Fosi V3 Mono Review. I Fried One! 🔥🤣 

We have contacted Erin to send back the unqualified product for analysis and research. We are very grateful to Erin for reviewing our product. We hope that our customers can provide more suggestions to improve our products.

"It sounds like an amplifier." damn man, if that isn't the realest thing I've ever heard! Nice review as always man

Don't throw it out, we need an autopsy!

Erin broke one of the biggest Audiophile rules. Never let the smoke out of the product. You must make sure the smoke remains inside the enclosure. 🤣

It’s actually a good thing that these get hot. These units use the chassis as a heat sink. They have thermal interface compound the amp chip rejecting heat directly into the chassis through a heat spreader. If the units were cold to the touch, that would mean that the chip is likely overheating due to a poor mount or missing thermal paste. However, it was probably overheating regardless due to torture testing.

Love your style. I rarely watch youtube reviewers, and when I do, I jump ahead constantly. With your videos, I rarely jump. Well done.

I really appreciated your no BS style! One of the rare youtube reviewers I can truely trust!

I have come to really like your channel, a no BS straight forward review process. Good, bad and everything in between. Very refreshing in a world of "this is the game changer, best of I've ever heard" reviewers

They do adapt to reviews and customer comments Fosi Audio is not a bad actor Great content as always Just order two sepetate power supplies

Thanks Erin. I was one of the first to sign up for the kickstarter on this amp because my Pioneer Elite uses a class D amp ( ICE) and my current outboard amp is class AB. I've never tried OpAmp rolling and like the form factor. FYI, you can order the amps with individual 48V/5A power supplies (PS) which I'm glad I did because multiple reviewers have had issues with the 10A PS.

Reminds me of the old audiophile story of the dealer calling up the amp designer and reporting a problem: "The amp is smoking." The manufacturer asks, "What color is the smoke?" These Fosi amps are more of a traditional high-end product than I thought.

Erins Smoke Lounge. Only place with more dangerous 2nd hand smoke than a cigar lounge.

To get this level of performance you would have to spend twice the amount of money on something like a Yamaha AS-501. However the Yamaha includes a pre-amp, so when you add a preamp to the FOSI it is a pretty good matchup for similar $$$. But we are talking amps here so amp for amp the FOSI gets her don for 1/2 the price.

Hey Erin, just wanted to say thanks for all the great reviews! Been watching for a couple years now and they have really helped me with my home theater purchases. Its rare to see folks use quantifiable data these days. I keep coming back because I didn't realise how interesting it would be to hear people talk about audio math 🤣. I would love to hear your thoughts on "V3 monos little brother" the normal V3.

Enjoyed this review, thanks a lot.

i have a Fosi V3 (2023 version) pushing a pair of Klipsch Heresy II with the preout going to an RSL speedwoofer s10mk2. going directly from my DAC to the V3 sounds adequate, i suppose, but i barely listened to that because I use an Adcom GFP-555II preamp in between them. with that preamp in the loop, I find the V3 to be wholly fulfilling for my purposes.

