Fosi v3 Mono Amplifier Reliability

[Connor1a]

So I just had a bit of a harrowing experience. I purchased the Fosi dual v3 Amp package off Amazon. The package came with 2 v3 mono amps and a 48v/10a power supply. Everything worked great for a day. I came back the next day, powered on the amps, one of them “snapped” loudly and the duo died. Zero output from either of them. I powered them off for a few minutes, tried again and still no output. The power lights on the amps lit, but no sound from either channel. So I boxed them back up and off they go back to Amazon. Looking at the reviews on Amazon, it doesn’t appear that this is a unique experience. With the great reviews here on ASR, I really want to like these amps, but an immediate fail worries me…

What’s the experience here? Have they been stable for those who’ve purchased them? ** As an aside, I was also plugging in a brand new pair of Lintons. That “snap” from the amp almost gave me a heart attack. I thought I’d blown my left channel speaker. I’m still hyperventilating……..

Thanks much….

 

[norcalscott]

I've had my pair of v3 Monos with the single power supply since they came out and have used them quite a bit for both music and for television sound in my listening room and have not had any issues at all with them. I also drive a pair of Lintons with them.

You may have just gotten a bad power supply (that's what it sounds like from your description anyway).

I'd just return them under warranty for a replacement set.

 

[Nopiano]

I got my Monos mid-August and popped them into my system in place of a Pass Labs XA25. (I’d previously tried the stereo v3). I chose the separate power supplies as that made more sense to me as I’m not running a desktop system. They’ve been 100% dependable, running with auto switch on.

The intention was to use then during the warmer weather, but they’ve stayed until earlier in November. Subjectively the Pass is a little richer, more saturated, like a nice photograph - but I can’t say that here! I think the Fosi pair are sensational for the money into my 4 ohm Sonus fabers.

 

[Skeptical_Aus]

I have had mine since July, two 48 v 5a PS. No issues at all.

 

[MaxwellsEq]

Have they been stable for those who’ve purchased them? ** As an aside, I was also plugging in a brand new pair of Lintons. That “snap” from the amp almost gave me a heart attack.

This reads like you were connecting the speakers with the amplifiers powered. I really hope that you were not!

 

[Connor1a]

This reads like you were connecting the speakers with the amplifiers powered. I really hope that you were not!

No… I was not connecting the speakers while the amps were powered on. I came back after a day using the amps, powered them on and they failed…

 

[pma]

This reads like you were connecting the speakers with the amplifiers powered.

Normal amplifier MUST survive this scenario. It may happen unintentionally that the speaker cable is released. Only a miserable, poor design would fail.

 

[martinus]

No problems here. My amps v3's are playing now for a couple of months without any hassle. They are powered by a 48v/10a power block. I do enjoy them every day. I did an op amp change for sound more of my liking. The amps are connected with audio monitor bronze bx2 speakers. Remarkable, one small screw of the xlr output at the backside of one of the amps was missing (?).

 

[MaxwellsEq]

Normal amplifier MUST survive this scenario. It may happen unintentionally that the speaker cable is released. Only a miserable, poor design would fail.

Yes I agree, the amplifier should survive. But I suspect the manual advises against it, and why take an unnecessary risk?

 

[Joe Smith]

While I don't own these, I remain suspicious of Fosi's promoting a single power supply with a splitter to power both mono's. Just seems like that's not the best solution if one's using monoblocks in the first place...?

 

[EERecordist]

I have their other products and I just leave them on - the ZA3 and the ZD3. Mine were China-shipped because I ordered direct, the crowd-funded stage of the ZA3. But returns are an advantage on Amazon. I have not had any problems.

It sounds like you encountered the classic infant mortality. Even with good quality practices, the failure rate can approach zero, but may not be zero.

I wrote a long post on reliability if you are interested. https://www.audiosciencereview.com/...reliability-science-in-audio-equipment.54018/

 

[Connor1a]

I've had my pair of v3 Monos with the single power supply since they came out and have used them quite a bit for both music and for television sound in my listening room and have not had any issues at all with them. I also drive a pair of Lintons with them.

You may have just gotten a bad power supply (that's what it sounds like from your description anyway).

I'd just return them under warranty for a replacement set.

I’ve returned them. Still scary when you’ve a new set of speakers and you hear that snap

I did an op amp change for sound more of my liking.

Which op amp did you choose?

 

[ban25]

I had a Topping PA5 drop a channel after a month (common problem). Back in the day, I had an SMSL Q5 Pro that was always hot regardless of the position of the standby/off switch. Anytime you connected or disconnected the DC power jack, it would arc, which scared the shit out of me. I would unplug that amp whenever I left the house for fear it might start a fire. Needless to say, I threw that thing out after a couple months.

I currently have a Fosi ZA3 powering the center channel of my HT system in mono mode and I have no complaints. The amp is connected via XLR and powered on and off via 12V trigger. Only gets moderately warm in use.

