Fosi Audio's First Dual-Mode Balanced Amplifier ZA3

[somebodyelse]

Will it not split the 2v input resulting weak input?

Only if your source has unusually high output impedance.

 

[GGroch]

Only if your source has unusually high output impedance.

Agreed. And there will be no difference in this from amps like the Fosi V3 that are wired as described by carpman. There is already a "y" adapter splitter, it is just inside the amp.

 

[Guddu]

Agreed. And there will be no difference in this from amps like the Fosi V3 that are wired as described by carpman. There is already a "y" adapter splitter, it is just inside the amp.

I thought external split, not internal. All good.

 

[Aaronb1138]

I like it a lot, ordered! (#3).

Some suggested changes before release:

- Mono/Stereo should be moved to bottom or back to avoid expected volume changes or electrical failures. What happens if you switch it by mistake?

- The Mono Balanced/Unbalanced input on the back should be labeled. What happens if you have both L/R inputs connected in mono mode?

- The Power switch should be moved from the volume knob to where the Input switch is now, and the Input moved to the Mono/Stereo spot. This is no big deal on the V3, but on dual mono amps keeping the volume precisely the same, and controlling things through a pre-amp is important. With the power switch in the volume you have to re-adjust each time. What happens when you have 2 amps connected in mono? Could there be a way to have one amp control both? A volume controlled Pre-out could perhaps work that way.

Trey To asks a good question in the Kickstarter comments: "When the amplifier is off, is the signal still getting passed through the sub out?" If you move the power switch that would become more important.

1) Agree on the moving the Mono / Stereo switch to the back with a slider switch as many are advocating.

2) Disagree with all who have said to move the input switch to the back. Personally I have a very simple use case -- and I think many other enthusiasts will have the same, which is 2 input devices.

In my case I have an SMSL D-6 and a turntable. I suspect many others might have a similar setup. For my Fosi V3, I finally got out an old school GE branded RCA audio + video (composite + S-video) switch box to stop swapping RCA cables. Interestingly enough, I got the SMSL D-6 for the ability to go to balanced inputs in the future, namely if the LA90 got a permanent "fix" for reliability. With the ZA3, I could yank the RCA switch box out of the cabling.

3) For symmetry on the front, move the XLR / RCA toggle to the right and replace the left toggle with On / Off / Trigger 3-way toggle (or 2-way [On] / [Off | Trigger]). The 12v trigger makes no sense unless it operates exclusively as a Power+Volume defeat, which is the most logical mode of operation given the lack of On / Off / Trigger switch. An On / Off / Trigger switch re-enables the Volume control assuming the existing trigger is in fact a Power+Volume defeat (otherwise how does 12v Trigger work???).

4) Not a fan of the Sub Out, would much prefer the fully buffered / input isolated A07 stereo output approach with no filters. I'm not sure what all the people asking for filters and slopes is about, I would much prefer that low pass and high pass (rumble) filtering be built into my sub amp with selectable 12 vs 24 dB slopes. Heck, I would rather use one of these - https://www.amazon.com/Amplifier-Audio-Subwoofer-Equalizer-Controller/dp/B07D6JTD4V/ if I am using a full range amp as a sub amp than have that extra cost of filters built into an amp.

5) PFFB. If implementing a PFFB can get to around a 94 or higher SINAD as seen with the JL Sylph D200, I think it makes a good case for a $120-150 (higher?) USD price point with a sufficiently stout 40-48v PSU at >5A. Oh, and go to Coilcraft or similar higher quality inductors if there is a sound quality or current handling increase to be had. The Fosi ZA3 here is claiming the same 88 SINAD of the V3, so the *only* big compelling feature is bridged mode.

All of that said, I doubt Fosi will be revising this device as much. I'll probably wait for them to release something with PFFB.

When Fosi, Aiyima, and others return to revising their "all in one" integrated designs with Bluetooth and 2.0/2.1 outputs (i.e. BT30D Pro / A07 Pro), it's worth an extra $10-20 for most people to get a remote for input, volume, and power control. If it has volume and BT input options, it really needs a remote. And either digital volume display (e.g. SMSL D-6) or volume tic mark LED arc around the volume knob while using an encoder wheel for volume if that is cheaper than motorized volume pots for remote control.

In the very opposite direction, as with the V3, ZA3, and A07 Max, a stripped down version with stereo / bridge mono, no volume control, just a trigger / power switch, integrated PSU (or shared across multiple "big brick" external PSU), and maxed out output quality definitely has a place in the market as shown by Topping.

