Fosi Audio's First Dual-Mode Balanced Amplifier ZA3

[howard416]

If it measures and sounds good, why spend more?
And if it’s costs that are keeping people from going active, an amp like this could solve that.
3e doesn’t have a problem solving all the issues you mentioned with a board that cost $100 and measures even better than the Fosi.

They're not selling a finished amp for the same cost that Fosi is selling this one.

 

[joqueval]

Finally the house.
First sound tests, good power reserve and a lot of detail in the reproduction.

 

[CamRector]

They're not selling a finished amp for the same cost that Fosi is selling this one.

No i didn’t say they were. I said that they have solved all the problems you mentioned for a board that costs $100 retail.
So like I said there is no reason why costs would be a factor in going with active crossovers.
With amps like these high quality bi/tri amping is for the masses.

 

[gordinho]

I currently have a sound devices USB pre 2 between a wiim mini and the ZA3. This is night and day compared to mini's DAC but I digress...

Since the ZA3 can take balanced I'm using that from the USB pre 2 but I hear it overloading ZA3's balanced input since distortion is obvious. USB pre 2 specs say

• Balanced XLR: +18 dBu with 100k ohm load

What is the max that the ZA3 is expecting? I noticed it sounded much better when I back off the dac's output but would be nice to know what I should be aiming for. I haven't compared yet to RCA output on the USB pre 2

 

[jackdanyal]

From the TPA325x Post-Filter Feedback spec sheet (ref. SLAA788A):

"PFFB offers many benefits including lower output noise, improved THD+N performance, improved IMD performance, lower output impedance, frequency response less affected by load impedance, and suppression of nonlinearities of the LC filter."
...
"Post filter feedback [PFFB] is implemented by adding a secondary feedback loop external to the amplifier. This feedback loop takes a fraction of the output voltage signal of the amplifier after the external LC filter and sends an error signal back to the input of the amplifier."
...
"The lower power performance which is very critical to how an amplifier actually sounds to a human ear is improved by roughly 5 dB with this PFFB configuration."

The typical plain TPA3255 gain is set to 21.5 dB, while TPA3255 PFFB gain is is set to 15.9 dB.

So, simply put, think of PFFB as the (LOW COST) tweak that puts the TPA3255 based amplifiers in the "big boys block", i.e., above the 100dB SINAD.

As a side note, it seems that these TPA3255 PFFB based amplifiers tend to perform better over a XLR input and using a PSU with 36 to 39V and generous amperage (say 10A ?). Hence the 39V/10A spec. The problem is that such a PSU, if from a reliable manufacturer (Mornsun, medical Meanwell, etc.), could be as expensive as the amplifier board itself.

All in all a plain amplifier (TPA3255 PFFB) with XLR input only, no sub-out, no other gimmiks and internal 39V/10A PSU, would be interesting if sold with a price tag of 200 to 250€. It will happen, eventually; if not from Fosi, then from one of the other ChiFi manufacturers.

the whole numbers are fine and good, but still, even with 80dB Sinad, the bottleneck is your speakers You will not hear ANY differences between 80db sinad and 100db sinad even with high-end speakers. also, we need to consider the ambient sound of the room while listening. so, why be mad about all those numbers and paying 3-4 times more for the specs you can't even hear in real life?

 

[Audiophilius]

Hello and greetings from Germany.

I have a question about my fosi.

I have a little problem with that. When I turn up the volume control from zero to the first tone, I first get sound on the left channel and later also on the right.

Do you have that too?

Can you please try it out? That would be very nice.

Have a nice day

 

[Power Pop 23]

Hello and greetings from Germany.

I have a question about my fosi.

I have a little problem with that. When I turn up the volume control from zero to the first tone, I first get sound on the left channel and later also on the right.

Do you have that too?

Can you please try it out? That would be very nice.

Have a nice day

I can replicate your experience but I get sound out of the right channel before I hear sound from the left channel. I control the volume of my ZA3 with another device and had not noticed this. Thank you.

 

[Zek]

I first get sound on the left channel and later also on the right.

I get sound out of the right channel before I hear sound from the left channel.

This indicates that the input potentiometers are of poor quality and do not control the left and right channels equally.

 

[Audiophilius]

I can replicate your experience but I get sound out of the right channel before I hear sound from the left channel. I control the volume of my ZA3 with another device and had not noticed this. Thank you.

Hi, thanks for your reply.

I know that analog potentiometers always have a difference in the lower range. Sometimes more, sometimes less, my Marantz pm 8005 has that too. I wasn't sure if the fosi was digitally controlled.

Do I have any losses if I turn up the pot on the fosi and adjust the volume with my dac?

Greetings

 

[Power Pop 23]

Do I have any losses if I turn up the pot on the fozi and adjust the volume with my dac?

Greetings

It is my understanding there can losses that are measurable but are not audible. Others may be better versed to answer this question.

 

[Audiophilius]

It is my understanding there can losses that are measurable but are not audible. Others may be better versed to answer this question.

Thank you for the answer.

