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Fosi Audio's First Dual-Mode Balanced Amplifier ZA3

ninetylol

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Williston Audio reviewed the amp and ran it on his SMD amp dyno AD-1 with the 48v 5 amp power block. It made
94w & 97w @ 1% distortion @ 8ohms
177w & 174w @ 1% distortion @ 4ohms
Mono it got interesting.
106w 1% @ 8ohms
193w 1% @ 4ohms.
So it appears the mono isn't bridged.
Interesting. So 30% more power than Aiyima a07 Max with 48v supply (which is fosis 48v supply in amirs tests)

Can anyone explain how they get more Juice from the chip or are the differences according to test methology?

Also mono seems useless in terms of more power.
 

K.Kevin

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Interesting. So 30% more power than Aiyima a07 Max with 48v supply (which is fosis 48v supply in amirs tests)

Can anyone explain how they get more Juice from the chip or are the differences according to test methology?

Also mono seems useless in terms of more power.
That’s wrong, you must have read the wrong graphs.

Amirs A07 Max review has more power in every measured metric than the reported ZA3 dyno test.

If we’re taking 1% distortion 48v bridged output, the Aiyima has around 225watts and the ZA3 reportedly 193w.

There are two complicating factors before drawing conclusions: firstly we are comparing results from two different reviewers with two different sets of equipment. Secondly, the YouTube channels dyno test was only at 1khz, and so it could be that the A07max has less power in other frequencies or the ZA3 has more power at other frequencies (that’s something Amir typically tests but that Williston channel doesn’t)

This is why I’m waiting for either Amir to review the ZA3, or for Williston to review the A07Max so we can have more clear apples to apples comparison.

One reason to believe the data is that previously the A07(regular) had more power than the V3 too. Both Amir and Williston’s reviews of those two confirm that. Aiyima seems to do something different that results in more power, at the expense of less Sinad. Fosi seems to prioritize Sinad, and seems to have less power.
 

Middle Earth

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@Fosi Audio admin mentioned it in response to my comment asking for such a thing on their Facebook group
Timeline unknown
 
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ninetylol

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That’s wrong, you must have read the wrong graphs.

Amirs A07 Max review has more power in every measured metric than the reported ZA3 dyno test.

If we’re taking 1% distortion 48v bridged output, the Aiyima has around 225watts and the ZA3 reportedly 193w.

There are two complicating factors before drawing conclusions: firstly we are comparing results from two different reviewers with two different sets of equipment. Secondly, the YouTube channels dyno test was only at 1khz, and so it could be that the A07max has less power in other frequencies or the ZA3 has more power at other frequencies (that’s something Amir typically tests but that Williston channel doesn’t)

This is why I’m waiting for either Amir to review the ZA3, or for Williston to review the A07Max so we can have more clear apples to apples comparison.

One reason to believe the data is that previously the A07(regular) had more power than the V3 too. Both Amir and Williston’s reviews of those two confirm that. Aiyima seems to do something different that results in more power, at the expense of less Sinad. Fosi seems to prioritize Sinad, and seems to have less power.
Im talking about Stereo measurements which Show ZA3 with 30% more power. (177W)

See:
AIYIMA A07 MAX stereo amplifier Power 4 ohm Bridged 48 volt power supply stereo sweep measurem...png
 

K.Kevin

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Im talking about Stereo measurements which Show ZA3 with 30% more power. (177W)

See:
View attachment 338033

You need to read up on how to read these graphs, or watch Amir’s tutorial video. You do not understand the numbers being compared because you keep quoting the ZA3’s 177w measurement when that’s not technically apples to apples.

The specific screenshot you posted is not of 1% distortion but of spec. Williston audio’s numbers were for 1% distortion. That is where they got 177w

I can grant you that Amir’s measurements said it shut down at 138w, so you may be thinking: necessarily, it could not meet 177w. But I have a hard time believing that wasn’t a unit to unit issue with Amir’s A07max. Other tests show the A07regulsr and the V3 have both had no problem getting more than 138w 2ch driven at 4 ohm. The 1% distortion specs for them from Williston are: 163 and 172 for the A07regular and V3 respectively. The A07max has upgraded design and ventilation to the regular A07, there is no reason it would shut down when the regular A07 doesn’t, unless it’s a faulty unit (which is maybe a bad mark against buying it for poor QC, but not on its actual ideal performance numbers)