In the bridged mono sub amp market, something of similar quality to the A07 Max / ZA3, built as mono only (save some parts cost), trigger / auto-sense input on (i.e. like many car amps) with low and high pass line level filtering. Put in a switch or jumper for 12 vs 24 dB per octave slope on the low pass and maybe 18 or 24 dB / octave for high pass. If I recall my electrical engineering correctly, a jumper or toggle switch should let you do a pretty easy 12 db / octave 80-300 Hz low pass that switches to 24 dB / octave 40-150 Hz low pass, allowing both ends of integration -- desktop / PC speakers playing down to ~200Hz with gentle roll off to a small sub versus more audiophile or home theater integration with larger speakers and a bigger sub. High pass for rumble filtering / sub protection should be at least 18dB / octave with a range ~12-50 Hz for various interesting homebrew subs like tapped horns and higher order enclosures that need a steep slope for driver protection. Another interesting design feature for dedicated sub amps would be a chassis design that can be either shelf / desktop based and has mounting holes to hang it on the back of a sub like a plate amp.

As far as cheap features that would be selling points to a wider audience, I'm waiting to see the first class D chip amp that includes a heat pipe between the chip and chassis as marketechture. It's largely unnecessary (?) for such fast transient cooling except perhaps in the above sub amp example running at topped out input voltage such as 52v input with 8-10A behind it and running hotter at all times.

 

[TonyJZX]

btw. Aiyima seem to want to upstart Fosi with this:

New AIYIMA TPA3255 amp

AIYIMA introduced a new amplifier with a TPA3255 chip and two VU meters. https://www.aliexpress.com/item/1005005921346880.html

audiosciencereview.com

but this isnt Aiyima's first daliance with XLR

 

[mike70]

I think the ZA3 is almost perfect ... it have a caveat with the not linear loading and then some functional / "cosmetic" things, like the highly exposed mono/stereo switch.

A ZA3 V2 with PFFB and that details "fixed" will be the perfect little amp. Something to forget about the cheaper Hypex products.

If the topping pa7 shows good reliability (it meets the previous reqs), would be the "saint grial" ... even the price tag is very close to Hypex.

 

[Jeromeof]

btw. Aiyima seem to want to upstart Fosi with this:

New AIYIMA TPA3255 amp

AIYIMA introduced a new amplifier with a TPA3255 chip and two VU meters. https://www.aliexpress.com/item/1005005921346880.html

audiosciencereview.com

but this isnt Aiyima's first daliance with XLR

I could be wrong but I would guess that AliExpress product isn't Aiyima or possible its a Aiyima board (as they sell plain board) packaged up by someone else with their own case

 

[GGroch]

I could be wrong but I would guess that AliExpress product isn't Aiyima or possible its a Aiyima board (as they sell plain board) packaged up by someone else with their own case

The last post in the thread you link to has Aiyima indicate genuine new products often start off without branding. It is the official Aiyima store.

 

[zeluxao]

The cut-off frequency range for the sub out is 20-300Hz.

Due to the restriction of the 32V/5A PSU, the power difference is not much. Anyway, we'll put a 48V/5A PSU as standard so you can get enough power.

Please, please, please add a volume bypass switch. It would make much more sense for use in mono mode. This would take care of volume matching with other units, making them essentially power amps. You could put it on the bottom. Oh, you could've kept the logo on top like in the v3. I thought that was a nice touch.

 

[TikBLang]

BTW, I changed my mind. I am more interested in a minimalist design where you just have a nice 'not' so bright power LED in front. (maybe just the logo is lit to cut cost) and that's it. This is a power amp and the volume, tone control, etc must be from a well-built preamp.

So if the new 'Fosi Audio power amp' will have the bridge output and no volume control, I will consider getting two. Heck, even a nice KIT (just a board) should also be an option to save money just like M03 but bare and with an option of not getting the power supply.
•Mode: Stereo (nice to have)
: Mono (bridge output - to get more power)
•Input: RCA (XLR is not a must)
•Output: Speaker Out, Sub Out (again sub out is an option)
•Amp Chip: Texas Instrument TPA3255
•Stereo Mode: 180W*2 @4Ω
•Mono Mode: 30W to 120W @8Ω
•Frequency Response: 20Hz-20kHz (±0.1dB)
•Power Input: DC 18V-48V

 

[GGroch]

For those who are following the A07-Max Stereo/Mono amp thread, it appears that Aiyima did not realize until 10/19 that only the Left Input on that amp is active when in Mono Mode. This is an important detail to have missed on an already shipping product and resulted in several pages of misinformation and will require a user manual rewrite.

The ZA3 may work the same way, or not. It has both XLR/RCA so may be different.

Fosi will certainly let us know, and as I previously suggested label the mono inputs on the rear panel, right?

In the A07-Max discussion it was pointed out that there are advantages to using a single input (Left), or summing both Left and Right for Mono Mode, depending on your use case. If you are powering a single speaker in its own zone (a kitchen perhaps) then summing would be good.

