Fosi v3 Mono Amplifier Reliability

[Connor1a]

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/

What are your thoughts on the extended warranties sold by Amazon (Asurion)? They currently have a deal where you pay 17$/mo and everything you purchase is covered by an extended warranty. They even grandfather in anything you’ve purchased in the prior 12 months. I come from a school of thought that 99% of the extended warranty plans aren’t worth the money, but for 17$/mo perhaps it makes sense. As a reliability testing guy, I’d be interested in your opinion. Thanks!

 

[Miser_Audioman]

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!

Wow, yeah our house is a 1929, internal circuits upgraded but anything in the brick is old school two prong which i don't use for anything serious. I wonder if we have an engineer who could explain this?

 

[Connor1a]

Wow, yeah our house is a 1929, internal circuits upgraded but anything in the brick is old school two prong which i don't use for anything serious. I wonder is we have an engineer who could explain this?

I’ve asked around including a couple of engineering friends plus an electrician. None of them had any great ideas. No one here on ASR either.

But I’m an IT guy who used to do complex problem resolution for a living. It’s too strange to be random that only right channel blew and that I was able to recreate the event on a second set of amps… It could be so exotic as to not show up on Fosi’s radar (so their tech support isn’t being clued in). Idk… It’s a weird one for sure.

 

[EERecordist]

What are your thoughts on the extended warranties sold by Amazon (Asurion)? They currently have a deal where you pay 17$/mo and everything you purchase is covered by an extended warranty. They even grandfather in anything you’ve purchased in the prior 12 months. I come from a school of thought that 99% of the extended warranty plans aren’t worth the money, but for 17$/mo perhaps it makes sense. As a reliability testing guy, I’d be interested in your opinion. Thanks!

Great to hear from other quality and reliability professionals on ASR! You know the bathtub curve.

One fee covering all Amazon purchases is interesting. I guess it depends on how much of that you have. Usually insurance programs are focused on collecting revenues and minimizing settlements. What is the size and stability of the insurance company? What is the customer service record?

In my long post I propose accelerated stressing within the no-cost return window. I would not pay for an individual device warranty to cover the low water mark of the bathtub, though I do pay for Applecare which I think is rationally designed and offers more services beyond replacement/repair.

It is sad much audio equipment is now throwaway, though hopefully recycled. For recycling, the classic book Cradle to Cradle is a good read. We are far from that on electronics and audio.

Good contribution to the discussion.

 

[RCS]

I had one V3 Mono fail not long after I got them. Worked fine when shutdown for the day, but then wouldn't work at all the next day.
Fosi was good about sending out a replacement board for it after I sent them a couple images and video of it not working.
It's been back up and running for a while now. The other original V3 Mono has had no issues.

After the failure, I did purchase their fans for it. They run very warm without the fans and are now cool to the touch. If you are concerned about the heat they produce, I recommend the fans. They are nearly silent and don't run very fast. A single USB cable runs both fans. They also come with rubber feet top and bottom. Cost is about $30.

They are running with the 10a single supply powering both through their power splitter.

(BTW, the ZD3 is in bypass mode. The Saga 2 runs the show.)

 

[pma]

Amir is clueless in the field of amplifier design and gives his recommendation to products that are obviously poorly designed.

 

[Joe Smith]

Amir is clueless in the field of amplifier design and gives his recommendation to products that are obviously poorly designed.

This is a sweeping generalization for sure...

Amir seems to me to do reasonable kinds of tests that identify pretty good or good enough type of normal products. And good higher-end products as well. Most people don't push their equipment to extreme use cases. If you plan to do so, yeah, probably a good idea to spend more and get higher levels of engineering and headroom, etc.

There are a fair numer of anecdotal problems cropping up with the V3 Mono that something may be amiss with the manufacturing or QC...but it's not yet clear.

My view has always been that the various Fosi, Aiyima and SMSL amps are better suited for moderate listening levels rather than sustained high volume, and I think that power splitting solution may be part of what's causing issues...

I expect it will get sorted eventually. This is why I like to be a "late adopter" for the most part.

I did get early samples of both the Fosi V3 stereo and the Aiyima A07 MAX and they are still working 100%. As are my older Aiyima A07, A04 and SMSL AO100 amps. Even the SMSL SA-50 I purchased over 7 years ago.

In all of that, one of the original SMSL SA-50 power bricks was the only thing that gave me trouble - the original one developed an audible 'whine', and I discarded it.

