Fosi Audio ZA3 Amplifier Review

[MJSullivan56]

My experience:

I ordered a 48v/5a Fosi ZA3 amp from Amazon and was pleased to learn that it would support 2ohm speakers. So I hooked it up in stereo mode to a pair of 20-year old Apple/Harman Kardon Soundsticks which have a nominal 2 ohm rating. I have to say, they sounded GREAT -- for all of 24 hours, after which the amp stopped producing any sound. I validated this by plugging in a 2nd set of 8ohm speakers as well as a 2nd input source -- still no sound. So I took advantage of Amazon's generous exchange policy and they sent me another ZA3 posthaste. The issue is that I am now gun-shy about using this amp with these old 2ohm SoundSticks. I guess I could rewire the SoundSticks to be 8ohm but I would prefer to keep them pristine as the design is gorgeous. I suppose another possibility would be to run the ZA3 in mono mode only and then pick up a 2nd ZA3, but that is starting to get expensive for a desktop system. I did try the replacement amp with a pair of 6ohm speakers which sound ok but the output is probably half of what the Apple speakers were providing at the same output settings. Thoughts as to how to proceed?

 

[Deleted member 72219]

My experience:

I ordered a 48v/5a Fosi ZA3 amp from Amazon and was pleased to learn that it would support 2ohm speakers. So I hooked it up in stereo mode to a pair of 20-year old Apple/Harman Kardon Soundsticks which have a nominal 2 ohm rating. I have to say, they sounded GREAT -- for all of 24 hours, after which the amp stopped producing any sound. I validated this by plugging in a 2nd set of 8ohm speakers as well as a 2nd input source -- still no sound. So I took advantage of Amazon's generous exchange policy and they sent me another ZA3 posthaste. The issue is that I am now gun-shy about using this amp with these old 2ohm SoundSticks. I guess I could rewire the SoundSticks to be 8ohm but I would prefer to keep them pristine as the design is gorgeous. I suppose another possibility would be to run the ZA3 in mono mode only and then pick up a 2nd ZA3, but that is starting to get expensive for a desktop system. I did try the replacement amp with a pair of 6ohm speakers which sound ok but the output is probably half of what the Apple speakers were providing at the same output settings. Thoughts as to how to proceed?

Here’s an experiment to try: hook up just one speaker and set the amp to Mono mode, then let it play for a few days to see if it holds up. If it does, then a second one for the other speaker would likely be a worthy upgrade. What do you think?

-Ed

 

[MJSullivan56]

sounds like a plan.

A nagging question I have would be: "Is the Fosi claim of supporting 2ohm speakers only meant for mono mode?"

 

[MJSullivan56]

further, it seems to me that it would be cheaper/better to pick up two Fosi mono amps and return the ZA3 while I still have the Amazon return window open.

 

[Deleted member 72219]

further, it seems to me that it would be cheaper/better to pick up two Fosi mono amps and return the ZA3 while I still have the Amazon return window open.

If you don’t plan to mess with op-amps and have a separate preamp or volume control at your source, a pair of V3 Monos will serve you better for sure, yes.

-Ed

 

[MJSullivan56]

If you don’t plan to mess with op-amps and have a separate preamp or volume control at your source, a pair of V3 Monos will serve you better for sure, yes.

I'm confused about this statement -- I thought the V3 mono supported swappable op-amps? Or is that wrong?

 

[Deleted member 72219]

I'm confused about this statement -- I thought the V3 mono supported swappable op-amps? Or is that wrong?

It does, but the enclosure is WAY smaller, so many op-amps that fit ZA3 won’t physically fit inside V3 Mono.

-Ed

 

[MJSullivan56]

It does, but the enclosure is WAY smaller, so many op-amps that fit ZA3 won’t physically fit inside V3 Mono.

-Ed

understood. thanks!

 

[dedede223]

Ok so, i'll make my ZA3 go back to amazon, the left chanel dropout regularly even after having check all the solder and replace the thermal past. it's not an overheating issue and doesn't seems to be a bad solder, maybe one OPamp is bad somewhere but i don't have the patience to test all of them and thing. I think i'll replace it with a V3. I would love to buy two V3 mono but it's a little bit too expensive for me.

