• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Fosi Audio V3 Mono Amplifier Review

Rate this amplifier:

  • 1. Poor (headless panther)

    Votes: 7 1.4%
  • 2. Not terrible (postman panther)

    Votes: 12 2.4%
  • 3. Fine (happy panther)

    Votes: 100 20.0%
  • 4. Great (golfing panther)

    Votes: 382 76.2%

  • Total voters
    501

totti1965

Active Member
Joined
Apr 7, 2023
Messages
268
Likes
226
Location
Bonn / Germany
@amirm : Will there be also a test of the serial version which will be out at the beginning of June?
It would be interesting to see the max. Version of the power supplies, according to kickstarter 2 x 48 Volt 10 A, which is new record for on chip amps! Can it squeeze even more power out of these tiny things?
If there will be another test, it would be totally interesting to see switching frequency in a test which runs up to 1,2 MHz, and how good it is suppressed.
Sorry, in case if anybody has asked these things before. I can’t read the whole thread.

Thorsten
 

SMen

Active Member
Joined
Jan 2, 2022
Messages
223
Likes
105
I thought Fosi stated the noise issue is only if you use one mono amp off the Y cable at one time. Nobody would use it like that, there's no real world use case for this. Fosi also said they would fix it or send 2 power supplies. When I bring on new equipment, I ALWAYS think I thought of everything, and I never did. I deal with this constantly at work in oil/gas.
Interesting that many measurements and tests are still there even though those aren’t practical in real world used case, its a big debatable topic here on ASR but I am not going there.
Appreciate what you said but IT change management process made me learn the need of testing in every way possible, every possible issues if possible.
You never know how creative a user could be using what they buy ;).

PE. and that’s where disclaimers can help, like if you are buying one psu to power up 2 amplifier units then “xyz” is expected……..
Exactly. Sounds like earthing issue when one of the units is turned off, and the other is on, but both units are connected with the Y cable.
Disclaimer a good idea.
I remember having buzzing turning off a valve amplifier as the power supply 'drained' for it to be fully "off". Apologies for the non technical description. No noise when it was on.
 

TheBatsEar

Major Contributor
Forum Donor
Joined
Jun 16, 2020
Messages
3,268
Likes
5,334
Location
Germany
How do you guys control volume with these monoblocks?
You control it at the source or use a pre amplifier. I for one use a MiniDSP Flex, it has a volume knob and a remote, acting as a pre amplifier for all connected sources (TV, CD, Computer). I also have a Wiim Pro Plus that can do the same. I had a Topping E30 that could do volume as well.

Will there be also a test of the serial version which will be out at the beginning of June?
Unlikely. It's just another chip amp and soon other things will capture our focus.
 

Yorkshire Mouth

Major Contributor
Joined
Apr 22, 2020
Messages
1,449
Likes
1,407
Location
God's County - Yorkshire
Sorry if I’ve missed this.

Comments on the gain switch appear to be ubiquitously vague. “Depending on your source…”. Excuse me? Depending on what specifically?

Would anyone care to elaborate?
 

EddNog

Active Member
Joined
Mar 1, 2024
Messages
133
Likes
136
Sorry if I’ve missed this.

Comments on the gain switch appear to be ubiquitously vague. “Depending on your source…”. Excuse me? Depending on what specifically?

Would anyone care to elaborate?
Different sources will have different starting gain levels, so the amount of gain at the power amp should vary as well to balance things out. My multimode preamp, for example, has a passive mode and a unity gain solid state buffer mode, but the tube buffer mode has a big gain, it’s nice to have only 20db gain on the balanced input of the V3 Mono since I do my critical listening in tube buffer mode. Granted, when using solid state buffer mode, I will simply turn the volume up on my preamp to compensate for background/casual listening, but in those situations, I don’t tend to raise the volume as high as I do in critical listening anyway.

-Ed
 

ninetylol

Addicted to Fun and Learning
Joined
Dec 7, 2019
Messages
721
Likes
701
You control it at the source or use a pre amplifier. I for one use a MiniDSP Flex, it has a volume knob and a remote, acting as a pre amplifier for all connected sources (TV, CD, Computer). I also have a Wiim Pro Plus that can do the same. I had a Topping E30 that could do volume as Well.
I have a WiiM too, but just in case the device resets itself or something else bad happens, you suddenly blow your speakers up with so much watts.
 