 

[roog]

Beyond carrying out a few basic checks on the bench with a dummy load before letting my V3 Monos loose on my speakers, (DC voltage at output/approx. gain/view waveform/DC Voltage from PSU), I am not able to offer any objective comments relating to reliability other than my two examples electrically matched very closely with each other and that they warm up during prolonged use evenly with no obvious differences between them or hot spots on the cases.

Remarkable little amps, although i do have to keep reminding myself that there is the power brick too to consider! I guess if you bundled the whole lot into a case for stereo, it would be a normal sized '2U' power amp box.

I have 'fixed' mine to the vertical face of sheet metal bookends, and I have glued some small rubber feet to the bottom of the bookends. The amps are each mounted in a vertical orientation with the amps unobstructed ventilation holes located top and bottom. The 'foot' of the bookend is slipped under the base of each speaker, they sit just behind each of their respective speakers with very short speaker cables, about 1ft.

 

[audioaudio]

I ordered my pair from the Fosi site. Long shipping times from Asia to NA Eastern seaboard. The pair (2 units with single 10a power supply) made odd noises and one popped and burned. This was on the second day. Caught the sounds and a smoking amp on video.

Fosi support were really good to deal with surprisingly. They offered a refund but asked if I wanted to wait a little while to get the latest revision. I was skeptical but budget meant I needed to wait instead of looking for an alternative.

From what I can gather they jumped the gun before proper QA. The first batches that went out (to YouTubers and some pre-orders) had the following issues:
1. Shipped without a power supply filter.
2. They had an issue where the red and ground speaker wires inside some units were reversed.
3. Some units were burning out quickly.

The first revision:
1. Included the power filter
2. Fixed the reverse wiring.

However the issue with units popping off and burning remained. As a result, a number of YouTubers didn't recommend the units. Understandably so.

My units were from that first revision. I waited for revision 2 because Fosi support was extending my warranty, and they claimed they were making changes to lessen the chance of amps burning out.

I've had my replacements now for a couple of months and haven't had a single issue. They run for hours every day and are my audio and TV speaker amps. They see a lot of use. However I never leave them running in standby. I don't think I'll ever 100% trust them but they have been solid and performing well powering magnepan 0.7s.

I recommend if budget is an issue - but keep an eye on them.

Quick edit: Heat. Neither my older units or replacements ever got/get hot enough to worry me. They run for hours and are fine to touch.

 

[Graham849]

Grok responds when I ask about one channel issues:

"These reports are anecdotal and not indicative of a systemic issue across all units. The absence of more recent, widespread complaints could suggest that:

1. The issue might have been isolated to certain production batches or early units.
2. Fosi Audio might have addressed any potential manufacturing or design flaws in subsequent production runs.

However, without more recent and comprehensive data:

• Reliability cannot be conclusively confirmed or denied based solely on these past incidents.

If you are considering purchasing or currently using a Fosi V3, it's advisable to:

• Check for any firmware or hardware updates from Fosi Audio. Manufacturers often release updates to address known issues.
• Look for more recent user reviews or discussions on forums like Audio Science Review, AVS Forum, or Head-Fi to gauge current user experiences with channel reliability.
• Consider the warranty and support provided by Fosi Audio. They offer a 24-month limited warranty, which might be beneficial if you encounter similar problems ().
  https://fosiaudio.com/pages/user-instruction-v3

Given the information available, there's no definitive evidence that the channel failure within 24 hours is still a widespread issue, but users should remain vigilant and consider these points when evaluating the reliability of the Fosi V3“

 

[audioaudio]

Through the conversations I had with Fosi, they mentioned they couldn't control the inventory that made it to resellers like AliExpress and Amazon. They're aware early faulty units did make it out in larger numbers than any company would like. It's very possible OP got 2 faulty units.

It seems easy to return faulty units and overall reports of units burning out is much lower than it was after release.

Overall I'm glad I held on and waited. For the price these things are great.

 

[ArturroD]

A few months ago I had Fosi v3 mono with separate power supplies. These were already improved versions with correct +/- speakers. They sounded good, but the left one burned out on the first day. I returned them to the seller. I no longer trusted their quality. I had SMSL Q5 Pro before, which was 100% reliable for many years and still works. Now I bought Eversolo AMP-F2, because it looks much more solid and I am happy.

