Fosi Audio ZA3 Amplifier Review

[HalSF]

It’s interesting to see the monoblock focus with the Fosi V3 migrate to the nominally stereo ZA3..

I’ve been happily using a single ZA3 to drive a pair of SourcePoint 8 speakers for about six months now. It replaced a vintage big-iron Musical Fidelity A/B amp without any discernible loss in sound quality and power.

 

[SoySalsaPicante]

It’s interesting to see the monoblock focus with the Fosi V3 migrate to the nominally stereo ZA3..

I’ve been happily using a single ZA3 to drive a pair of SourcePoint 8 speakers for about six months now. It replaced a vintage big-iron Musical Fidelity A/B amp without any discernible loss in sound quality and power.

Gotta' love SourcePoint 8. Simply amazing speakers, and not terribly hard to drive!

 

[scruffy1]

four weeks in and a bit of tuning the balance given speaker placement, and reverting the xlr to 4v (because afaik there's no great benefit to a hot signal... although happy to take advice), and i have to say it has been a wonderful experience

i'm really enjoying the clarity and dynamics

 

[Witterings]

I've a pair set up as monoblocks using a Bluesound Node as Preamp and for sub out and crossover set to 90Hz.

I had been using them at 3/4 volume but the day before noticed one channel sounded very "muffled" so turned them both up to full using the Node to control the volume and the muffled sound disappeared.

I don't normally play music loud in this room but yesterday cranked it up quite a bit but probably only 60% on the volume on the Node and noticed there was quite a bit of distortion when I did.
I tried switching the sub off so the mains were full range and it did sound better but I wonder if the extra range was masking the distortion.

My speakers are Elac B5.2.

Anybody any ideas if turning them up to full may have introduced the distortion although I do wonder if one of the amps has something wrong with it due to the "muffled sound" I was experiencing al lower volume on the one channel.

 

[yallkok]

I'd like to share a test I performed with you.
I purchased a Fosi filter and applied it to the power supply of the ZA3.
I also added a ferrite core near the connector.
I noticed a big difference.
You might call it a placebo effect.
Instead, I noticed a big difference in the bass, which became faster and much more dry.
I have some reference tracks with high compression that I had trouble listening to before.
Has anyone else tried the same setup?

 

[Pulkass]

I'd like to share a test I performed with you.
I purchased a Fosi filter and applied it to the power supply of the ZA3.
I also added a ferrite core near the connector.
I noticed a big difference.
You might call it a placebo effect.
Instead, I noticed a big difference in the bass, which became faster and much more dry.
I have some reference tracks with high compression that I had trouble listening to before.
Has anyone else tried the same setup?

What the heck is a Fosi filter?

 

[SoySalsaPicante]

What the heck is a Fosi filter?

Probably the filter that comes with a pair of V3 Monos but one PSU and a y-split cable.

More importantly what is dry? What is wet?

 

[staticV3]

What the heck is a Fosi filter?

Fosi Audio DC Power Filter

Noise suppression: Through the combination of filter capacitors and inductors, the power filter effectively suppresses conducted and radiated interference, reducing the impact of electromagnetic interference on devices. Power purification: Filters out high-frequency noise and harmonics from the...

fosiaudio.com

Originally designed for powering two V3 Monos off a single 48V10A supply with a Y-splitters, to help with noise issues that arise from that: https://www.ti.com/lit/an/slaa787/slaa787.pdf

 

[yallkok]

Yes, exactly that filter.
I was convinced first by the very reasonable price and then by a user's comment under the product description (also attaching the following images):
"I use it with ZA3. I measured what effect this product has. The second photo is without it, the noise is 180mVpp. The first photo is with it, the noise went down to 80mVpp.
In my environment, I was able to reduce noise by more than half. I think this is a very cost-effective product."

 

[antcollinet]

Fosi Audio DC Power Filter

Noise suppression: Through the combination of filter capacitors and inductors, the power filter effectively suppresses conducted and radiated interference, reducing the impact of electromagnetic interference on devices. Power purification: Filters out high-frequency noise and harmonics from the...

fosiaudio.com

Originally designed for powering two V3 Monos off a single 48V10A supply with a Y-splitters, to help with noise issues that arise from that: https://www.ti.com/lit/an/slaa787/slaa787.pdf

It will of course make no difference for noise coming from mains.

 

[antcollinet]

I was able to reduce noise by more than half. I think this is a very cost-effective product."

Except you are looking at PSU noise - which unless severe, makes no difference at the output of the amp, due to the massive PSRR of these devices.


The output noise of this amp with the stock power supply is around 14uV (micro volts) - less than 1/3500th the level of the PSU noise shown in your (unfiltered) measurements. And I'd be prepared to bet that little to none of that output noise comes from the PSU noise.

 

[HalSF]

I'd like to share a test I performed with you.
I purchased a Fosi filter and applied it to the power supply of the ZA3.
I also added a ferrite core near the connector.
I noticed a big difference.
You might call it a placebo effect.
Instead, I noticed a big difference in the bass, which became faster and much more dry.
I have some reference tracks with high compression that I had trouble listening to before.
Has anyone else tried the same setup?