 

[Deleted member 72219]

Ok so, i'll make my ZA3 go back to amazon, the left chanel dropout regularly even after having check all the solder and replace the thermal past. it's not an overheating issue and doesn't seems to be a bad solder, maybe one OPamp is bad somewhere but i don't have the patience to test all of them and thing. I think i'll replace it with a V3. I would love to buy two V3 mono but it's a little bit too expensive for me.

You need two of them (V3 Mono) if you are driving two separate speakers, one per speaker.

-Ed

 

[burkm]

The question is, if Your "2Ohm" speakers impedance drops heavily below the 2 Ohm limit. I guess, that the statement "2 Ohm" may describe the lowest limit the speaker may reach. A "normal" speaker may undercut the general description "x Ohm", as far as I know, by 20%. That would provide a lower limit of the impedance of 1.6 Ohm, but I don't know, if that is what Fosi Audio means by its descrption.

Anything "2 Ohm" or below means quite high currents, which could be problematic for any power amp. In past times, only very few power amps ever could go below 2 Ohm load.
They were usually quite heavy and expensive (class A/B). I remember from past times a few problematic "Infinity" speakers, which would need special power amps to handle their difficult to drive load. Nowadays most speakers are designed to not cross the "4 Ohm" description, meaning, meaning they won't go below 3.2 Ohm impedance.
This will be handled by most "standard" amps without problems.

Is there an "Impedance" diagram or graph avilable for Your "2 Ohm" speakers ?

 

[burkm]

understood. thanks!

User "EddNog" probably means only those OP amps, which are assembled using discrete elements and thus need additional vertical space. Standard OP amps (DIP types etc.) can be used (and replaced) normally.

 

[Deleted member 72219]

User "EddNog" probably means only those OP amps, which are assembled using discrete elements and thus need additional vertical space. Standard OP amps (DIP types etc.) can be used (and replaced) normally.

Precisely correct.

-Ed

 

[juliangst]

Does anyone know if there are plans for a Fosi Audio Amp like this one that also includes a high pass filter for the amplified channels?

 

[CrypticSignal]

Hi all, I bought a Fosi ZA3 today but there's something wrong with it. I have my subwoofer connected to it via the subwoofer output on the amp. Sometimes there's sound from the subwoofer and sometimes it stops getting sound. Whenever there isn't any sound coming from the subwoofer, I need to restart the amp and then I get sound from the subwoofer. It's weird.

Nothing wrong with settings or anything like that, I don't change anything. I just need to keep restarting the amp. The RCA cable was bought this month and it's not loose, I'm using the same cable I used to connect the subwoofer to my Bluesound Powernode and I never had this issue with that. Regarding the outputs to my speakers, that always works.

Anyone know what the issue could be or have I just received a defective one?

 

[Zek]

Anyone know what the issue could be

Maybe there is a loose contact on the subwoofer out connector or the connector is poorly soldered.

 

[Dennis_FL]

Hi all, I received a Fosi ZA3 today but there's something wrong with it. I have my subwoofer connected to it via the subwoofer output on the amp. Sometimes there's sound from the subwoofer and sometimes it stops getting sound. Whenever there isn't any sound coming from the subwoofer, I need to restart the amp and then I get sound from the subwoofer. It's weird.

Nothing wrong with settings or anything like that, I don't change anything. I just need to keep restarting the amp. The cable is not loose, I'm using the same cable I used to connect the subwoofer to my Bluesound Powernode and I never had this issue with that. Regarding the outputs to my speakers, that always works.

Anyone know what the issue could be or have I just received a defective one?

Is your subwoofer on Auto and shutting itself off.

 

[CrypticSignal]

Is your subwoofer on Auto and shutting itself off.

It's not that, it's even happened during the middle of a song where I stopped getting output from the subwoofer.

 

[Dennis_FL]

It's not that, it's even happened during the middle of a song where I stopped getting output from the subwoofer.

It could be --- can you turn auto off?

 

[CrypticSignal]

It could be --- can you turn auto off?

I don't think it's set to auto. The setting in the SVS app for "SUBWOOFER STANDBY" is set to "ON" rather than "Auto" (see attached screenshot) which I'm assuming means it's on all the time.

And I haven't had this issue when using the subwoofer with the Bluesound Powernode or WiiM amp, just with the Fosi.

Also, it shouldn't be going to standby during a song even if the subwoofer was set to auto, after a quick Google, it should only go into standby after 20 minutes.