Fosi Audio's First Dual-Mode Balanced Amplifier ZA3

[Jeromeof]

@Fosi Audio
I received ZA3 yesterday and my first impression was "excellent craftsmanship".
You guys have produced such an eye candy, it wins half the battle just by its looks for me.
Clear and punchy sound, very powerful. Running cool with 48v PSU.

Fosi ZA3 TPA3255 Mono/Stereo Switchable Amplifier, and vs Aiyima A07 Max

*** Note: No measurements are included in this thread *** While I hope a Review with measurements comes through soon, I am putting together my observations here hoping to provide some clues to someone looking for ZA3 and quick comparison with Aiyima A07 Max. Few other threads related to these...

www.audiosciencereview.com

Totally agree - it's a very impressive looking (and sounding) amplifier - I am pretty sure it will measure as well as the V3 (or A07 MAX) whenever @amirm get around to measuring it.

 

[Jeromeof]

Found this today - a factory tour of Fosi Audio

[Factory tour] A reportage from the Fosi Audio headquarters in Shenzhen, China

Fosi Audio, a small Chinese audio company with new ideas and designs. Our Cora Chou reports for TNT-Audio - Internet HiFi magazine - www.tnt-audio.com

www.tnt-audio.com

 

[Joe Smith]

I just put in a plug to my contact at Fosi for them to send one of these to Amir...I'm very interested to see how this one measures compared to the V3. That on-off knob feature would make this a pretty functional monoblock solution.

 

[crack_squirrels]

@Fosi Audio What time does the kickstarter *end* on the 24th? I ask because that is the day I get paid and so if I wanted to back it for the 2x48v package it's pretty tight!

 

[Toku]

I have continued to evaluate Fosi's ZA3 prototype, and I have summarized my impressions so far.

1. The ZA3 itself does not generate much heat.
I use the included 48V/5A power supply for the ZA3, but the Fosi ZA3 generates very little heat and is only a little warm. The Fosi V3 also generates less heat, but the ZA3 has a larger case, so it generates even less heat.
For comparison, AIYIMA's A07 and A07 Max with a power supply voltage of 40V are placed side by side, but compared to these, the heat generation of ZA3 is definitely lower.
The magnitude of heat generation is in the order of ZA3 < V3 < A07 Max < A07.
However, I find it a bit strange why there is such a difference in heat generation between amplifiers using the same TPA3255.

2. Power ON/OFF operation is unstable.
The power is controlled by pushing the volume knob, but sometimes this does not work even if you try it. In such a case, if you double push or push for a long time, it will work. This is a very fickle behavior and needs improvement. It seems that this type of push operation method was probably chosen by adopting a 12V trigger. I think it will probably be improved in the production version.

3. There are no pop noises or anything like that.
There is no pop or click noise when turning the power on/off or switching inputs. Also, you won't hear any noise from the speakers during silent periods. Very excellent.

4. Stereo/monaural switching operation
Switching between stereo/mono on the front panel is very smooth. There is no pop noise caused by switching.
However, once this switching operation is performed, it will not be performed frequently thereafter. Therefore, I think it is better to attach it to the rear panel or bottom plate than to the front panel.

5. SUB output behavior
The ZA3's SUB output is designed to change output in conjunction with the volume control. Additionally, the SUB output has a built-in low-pass filter with a cutoff frequency of 200Hz to cut unnecessary frequency components.
However, depending on the application, a lower frequency setting may be required.

6. 12V trigger operation
A 12V trigger is available for ZA3. I prepared a 12V power supply and a 3.5mm 2-prong plug and tried it many times, but it didn't work. It's a very simple operation, just apply +12V, but for some reason it didn't work.

7. The sound quality of ZA3 is in the same trend as Fosi V3. It has a calm and smooth sound quality. Compared to the conventional class D amplifier using TPA3255, the high-pitched sparkle and roughness are suppressed and the sound quality is more sophisticated.

8. Precautions for use
The input sensitivity of ZA3 is designed to be the same level for both RCA and XLR. Therefore, if you connect a device with an RCA/XLR output of 2V/4V, such as a recent DAC, you will feel a level difference when switching inputs. However, for older people like me, this setting is more familiar. Therefore, this setting can also be accepted.