Okay this is likely to get long... First let me point out that *properly implemented* the TPA3255 chip is a first class amplifier. It ticks all the right boxes for a high fidelity device and as we've seen in ranking reviews it scores right up with the best of them. I know everyone wants the 48 volt supplies so they can suck maximum power from these little amplifiers to feed their 4 inch bookshelf speakers. But that is a mistake, as this and other reviews are showing us. (And I've been explaining for over a year) Heat is a problem; especially in these super tiny mini-amp cases with almost no airflow. We saw it in the original A07, the TB10D, and several others where, if pushed these tiny amplifiers overheat and go into protection on 48 volt supplies. To prevent that you need either a much larger heat sink and forced air cooling or you need to run them at a lower voltage that does not produce so much heat. And before you jump... bolting the chip to the bottom of the case is NOT an adequate solution. That these things get hot enough to burn you, it has to be obvious the case is not radiating the heat away into the air... it is simply getting hot and, trust me, inside that case will be a lot hotter! So, we are left with just one option... turn down the power. In bench testing of these mini-amps, there is a common theme that around 38 to 40 volts, running 1% below clipping, the cooling solution will be overwhelmed and temperatures will begin to rise, more or less out of control. Eventually the amplifier will get so hot that it will go into a thermal panic and shut itself off. This behaviour is exacerbated in the V3Mono amplifier by the "Auto" sensing circuit that will try to turn it right back on while still blistering hot. 40 volt power supplies that will plug into the back of these amps are not commonly available. The closest you're going to get is 36 volts. Thus my recommendation is that you should not run these TPA3255 mini-amps on more than 36 volts. Testing with 36 volt 5 amp supplies these little guys will get warm but not "drop the cup" hot. They will run day in and day out without thermal or current based shutdowns and the odds are they will last a lot longer. ===== A second mistake present in the V3Mono is the sharing of a power supply. The resistance of the DC power leads provides a path through which two (or more) TPA3255 chips may interact in unfavourable ways. When you have multiple chips on a single supply, you are required to provide an external synchronized clock to prevent this. The chip has Master and Slave modes to accommodate this requirement. (Data Sheet page 24) This is not happening when you use the Y connector on the single power supply and a couple of reviewers have reported noise at idle because of it. Although unconfirmed, this problem may be exacerbated by the Post Filter Feed Back networks added to deal with the issue of load dependencies. (That nobody is going to hear anyway) The simple answer here is to use two separate supplies so that no interaction between amplifiers occurs. ===== So what is the best way to set up with these V3Mono amplifiers? 2 V3Mono amplifiers with 2 separate 36 volt, 5 amp supplies. This will give you approximately 75 watts per channel on 8 ohm loads and about 140 on 4 ohm loads... with very low distortion, much less heat, no protection trips and perfectly good sound quality. But most importantly it will last for years instead of weeks.

Best to get 2 x 10 amp supplies with 2 amps.

A refreshingly thorough and honest review. Very interesting. Bravo! Consider yourself subscribed.

Great test and comments! Many thanks!

would it be possible to open the burnt one and see what could have happened? output filter caps maybe? thanks

Comparisons between tubes and solid state are often audible, because the tube products distort the sound - in ways many listeners find pleasant, yes, but tubes color the sound and so you can hear a difference.

It just goes to show that there’s very little point in throwing Continuous amounts of money at amplifiers. Just find one that has enough power, measures well, has all the features you need, and be done with it. Instead, just Invest the money into speakers that work best for your room and listening preferences, and maybe look at some room treatment if the wife/ GF allows it 😂

Six years in the Navy as an electronics technician and 40 years repairing office machines. I have smelt the horrible smell of electronics burning many times. LOL

Any experience/opinions on the Fosi V3 Mono vs. Class A/B options like the Schiit Vidar?

Ho apprezzato molto l'onestà della recensione!!!

I ordered a pair of these, but they're not going on my desk; they're going to my home theater. My AVR has fairly weak amplification but full 7.1 pre-outs, so I'll be using a pair of these to power my main stereo pair. The other five speakers/surrounds will then be powered by the internal amplification. I've been thinking of getting a 3-channel unit but these are so cheap I'm starting with a pair, and if they perform as I expect (there's little chance I'll try to pump 240 watts through them constantly so I really don't expect them to fry) I may add a third for the center. Great deal for amplifiers capable of outputting this amount of raw power with good distortion numbers. I did get the two-power-brick solution, just more flexible than a shared one, and apparently better.

I very much appreciate your blind testing. In the end, it's the only kind of subjective testing that's reliable.

I love your honesty at the start 👍 Sounds like an amplifier 😂

Awesome shirt man. Great review, love the measurements.

Excellent review as usual 👍💯👍

Erin ... how much time do you spend getting these measurements of yours? Seriously, you're talking about hours ... I can usually get the same data in under 10 minutes.

Smokin review there Erin! 😆xx

So, Erin... in the end, did you like how the V3 monos sounded or not? I understand your "no BS" style, but some explanations and/or comparisons would be nice :)

Measurements appear to show that PFFB is effective, holding response variation to under 0.5 dB. Do you hear it? Maybe, maybe not, but when you can start from something that is known not to possess an issue, that's always the safer hardware choice.