Like I said, the A07 max appears to have more power (so far) everywhere else, it’s just excluding the amp shut-down in Amir’s review. I’m looking forward to Amir’s review of the ZA3 to complete the data set
 

G-Can

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Who cares,

I believe Fosi would be smart to come up with straight forward mono amp, or even pack them up in one box, it shouldn't be that complicated. Heck, they could make 2ch power amp, 3ch power amp, just stacking a few of ZA3 in one box
 

Hertel

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Talvez já tenha sido respondido neste tópico e eu não o tenha encontrado, mas basicamente:

Qual é o propósito de operá-los como monoblocos se a potência de saída aumenta apenas 10% ou 20%? A potência não deveria quase dobrar no modo bridge?

Em outras palavras: Qual é a vantagem de comprar dois e operá-los no modo mono quando a potência é essencialmente a mesma? Isso é realmente destinado apenas a pessoas com alto-falantes de 2 ohms?

Editar: Além disso, li sobre o PFFB, mas ainda não encontrei uma boa descrição de como ele altera especificamente o som do amplificador. Entendo perfeitamente como é um design melhor em geral, mas é uma tecnologia que deixaria o ouvinte entusiasmado em comparação com um designer de placa?

Talvez Fosi ou outra pessoa pudesse descrever em termos leigos *por que* você gostaria de atualizar para dois amplificadores PFFB executados em modo mono, da perspectiva de um ouvinte.

Edição II: Acho que deveria voltar um pouco, uma das melhores descrições do 'porquê' do PFFB pode vir diretamente desses itens no whitepaper da TI:

".. 5. Ruído de saída O ruído de saída é quase reduzido pela metade para sistemas com PFFB implementado. Quanto menor o nível de ruído, melhor os usuários serão capazes de ouvir os pequenos detalhes no áudio..."

".. 7. THD + N vs Potência .. esta curva é útil para ver como o amplificador funciona em potências mais baixas que são críticas para o som do amplificador em volumes de sala típicos, como 1 W a 10 W. ... Quanto mais baixo o desempenho de potência, que é muito crítico para a forma como um amplificador realmente soa ao ouvido humano, é melhorado em aproximadamente 5 dB com esta configuração PFFB....


Portanto, devo presumir que você poderia ouvir mais detalhes em volumes muito baixos, já que pode estar usando isso em campo próximo?

.
The way Fosi implemented the mono mode (PBTL) in the ZA3 does not allow for a large gain in power. I don't know, however, if this is a limitation of PBTL or the fact that each ZA3 already has two tpa3255s connected in bridge mode, not allowing this to be done a second time with another ZA3 to double the power. Despite this limitation, the monoblock mode implemented by Fosi has two benefits: the first is a better separation of the left and right channels and the second is more current for the speaker at frequencies where the impedance drops to close to 2 ohms. Be aware that even speakers labeled as 8 ohm at some frequencies may have a significant drop in impedance. In this case, they will require a lot of electrical current from the source and being in monobloc mode can be an advantage.

I could be wrong, but it seems like you are confusing the way Fosi implemented the monoblock in the ZA3 (PBTL), with PFFB (Post-Filter Feedback). This feature, whose advantages you described, was not implemented by Fosi in the ZA3, but is expected to be implemented by the monoblock that the brand is developing.
 
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pollock0424

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Does anyone know if this will experience bus pumping issues when driving low impedance 87db efficiency speakers? My Purifi 1ET7040SA Buckeye Amps have been experiencing bus pumping.
 

jooc

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The way Fosi implemented the mono mode (PBTL) in the ZA3 does not allow for a large gain in power. I don't know, however, if this is a limitation of PBTL or the fact that each ZA3 already has two tpa3255s connected in bridge mode, not allowing this to be done a second time with another ZA3 to double the power. Despite this limitation, the monoblock mode implemented by Fosi has two benefits: the first is a better separation of the left and right channels and the second is more current for the speaker at frequencies where the impedance drops to close to 2 ohms. Be aware that even speakers labeled as 8 ohm at some frequencies may have a significant drop in impedance. In this case, they will require a lot of electrical current from the source and being in monobloc mode can be an advantage.

