Fosi Audio V3 Amplifier Review

[Dogamondo]

Hi guys,

Noob question - I have a 50W @4 bass shaker that I am going to run from one of the channels of the Fosi v3 (with 48v power supply). The other channel will be running a 500W @4 shaker (so no issues blowing that one up at full power).

I'm trying to figure out how high I can set the software gain on the 50W channel without blowing up the shaker. Unfortunately I can't just plug it in like a normal speaker and turn the volume up until it starts to distort as I have no idea at what point the shaker is getting too much power.

The shaker is rated at 50W RMS and 100W "Max".

From what I understand, with the 48v power supply I'm getting a max (peak) of about 140W per channel from the Fosi. So would I be safe running the 50W shaker at about 60-70%? Ideally I'd like to run it as loud as I can safely get away with.

Thanks!

 

[doug s.]

Hi guys,

Noob question - I have a 50W @4 bass shaker that I am going to run from one of the channels of the Fosi v3 (with 48v power supply). The other channel will be running a 500W @4 shaker (so no issues blowing that one up at full power).

I'm trying to figure out how high I can set the software gain on the 50W channel without blowing up the shaker. Unfortunately I can't just plug it in like a normal speaker and turn the volume up until it starts to distort as I have no idea at what point the shaker is getting too much power.

The shaker is rated at 50W RMS and 100W "Max".

From what I understand, with the 48v power supply I'm getting a max (peak) of about 140W per channel from the Fosi. So would I be safe running the 50W shaker at about 60-70%? Ideally I'd like to run it as loud as I can safely get away with.

Thanks!

here's a quote from another forum, re: the 3255 ti chip in the v3:
"From TI's curves, it looks like the power output spec at 4 ohms, 1% THD and in stereo mode is 225 RMS watts per channel. This requires an 11 amp, 48 v power supply. Try the Fosi V3 or Aiyima A07 with a very high dissipation dummy load and you will see that kind of output. You will also need an oscilloscope, an audio signal generator and true RMS voltmeter."
(audioholics)

so, considering peak power w/the hi-amp p/s is 300wpc, that would equate to ~100wrms w/48v p/s if its peak is power rating is 140wpc. so, just plan on buying another 500w@4 ohm shaker when you blow up the smaller shaker.

maybe you won't blow up the small guy. (not sure how you'd measure the power the shaker is seeing, but i'd restrict the amp's output to 50% to be safe, if not able to measure.) but why would you want to do this anyway - restrict the larger shaker to 60-70% power?

doug s.

 

[Dogamondo]

here's a quote from another forum, re: the 3255 ti chip in the v3:
"From TI's curves, it looks like the power output spec at 4 ohms, 1% THD and in stereo mode is 225 RMS watts per channel. This requires an 11 amp, 48 v power supply. Try the Fosi V3 or Aiyima A07 with a very high dissipation dummy load and you will see that kind of output. You will also need an oscilloscope, an audio signal generator and true RMS voltmeter."
(audioholics)

so, considering peak power w/the hi-amp p/s is 300wpc, that would equate to ~100wrms w/48v p/s if its peak is power rating is 140wpc. so, just plan on buying another 500w@4 ohm shaker when you blow up the smaller shaker.

maybe you won't blow up the small guy. (not sure how you'd measure the power the shaker is seeing, but i'd restrict the amp's output to 50% to be safe, if not able to measure.) but why would you want to do this anyway - restrict the larger shaker to 60-70% power?

doug s.

Thanks Doug,

I was planning to run both shakers with the V3's output at 100%. I was then going to use software DSP to hard limit the small guy to about 60% in the hopes that I would not blow it up.

I've been messing around with it tonight using the stock 36V supply and have managed not to destroy the small shaker with the V3 knob at around 3 o'clock. I'm set to receive the 48V tomorrow so that'll be a different ball game!

 

[doug s.]

Thanks Doug,

I was planning to run both shakers with the V3's output at 100%. I was then going to use software DSP to hard limit the small guy to about 60% in the hopes that I would not blow it up.

I've been messing around with it tonight using the stock 36V supply and have managed not to destroy the small shaker with the V3 knob at around 3 o'clock. I'm set to receive the 48V tomorrow so that'll be a different ball game!

if you can limit the one channel of the v3 w/o limiting the other, you should be ok. but figuring out a way to measure the reduction would be best.

doug s.

 

[gasolin75]

Mono amp available april 20th

 

[morillon]

just sym, no asym too....

 

[Yorkshire Mouth]

Mono amp avaiable april 20th

View attachment 360549

MY BIRTHDAY!

Erm...and Hitler's.

 

[PlasticDoc]

Mono amp available april 20th

Mono amp available april 20th

The name should have been Fosi M (Fosi Mono).
The name of the new Fosi Stereo PFFB could be Fosi S (Fosi Stereo).
Simple and self-explanatory names are part of good design.

 

[Eddie87]

Quick question, would it be better to have the volume control in Windows 11 set to 100% and then control the volume through the Fosi V3 amp, or can I just leave the amp at maximum volume and control it through Windows?

 

[Zek]

can I just leave the amp at maximum volume and control it through Windows?

I wouldn't trust the volume control in Windows - to accidentally fry my speakers.

