Fosi Audio V3 Mono Amplifier Review

[wyup]

There are no standards for gain in amplification. When I first started to test them, I used 29 dB which was some recommendation by THX. That gain factor though assumed very anemic sources. Just about every DAC I test has far higher output voltage. A high gain amplifier adds noise then for no reason. I picked 25 dB as to not deviate too much from the old gain factor so tests would still be comparable for the most part. This amp gets full power with 2.8 volt input vs 4 volts that is available.

Why don't they set full power for 4 volts instead, so we don't have to attenuate and amplify noise at the same time? Most music today is maximized and has a few db of dynamic range, and hardly ever we reach for full potentiometer at home, so that we don't ever reach clipping.

I bypassed the input buffer stage on a Hypex NC122MP amp, for a total of 13db gain, perfect for my needs. (26db default was too much, I found hard to regulate volume in the first degrees, too much gain for nothing. That amp reached full power at 1.17V at 4 ohms for balanced inputs!)

 

[Tell]

I can answer that from my perspective. Audio equipment for me is also a display of art, it adds to the ambience giving visual and tactile satisfaction. . .and it helps that I have the space for it.

As examples, look at these two amps, stunning beauty, yes, it costs more and that is not the purpose of these Fosi as they are meant for the budget friendly. . .I get it.

Anyway, let me stop before I get a warning for veering off topic.

Yeah I can somewhat see that, I just put an old Marantz 2015 in my living room since the PSU in my class-D gave up, and while I do like a sexy amp as well I don't see any reason for them to be that big, especially nowadays when they don't have a tuner or no need for a big toroid and heatsinks.
But I would love to see Fosi doing these amps with a bit of retro design to complement that awesome performance, so maybe some brushed steel and wood sides in their next amplifier?

 

[Anton D]

that amplifiers will work perfectly as the Fossi ... is only a matter of paying for beauty. And is totally right, is your money.
what i feel "wrong" is to get a bank loan / mortgage to pay for an amplifier that sounds the same.

I am yet to meet an audio enthusiast who resorted to a mortgage or financial hardship in order to buy any amplifier.

I'd love to see the mortgage lender's face when someone said that the loan was to finance buying an amplifier!

 

[Jhify]

Pity you do not measure complex output impedance, instead of those plots into 4/8 Ohms. R + jwL output impedance would tell much more.

Other than that, 19+20kHz result is poor, as well as distortion at higher frequencies.

Can you hear those ? I’m 32 and can’t hear much above 17k. I don’t think 15 years old are much interested in audiophile stuff it won’t be an issue.

 

[antcollinet]

Can you hear those ? I’m 32 and can’t hear much above 17k. I don’t think 15 years old are much interested in audiophile stuff it won’t be an issue.

The 19+20 IMD test generates intermodulation distortion tones as high as -70dB. Similar distortion will be generated by the intermodulation of any two tones. This is quite possibly the cause of the distortion "grass" seen at the high frequency end of the multi tone test.

 

[dpuopolo]

It's too much money. Implementing PFFB only requires a handful of components and could probably easily be incorporated in just about ANY Fosi and Aiyima product for an under $2.00 manufacturing cost increase. $280.00 for a stereo pair of these is about $140.00 too much $$.

 

[Kachda]

It's too much money. Implementing PFFB only requires a handful of components and could probably easily be incorporated in just about ANY Fosi and Aiyima product for an under $2.00 manufacturing cost increase. $280.00 for a stereo pair of these is about $140.00 too much $$.

Looks like you have an opportunity to corner the market when you launch your product!

 

[testp]

..the heck, 15 pages less than a day! i can't read that fast

 

[dpuopolo]

Looks like you have an opportunity to corner the market when you launch your product!

I bought a 3e stereo amp board for 134 dollars shipped. Its 6 amp 48 volt power supply was another $40.00. For $174.00 I got 99% of what two of these give me (Not to mention that the 3e has 2 db better SINAD) . If you want to spend $106.00 more to get a bit less than be my guest.

 

[Jhify]

The 19+20 IMD test generates intermodulation distortion tones as high as -70dB. Similar distortion will be generated by the intermodulation of any two tones. This is quite possibly the cause of the distortion "grass" seen at the high frequency end of the multi tone test.