 

[GGroch]

I have continued to evaluate Fosi's ZA3 prototype, and I have summarized my impressions so far.

5. SUB output behavior
The ZA3's SUB output is designed to change output in conjunction with the volume control. Additionally, the SUB output has a built-in low-pass filter with a cutoff frequency of 200Hz to cut unnecessary frequency components.
However, depending on the application, a lower frequency setting may be required.

Good stuff Toku, thanks for this.

A general question on Sub-Outs, I'd like your opinion. My guess is that 99% of the time it will be connected to an active subwoofer that has its own built in adjustable LPF. The best LP cut-off frequency will vary widely depending on speakers/location/room. Why is a non-adjustable LPF built into an amp's sub out of any advantage over just making it full range. I can see how a HPF on the Speaker outs could be an advantage, but can't see the point in this.

I know an LPF is an often requested audiophile feature for sub outs, but do not know why.
I would think a full range variable stereo line out may have additional utility.

 

[Guddu]

@Toku Excellent observations, I would jump in as well with few here based on my experience with pre-release unit.

1. The ZA3 itself does not generate much heat.
I use the included 48V/5A power supply for the ZA3, but the Fosi ZA3 generates very little heat and is only a little warm. The Fosi V3 also generates less heat, but the ZA3 has a larger case, so it generates even less heat.
For comparison, AIYIMA's A07 and A07 Max with a power supply voltage of 40V are placed side by side, but compared to these, the heat generation of ZA3 is definitely lower.
The magnitude of heat generation is in the order of ZA3 < V3 < A07 Max < A07.
However, I find it a bit strange why there is such a difference in heat generation between amplifiers using the same TPA3255.

Heat management is unreal, probably better than most of the available amplifiers.
I expected the bottom plate to be a bit hotter, but it gets barely warm.
Its like TPA3255 chip itself isn't generating much heat to expose off, gain also doesn't feel shy. I would try to get a thermal scan if possible.
Whatever @Fosi Audio have done here to lower down heat is working really good with this amplifier.

At least, it feels safe to leave it powered ON all the time.

2. Power ON/OFF operation is unstable.
The power is controlled by pushing the volume knob, but sometimes this does not work even if you try it. In such a case, if you double push or push for a long time, it will work. This is a very fickle behavior and needs improvement. It seems that this type of push operation method was probably chosen by adopting a 12V trigger. I think it will probably be improved in the production version.

I have few other equipment's which use volume knob for ON/OFF with longer press and input selection with quick press. One of such device is Fosi's K5 pro DAC.
Coming from other device experience, I thought ON/OFF push sequence has to be with hold, I mean needs to be pressed a bit longer than a quick push and release.
If it is supposed to work with quick push and release then there is surely something wrong, but it is a push + hold operation by design then it has worked for me almost every time without any issues.

3. There are no pop noises or anything like that.
There is no pop or click noise when turning the power on/off or switching inputs. Also, you won't hear any noise from the speakers during silent periods. Very excellent.

With 3 different speakers, ELAC DBR62, Borea 03 and Paradigm Monitor v3 .4, I have heard a very faint pop noise every time the unit is powered off.
But its is so low that the relay switching noise overpowers it every time.

4. Stereo/monaural switching operation
Switching between stereo/mono on the front panel is very smooth. There is no pop noise caused by switching.
However, once this switching operation is performed, it will not be performed frequently thereafter. Therefore, I think it is better to attach it to the rear panel or bottom plate than to the front panel.

Worked for me every time without any issues as well.
@Fosi Audio I absolutely liked the way speaker connections are managed. Because speaker wires aren't needed to be rearranged, it avoids any risk of speaker miswiring and such accidents.
However, would appreciate a bit more information would be helpful on this operation. Because the speaker connections in mono is different than so many other similar operations amplifiers, it makes me think if mono mode just disables/shutdown one channel like you are just using 1 channel on stereo amplifier or performs any sum up to provide all available output power to mono channel?

6. 12V trigger operation
A 12V trigger is available for ZA3. I prepared a 12V power supply and a 3.5mm 2-prong plug and tried it many times, but it didn't work. It's a very simple operation, just apply +12V, but for some reason it didn't work.

Did you try 12v input from any other amplifier/DAC/AVR?
I tried it more than 10-12 times with Yamaha TSR700 AVR and it worked every time without any failure.

