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Fosi Audio V3 Amplifier Review
- Thread starter amirm
- Start date
No problem here Fosi Audio TB10D quality 32v 10a power supply
Mabye the amp+ the a standard laptop power supply doesn't provide enough power at low levels, volume, like a car with not enough tourqe at low rpm
Someone wrote about a Fosi Audio TPA3255 amp it distorts above 75% or 3 o'clock
That is not how amps work.
Low levels are low power. You don't need high power at low levels.
But you need current, mabye the power supply is under avarage quality
So a video where the lower on paper power supply beat the high powered powered supply
It is not gain I'm talking about. I feel there is a change in the bottom end response itself after the gain reaches a point. Also I feel the overall tone itself is changing.
I tried turning up the volume to max and adjusting it in my preamp. The case is still the same
After a particular point, the bass seems to be balanced and also the tone seems to get alright. I tried with many speaker pairs . It's still the same.
I tried turning up the volume to max and adjusting it in my preamp. The case is still the same
After a particular point, the bass seems to be balanced and also the tone seems to get alright. I tried with many speaker pairs . It's still the same.
No, you don't. Well you do - but low curent. Even if the PSU is poor, low levels with never test it. And bear in mind that the good PSU in that video is supplied by FOSI.
Power = VxI
and I = V/R
So for low power you turn down the amp so it outputs lower voltage. The low voltage across the impedance of your speaker results in low current.
The only time you need high power = approaching the limits of volts, and the limits of current from the PSU is when. you are approaching maximum levels/volume/power from your amp.
Most likely the reason for the perception of poor bass at low levels are the way we perceive different frequencies at different levels. At lower volumes there needs to be relatively more bass SPL ccmpared to mid range SPL in order for it to sound as strong. So called Fletcher–Munson curves:
Equal-loudness contour - Wikipedia
This is the reason for "loudness" switch on some (typically vintage) amps. It is also why many graphic eq apps offer a "loudness" equalisation preset.
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ASR has done a few older Yamaha amps and receivers and they bench quite well... even the sub $50 garage sale units out there
I think there's been a few reports here there and everywhere of the V3 not seeming to have enough power and then you get people from williston randy and even Zeos saying the thing has heaps of power... and so who to beleive?
I'm of the opinion that people who complain of low power are doing somefhing wrong.
Their sources lack gain or voltage or something along those lines. But if you're telling me the idiot brigade (so to speak!) from Amir down says that is has heaps of power, outside of load invariance, then why would i believe the outliers.
Is the TPA 3255 known to lack power? Then why would anyone think Fosi is delivering less power? doesnt make sense
I think there's been a few reports here there and everywhere of the V3 not seeming to have enough power and then you get people from williston randy and even Zeos saying the thing has heaps of power... and so who to beleive?
I'm of the opinion that people who complain of low power are doing somefhing wrong.
Their sources lack gain or voltage or something along those lines. But if you're telling me the idiot brigade (so to speak!) from Amir down says that is has heaps of power, outside of load invariance, then why would i believe the outliers.
Is the TPA 3255 known to lack power? Then why would anyone think Fosi is delivering less power? doesnt make sense
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As my last post - see Fletcher Munson. That is how we hear. You'll probably perceive the same on your A07 if you base the comparison on actual power levels rather than volume knob position.
I didn't do any comparison based on volume pot level.
I know the difference between log and linear pots.
This is my second unit I have been testing. I'm getting the same thing.
I'm of the opinion they are comparing with similar amps that have liner rather than the logarithmic volume control on the V3.
With. linear control with the POT at 50% (Say 12 o'clock) you are already at 50% of the voltage output = 1/4 of the power. But because of the logarithmic way we perceive volume (10x power to double volume), that 1/4 power represents about 66% of full perceived volume.
That is why a log pot should be used. That way you get aproximately linear relationship between pot position, and perceived volume.
So with a log pot - the 50% position will give 50% of full volume - so (given that you need 10x power to double the volume) - that means only 1/10th the power, instead of 1/4 with a linear pot.
So somone comparing an A07 with the V3 may be expecting similar sound with similar volume dial positions. They will not get it. At the same position, the V3 will sound much weaker - because it is putting out 1/4 of the power of the A07. To comparre properly the volume pot must be adjusted so both amps are putting out the same power.
Well given that this amp has a flat frequency response, low distorition, and can (probably) output more power than you are using when you detect this change AND can maintain that power at low frequency down to 20Hz - what else do you think is going on?
How are you level matching for the comparison? Or are you not comparing at all? Because what you are describing sounds like classic Fletcher Munson. If that is what it is, then it has nothing to do with the amp performance, and everything to do with chosen output level, and with how consequently your ears and brain work together to perceive the bass.
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We can try to find the real reason, but at certain point if nothing can explain what one hears, one may have to bite the bullet and set up an apple to apple double blind listening test, or at least do it single blind if double blind is too difficult to do. That's if one really want to find the reason and have the time to do it.
agreed. believe the typical reason is they lack enough gain input which is what I experienced on initial testing.. until I figured it out. now all is good.
@Fosi Audio ... there's some ETA to the monoblock versions? 
I tried level matching the a07 and fosi v3 with the help of a microphone and an old recording software which I had in my pc. It's still the same.
At same volume level, the low frequency response from v3 is very poor until it reaches a particular level
what means "very poor"? that's a totally subjective question ... maybe the Fosi is clear and transparent to the source and the other amp have a "fat" bass.
a better test can be using specific bass frequencies with a generator, with previous gain matching based on pink noise (REW + Umik-1 is what i use)
that will be something more real, what is "poor bass" for you can be the "real bass" in the recording for me.
So your hypothesis is that at different positions of the potentiometer the frequency response of the fosi v3 changes?
That would be VERY strange
SuperDerpBro
Active Member
Just an update.
They are finally allowing me to return. However, they are making me pay shipping. Not really worth it, lol.
They are finally allowing me to return. However, they are making me pay shipping. Not really worth it, lol.
Hi all!
Quick review of V3
First i tried with 48V PSU and amp is clearly overheating!! About 50-60 degrees around whole enclosure. Could be something wrong with PSU (looks like original, but without Fosi inscription)? Then i hooked 32V and temperature dropped almost on ambient temperature around 25 degrees, but sound degraded- much of low listening volume bass was gone, amp lost grip. Boxes are Wharfedale Denton 80, 6 ohm, 86db eff.
So for 100 EUR good amp without sterile class d sound but overheating is clearly issue here. I had similar class d amp Nuforce Icon which is much better sounding and also stone cold in operation.
Quick review of V3
First i tried with 48V PSU and amp is clearly overheating!! About 50-60 degrees around whole enclosure. Could be something wrong with PSU (looks like original, but without Fosi inscription)? Then i hooked 32V and temperature dropped almost on ambient temperature around 25 degrees, but sound degraded- much of low listening volume bass was gone, amp lost grip. Boxes are Wharfedale Denton 80, 6 ohm, 86db eff.
So for 100 EUR good amp without sterile class d sound but overheating is clearly issue here. I had similar class d amp Nuforce Icon which is much better sounding and also stone cold in operation.
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