Fosi Audio ZA3 Amplifier Review

[MCH]

I redid the test on a 1 kHz sine wave. On the graph in red, the measurement at 2.24 V of the input voltage to the amplifier and the output voltage of 2.9 V on a resistive load of 8 Ohms. In green on the graph, the measurement at 0.16 V of the input voltage to the amplifier and the output voltage of 2.9 V on a resistive load of 8 Ohms. As you can see on the graph, there are harmonic peaks - in red. The graph of measurements at 0.9 Volts coincides with the graph of 0.16 volts.

View attachment 391315

I then recorded some music (Audio test - 84 - Robin S _ Luv 4.wav) with 2.24V going into the amp and 2.9V coming out and found RTA analysis a THD of 102.7%
View attachment 391316

After that I recorded music, with 0.9V entering the amplifier and 2.9V coming out and found found RTA analysis THD 13.5%
View attachment 391319

Finally I decided to measure how many volts my sound card produces when listening to dance tracks and saw a signal of 1.5V
View attachment 391320

I have to state the fact - XLR/TRS connection in ZA3 is completely useless Most DACs give a signal to the amplifier input greater than 0.9V

Have you measured your 2.24V signals in loopback (without the amplifier, just DAC out directly to ADC) to check out all is good? In your screenshot in post #643 I see raw is indicating your signal is clipping.

 

[FanatNsk]

Have you measured your 2.24V signals in loopback (without the amplifier, just DAC out directly to ADC) to check out all is good?

The message about the clipping is given by the REW generator; there is no clipping at the sound card input.

Here is a loopback measurement of my sound card 2.24V

 

[FanatNsk]

I found another problem with Fosi ZA3, at very low volume the left channel is quiet, the right one is audible. Perhaps this is a defect of my amplifier, can someone check it for themselves, smoothly reduce the volume to zero and compare the volume of the left and right channels.

 

[EddNog]

I found another problem with Fosi ZA3, at very low volume the left channel is quiet, the right one is audible. Perhaps this is a defect of my amplifier, can someone check it for themselves, smoothly reduce the volume to zero and compare the volume of the left and right channels.

Cheap volume attenuator (potentiometer). They have to cut costs somewhere.

-Ed

 

[staticV3]

I found another problem with Fosi ZA3, at very low volume the left channel is quiet, the right one is audible. Perhaps this is a defect of my amplifier, can someone check it for themselves, smoothly reduce the volume to zero and compare the volume of the left and right channels.

Common issue of all potentiometer-based volume controls.

To fix it, turn down the audio source device and turn up the Fosi to compensate.

 

[FanatNsk]

Common issue of all potentiometer-based volume controls.

To fix it, turn down the audio source device and turn up the Fosi to compensate.

I had cheaper amplifiers, on TPA3116 (Aiyiama B01, Aiyiama A03), TPA3255 (BRZHiFi X21, O-noorud D3, Fosi V3, ZK-AS21) also amplifiers on TAS (O-noorus DA10, Aiyiama D05) - none of these amplifiers had problems with the volume control at low volume, Fosi ZA3 is a fiasco!

 

[somebodyelse]

I had cheaper amplifiers, on TPA3116 (Aiyiama B01, Aiyiama A03), TPA3255 (BRZHiFi X21, O-noorud D3, Fosi V3, ZK-AS21) also amplifiers on TAS (O-noorus DA10, Aiyiama D05) - none of these amplifiers had problems with the volume control at low volume, Fosi ZA3 is a fiasco!

That's more a matter of luck than design. Potentiometers have a specified range of matching for the two channels. Most fall nearer the middle of the range (good matching) while some fall nearer the limit. Unfortunately you've got one of those this time. Manufacturers can buy potentiometers with tighter tolerances, or test them all before use to reject the worse ones, but those add to the cost.

 

[FanatNsk]

That's more a matter of luck than design. Potentiometers have a specified range of matching for the two channels.

I agree, there are often regulators with an imbalance of 1-2 dB, but in this case the difference is 10 dB.

 

[somebodyelse]

I agree, there are often regulators with an imbalance of 1-2 dB, but in this case the difference is 10 dB.

View attachment 392744

What range of volume control does this apply over? And you're sure you didn't accidentally enable the pad on one of the inputs?

 

[FanatNsk]

What range of volume control does this apply over? And you're sure you didn't accidentally enable the pad on one of the inputs?

The channel imbalance is audible at low volume of the speaker system, about <50 dB, at higher volume everything is fine, it is usable, but unpleasant, sometimes I listen to music at night at low volume.

 

[Power Pop 23]

Fosi Audio is discounting the price (ranging in price from $87.99 to $107.99) of new samples of the ZA3 amplifier in select configurations - with or without a 32 or 48 volt power supply unit - on Ebay:

Fosi Audio ZA3 TPA3255 Balance Stereo Amplifier Home Audio Mono Subwoofer AMP | eBay

Audiophile-Grade Components: The ZA3 features the TPA3255 high-end Class-D amp chip and utilizes premium Japanese NCC, ELNA, and German WIMA capacitors, and Japanese Sumida inductors for exceptional audio quality.

www.ebay.com

 

[Miiksuli]

Front op-amps are for RCA input?

 

[Spiky]

Hello!

I'll ask here too

I have a Fosi V3 2024 stereo amplifier, on which a t.amp amplifier is connected to the preout, which drives the subs.
My question is, would it make sense to replace it with a ZA3 that has a separate sub output?

 

[KR500]

The channel imbalance is audible at low volume of the speaker system, about <50 dB, at higher volume everything is fine, it is usable, but unpleasant, sometimes I listen to music at night at low volume.

Maybe try contacting Fosi Audio about this to see what they say.
It appears they listen to feedback from the community and might address issues in further production ?
The JDS Labs Atom 2 amp I use has a really good potentiometer gain knob with excellent channel balance and operation.
So, it is doable at this price point if attention is paid to securing the right part and implementing it

 

[burkm]

It depends, because the ZA3 has the same amp chip (TPA3255) as the V3 Stereo (and the V3 Mono), but the (passive) subwoofer out is somewhat different, if I remember correctly.
The "new" V3 (2024 Version. sold out ?) has a volume controlled output for a 2nd amp, but it can't handle a passive subwoofer without an additional amp, just an active one. It doesn't have a "subwoofer out", so you would need some kind of a low pass filter in front of the active subwoofer and the amp section (full bandwidth) is (almost) the same as for the ZA3.
Ususally You have at least a low pass filter for the (active) "Subwoofer out" and a high pass filter for the (passive) main speakers.
The (normal) V3 stereo version doesn't have PFFB correction either, which the V3 Monos have.
As already suggested, try to communicate with the Fosi Audio support about Your question...

 

[FanatNsk]

Maybe try contacting Fosi Audio about this to see what they say.

They said it was normal.

 

[40 Inferno]

They said it was normal.
View attachment 396855

I recently bought a ZA3 to replace my Dayton Audio HTA100, which had a similar problem with channel imbalance at low volume. I bypassed it by lowering source gain and turning up amp volume, and that helped but increased noise floor. The Fosi actually works fine but this does seem to be an issue with cheap amps. The customer support at Parts Express was better though (they acknowledged that it's a problem and offered to replace the amp).

 

[chomi]

I just want to confirm if the fosi v3 with a 48v psu runs warm to touch when just idle?

 

[EddNog]

I just want to confirm if the fosi v3 with a 48v psu runs warm to touch when just idle?

Yes.

-Ed