7. The sound quality of ZA3 is in the same trend as Fosi V3. It has a calm and smooth sound quality. Compared to the conventional class D amplifier using TPA3255, the high-pitched sparkle and roughness are suppressed and the sound quality is more sophisticated.

Do you mind telling which all speakers have you on your setup?
With my setup, sound is very addictive specially with video content. Very engaging and punchy, however kind of forward.
I can easily see the difference switching to A07 Max and PA7.

 

[Guddu]

I can see how a HPF on the Speaker outs could be an advantage, but can't see the point in this.

Good point, having sub-out is a useful feature but problem still remains with the speakers if they keep on playing lower frequencies as well. If speakers aren't good enough with low frequencies in such case then overall impact may become undesirable specially when volume is turned UP on the amp.

 

[Bene]

hi. can anyone recommend a dac or even a cheap pre-amp with 12v trigger? I have a power amp from Emotiva without remote

 

[Andysu]

 

[Toku]

Good stuff Toku, thanks for this.

A general question on Sub-Outs, I'd like your opinion. My guess is that 99% of the time it will be connected to an active subwoofer that has its own built in adjustable LPF. The best LP cut-off frequency will vary widely depending on speakers/location/room. Why is a non-adjustable LPF built into an amp's sub out of any advantage over just making it full range. I can see how a HPF on the Speaker outs could be an advantage, but can't see the point in this.

I know an LPF is an often requested audiophile feature for sub outs, but do not know why.
I would think a full range variable stereo line out may have additional utility.

Indeed, even if you don't install an LPF, most active SWs have their own built-in LPF, so I don't think it's necessary.
However, I think the ZA3's LPF will be useful if you want to easily configure it with a power amplifier and passive SW. The reason for passing the LPF at this time is that if the extra frequency components are output to the SW, it will function as a full-range speaker and muddy the sound of the main speaker. Therefore, an LPF is necessary to function only on the necessary bass components. At this time, even if the bass components are output from both the SUB and main speakers, to the human ear, the volume of the bass only increases, but the sound quality is not affected.

 

[K.Kevin]

Does anyone here know/reckon if these would sound better or worse than the internal amps in a Denon X3800h?

I have a pair of used BMR’s, they droop down to 3ohm impedance for much of the bass frequencies. I tried the receiver up against an aiyima a07 32volt, I know there’s a huge power imbalance there, but I level matched them as best I could. I felt like the aiyima still provided crisper and tighter bass, like the bass guitar cut through the mix better than on the Denon. I did think the Denon had more pleasing mids and higher frequencies though. Is what I heard because these class D amps can provide more current at lower ohms, or that they’re more impervious to those droops?

 

[space_duck]

Would really prefer an adjustable LPF on the sub out, as my desktop subwoofer (Yamaha YST-FSW150) does not have an adjustable filter and sounds quite bad above 100Hz.

 

[Jeromeof]

So was playing around with the 12V trigger with a Wiim Pro and checking the power consumption.

So in 'standby' waiting for the 12V trigger it was consuming 0.7 watts - then once it was triggered it was around 7 watts driving my Q-Acoustics and a subwoofer.

It a good combination I think with the triggers though you need a 2.5mm to 3.5mm cable trigger cable.

 

[Joe0429]

I purchased two sets of Fosi Audio ZA3 amplifiers with 48V5A power supplies from Taobao. These amplifiers should already be the official release version, as there are already many buyer reviews on the Taobao page.

Packaging:
The two sets of amplifiers were only packaged in bubble wrap bags, which resulted in dents to the amplifier boxes during shipping. Fortunately, the amplifiers were not damaged. I would suggest that @Fosi Audio consider using a cardboard box to protect the product during packaging, as other brands do.

Appearance:
There are many budget amplifiers available on Taobao, and they all have a similar appearance. Fosi makes the ZA3 look different in terms of exterior design. The orange volume knob and orange power indicator light complement each other well. The shape of the bottom makes the ZA3 less brick-like, and it may also help with heat dissipation.