 

[G-Can]

Mono amp available april 20th

View attachment 360549

this makes no sense, it looks like ZA3 without volume knob, and will most likelly cost same money as ZA3.
btw, I have a spare V3 with 48V if anyone is looking for one, as I got ZA3 for my HT setup.

 

[mike70]

this makes no sense, it looks like ZA3 without volume knob, and will most likelly cost same money as ZA3.
btw, I have a spare V3 with 48V if anyone is looking for one, as I got ZA3 for my HT setup.

Have all the sense, because is the first Fosi amplifier with PFFB and as pure power amp, without volume control.

 

[Otovo]

Thank you all for your enthusiastic attention and your dedication, which has touched us. Due to the traditional Chinese festival of Dragon Boat Festival in the past few days, we were unable to interact with everyone on the forum regarding this issue in a timely manner. We ask for your understanding.

As a company, we deeply understand the importance of integrity, so we would like to explain the issue regarding the op-amp. Our NE5532 op-amps were directly purchased from TI's official website. We have retrieved the purchase order records and attached a screenshot of the order. Please be aware that certain confidential information has been blurred for security reasons. We hope this serves as proof that we are using genuine components.

We are also curious about why the NE5532 op-amps we use may appear different from what you have in hand. Therefore, we have sent an email to contact TI to seek an official explanation. Once we receive a response from them, we will promptly share relevant screenshots to inform everyone.

We encourage everyone to continue monitoring our products and work. If you notice anything suspicious, please feel free to raise it to us. We will make every effort to communicate with you and address any concerns you may have.

View attachment 294768

This is top notch product ownership!

 

[G-Can]

Have all the sense, because is the first Fosi amplifier with PFFB and as pure power amp, without volume control.

what does PFFB mean, what are actual benefits? Compared to regular ZA3?
Im fed up with Fosi bringing new product every 3 months, and everytime its something that would work better for my use.

Now I think that they will come up with stereo power amp as well, or 3ch amp which again would be better in my case then a bunch of these monos.

 

[somebodyelse]

what does PFFB mean, what are actual benefits? Compared to regular ZA3?

Post-Filter FeedBack - in general it offers improved noise and distortion performance, and reduced load sensitivity, than when not using it on the same amp. See TI's application note for some comparisons.

 

[doug s.]

Quick question, would it be better to have the volume control in Windows 11 set to 100% and then control the volume through the Fosi V3 amp, or can I just leave the amp at maximum volume and control it through Windows?

having the volume pot at 100% effectively takes it out of the circuit. yes, you still have the wiring there, but the pot itself is at its least interference if it's wide open. so, i'd leave the windows setting at 100%, as i'd think its quality is not as good as what's in the fosi.

doug s.

 

[G-Can]

Post-Filter FeedBack - in general it offers improved noise and distortion performance, and reduced load sensitivity, than when not using it on the same amp. See TI's application note for some comparisons.

yeah, i read about it later. but V3 is great as it is, dont see where is this PFFB noticeable in general use. Is there an actual audible difference to sound output, or this is just spec war.

 

[Joe Smith]

yeah, i read about it later. but V3 is great as it is, dont see where is this PFFB noticeable in general use. Is there an actual audible difference to sound output, or this is just spec war.

I like the sound of the V3 just fine...using at present with some Elac Debut 6.0 speakers. I think for people with speakers that lean even further towards a bright sound, the rise in high frequencies may be an annoyance. For me, with my hearing top end at about 12khz, it's not a factor. If you look at Amir's graphs, the difference is pretty slight. The V3 has about +1 db at 20khz, the new mono amps about +.5 to .6 db at 20khz. Fosi had posted a revised graph that shows even less of a rise, which is cool. I think that's what they need to do for these to be considered competitive with the lower range of Hypex-based amps.

The other issue/improvement would be if one wants more power than the V3 can offer. Again, not a factor for me, as I'm using with a 36v power supply and it's plenty loud for our smaller room applications.

 

[doug s.]

yeah, i read about it later. but V3 is great as it is, dont see where is this PFFB noticeable in general use. Is there an actual audible difference to sound output, or this is just spec war.

if you look at frequency response and impedance graphs of speakers, you can determine if an amp w/o pffb will make a difference in your speakers. in the majority of cases, the answer will be no. the impedance of the speaker needs to be really high (or low) to affect the speaker's output - it will increase or decrease depending on the speaker's output being above or below 8 ohms at high frequencies. and even if the response is increased (or decreased) a db or two above, say, 10khz, most people will not be able to hear a difference. re: the improved distortion levels, there's no way you could hear the difference as distortion levels are already below audibility.

doug s.

 

[somebodyelse]

yeah, i read about it later. but V3 is great as it is, dont see where is this PFFB noticeable in general use. Is there an actual audible difference to sound output, or this is just spec war.

I suspect the noise and distortion difference won't be audible. Load dependency may be, depending on the load. See Erin's tests of the za3 or Wiim Amp to see the 0.5dB peak at ~2kHz produced by a 20R impedance peak for an example of why it may be audible even to the older population. Some speakers have more extreme impedance swings that would produce larger changes, others not so much, so you would need to check. You can correct for it with filters - say the PEQ in the Wiim Amp.