Cal_Cobra

Member
Joined
Mar 19, 2024
Messages
48
Likes
35
Interesting that many measurements and tests are still there even though those aren’t practical in real world used case, its a big debatable topic here on ASR but I am not going there.
Appreciate what you said but IT change management process made me learn the need of testing in every way possible, every possible issues if possible.
You never know how creative a user could be using what they buy ;).
And even with a UE/UI testing process, bugs, glitches, user oddities, etc., still remain the norm. I've worked in tech, interfacing with engineering, and manufacturing for decades [albeit far more complicated devices, some with 32 layer PCBs), and even the best thought out and tested products, still encounter challenges upon release.

Thus far Fosi Audio appears both receptive to "criticism" as well as exhibiting a great desire to satisfy their customer base by building products demanded by audio enthusiasts at bargain basement prices.
 

36mbbj

New Member
Joined
Apr 21, 2024
Messages
3
Likes
9
Add BLUE back-lit VU meters and we have a winner ;)
Whilst it would be nice eye candy, it would add to the cost of the end product without any audible benefit. We are talking about a low-cost true dual-mono power amp, the key words here being "low" & "cost". If not having VU meters is the price to have a very decent (to put it mildly) power amp that sells for what a NAD 3020 used to sell for, I'm willing to sacrifice the eye candy. Sometimes, less is truly more.

It feels like you're on the same wavelength as us! We've recently begun exploring a similar solution – housing multiple amplifier boards within a single chassis and incorporating an internal power supply

@Fosi Audio : glad to hear I'm not the only one that thought of that! I'll probably remind you of the very obvious, but from my years in the hobby, I've observed how the power supply is a very critical part of amplification. A badly-designed or underspec'd power stage can turn an otherwise stellar amplification design into, well, cr\*p. There's a reason why very expensive audio gear has sizeable power supply stages - my current power amp has beer can sized capacitors and a toroidal transformer the size of a Christmas pudding, for example.

I'd also add: if you are considering making a traditional looking power amp, a matching pre-amp would be in order to provide a complete solution. Methinks a simple & clean full analogue design with an optional & upgradable internal DAC, maybe with a similar phono stage (internal, optional & upgradable) to complete the picture as they say, sold for a similar price to the power amp, could be a hit in the market.
 

TheBatsEar

Major Contributor
Forum Donor
Joined
Jun 16, 2020
Messages
3,268
Likes
5,334
Location
Germany
I have a WiiM too, but just in case the device resets itself or something else bad happens, you suddenly blow your speakers up with so much watts.
Collect 10 documented cases where this led to damage of property. In other words: sometimes we suffer more in our minds than reality.
 

AndyLu

Active Member
Forum Donor
Joined
Jan 20, 2020
Messages
196
Likes
373
I have a WiiM too, but just in case the device resets itself or something else bad happens, you suddenly blow your speakers up with so much watts.
It looks like an 'old fashioned' power amp seems like a new concept to you :) (correct me if I am wrong).
Power amplifiers without volume control are nothing new and pretty standard. They are supposed to be used with a pre-amp with a rotary volume control and/or an old fashioned potentiometer. People are using them this way for decades already. As far as I understand Fosi made these mono blocks on purpose without volume control because users asked for it.
You may not be the intended use case or maybe (while it can be used for this purpose) a WiiM is not the most appropriate?

No offense but to quote @Anton D your post "makes me feel old" too ;)
 
Last edited:

36mbbj

New Member
Joined
Apr 21, 2024
Messages
3
Likes
9
I never realized how many people are unfamiliar with the old fashioned power amplifier thing.

Makes me feel so old!!
You might be horrified to realise how many young people never heard or even just saw a proper sound system, with real loudspeakers... or never realised you could sit down and actually listen to music without doing something else at the same time.

For too many, if it's not listening to music through earbuds as they are riding mass transit, it's bringing out a battery powered portable speaker thing as they are busy with something else, because they have to be "productive" or "efficient". I've lost count of the number of jaws that had to be picked off the floor after I make them sit down in my music room and tell them to shut it as I put on some music. "Just listen" I tell them and you can just see from the expression on their faces that they never heard music played through a proper hi-fi setup. Even music they thought they knew becomes something totally new to them, they're hearing things they never heard before.