 

[Jeromeof]

For those who are following the A07-Max Stereo/Mono amp thread, it appears that Aiyima did not realize until 10/19 that only the Left Input on that amp is active when in Mono Mode. This is an important detail to have missed on an already shipping product and resulted in several pages of misinformation and will require a user manual rewrite.

The ZA3 may work the same way, or not. It has both XLR/RCA so may be different.

Fosi will certainly let us know, and as I previously suggested label the mono inputs on the rear panel, right?

In the A07-Max discussion it was pointed out that there are advantages to using a single input (Left), or summing both Left and Right for Mono Mode, depending on your use case. If you are powering a single speaker in its own zone (a kitchen perhaps) then summing would be good.

I think the difference is really whether Mono as a feature means wanting just mono (i.e. summed) output or Mono means enabling the Amp for use in a pair as a separate Monoblock.

 

[carpman]

I think the difference is really whether Mono as a feature means wanting just mono (i.e. summed) output or Mono means enabling the Amp for use in a pair as a separate Monoblock.

Exactly. You'd ideally have a switch on the back or underneath that had: Stereo, Mono (Summed), Mono (Block) - or whatever description will not confuse the hell out of people. And certainly a clear manual to go with the product with pictorial wiring examples.

EDIT:

Or:

• Stereo
• Mono (Solo) -- -i.e. summed
• Mono (Paired) -- i..e. mono block

C.

 

[TikBLang]

Exactly. You'd ideally have a switch on the back or underneath that had: Stereo, Mono (Summed), Mono (Block) - or whatever description will not confuse the hell out of people. And certainly a clear manual to go with the product with pictorial wiring examples.

EDIT:

Or:

• Stereo
• Mono (Solo) -- -i.e. summed
• Mono (Paired) -- i..e. mono block

C.

This confusion makes me not to read the specs further. Being a total beginner, I'll be a bit happier if all these Chinese amp makers will make it so obvious (being bold/clear and mark their product) if they are talking in root-mean-square or in Peak-music-power-output so one can easily add everything up in your head. Most of them just simply indicate the wattage and at the back of my head, I'm thinking if the device (speaker and amps) are all rated in rms. Still hoping...

 

[Slayer]

I apologize if this has been said already, but i didn't see it anywhere.
@Fosi Audio I would like to see a gain (input sensitivity) knob adjustment on the rear of the amp. What is the gain currently?

 

[Guddu]

Exactly. You'd ideally have a switch on the back or underneath that had: Stereo, Mono (Summed), Mono (Block) - or whatever description will not confuse the hell out of people. And certainly a clear manual to go with the product with pictorial wiring examples.

EDIT:

Or:

• Stereo
• Mono (Solo) -- -i.e. summed
• Mono (Paired) -- i..e. mono block

C.

Don't think there is any such implementation available with 1 stereo and 2 different mono modes (probably except some evaluation board).
But:
Stereo - normal operation
For non-PBTL, single channel - you can simply connect 1 RCA channel and get single speaker output
For PBTL - A switch or jumper would do the job, but the output isn't too far higher than BTL.

Example: Many implementations limit it to approx. 1 x 250.

Have you come across any 1 x 600 implementation, would be good to know?

*** I might be partially correct on this, would expect someone to chime in to help in that case.

 

[carpman]

For non-PBTL, single channel - you can simply connect 1 RCA channel and get single speaker output

Yes, but this doesn't give you (summed) mono (so you'd have to feed the amp a mono signal first) - it just gives you a single channel (Left OR Right). Who of those that have a single (non-sub) speaker to hand, want to listen to just one channel of a stereo mix? Thus the point @Jeromeof made which I agree with. There are 3 potential users: 1) Stereo, 2) Mono-Single-Speaker (Summed), 3) Mono-Dual-Speaker (Monoblock / Paired).

If the amp doesn't do the summing, then it has less appeal, for me at least.

C.

 

[Guddu]

Yes, but this doesn't give you (summed) mono (so you'd have to feed the amp a mono signal first) - it just gives you a single channel (Left OR Right). Who of those that have a single (non-sub) speaker to hand, want to listen to just one channel of a stereo mix? Thus the point @Jeromeof made which I agree with. There are 3 potential users: 1) Stereo, 2) Mono-Single-Speaker (Summed), 3) Mono-Dual-Speaker (Monoblock / Paired).

If the amp doesn't do the summing, then it has less appeal, for me at least.

C.

Okay, Can you point me to an amplifier which does this summing, want to see how does it work and look.

P.E. I meant TPA3255 based amplifier

 

[Zek]

2) Mono-Single-Speaker (Summed),

What is the purpose of such a way of connecting a stereo source to a mono amplifier?

 

[carpman]

What is the purpose of such a way of connecting a stereo source to a mono amplifier?

This kind of thing - when you've got a spare speaker and a quiet kitchen.