplifiers after all, they’re not multifunction devices.

Heck, the initial review and measurements by Amir already told 98% of the story!

-Ed

 

[SMen]

I mean they work, they sound great, there have been no reliability or operational issues. They are just monobloc power amplifiers after all, they’re not multifunction devices.

Heck, the initial review and measurements by Amir already told 98% of the story!

-Ed

Okay. Well, I think you should put your ZA3’s back and flog em then...

...

I mean, they all sound the same because beyond the levels of human hearing etc.

I only have a stereo unit to compare - nothing mono-blockable. One thing I'll be doing is seeing if my db meter is any different at my preferred listening levels. Stuff like that.

Anyway - I am not being fair as I would not expect a proper view before more time than this . The real answer will be how many people are still using them after a year...

 

[EddNog]

Okay. Well, I think you should put your ZA3’s back and flog em then...

...

I mean, they all sound the same because beyond the levels of human hearing etc.

I only have a stereo unit to compare - nothing mono-blockable. One thing I'll be doing is seeing if my db meter is any different at my preferred listening levels. Stuff like that.

Anyway - I am not being fair as I would not expect a proper view before more time than this . The real answer will be how many people are still using them after a year...

Well…I do feel that they sound a bit better than the ZA3s. What is mostly noticeable is the very highest frequencies where the PFFB comes into play, as there is a more natural feel to the, “air,” and, “spaciousness.” Of course now I’m sure I’m just providing ammunition for ASR members to fire at me, but be that as it may, that is my observation between the ZA3s (which I’ve passed on to my father to drive his Magnepan LRS+ planar loudspeakers) and these V3 Monos (which I am using to push KEF LS50 Metas).

-Ed

 

[DavidMcRoy]

I’m currently using two stereo V3s to drive a pair of 2-way “difficult load” speakers via active DSP crossovers and they work fine. The four V3 monos with a pair of 48V 10A power supplies and filters I await will give me better headroom on movie soundtracks that have ridiculous dynamic range and otherwise probably sound identical. No mysteries, no drama from these quarters.

 

[SMen]

Well…I do feel that they sound a bit better than the ZA3s. What is mostly noticeable is the very highest frequencies where the PFFB comes into play, as there is a more natural feel to the, “air,” and, “spaciousness.” Of course now I’m sure I’m just providing ammunition for ASR members to fire at me, but be that as it may, that is my observation between the ZA3s (which I’ve passed on to my father to drive his Magnepan LRS+ planar loudspeakers) and these V3 Monos (which I am using to push KEF LS50 Metas).

-Ed

Yes I know, but thank you for sticking your head above the parapet.

I will share when I eventually get mine.

I’m currently using two stereo V3s to drive a pair of 2-way “difficult load” speakers via active DSP crossovers and they work fine. The four V3 monos with a pair of 48V 10A power supplies and filters I await will give me better headroom on movie soundtracks that have ridiculous dynamic range and otherwise probably sound identical. No mysteries, no drama from these quarters.

I will be using quite efficient 8ohm speakers 90db +, with 'take no prisoner' tweeters, and some fairly 'take no prisoner' vinyl records from the 60s!

But that is for another time.

 

[Skeptical_Aus]

I received mine yesterday. They work. I like them. Hope they last. Great value for money. Powering Klipsch Heresy IV speakers.

 

[thunderchicken]

I’m having a weird DC issue with mine. I have the Hypex preamp and use the balanced connections. When I adjust the volume, there’s a pattern of popping and hash noise consistently at certain levels. The drivers visibly pop out at two of the noisy levels. Not sure if it’s the amp or preamp.

 

[Sokel]

I’m having a weird DC issue with mine. I have the Hypex preamp and use the balanced connections. When I adjust the volume, there’s a pattern of popping and hash noise consistently at certain levels. The drivers visibly pop out at two of the noisy levels. Not sure if it’s the amp or preamp.

You should immediately check this with a DMM unless the speakers connected are sacrificial.
Probably the reason is the pre,so start there.

Does monos have DC input protection of some kind?

 

[timiambeing]

So come on some of you who have received theirs. This is the user impressions thread! Do your worst!

Ok, well I’ve had mine for a few days, powered on and playing quietly to themselves. Coming from a V3 integrated orange knob thingy my first impressions after five minutes were - underwhelm… certainly they were louder, much louder, so much louder I had to reduce the gain with the little switch on the back. The bass was ponderous and heavy though.

I use a LUMIN U1 Mini with LeedH volume control, so I tried that directly without a preamp, and couldn’t get it above 20% before the sound was way too loud (I have single driver full range speakers - very efficient). Went back to the little Fosi P3 I’d been using with the V3 and now I can use say 50-60% digital volume control and around a third on the P3 knob. P3 on its own as a preamp doesn’t work, couldn’t get the volume off the starting position more than a few millimetres - I have had this problem with my Pontus II DAC before though, sometimes I have had to use in line attenuators at 15dB to bring the output down - it says 2v but it’s very loud, certainly couldn’t consider balanced output.

Anyways, after a couple of days running in I put the V3 back in and compared with the V3 mono’s and indeed then I noticed there was a bit more definition from the mono’s, mostly top end information, bass was heavier and a tad ponderous. I measured the room again and found the usual hump at around 80hz was a few decibels louder than with the V3. Taming that made comparisons easier.