I too feel old when they look at my music collection and they say "all of this is music?".
 

great04

Member
Joined
Dec 5, 2023
Messages
16
Likes
6
Looks very good regardless of price. If you are going to need 2 of them, Just make sure to get separate power supplies. I heard they are bundling 2 of them with just one 48 V 10 AMP power supply( instead of 5 amp)which will probably defeat the benefits of the design of this product. Question, the XLR/TRS input is it really a Balanced input? Or just for purpose of more flexibility or amount of inputs?
What is the difference between separate 5A power supplies and on 10A supply? What is the design benefit you mentioned? Thanks
 

TonyJZX

Major Contributor
Joined
Aug 20, 2021
Messages
2,117
Likes
2,052
the problem then is that there's a hole in the marketplace for a suitable priced preamp to match these units

the fact that people are out there searching and not finding much says it all
 

Rafaille

Active Member
Joined
Dec 5, 2021
Messages
110
Likes
61
the problem then is that there's a hole in the marketplace for a suitable priced preamp to match these units

the fact that people are out there searching and not finding much says it all
Depends on what you call a preamp. If no phono stage is needed then pretty much any modern DAC with volume control will do. No hole in the marketplace there.
 

Sokel

Master Contributor
Joined
Sep 8, 2021
Messages
6,510
Likes
6,673
the problem then is that there's a hole in the marketplace for a suitable priced preamp to match these units

the fact that people are out there searching and not finding much says it all
If we're talking about a preamp with a precise,motorized analog pot who can last a long time and not glitch and burn gear and ears the pot alone can go half the price of the mono's,just as a component.
Relay based ones relay heavily on the relay's quality,which is no cheap either for the nice ones.

And all the above without even putting them on the PCB,in a case with connectors,PSU,etc.
It's not going to be easy.
 

Adrian Parker

Member
Joined
Apr 10, 2024
Messages
17
Likes
2
I'm glad to respond to all your concerns above.:)

1. V3 Mono employs a unique cooling design. We closely attach the amplifier chip's heatsink to the chassis, effectively turning the entire chassis into a radiator. Additionally, we have included vent holes on both sides of the chassis to enhance air circulation. Since the chassis serves as a radiator, its surface temperature may seem a bit high. However, this indicates that the heat from the TPA3255 amplifier chip is being effectively transferred to the chassis, allowing the V3 Mono to stably maintain high power output continuously. So, there is no need to worry.

2. We are currently resolving this issue. If it is not perfectly resolved, we will offer you the dual power supplies set instead.

3. The standard op-amp in V3 Mono is the NE5532, which is known for its ability to reproduce sound in a true and natural manner without altering the original timbre. If your DAC or preamp already has tone-tuning functions, there is no need to roll the op-amp. The design of replaceable op-amps is particularly favored by many DIY enthusiasts. Among our fans, many users opt for renowned op-amps like the Sparkos SS3602, Burson V7/V6/V5i, and MUSES02. They enjoy experimenting with different op-amps to experience various sound signatures, which they find quite intriguing.

4. Yes, you can add more sets if needed. Please leave a message for our team on Kickstarter, and my colleague will guide you on how to add them.

5. V3 Mono is designed as a power amplifier; hence, it is typically used in conjunction with a preamp. You can connect a subwoofer to the preamp to setup your system.
Thanks for the prompt updates. It is appreciated:.
1 Understood.
2 I would even be happy to pay difference for 10A power supplies if it means reduced heat, or have one of each of 5A and 10A. I am looking to bi-amp, and drive some very large 8Ohm speakers, and need all the power I can get-when needed. 10inch sub and 2.5 Mid + Tweeter
3 I am still confused over opamps. How many in each V3 amp, and how many needed if I use XLR? Also my Leema Pre amps do not have tone controls. Would this mean an opamp 'roll' would help?
Will Sparkos Pro fit? I know they are crazy expensive, but knowing if they fit is the question. Also are they suited to a power amp? Everything I have seen on the SS3602s has been great, so would be the obvious choice - but still expensive. Can other readers suggest best alternatives?
4 I have doubled* my order :) Which has also doubled postage, this cannot be right?
- *Do we get free T shirts for doing that? How nice would that be :)
5 OK. My preamp has no sub out , line or XLR - not sure both will work together, if they do then problem solved, gain differences can be solved by 'volume' controls on sub.
Pre release I did ask for V3 mono to have sub out - as stereo V3 does. Shame.
 