 

[Connor1a]

Through the conversations I had with Fosi, they mentioned they couldn't control the inventory that made it to resellers like AliExpress and Amazon. They're aware early faulty units did make it out in larger numbers than any company would like. It's very possible OP got 2 faulty units.

It seems easy to return faulty units and overall reports of units burning out is much lower than it was after release.

Overall I'm glad I held on and waited. For the price these things are great.

My apologies, but I disagree.

The v3 kits were out of stock several times on Amazon (where I purchased them) before I bought mine (twice). That implies that there were multiple OEM shipments between China and Amazon‘s distribution centers. My receiving two bad units on that kind of volume, plus taking into account the similarly negative reviews on Amazon, here and on other AVS sites, implies either a significant statistical anomaly or the number of failed units that Fosi shipped out had to have been much larger than they’ve admitted to. Personally, I think it’s the latter.

I think Fosi did what a lot of manufacturers would do. They had a QA miss. They understood that they had bad units out in the wild. It would’ve been too expensive / almost impossible to issue a recall so they relied on consumers to do the recall for them. I’m not suggesting that I agree with the tactic, but I can understand that they didn’t have many other options open to them. To be fair, when I spoke to them, they were willing to replace my defective kit fairly quickly. They also offered me a 40% discount on their other products for my troubles. So as far as recovering customer satisfaction, I think they did what they could.

However, that doesn’t mean that I don’t think they shouldn’t have done a better job at quality control upfront nor does it mean that I don’t think that their helpdesk shouldn't have been better prepared. In other words, I get that Fosi “did what they could” once they started seeing their units failing, but whether or not it was easy to return the failed unit(s) or whether the number of failures is now decreasing does nothing to pay me back for the time and effort I spent dealing with this issue. Further, it does nothing to improve my sense of confidence that Fosi won’t let another batch of failed units out into the distribution pool the next time they buy more inventory from their third party manufacturer(s).

Ultimately, regardless of their customer service recovery, the core issue is that they allowed units that were prone to failure out into the distribution pool and there’s really nothing that we’ve seen to imply that they won’t do that again.

Just my two cents.

 

[cprogrammer]

I had one of my two V3 mono failed today. It happened right in front of me. Suddenly there was a kind of a crackling sound from inside and white smoke came out of the right side vents. There was a peculiar smell that filled the air. Speakers were connected. I immediately jumped and switched off the supply. I disconnected the speaker to the failed unit and connected a cheap speaker to the failed unit. Switched on the supply and played music. No sound. The lights comes on, the relay makes clicking sound when you use the toggle switches. Tried both XLR and RCA inputs. No sound from the failed unit. Lucky for me that my speaker is safe (Polk Rti A9). Then I opened the unit. Nothing seems to be burnt, but the peculiar smell is there in front of the right side large capacitor. I got the units in Oct 2024 and have emailed Fosi support. They asked me to send pictures of the PCB inside. Waiting for them to reply back. So time being, I'm back to my valve amp that the V3 Mono had replaced. Here are 3 photos

One of the caps, the plastic label doesn't go over the edge. Doesn't look bulged out to me. So not sure if it is the cap that failed

The bottom side

 

[Miser_Audioman]

is there consistently in the failures, a bad bunch of capacitors for example?

 

[DACsNoMore]

I got first two as separates - both came with visually different power supplies 48V 5A. One looked like refurbished and I have to keep it on gain +3db to match with other unit that looked brand new, retuned those and bought official fosi pair kit with single 10A power brick from "fosi outlet" seller on Amazon - it came in damaged packaging, but the content was intact. I since upgraded opamps #2 and #3 to MUSES02 and it is working fine and stable. No speaker polarity issue as I inspected both during opamp upgrade.

If you dare to upgrade opamps - MUSES02 pins are very delicate, so be very careful with those - use IC insertion tool and insert it into DIP8 raiser adapter and then instal it in amp. The reason to use raiser adapter - it is easier to insert and remove multiple times. I had one pin bent during insertion and when attempted to remove it - another pin got stuck in the PCB socket and broke off from the chip and piece of it left inside the socket, basically rendering whole amp unusable (different amp upgrade with tight difficult access to DIP8 sockets, not as easy as on Fosi V3). Took some creativity to recover from this mess.

 

[estebandido]

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 (?).

Hi martinus! I also have the same Monitor Audio Bronze BX2 speakers, and I’m very curious about how they sound with your v3 amps. How would you describe the sound of that combination? If possible, could you share a short video of them in action? I’d really appreciate it!​