 

[martinus]

I’ve returned them. Still scary when you’ve a new set of speakers and you hear that snap

Which op amp did you choose?

Muses02

 

[DavidMcRoy]

I have 6 Fosi Audio V3 Monos. They drive the 4 Ohm 12" woofers and ESS Heil AMT tweeters

in the stereo pair of custom DIY dipoles I built. No issues at all. One of them went into protection mode when I inadvertently shorted the output, but of course they're supposed to do that.

 

[Connor1a]

I have 6 Fosi Audio V3 Monos. They drive the 4 Ohm 12" woofers and ESS Heil AMT tweeters View attachment 414085in the stereo pair of custom DIY dipoles I built. No issues at all. One of them went into protection mode when I inadvertently shorted the output, but of course they're supposed to do that.

Nice rack….

Glad to hear your experience has been better than mine with Fosi. Give their generally good reviews, I can only assume that I received a bad set of units or that there was something going on in my electrical system. I’ve since replaced mine with a set of NCx500 monoblock amps which have been running flawlessly so go figure. Anyway, thank you for the reply. Enjoy your kit. It looks awesome!

 

[Miser_Audioman]

I ordered with two power supplies. I have been driving old Paradigm Monitor 7s with them which are efficient, using and not using high pass filter for subwoofer. Other than the phase issue described elsewhere, these have basically been perfect. I thought about getting the new Buckeye amp but really seems like a waste of money. They get warm, but that just doesn’t seem to be a genuine issue in my setup, and i keep them stacked. Im having a good experience with the ZD3 Dac as well.

 

[Unbalanced]

I have been running a pair of V3 Monos with separate PSUs since late August of this year. They are on for 14 hours a day. One of them had an issue out of the box with entering standby and I replaced it. Thank goodness for Amazon returns. Fosi support was disappointing. Since that time everything has been running fine.

 

[Connor1a]

I ordered with two power supplies. I have been driving old Paradigm Monitor 7s with them which are efficient, using and not using high pass filter for subwoofer. Other than the phase issue described elsewhere, these have basically been perfect. I thought about getting the new Buckeye amp but really seems like a waste of money. They get warm, but that just doesn’t seem to be a genuine issue in my setup, and i keep them stacked. Im having a good experience with the ZD3 Dac as well.

Forgive me if this is a repeat. I’ve had this conversation several times now. I’ve lost track of the threads…

The plot thickened… I was able to recreate the issue with a second set of amps. I ordered a replacement kit (shared 48v/10a power brick w/ 2 v3 monobrick amps). I powered them up on day 1. Everything checked out great. I powered them off for the night. I came back the next day and powered them on again and the right channel amp blew again. The left channel amp was fine. I boxed them up and back they went.

I live in a circa ‘30s / ‘40s house with vintage wiring. It’s all up to code, however, I tested the receptacle I used for the amps anyway. Voltage was fine, amperage was fine, but it had a ground fault (the receptacle isn’t grounded). After speaking with an electrician and several engineers, a ground fault “should not have” caused the issue, but no one can explain why the amps failed. This includes an exchange with Fosi. The ground fault is the only abnormality. I wasn’t able to test “phasing” which to me, a non technical guy, seems like a reasonable place to look, but no one else thought it was likely to have been causing the strange occurrences. Looking online, there are reviews where only one of the two amps in the kit failed so maybe this is an issue with a small number of power bricks (though no one can explain why the Y connecter would have anything to do with the failures - ie why the power brick might be causing only one channel to fail - there’s nothing in the online reviews starting which channel failed).

If it is a problem with a small batch of power bricks, Fosi will undoubtedly replace any failed units and they’ll be worked out of the installed base. If it was the electrical in my home, it’s highly unlikely someone else will have the same problem (though as a indicator, I’ve since replaced the Fosis with a pair of NCx500 monoblocks - they’re cranking along without issue). We may never know.

Thanks for your post. I’m glad things are working out for your kit. Enjoy the lovely sounds!

 

[Connor1a]

I have been running a pair of V3 Monos with separate PSUs since late August of this year. They are on for 14 hours a day. One of them had an issue out of the box with entering standby and I replaced it. Thank goodness for Amazon returns. Fosi support was disappointing. Since that time everything has been running fine.

IMHO, as a nontechnical guy, I think the failure(s) had something to do with the shared power supply and my vintage ‘30s / ‘40s wiring. However, even though I recreated the problem, no one else shares my opinion. Or rather, no one else has a strong opinion as to what could have caused the issue(s). That includes non-responsive Fosi technical support. So we’ll chalk it up to gremlins.

I’ve since gone with a pair of NCx500 monoblocks and they’ve been cranking out sound without issue. Glad you have your system up and running. Enjoy and thanks for the reply!