Luckily it's only in the lower area but still not good. I use xlr so the area is even more sensitive.

I still have the Smsl ao200mk 2, thanks to the digital control this problem doesn't exist.

Greetings

 

[T&T]

Still waiting for Fosi to send the Z3 to Amir?
I think Aiyima rush to send 07Max as is with 53v before went on sale, why?
And Fosi will send to Amir an upgraded version of the Z3, to manipulate the sales.
I have the 07Max with 63v capacitors, is way superior than the V3

 

[PlasticDoc]

why be mad about all those numbers and paying 3-4 times more for the specs you can't even hear in real life?

1. The added cost for the TI PFFB would be 15€ more, not 3-4 times more.
2. The added cost would be even less if using the so called "differentiating postfilter" (which is just a single 100pF capacitor that connects loudspeaker out to audio in, as described in the post "TPA3255 oscillation issues" at diyaudio.com). This one would cost a few cents only.
3. Regarding "the specs you can't even hear in real life", isn't audiosciencereview.com, the forum that yor are in, all about measuring (in order to improve) all those specs that can and that can't be heard in real life?
4. It is known, because it is in the manufacturer's spec. sheet and because it has been measured time and again, that the non postfilter feedback implementations of circuits based on the TPA3255, have a hump in the higher frequencies region that manifest on speakers with impedances on the highish side (>= 8R).

 

[howard416]

1. The added cost for the TI PFFB would be 15€ more, not 3-4 times more.
2. The added cost would be even less if using the so called "differentiating postfilter" (which is just a single 100pF capacitor that connects loudspeaker out to audio in, as described in the post "TPA3255 oscillation issues" at diyaudio.com). This one would cost a few cents only.
3. Regarding "the specs you can't even hear in real life", isn't audiosciencereview.com, the forum that yor are in, all about measuring (in order to improve) all those specs that can and that can't be heard in real life?
4. It is known, because it is in the manufacturer's spec. sheet and because it has been measured time and again, that the non postfilter feedback implementations of circuits based on the TPA3255, have a hump in the higher frequencies region that manifest on speakers with impedances on the highish side (>= 8R).

To your 1), isn't that just half the story? What do you do about the lost gain?

 

[PlasticDoc]

To your 1), isn't that just half the story? What do you do about the lost gain?

What lost gain? It seems that there is no evidence of it in amirm's review of 3e audio TPA3255 260-2-29A Amplifier Review (a properly engineered TPA3255+PFFB).

 

[saberger0357]

Couldn't resist and bought one direct from Fosi yesterday. Since I already have a two other Fosi's, and two Ayima's, didn't need a PSU, so hundred and change was the damage. I'll be surprised if it's that much better then either the V3 or a07 to make it worth the money, but curiosity got the best of me. And it will also get the best of me when I decide to order the a07 Max. Just waiting for Amazon to have a sale on that one.

 

[Joe Smith]

I continue to eagerly await Fosi coming out with a V3 form factor solid-state preamp, or a small integrated amp with multiple inputs and a remote.
Now that Schiit has apparently discontinued the Saga S preamp, there's a wonderful slot for a baby integrated or pre in the $200 range for the overseas manufacturers.

 

[gizmo90]

I continue to eagerly await Fosi coming out with a V3 form factor solid-state preamp, or a small integrated amp with multiple inputs and a remote.
Now that Schiit has apparently discontinued the Saga S preamp, there's a wonderful slot for a baby integrated or pre in the $200 range for the overseas manufacturers.

I came to this thread to say the same thing. An integrated would be awesome. Be even cooler if they used two TPA chips for BTL and built in PSU.

 

[ViperDom]

Can these be effectively used as monoblocks in a 2.X system?
Any concern that every time you turn them on/off by pushing the volume knob the L-to-R levels will get out of wack?
Similar concern for multichannel system...

Questions:
1. Is the analog dial smooth in action or is it notched such that the level stays put if you carefully push straight into it to turn on/off?
2. If you have multiple units plugged into a common powerstrip can you turn them all on at once by flipping the strip's switch or do the fosi amps still require the button push to be activated?

 

[doug s.]

i looked at this amp and at the v3; unless one really needed balanced inputs, i don't see why one wouldn't simply buy the v3.

sinad on the v3 is 88db vs the za3's 89db, but distortion specs are half, snr is 4db better, and power is 50% more. (at least per mfr; it seems asr's/amir's v3 measurements indicate the specs are optimistic? i've not seem measurements of the za3's).

retail prices (15% discount coupon is offered at present) are $90/32v; $110/48v; $140/48v-gan for the v3, vs $130/32v; $150/48v; (no gan ps offered?) for the za3.

does the za3 sound better than the v3? i've just started reading the asr reviews, and haven't seen that. if you want two amps, just buy the two v3's; and only use one channel; it will still make similar (or more?) power than za3's bridged. and, the subwoofer out "feature" is worthless, imo, as subs should be run in stereo, w/the mains hi passed, so they and their amp(s) won't see the low frequencies.

comments appreciated.

thanks,

doug s.