Fosi Audio V3 Amplifier Review

[Ropeburn]

A couple years ago I bought a V3 Stereo 32V $70 as a backup amp. I tried it, it worked fine then stored it away. A casual observation, most 3255 PFFB implementations only reduce peaking slightly, I'm unsure why that is? I reasoned if your speaker impedance doesn't rise at high frequency (mine don't) then peaking isn't a problem!

The peak is relatively slight to begin with, inside hearing range anyway. The bigger point of that correction is so that amp behaviour doesn't change with different speakers, and stays the same predictably.

There's also a, let's call it nerdy side to this. When I see that:

...I cringe and think "yeah, no thanks". I can't hear above 15kHz so that's entirely inconsequential in reality even with speakers that would bring that out. Even that +1dB at 20kHz wouldn't annoy toddler ears in the slightest, hardly noticeable at all. I just like properly designed things, that's all. It's a matter of principle.

 

[Joe Smith]

I like to not make perfection be the enemy of the very good… Doesn’t bother me in the least. It’s a $90 device, after all.

 

[somebodyelse]

The peak is relatively slight to begin with, inside hearing range anyway. The bigger point of that correction is so that amp behaviour doesn't change with different speakers, and stays the same predictably.

There's also a, let's call it nerdy side to this. When I see that:

View attachment 519491
...I cringe and think "yeah, no thanks". I can't hear above 15kHz so that's entirely inconsequential in reality even with speakers that would bring that out. Even that +1dB at 20kHz wouldn't annoy toddler ears in the slightest, hardly noticeable at all. I just like properly designed things, that's all. It's a matter of principle.

You'd do better looking at tests with a dummy speaker load than pure resistive as then you'd see the variations in output around crossover frequency. Whether they're big enough to be audible, or bigger than unit to unit variation, will depend on the speaker impedance curve.

 

[TheWalkman]

The dawn and reappearance of class D amps had happened just prior. With the introduction of the PFFB technology this may improve further. TI might even provide a new and more powerful incarnation of the 3255 chip. We will see....

Not to split hairs, but the Class D chip that the Fosi is based on, the Texas Instruments TPA-3255, was introduced nearly a decade ago. Though there were initially many cheap, no-so-clean implementations, manufacturers have really upped their games to make these great little amps.

https://www.ti.com/lit/ds/symlink/tpa3255.pdf?ts=1774150139854&ref_url=https%3A%2F%2Fwww.ti.com%2Fproduct%2FTPA3255%3Futm_source%3Dgoogle%26utm_medium%3Dcpc%26utm_campaign%3Dasc-null-null-GPN_EN-cpc-pf-google-ww_en_cons%26utm_content%3DTPA3255%26ds_k%3DTPA3255%26DCM%3Dyes%26gclsrc%3Daw.ds%26gad_source%3D1%26gad_campaignid%3D14388345080%26gbraid%3D0AAAAAC068F1VJdKoSiOd3mjM2bHRGmIOc%26gclid%3DCjwKCAjwg_nNBhAGEiwAiYPYA6FT7OgUTyE6E8GBnYSjoKG0uHo4_ofBM8s7KsYSqf-BYGGAi6LoEhoCVO8QAvD_BwE

$100 buys a nice little amp these days.

To digress a bit, my first exposure to the new, digital amps goes back to the Sonic Impact, Tripath amps from around 20 years ago.

​

https://www.tnt-audio.com/ampli/t-amp_e.html

Though these were really little more than toys, to someone who had historically spent hundreds of dollars on Harmon Karson, JVC or Sony amps (me), $30 for a tiny little, “digital” amp was a real eye opener.

The new Class Ds - either TI based 3255s or the higher powered Purifi or Hypex designs have completely changed the audio landscape for those of us who still appreciate, clean, loud, impactful audio.

 

[Ropeburn]

Not to split hairs, but the Class D chip that the Fosi is based on, the Texas Instruments TPA-3255, was introduced nearly a decade ago. Though there were initially many cheap, no-so-clean implementations, manufacturers have really upped their games to make these great little amps.

https://www.ti.com/lit/ds/symlink/tpa3255.pdf?ts=1774150139854&ref_url=https%3A%2F%2Fwww.ti.com%2Fproduct%2FTPA3255%3Futm_source%3Dgoogle%26utm_medium%3Dcpc%26utm_campaign%3Dasc-null-null-GPN_EN-cpc-pf-google-ww_en_cons%26utm_content%3DTPA3255%26ds_k%3DTPA3255%26DCM%3Dyes%26gclsrc%3Daw.ds%26gad_source%3D1%26gad_campaignid%3D14388345080%26gbraid%3D0AAAAAC068F1VJdKoSiOd3mjM2bHRGmIOc%26gclid%3DCjwKCAjwg_nNBhAGEiwAiYPYA6FT7OgUTyE6E8GBnYSjoKG0uHo4_ofBM8s7KsYSqf-BYGGAi6LoEhoCVO8QAvD_BwE

$100 buys a nice little amp these days.