I would love to see Erin do an ABX of a big boy amp vs an inexpensive one like a fosi to see if there's a difference. I once did an AB test of a mcintosh car amp vs a phoenix gold amp and heard a very very subtle lift below 50hz in the mac that made it sound a little more 3D

The bass quality z3 is match with 2 mono amp ?? My curious

I appreciate that you at times seem to come across as over critical. I usually am complaining about reviewers not being critical enough. Especially on the new Chinese brand Amazon like products. Thanks for keeping it real, even if you seemed a bit overly critical on some reviews.

Can you take the cover off the failed amp and see what component died?

I have the Cherry amps and they sound wonderful.

As i mentioned earlier use laptop cooling fans under them. For the 48volt power supply's. Problem solved. More power. And cool amps. Find laptop cooling pads with very low noise. The pads can be switched on and off as needed. When the temperature gets up to a certain point perhaps one pad will cool 2 amps

Id love to get another one to complement the 2 that i bought from their kickstarter. I really wanna see these get used in car audio Class D PFFB TI Amplifiers.

It seems like these V3 Mono each need their own power supply to fully function properly. As also shown by Williston Audio Labs RU-vid channel. Look forward to you testing these again with 2 x 5a psu or 2x 10A psu... Also look forward to you ABX testing these (with 2x psu) against your big chunky A or AB amps et... that will be informative.

Is there a guideline for speaker sensitivity? Im guessing 90+ is recommended. My 81db efficient speakers would stress them, hard.

For me, these are perfect, but I'm a ludite who believes a really good 2.1 home theater is superior to any number of surround channels. So two of these will be powering my mains once I get them. No volume knob and and auto on/off are critical in a house where i am the only one who knows how the system works.

I'm wondering how one of these would cope replacing the dodgy 150 watt plate amp on my old 12" Wharfedale Powercube 12+ Subwoofer.

Thanks for the review Erin. Too bad about the smoke. Maybe Fosi will send a replacement.

Nice amps to make up an active speaker system.

Erin is becoming FOsi's Quality Analyst! Man, you have to be compensated more :D

Great honest review

The thing i always want to know with these things are do they have speaker protect and could this be tested, the small form factor is tempting but not at the risk of losing some actually decent speakers which cost 10 times what the amp costs

Thank you Erin!

The Mono version of the V3 is running in BPTL mode and has a second feedback loop behind the output filter (PFFL). TI already published the idea of the second feedback loop when the chip came out (some years ago), but the EVO board did not have it. It might be that the 2nd loop is causing some instability under certain circumstances, which could be why the unit died in your testing. Not many manufacturers use the 2nd loop (only one DIY module, as far as I remember), so maybe others noticed the problem. No idea what happens when the output coil (often too small) reaches the saturation point together with the 2nd loop......

good luck with the move. the Klippel going too - you got a place to set it up???

Appreciate your take as always.

Erin, great review! Class D biggest claim to fame is their efficiency and not getting hot so I see it might not be a good idea running several of these in a HT system.

Wish you had an ABX against a “big boy” amplifier.

Anyone know when Fosi will start shipping these out?

Most likely the thermistor at the amplifier power input failed... in my Fosi V3 it was the one that smoked...

So it basically fried itself because it got too hot? Am i getting this right? Because that should never happen under normal circumstances as a well-designed amplifier should have protection against that, not just for it's own protection but for the protection of others too, I've seen amps go up in smoke before and I've had some go up myself and it's honestly scary. I can't imagine what would happen if it had caused a fire which is very possible. I've owned a few amps from fosi and they've been pretty good and reliable so far but if this becomes a widespread problem with this particular model they definitely need to address it, an overheating amp should not just simply kill itself and possibly start a fire. It's like saying that a car's engine killed itself because it overheated, the computer inside the car should simply not allow that to happen if it had the proper safety mechanisms in place.

I have read other reviews having issues with the big power supply. I wonder how hot those get just playing loud music for a extended period of time?

So the conclusion is better not buy these or use then with a 32V 5A power sources like I'm using in my TDA7498E class D HIFI cheap amp ;)

yeah, we need a tear down of the blown up amp!