I could be wrong, but it seems like you are confusing the way Fosi implemented the monoblock in the ZA3 (PBTL), with PFFB (Post-Filter Feedback). This feature, whose advantages you described, was not implemented by Fosi in the ZA3, but is expected to be implemented by the monoblock that the brand is developing.

Thank you for the explanation on the FOSI monoblock implementation. It's interesting, but as of now I don't see how the ZA3 would be a better candidate to run class D monoblocks than the less expensive, more powerful and seemingly fully-bridgeable A07 Max. If I were to buy just one class D amp for a 2.0 or 2.1 stereo application I'd probably get the Za3 though.

Yes, I was also talking about PFFB in the same post, I wasn't confusing the two but just trying to cram two questions I had in one post.

1704133671493.png
 

K.Kevin

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Thank you for the explanation on the FOSI monoblock implementation. It's interesting, but as of now I don't see how the ZA3 would be a better candidate to run class D monoblocks than the less expensive, more powerful and seemingly fully-bridgeable A07 Max. If I were to buy just one class D amp for a 2.0 or 2.1 stereo application I'd probably get the Za3 though.

Yes, I was also talking about PFFB in the same post, I wasn't confusing the two but just trying to cram two questions I had in one post.

View attachment 338821
Aiyimas numbers you pasted have been proven false too though. A07Max has the same bridge functionality as the ZA3. It’s not a matter of one being “fully bridge able”, because they are both limited by the TPA3255 PBTL functionality. They are both “fully bridged” already.


The A07Max measurements suggest that it potentially has more power output than the ZA3 when in PBTL mono mode. However, it’s not double the power, or anything like that. It’s potentially 20-30watts more power measured at 1%thd. The reason I keep using “potentially” is explained in my previous post #366 in this thread.


Please do not spread misinformation. This thread is rife with people throwing “facts” and specs around that are simply not true.
 

jooc

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Please do not spread misinformation. This thread is rife with people throwing “facts” and specs around that are simply not true.

OK... But I'm not 'spreading misinformation,' I'm commenting on what appears to be the available data and looking for advice on interpreting what I'm seeing. Kinda the purpose of this forum, no?
 

K.Kevin

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OK... But I'm not 'spreading misinformation,' I'm commenting on what appears to be the available data and looking for advice on interpreting what I'm seeing. Kinda the purpose of this forum, no?
You spread misinformation when your post writes that the A07 Max is “more powerful and seemingly fully-bridgeable” than the ZA3 … (that part is copied and pasted from your post).

The “available data” you mention is not really all the available data is it? The data you’re referring to has already been dissected and discussed in this thread and in Amir’s A07Max review thread. And it’s basic forum etiquette to read prior posts so as to limit the repetitive “noise” with redundant posts flooding a thread.

One more gripe is Amir’s review of the A07max gives you verified numbers that will already show you those numbers you screenshotted are inaccurate. If you saw that review, I’m not sure why you would think the A07max is in any way more/fully “bridged” than the ZA3.

So yeah, glancing at some data, then commenting on it, without doing due diligence to make sure you haven’t missed other readily available data is what I consider misinformation to be more responsible/careful about.

I don’t mean to make a mountain out of a molehill here, but it’s just because it degrades the quality of these forums. Too many people on these threads feel compelled to waltz in and repeat/forward inaccurate claims they actually have no clue about… and nobody was forcing them to do it, they could have just said nothing, or come here with questions to learn more… I just call it out for what it is.
 

jooc

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You spread misinformation when your post writes that the A07 Max is “more powerful and seemingly fully-bridgeable” than the ZA3 … (that part is copied and pasted from your post).

The “available data” you mention is not really all the available data is it? The data you’re referring to has already been dissected and discussed in this thread and in Amir’s A07Max review thread. And it’s basic forum etiquette to read prior posts so as to limit the repetitive “noise” with redundant posts flooding a thread.

One more gripe is Amir’s review of the A07max gives you verified numbers that will already show you those numbers you screenshotted are inaccurate. If you saw that review, I’m not sure why you would think the A07max is in any way more/fully “bridged” than the ZA3.

So yeah, glancing at some data, then commenting on it, without doing due diligence to make sure you haven’t missed other readily available data is what I consider misinformation to be more responsible/careful about.