To digress a bit, my first exposure to the new, digital amps goes back to the Sonic Impact, Tripath amps from around 20 years ago.

View attachment 519564

https://www.tnt-audio.com/ampli/t-amp_e.html

Though these were really little more than toys, to someone who had historically spent hundreds of dollars on Harmon Karson, JVC or Sony amps (me), $30 for a tiny little, “digital” amp was a real eye opener.

The new Class Ds - either TI based 3255s or the higher powered Purifi or Hypex designs have completely changed the audio landscape for those of us who still appreciate, clean, loud, impactful audio.

And well over 20 years later, people keep calling these "digital", while there's precisely nothing digital about these fully analog systems. Many of them don't even have a fixed clock per se but are self-oscillating systems that change frequency dynamically under load. Lol

There are some digital class D amplifiers, called FDA or powerDAC, but these are rare and the exception to the rule.

I very much like my fully analog Hypex amp. It's so warm...

 

[gasolin75]

Not to split hairs, but the Class D chip that the Fosi is based on, the Texas Instruments TPA-3255, was introduced nearly a decade ago. Though there were initially many cheap, no-so-clean implementations, manufacturers have really upped their games to make these great little amps.

https://www.ti.com/lit/ds/symlink/tpa3255.pdf?ts=1774150139854&ref_url=https%3A%2F%2Fwww.ti.com%2Fproduct%2FTPA3255%3Futm_source%3Dgoogle%26utm_medium%3Dcpc%26utm_campaign%3Dasc-null-null-GPN_EN-cpc-pf-google-ww_en_cons%26utm_content%3DTPA3255%26ds_k%3DTPA3255%26DCM%3Dyes%26gclsrc%3Daw.ds%26gad_source%3D1%26gad_campaignid%3D14388345080%26gbraid%3D0AAAAAC068F1VJdKoSiOd3mjM2bHRGmIOc%26gclid%3DCjwKCAjwg_nNBhAGEiwAiYPYA6FT7OgUTyE6E8GBnYSjoKG0uHo4_ofBM8s7KsYSqf-BYGGAi6LoEhoCVO8QAvD_BwE

$100 buys a nice little amp these days.

To digress a bit, my first exposure to the new, digital amps goes back to the Sonic Impact, Tripath amps from around 20 years ago.

​

View attachment 519564

https://www.tnt-audio.com/ampli/t-amp_e.html

Though these were really little more than toys, to someone who had historically spent hundreds of dollars on Harmon Karson, JVC or Sony amps (me), $30 for a tiny little, “digital” amp was a real eye opener.

The new Class Ds - either TI based 3255s or the higher powered Purifi or Hypex designs have completely changed the audio landscape for those of us who still appreciate, clean, loud, impactful audio.

soooo ugly more than the tesla truck

 

[JSG1469]

I bought a V3 when they were first released. I couldn’t find the receipt but am fairly certain it was September of 2023. I have the amp connected to an Amazon Alexa to power a pair of Elac DBR62s.

The amp has been powered on, virtually continuously, for two and a half years and it is used virtually every day to stream music, news, podcasts, etc. unless I’m on vacation. There have been no issues at all.

Like a lightbulb in your home, turn it on, stop worrying and focus your energy on finding some great, new music tracks and enjoy your new setup. All will be fine.

There is no "worrying" involved. It was a simple question, which you answered. Thank you.

 

[HighFutility]

Looking for a bit of help with a fosi v3 set up. I was thinking of creating a separate post given that others for sure have this issue.

My current setup is computer> fosi v3 > Mechano-23 (https://www.audiosciencereview.com/...ers-h-v-off-axis-measurements-included.41757/).
I am using peace APO as an equalizer.
I have a crown xls 1502x sitting around and I thought, hey why don't I hook up a sucker to this bad boy.
This is the dilemma, the pre-out is full range, the volume pot does not control the sub out volume. The crown xls1502 has a high pass filter option so that should help me on one front. How do I go about integrating the sub woofer with the Speakers?
My initial thought process was to unplug the speakers use REW sub cal to get the sub running to 75db or maybe a few db higher or 80db. Who doesn't love bass? What is the general rule of thumb with sub woofer integration anyways?
GREEN = NO EQ @ 75 DB 1-20 KHZ Speakers
BLUE = SUB CAL(30-80)HZ @ 75DB. Test ran at 1-500hz (pre out sends full range signal)
Brown = CAL(30-80)HZ @ 75DB. Test ran at 1-500hz (used LPF on 1502XLS @ 200hz) test. Works!

Psychoacoustic smoothing

This is the original speaker set up in green @ 75db
as well as the sub set to 75db with a LPF @ 200hz

When I was not using the pre-out I was using peace APO to eq the speakers. Now that I am using the fosi preout How do I go about eq the sub woofer without blowing up my speakers? Is there a way to eq the pre-out signal path only? Or whatever I send to peace APO will eq both the speakers and the pre out sub? Which is what im leaning towards. I guess I can safely apply the speaker eq again and change the lpf to a lower setting on the xls to prevent boosting the overall frequency?