It would have been interesting to see the results of running each amp on a separate 10 amp supply.😊😊

I think these fosi products would be great in a budget AV Rack. They don't take up much room and they are so inexpensive. Get 3 of these for your LCR and you've realistically got more power than you need. If one dies it's a cheap drop in replacement.

Does anyone know if these would be good for the Wharfedale Lintons? Or is there something better that you would recommend?

Just fire, ... straight up.

Did you test 3a audio 48029a

I don’t know if I missed it but can you use one of the big power supplies with one amp?

I recently purchased the Fossi Audio bt20a pro for $79 and it was a good value. Driving a pair of Klipsch b20 bookshelf speakers sound is good and loud enough to fill a medium sized room with sound.

I already did some tests with TPA3255 boards (not Fosi's). The stereo amps clipped in the more complex passages, while the mono cards were able to play good in my speakers. I think this chip plays wonderfully well in simple systems, but it doesn't compare to high end systems. They play better than some expensive amplifiers, it's true. When the amplifier is well built and consequently expensive, (mine is a tube with Duelund capacitors, good transformers, etc.) there is no comparison, but this is unfair with the 3255.

I love the smell of burnt electronics in the morning. It smells like victory. Rock on!

I was thinking about getting an audiolab amp for my main system but if it’s ’just an amplifier’….i may as well save £800 and just get the VA3????

Erin, are you no longer in "cahoots" as it were, with Amir? Or more like an audio "Knight Errant"? I think we're all tilting at proverbial windmills, but "sounds like an amp" is that the sound of one hand clapping, or like what exactly?

$500-1000 AB amps are the ones Erin should be ABX'ing. This is the gear that could be made obsolete by Ti & HYPEX

I have three "big boy" amps that have high current capacity and 125, 100 and 200 wpc. Two of them weigh 70lbs each and the other is much lighter at 30lbs. The oldest one is now 33yrs old and it is my main 2-channel amp. I bought it on sale for $999 in 1991. I know that it won't last forever and class D is probably the future. I was curious about these and checked out the the kickstarter. You can buy these with either two 48v/5a or two 48v/10a power supplies. I ordered two with the 48v/5amp power supplies. I'm just really surprised that Fosi didn't send the 2x 48v/5a version out to reviewers. In my opinion, mono amps should have their own power supplies and not a shared power supply or they're not really mono amps.

audioscience tested the amps at 4ohms got 250 watts that’s at 1 percent thd . at 2 ohms 462 watts same 1 percent thd.

Erin always bends-over backwards to be transparent regarding his honest perspective on the equipment. Fosi made themselves look good, responding to negative feedback by trying to fix the problem. I wish more American companies were the same, instead of treating every customer as a one and done.

No Noise issues splitting the PSU to 2 amps?

V3 mono how much price?

What can one do to kindly request the one you're giving away? Pay for shipping? Ok. I'm in. Thanks

Cool and affordable, but not for me.

I would love to get my hands on the toasted unit please send it to me. I'll pay for shipping.

I think i might have seen a review for these. Maybe just one..

Dont throw the burnt one away. Give it with the working one. I would be ahppy to strip it down and autopsy ti and see how easy it is to repair.

Pointless to have 2 amplifiers with only 1 power supply. That defeats some of the purpose of monoblocks. Tell fosi to ship them each complete w/ own psu

Wonder if it would not have blown with two 5 amp bricks?

They make V3 Mono because of PFFB,and now ,no one can hear difference vs ZA3?

Guess they got confused about what people meant by a “warm” amp

Should have released this on Fried-day

That was the most unenthusiastic endorsement I think you have given to date 😂

Fosi audio is on kickstarter? Aren’t they a faceless chinese company with no public address?

Well, actually you can send it to me! I'll fix it no prob and gonna use it. :)))

Magic Smoke Loss!

This Rocky shirt smokes (no pun intended)!!

Be nice box it up, send it back to them.Then they can figure out what kind of damage you did and how do uh prevent it next time

y not give away the damaged 1 to? I am sure some DIYer can use it for parts (eg case, knobs, etc). Good to recycle. Nice of u to give away instead of selling, also

Played Smokey Robinson

thumbs up for smoking!

Class D amps are not supposed to get hot like this, are they? That's what I thought.