As someone currently using the ZA3 as the amp in my main system, I’m puzzled by the reasoning here - that “I have some reference tracks with high compression that I had trouble listening to” therefore a Fosi filter and a ferrite core added to the chain make sense and now those tracks sound okay plus the bass is “faster” and “much more dry.”

I just don’t recognize the problem much less the efficacy of the solution here. I hear no noise or distortion or bass problems with the ZA3.

 

[Gilbus]

Hello guys.
I want to buy a compact class D amplifier. I have a pair of Polk ES15 and the amplifier will be coupled with a wiim pro streamer. Would the ZA3 be a good choice for a budget of at most 200€? There are better alternatives?
Thank you very much.

 

[AudioSceptic]

Hello guys.
I want to buy a compact class D amplifier. I have a pair of Polk ES15 and the amplifier will be coupled with a wiim pro streamer. Would the ZA3 be a good choice for a budget of at most 200€? There are better alternatives?
Thank you very much.

I would go to the review index at <https://www.audiosciencereview.com/forum/index.php?pages/Reviews/> and see what else has been tested here. There'a a search box and you can sort on any of the columns.

 

[xanalog]

Fosi Audio DC Power Filter

Noise suppression: Through the combination of filter capacitors and inductors, the power filter effectively suppresses conducted and radiated interference, reducing the impact of electromagnetic interference on devices. Power purification: Filters out high-frequency noise and harmonics from the...

fosiaudio.com

Originally designed for powering two V3 Monos off a single 48V10A supply with a Y-splitters, to help with noise issues that arise from that: https://www.ti.com/lit/an/slaa787/slaa787.pdf

Thank you @staticV3,
I bought one with plans to possibly use it for a car-audio application, which I am slowly gathering hardware for.
Lacking any (FOSI provided) substantive data about its filtering characteristics, I am hoping the filter may come in handy if the 2 FOSI CA30 PowerAmps show noise issues.
But this:

... is iffy.

 

[antcollinet]

Thank you @staticV3,
I bought one with plans to possibly use it for a car-audio application, which I am slowly gathering hardware for.
Lacking any (FOSI provided) substantive data about its filtering characteristics, I am hoping the filter may come in handy if the 2 FOSI CA30 PowerAmps show noise issues.
But this:
View attachment 540338
... is iffy.

What is iffy about it?

 

[staticV3]

Hello guys.
I want to buy a compact class D amplifier. I have a pair of Polk ES15 and the amplifier will be coupled with a wiim pro streamer. Would the ZA3 be a good choice for a budget of at most 200€? There are better alternatives?
Thank you very much.

I'd buy either the 3e Audio A5se, or the Topping Mini300.

Both have no load dependent frequency response, and both have noise and distortion that's at the limit of what the TPA325x can do.

Fosi, Aiyima and co OTOH tend to leave some potential on the table.

Edit:
Also, I'd apply the following Parametric EQ parameters using the WiiM Pro, for a more neutral in-room response:

Preamp: -3.3 dB

Filter  1: ON PK Fc   621 Hz Gain -2.22 dB Q 2.97
Filter  2: ON PK Fc  2168 Hz Gain +1.37 dB Q 1.10
Filter  3: ON PK Fc  3650 Hz Gain -2.95 dB Q 2.50
Filter  4: ON PK Fc  6585 Hz Gain -2.50 dB Q 3.00
Filter  5: ON PK Fc 11476 Hz Gain -2.15 dB Q 2.62

Those filters are designed to correct the Polk ES20's midrange and treble:


Although we don't have data for the smaller ES15, other bookshelves from Polk have measured fairly similar between smaller and larger models:

 

[Gilbus]

I would go to the review index at <https://www.audiosciencereview.com/forum/index.php?pages/Reviews/> and see what else has been tested here. There'a a search box and you can sort on any of the columns.

Thank you very much. I sow that and there are indeed other possible choices. For exemple there are the Topping Mini 300 and PA5 II or the AYIMA A80 and A20 that could be interesting but I do not know exactly how to choose.

 

[xanalog]

What is iffy about it?

I hate to answer yours w/3, but I must...
Can you tell me what this thing exactly filters? In an objective manner?
When I see someone saying audio "filter", I instantly visualize an insertion loss versus frequency plot.
What do you visualize?

 

[Richard G]

I'd buy either the 3e Audio A5se, or the Topping Mini300.

Both have no load dependent frequency response, and both have noise and distortion that's at the limit of what the TPA325x can do.

Fosi, Aiyima and co OTOH tend to leave some potential on the table.

Edit:
Also, I'd apply the following Parametric EQ parameters using the WiiM Pro, for a more neutral in-room response:

Preamp: -3.3 dB

Filter  1: ON PK Fc   621 Hz Gain -2.22 dB Q 2.97
Filter  2: ON PK Fc  2168 Hz Gain +1.37 dB Q 1.10
Filter  3: ON PK Fc  3650 Hz Gain -2.95 dB Q 2.50
Filter  4: ON PK Fc  6585 Hz Gain -2.50 dB Q 3.00
Filter  5: ON PK Fc 11476 Hz Gain -2.15 dB Q 2.62

Those filters are designed to correct the Polk ES20's midrange and treble:
View attachment 540341

Although we don't have data for the smaller ES15, other bookshelves from Polk have measured fairly similar between smaller and larger models:
View attachment 540342 View attachment 540343

EXCELLENT information

Respect and thank you