Is the only way to solve this is to set the HPF to the lowest setting on the xls, apply peace apo eq and then slowly increase HPF on the xls as well as the gain nob to sort of eq the sub independantly.

Alternative is throw in a minidsip between the xls and fosi pre out, but I wanted to keeop this cheap and cheerful

EQ im using is FF from https://www.spinorama.org/speakers/XMechanik Mechano23 DIY/ASR/index_asr.html




TIA

 

[antcollinet]

I was thinking of creating a separate post given that others for sure have this issue.

You should - review threads are primarily for discussing the review and the product. Perhaps some quick help topics. But this question is going to get quite involved.

I would move it to the room acoustics and general speaker discussions sub forum. (There doesn't seem to be one more appropriate for sub integration)

 

[HighFutility]

You should - review threads are primarily for discussing the review and the product. Perhaps some quick help topics. But this question is going to get quite involved.

I would move it to the room acoustics and general speaker discussions sub forum. (There doesn't seem to be one more appropriate for sub integration)

Thanks for the reply.

 

[Håkan]

Sorry, but I don't want to read through all 161 pages of the thread for an answer to my question…
But I have a question about the Fosi V3 stereo amplifier and whether it can handle impedances below 4 ohms?
I'm thinking of buying a V3 to have in my garage gym where it will drive an old 12 inch passive Canton Plus C subwoofer (double voice coil 2x4 ohms) and a pair of small Yamaha NX-E700s.
If I remember correctly, Plus C goes down just below 4 ohms and I would like to know if anyone has measured the power of V3 below 4 ohms?

 

[antcollinet]

If I remember correctly, Plus C goes down just below 4 ohms and I would like to know if anyone has measured the power of V3 below 4 ohms?

Looking at review, there were no measurements carried out below 4 ohm.


But like any amp rated for nominal 4 ohm, it will be fine driving down to lower impedances seen on typical 4ohm nominal speakers. If yours are only just below 4 it will be fine.

Plus the chipset used has ratings down to 2ohm.

 

[Håkan]

Looking at review, there were no measurements carried out below 4 ohm.


But like any amp rated for nominal 4 ohm, it will be fine driving down to lower impedances seen on typical 4ohm nominal speakers. If yours are only just below 4 it will be fine.

Plus the chipset used has ratings down to 2ohm.

Thank you!

Below 4 ohms at maybe 40 to 60 hz can be challenging for an amplifier.
But the amp is cheap and If something Will happen to it I will not go broke

 

[peng]

Thank you!

Below 4 ohms at maybe 40 to 60 hz can be challenging for an amplifier.
But the amp is cheap and If something Will happen to it I will not go broke

It is only challenging if you push it high enough for lone enough time, so it depends on how loud you listen, that is, how you use it in your applications.
Example:
The V3 stereo amp, even with the 32 V 5A power supply, should be able to drive 4 ohm nominal speakers all day long the output is not pushed to much above 30 W, or 15 W 2 ohms. That's so called "continuous", if the concern is about dips to below 4 ohms at certain frequencies, that is not a big deal because the chip and the power supply can handle higher output for short durations.

 

[steve-z]

Bought a Fosi V3 with 48v psu a few days ago to power a little setup for my bedroom.
A few years ago I bought another mini amp, the British made Amptastic Mini 1 which used the Tripath chip, it sounded pretty good if a little bright, it cost £129, unfortunately it's use was a bit limited as it only delivered around 10wpc into 4 ohms. Seems astonishing to me that Fosi can produce an amp that can deliver 140w into 4 ohms for £20 less, it also seems to be much more transparent, not emphasising any part of the frequency range, giving a see through to the music quality. It's a testament to the amp that it's still selling in large quantities having been on sale now for over 3 years.
My V3 is driving a pair of Fyne Audio F300i speakers, tiny and inexpensive but the V3 really makes them sing, total cost under £300.

 

[Joe Smith]

Bought a Fosi V3 with 48v psu a few days ago to power a little setup for my bedroom.
A few years ago I bought another mini amp, the British made Amptastic Mini 1 which used the Tripath chip, it sounded pretty good if a little bright, it cost £129, unfortunately it's use was a bit limited as it only delivered around 10wpc into 4 ohms. Seems astonishing to me that Fosi can produce an amp that can deliver 140w into 4 ohms for £20 less, it also seems to be much more transparent, not emphasising any part of the frequency range, giving a see through to the music quality. It's a testament to the amp that it's still selling in large quantities having been on sale now for over 3 years.
My V3 is driving a pair of Fyne Audio F300i speakers, tiny and inexpensive but the V3 really makes them sing, total cost under £300.

The V3 is still a very good small amp, it holds up well!