I don’t mean to make a mountain out of a molehill here, but it’s just because it degrades the quality of these forums. Too many people on these threads feel compelled to waltz in and repeat/forward inaccurate claims they actually have no clue about… and nobody was forcing them to do it, they could have just said nothing, or come here with questions to learn more… I just call it out for what it is.

Dude, what 'degrades the forum' is attitudes like yours. I wanted to ask a question about seeming discrepancies in the data in light of a purchase decision. Have a happy New Year.
 
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AdamG

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You spread misinformation when your post writes that the A07 Max is “more powerful and seemingly fully-bridgeable” than the ZA3 … (that part is copied and pasted from your post).

The “available data” you mention is not really all the available data is it? The data you’re referring to has already been dissected and discussed in this thread and in Amir’s A07Max review thread. And it’s basic forum etiquette to read prior posts so as to limit the repetitive “noise” with redundant posts flooding a thread.

One more gripe is Amir’s review of the A07max gives you verified numbers that will already show you those numbers you screenshotted are inaccurate. If you saw that review, I’m not sure why you would think the A07max is in any way more/fully “bridged” than the ZA3.

So yeah, glancing at some data, then commenting on it, without doing due diligence to make sure you haven’t missed other readily available data is what I consider misinformation to be more responsible/careful about.

I don’t mean to make a mountain out of a molehill here, but it’s just because it degrades the quality of these forums. Too many people on these threads feel compelled to waltz in and repeat/forward inaccurate claims they actually have no clue about… and nobody was forcing them to do it, they could have just said nothing, or come here with questions to learn more… I just call it out for what it is.
You can learn how to say this in a less aggressive and angry way. Try please. Thank you.
 

howard416

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my point is to get rid of the “integrated” aspect of this and focus more strictly on a power amp. It’s almost 2024 and if you’re not bi/triamping and utilizing DRC, you are way way behind.
These amps are almost the perfect modern solution. Almost
I feel like most of the people who plan to do active crossovers aren't the people who only have $150 for a 2-channel amp.

IMHO the niche for this type of amp is for a nearfield/smaller setup (e.g. PC/budget monitoring) where you have 2 bookshelf + 1 sub and you're looking for a low-complexity, medium cost system with "good enough" fidelity. Thus, sub-out saves a ton of setup time and a decent chunk of $$, while balanced helps significantly with grounding issues that would be more noticeable up close.

PFFB also would definitely push the amp into "good enough" territory. But, since you lose an appreciable amount of gain because of it, it would increase the cost of the amp since you now need an extra internal (very low noise) pre-amp stage to get back that gain. Fosi for sure would not want to sell an amp with less than 20 dB gain, probably closer to 24-26 in order to snag customers with sources maxing out around 1.5 V or so.
 

CamRector

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I feel like most of the people who plan to do active crossovers aren't the people who only have $150 for a 2-channel amp.
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.
 

G-Can

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Im at the point I need an power amp that would run two Kef Q300, as my AVR can decode full 11 channels, but only power 9, so need an amp with 12V trigger, that can give 80-90W connected to AVRs preouts.

ZA3 fits the bill pretty good, but Im open to options, under $300
I am currently using Fosi V3 with 48V brick (that I took from my desktop setup temporarily), and it does the job pretty good so far.

any ideas? should I wait for stock of ZA3 or is there anything remotelly similar. A07 max is out of equation due to no 12V trigger.
 

Guddu

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Im at the point I need an power amp that would run two Kef Q300, as my AVR can decode full 11 channels, but only power 9, so need an amp with 12V trigger, that can give 80-90W connected to AVRs preouts.

ZA3 fits the bill pretty good, but Im open to options, under $300
I am currently using Fosi V3 with 48V brick (that I took from my desktop setup temporarily), and it does the job pretty good so far.

any ideas? should I wait for stock of ZA3 or is there anything remotelly similar. A07 max is out of equation due to no 12V trigger.
ZA3 should do the job for your height channels with AVR, you should be good as long as you setup it up considering lower input sensitivity of ZA3.
 

G-Can

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ZA3 should do the job for your height channels with AVR, you should be good as long as you setup it up considering lower input sensitivity of ZA3.
I will be using it for the Fronts. They will pull way more power from the AVR then the heights, so Id rather let Fosi feed front speakers, at least thats my logic in my head :D
 
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