EddNog

Active Member
Joined
Mar 1, 2024
Messages
133
Likes
136
Depends on what you call a preamp. If no phono stage is needed then pretty much any modern DAC with volume control will do. No hole in the marketplace there.
You say this, but the way some of these DACs is built, using the volume control is not practical. For example, I used to use an SMSL DO100 DAC and if I relied on the volume control in it, there was loud cracking noises from the speakers every time the sample rate changed from song to song. That makes using the DAC itself for volume control impractical in real use. The only way to eliminate or mitigate that problem was to turn down the volume at the amplifier, an option that is there with an integrated amp or a power amp with variable gain (like the GCC-100 I was using before) or volume attenuator (like the Fosi ZA3), but setting gain/volume down and using a much higher volume range/setting at the DAC, but with a power amp with no attenuator or variable gain control, you cannot avoid this on DACs with that sort of noise when changing sample rates.

-Ed
 

EddNog

Active Member
Joined
Mar 1, 2024
Messages
133
Likes
136
Thanks for the prompt updates. It is appreciated:.
1 Understood.
2 I would even be happy to pay difference for 10A power supplies if it means reduced heat, or have one of each of 5A and 10A. I am looking to bi-amp, and drive some very large 8Ohm speakers, and need all the power I can get-when needed. 10inch sub and 2.5 Mid + Tweeter
3 I am still confused over opamps. How many in each V3 amp, and how many needed if I use XLR? Also my Leema Pre amps do not have tone controls. Would this mean an opamp 'roll' would help?
Will Sparkos Pro fit? I know they are crazy expensive, but knowing if they fit is the question. Also are they suited to a power amp? Everything I have seen on the SS3602s has been great, so would be the obvious choice - but still expensive. Can other readers suggest best alternatives?
4 I have doubled* my order :) Which has also doubled postage, this cannot be right?
- *Do we get free T shirts for doing that? How nice would that be :)
5 OK. My preamp has no sub out , line or XLR - not sure both will work together, if they do then problem solved, gain differences can be solved by 'volume' controls on sub.
Pre release I did ask for V3 mono to have sub out - as stereo V3 does. Shame.
Just in regards to the op-amps, there are three in each V3 Mono. One near the back does the job of converting RCA/single-ended input signals to balanced in order to function with the balanced architecture of the amplifier, so if you’re using XLR, that op-amp does not come into play. Towards the front of the amp, there are another pair of op-amps, and they both play into actual amplification, so if you’re going to roll for sound, you would play with those. Fosi told me they don’t need to match, and you can change just one if you wanted, and to feel free to experiment. Personally, I plan to stick to trying matching pairs there. As to spacing, it is hard to tell from images if the Sparkos SS3602 will fit there. The Burson V7s will fit, and that’s what I plan to run there. The one on the back for converting single-ended input to balanced does appear to have the room for the SS3602.

-Ed
 

AndyLu

Active Member
Forum Donor
Joined
Jan 20, 2020
Messages
196
Likes
373
Thanks for the prompt updates. It is appreciated:.
1 Understood.
2 I would even be happy to pay difference for 10A power supplies if it means reduced heat, or have one of each of 5A and 10A. I am looking to bi-amp, and drive some very large 8Ohm speakers, and need all the power I can get-when needed. 10inch sub and 2.5 Mid + Tweeter
3 I am still confused over opamps. How many in each V3 amp, and how many needed if I use XLR? Also my Leema Pre amps do not have tone controls. Would this mean an opamp 'roll' would help?
Will Sparkos Pro fit? I know they are crazy expensive, but knowing if they fit is the question. Also are they suited to a power amp? Everything I have seen on the SS3602s has been great, so would be the obvious choice - but still expensive. Can other readers suggest best alternatives?
4 I have doubled* my order :) Which has also doubled postage, this cannot be right?
- *Do we get free T shirts for doing that? How nice would that be :)
5 OK. My preamp has no sub out , line or XLR - not sure both will work together, if they do then problem solved, gain differences can be solved by 'volume' controls on sub.
Pre release I did ask for V3 mono to have sub out - as stereo V3 does. Shame.
About your point 5:
The V3 mono blocks are power amps. Power amps by definition only have speaker outputs and no dedicated sub outs. The stereo V3 you are talking about is an integrated amp (that means a pre-amp and a power amp in one box). Pre amps can have sub-outputs, hence the stereo V3 has them. Power amps are only meant for speakers. So even if you asked for sub-outs on the V3 mono blocks, that is not the place for them. To say that is a 'shame' is a bit misplaced because this is not something you can blame Fosi for. As far as I know there are no dedicated (without volume control) power amps on the market with dedicated outputs for subs. Of course there are subs (like Rell) which accept speaker outputs from power amps, but that is a whole other subject.
 
Last edited:
Top Bottom