You are right and we would have all loved to see the 18bits range flat to 20k but the perf is most likely still beyond human hearing all over the spectrum.

 

[AdamG]

You are Ozzy and ICMFP

Context matters and I suspect you may have missed my previous post where I threatened (jokingly of course) to bring in Mike Tyson to obtain compliance. Thus the Ear joke to, as it happens. A member whom’s username includes a reference to a certain relevant body part. It just fell into place. Chew on that Sir!

 

[Tell]

Can you hear those ? I’m 32 and can’t hear much above 17k. I don’t think 15 years old are much interested in audiophile stuff it won’t be an issue.

The thing is that IMD can be heard further down in the frequency response. This is one of the reasons why 192khz samples rates is a bad idea.

It's too much money. Implementing PFFB only requires a handful of components and could probably easily be incorporated in just about ANY Fosi and Aiyima product for an under $2.00 manufacturing cost increase. $280.00 for a stereo pair of these is about $140.00 too much $$.

I've been wondering about this exact thing, how hard and expensive it would be to implement. Hopefully maybe those cheap chinese diy TPA3255 board will start implement them sooner or later, letting us diy:ers building really good and really cheap amps ^^

 

[amirm]

The 19+20 IMD test generates intermodulation distortion tones as high as -70dB. Similar distortion will be generated by the intermodulation of any two tones. This is quite possibly the cause of the distortion "grass" seen at the high frequency end of the multi tone test.

That kind of spectrum is not going to happen in music. That is the reason I didn't run that test for the longest time. I am running it now only to make it easier to compare to Stereophile tests.

 

[MvZ]

Hi,
What are the opamps for? Is this only for creating a balanced signal for the amp chip from rca input and the single ended gain settings or does this also affect the xlr input signal. If so, what is the purpose? An additional buffer?

BR, Moritz

 

[kemmler3D]

The thing is that IMD can be heard further down in the frequency response. This is one of the reasons why 192khz samples rates is a bad idea.


I've been wondering about this exact thing, how hard and expensive it would be to implement. Hopefully maybe those cheap chinese diy TPA3255 board will start implement them sooner or later, letting us diy:ers building really good and really cheap amps ^^

I'm not sure on this, but I think I read somewhere here that TI has a patent on PFFB in this context. If they charge a (say) $10 licensing fee, then after everyone's made their margins, that could be adding quite a bit to the MSRP.

 

[brunes]

I was checking out my silly dual mono 3e audio build, micro audio SMPS with a modshop custom case, this came in around 700 euros, so two of these Fosi audios are cheap!

 

[Ze Frog]

It's too much money. Implementing PFFB only requires a handful of components and could probably easily be incorporated in just about ANY Fosi and Aiyima product for an under $2.00 manufacturing cost increase. $280.00 for a stereo pair of these is about $140.00 too much $$.

Too much money, lol.

Well what about all the manafacturers selling stuff that can't compete at 10x...20x the price. Considering it's using components that are of quality you won't always find in gear at those prices and it's insane value. Granted we all have different idea of value, but name something that does the same with equal quality and cost at your $140 target...

 

[Doodski]

It's too much money. Implementing PFFB only requires a handful of components and could probably easily be incorporated in just about ANY Fosi and Aiyima product for an under $2.00 manufacturing cost increase. $280.00 for a stereo pair of these is about $140.00 too much $$.

I have heard this argument many times and one is not paying for the parts they are paying for the technology and the designer(s) time and effort and of course markup. If you don't like that try designing yourself.

 

[brunes]

It also makes the audiophonics 3e (stereo) implementation look expensive 499 euro...

 

[Extreme_Boky]

Hi,
What are the opamps for? Is this only for creating a balanced signal for the amp chip from rca input and the single ended gain settings or does this also affect the xlr input signal. If so, what is the purpose? An additional buffer?

BR, Moritz

The input OPAmp handles balanced <-> single-ended choice

The other two OPAmps:
- one is the pre-amp/buffer for TI IC
- the second one caters for PFFB implementation