Power Switch:
I connected the ZA3 to the Wiim Pro and a pair of 6 ohm floorstanding speakers. Turning the power on and off is accomplished by pressing and holding the volume knob for two seconds. When the power is turned on, there is a 2-second softstart delay before sound is output. When the power is turned off, the power relay disconnects first, and then the remaining power is slowly consumed within a few seconds. The power can be turned on again without waiting for the power light to go out completely.
I have not encountered a situation where the device needs to wait 1-2 minutes to restart after being turned off. My two ZA3s only produce a very faint popping sound when I put my ear close to the speakers when they are turned on.

Compatibility and Convenience:
The power switch that can retain the volume position and the 12V trigger function are the reasons why I chose ZA3 instead of A07 Max. These two features make the ZA3 well-suited for use with a source that has a 12V trigger out or as an external power amplifier for an AV receiver.
When the Wiim Pro plays music or enters standby mode, the ZA3's power is automatically turned on/off. This is very convenient and energy-saving. My wife appreciates that she can easily play music without having to learn how to operate an amplifier.

Volume Control:
Regarding the relationship between volume control and input level, the 6 o'clock to 8 o'clock position is almost unusable, regardless of the input level. The input sensitivity of the ZA3 is 0.775V. When a 4V balanced signal is input, the usable adjustment range is from approximately 8 o'clock to 10 o'clock, making it difficult to make fine adjustments to the volume. A gain selection switch would be a valuable addition to improve volume control.

Mono Mode:
The ZA3's mono mode utilizes the right channel R+, R- terminals instead of the L+, R+ terminals. I tried switching modes while music was playing, and the internal relay immediately disconnected the output and resumed playback after 2 seconds. While there are no apparent safety concerns, it is questionable how often users would switch between stereo and mono mode.
The only practical use I can envision is if you have two ZA3s and use them as an external power amplifier for an AV receiver. Two ZA3s can drive four channels when watching movies, and they can switch to mono mode to drive the left and right channels when listening to music.

AC Adapter:
The included adapter's AC plug is a Type A plug without a ground pin. There is a slight discomfort when touching the case. I am unsure whether the Kickstarter version has the same issue. Fosi's GaN 48V adapter utilizes a Type B form with a ground pin. I hope that Fosi considers switching to AC plugs with ground pins for all adapters.

Speaker Wire Connection:
The speaker wire I use is Canare 4s8. The binding posts are smaller than the normal size, and the spacing between them is too close. It is challenging to connect the binding posts without using banana plugs. The arrangement of the A07 Max provides a better solution for this issue.

Overall Impression:
Overall, I am satisfied with the performance of the ZA3. I would like to see Fosi incorporate the advantages of the 12V trigger and power switch into future models, along with adding a gain selection switch and PFFB. Additionally, addressing the shortcomings mentioned above would further enhance the overall user experience.

 

[space_duck]

Mono Mode:
The ZA3's mono mode utilizes the right channel R+, R- terminals instead of the L+, R+ terminals. I tried switching modes while music was playing, and the internal relay immediately disconnected the output and resumed playback after 2 seconds.

Is it actually a bridged mono mode or does it just disable the left channel?

 

[Middle Earth]

Hey there, here's an update on the ZA3. We uploaded a video demonstrating the mono mode.

I will be interested in those soon to be released Fosi speakers as to how they sound and the price point. To date Fosi has released only one passive speaker that costs about $400 for a pair and they have gone unnoticed. It will be interesting to see if Fosi can add something to the passive speaker market with that new two-way bookshelf And really get into that mix.

 

[OldTimer]

Hey there, here's an update on the ZA3. We uploaded a video demonstrating the mono mode.

How about bi-amping using dual Fosi V3 bridged by pre-out? Which one is better?

 

[Guddu]

Is it actually a bridged mono mode or does it just disable the left channel?

I have tried to find out more on this earlier, but couldn’t find anything that suggests bridged mono. Fosi documentation also doesn’t have this information.
Most amplifiers use different speaker connections when switched to mono, but ZA3 uses terminals of one of the speaker as it is (right speaker in this case).

 

[Toku]

Did you try 12v input from any other amplifier/DAC/AVR?
I tried it more than 10-12 times with Yamaha TSR700 AVR and it worked every time without any failure.

Do you mind telling which all speakers have you on your setup?

Currently, I don't have any equipment with a 12V trigger output around me. So I tested it using a 12V DC power supply instead.

The speakers currently connected are QUAD S-2. In addition, I will be using two sets of self-made full-range speakers.