All in all I would say the V3 was easier to listen to, plenty dynamic enough, lots of speaker control and enough resolution to please anyone. The V3 Mono’s are brighter, no more dynamic, heavier bass and quite a lot more - in ‘yer face. I can’t say I would call them an upgrade, unless you have hard to drive speakers of course. They may use newer technology with PFFB but I can’t hear that and maybe my speakers aren’t a bothersome load.

All that said and done, for the price they are remarkable, I’m comparing in a system that usually has a Line Magnetic valve amp at £2k (when it isn’t broken!) so all the above is being very picky. Class D is a real competitor these days and Fosi should be applauded for punching way above their weight with these little amps they keep releasing.

My only caveat would be, they run very, very hot - untouchable hot - so how long they will last is anyone’s guess! Oh and the auto switch on mode doesn’t seem to go by signal input, more like volume input? Running in with barely any noise coming through the speakers one of them kept shutting off, then the other joined it - upping the volume a tad kept them both on. I suppose it would still be useful if you have these amps out of the way and can’t easily get at them.

Other than that it’s early days, I do wonder what they would sound like with a very good passive preamp as the P3 is hardly stage of the art, using no preamp with the LUMIN volume control they did have a different character, but like I say I would have to get the inline attenuators out again… might do that for a bit if fun!

 

[SMen]

Ok, well I’ve had mine for a few days, powered on and playing quietly to themselves. Coming from a V3 integrated orange knob thingy my first impressions after five minutes were - underwhelm… certainly they were louder, much louder, so much louder I had to reduce the gain with the little switch on the back. The bass was ponderous and heavy though.

I use a LUMIN U1 Mini with LeedH volume control, so I tried that directly without a preamp, and couldn’t get it above 20% before the sound was way too loud (I have single driver full range speakers - very efficient). Went back to the little Fosi P3 I’d been using with the V3 and now I can use say 50-60% digital volume control and around a third on the P3 knob. P3 on its own as a preamp doesn’t work, couldn’t get the volume off the starting position more than a few millimetres - I have had this problem with my Pontus II DAC before though, sometimes I have had to use in line attenuators at 15dB to bring the output down - it says 2v but it’s very loud, certainly couldn’t consider balanced output.

Anyways, after a couple of days running in I put the V3 back in and compared with the V3 mono’s and indeed then I noticed there was a bit more definition from the mono’s, mostly top end information, bass was heavier and a tad ponderous. I measured the room again and found the usual hump at around 80hz was a few decibels louder than with the V3. Taming that made comparisons easier.

All in all I would say the V3 was easier to listen to, plenty dynamic enough, lots of speaker control and enough resolution to please anyone. The V3 Mono’s are brighter, no more dynamic, heavier bass and quite a lot more - in ‘yer face. I can’t say I would call them an upgrade, unless you have hard to drive speakers of course. They may use newer technology with PFFB but I can’t hear that and maybe my speakers aren’t a bothersome load.

All that said and done, for the price they are remarkable, I’m comparing in a system that usually has a Line Magnetic valve amp at £2k (when it isn’t broken!) so all the above is being very picky. Class D is a real competitor these days and Fosi should be applauded for punching way above their weight with these little amps they keep releasing.

My only caveat would be, they run very, very hot - untouchable hot - so how long they will last is anyone’s guess! Oh and the auto switch on mode doesn’t seem to go by signal input, more like volume input? Running in with barely any noise coming through the speakers one of them kept shutting off, then the other joined it - upping the volume a tad kept them both on. I suppose it would still be useful if you have these amps out of the way and can’t easily get at them.

Other than that it’s early days, I do wonder what they would sound like with a very good passive preamp as the P3 is hardly stage of the art, using no preamp with the LUMIN volume control they did have a different character, but like I say I would have to get the inline attenuators out again… might do that for a bit if fun!

Interesting. I wonder how efficient your speakers in fact are? 96db?

This is valuable feedback for those with efficient speakers. Mine are 90/91 8ohm. I am tempted by one of these - the b model which seems to be very tightly toleranced.

relay volume control finished machine B Might be worth checking out.

 

[gazza58]

arrived today with 2x5A
after 2 hours of operation instead of the fosi ZA3
better curtain in width and depth
qobuz bitperfect with pi4 with I2S out card on smsl do300ex as pre-dac
almost excessive power with my Borea BR8
with heat gun max temperature from 49° above, up to 36 below

 

[joostdh]

I got my two V3 monos yesterday, both with the 5A adapter. Their small size makes them almost cute. They feel solid, well made and I like the clicky switches. The adapter is less cheap looking than most adapters.

I intend to use them in my living room once the Wiim ultra comes. For now I’ve hooked them up via XLR to the RME ADI-2 DAC, which is fed from my iMac, to drive a set of Q Acoustics 3010i in a near field setup.

It sounds… good. I can’t say much more yet because this is a temporary setup and I have nothing to compare it with as such.

Hopefully everyone gets theirs soon.

 

[Negatywny]

Hopefully everyone gets theirs soon.

haha, thx bro

 

[thunderchicken]

You should immediately check this with a DMM unless the speakers connected are sacrificial.
Probably the reason is the pre,so start there.

Does monos have DC input protection of some kind?

I’m assuming because of my issue that they’re DC coupled.

I reached out to CS at diyclassd.com about it. Hopefully we can troubleshoot and I won’t have to return it.

 

[jvdburgt]

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?

 

[Giro413]

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.