Fosi Audio ZA3 Amplifier Review

[GM3]

when I say I suggest they optimzied it for the ASR protocoll I mean that the whole product is designed like that

Just to be clear, is this something which can be affirmed, or just a possibility?

I'm not technically literate enough to be certain, but the way I interpreted the situation, it could also simply be that Amir's test procedures could be said to be somewhat incomplete, and fail to detect issues under certain conditions, ex; given particular speaker loads. Could very well be an oversight or just product limitation; not necessarily that entire lines of products were optimized for the ASR test procedure... Or is there some telltales of intent in the design?

That aside, I think that this revelation could be a shock for many, who believed that the current set of measurements basically demonstrated that they would work equally well in all cases, or even better than, class AB or other more expensive amps... (YMMV, interpretation, etc.) Turns out this may not be the case... Kind of a big deal, here's an example; I mean, I'm not blaming anyone, as given the industry going with measurements and somewhat dismissing subjective reports or opinions in favor of objective data is understandable... But at minimum, a lot of assertions, conclusions, etc., should be re-examined given this new data.

 

[hmt]

No, it is just a hypothesis and certainly possible. Affirmation will be difficult since no one would admit that. But I think it is well known that some of those Chinese Hifi brands (which abbreviation may not be spoken out) did some research in forums like this in the past to develop a market for those products. It may work out well but in some cases not so. I mean, this SINAD record DACs don't come out of nowhere.

 

[Xcaliber]

I saw a lot of people suggesting to set the gain/volume at MAX on these TPA amps, then adjust the volume from the source/DAC/preamp afterward?

I don't know about you but when and if your DAC or preamp have a hiccup, the amp will be going full tilt suddenly and be sending max power straight to your speakers, worst case scenario...enough distortion to blow the speakers, worst case scenario...it may cause permanent damage to your hearing.

Personally, I do it the other way around like how we tune and setup car audio back in the days:

1)set the gain on amplifier to the lowest level in the beginning
2)play a full spectrum sine wave sweep, on loop
3)slowly turn up the volume on the source/preamp/DAC to about 90%, leave the last 10% as headroom, if at this point your speaker is playing loudly, then back down the volume control and skip step 4 below and leave the gain on the amp at the lowest gain, if not...proceed to step 4.
4)then turn up the gain on the amplifier slowly, to a level as loud as you deemed appropriate (or could tolerate), without clipping the amp or hearing ANY audible or measureable distortion, then back down the gain a notch.
5)turn the main volume from source/preamp/DAC back down to a sane level
6)only use the main source/DAC/Preamp as volume control, and leave the gain control on the amp alone.

That's a much a safer approach for me personally, to prevent the amp accidentally go full tilt. At normal listening level, you shouldn't need the full power output from these TPA3255 amps unless you're powering huge towers, with listening position at well over 15ft away, and in a very large room, if that's the case you'd need a more powerful amp.

 

[Talisman]

I saw a lot of people suggesting to set the gain/volume at MAX on these TPA amps, then adjust the volume from the source/DAC/preamp afterward?

I don't know about you but when and if your DAC or preamp have a hiccup, the amp will be going full tilt suddenly and be sending max power straight to your speakers, worst case scenario...enough distortion to blow the speakers, worst case scenario...it may cause permanent damage to your hearing.

Personally, I do it the other way around like how we tune and setup car audio back in the days:

1)set the gain on amplifier to the lowest level in the beginning
2)play a full spectrum sine wave sweep, on loop
3)slowly turn up the volume on the source/preamp/DAC to about 90%, leave the last 10% as headroom
4)then turn up the gain on the amplifier slowly, to a level as loud as you deemed appropriate (or could tolerate), without clipping the amp or hearing ANY audible or measureable distortion, then back down the gain a notch.
5)turn the main volume from source/preamp/DAC back down to a sane level
6)only use the main source/DAC/Preamp as volume control, and leave the gain control on the amp alone.

That's a much a safer approach for me personally, to prevent the amp accidentally go full tilt. At normal listening level, you shouldn't need the full power output from these TPA3255 amps unless you're powering huge towers, with listening position at well over 15ft away, and in a very large room, if that's the case you'd need a more powerful amp.

The safest approach is not to use a DAC as a preamp directed to a power amplifier. Many think differently but for me it remains an absurd risk, I know

 

[Xcaliber]

The safest approach is not to use a DAC as a preamp directed to a power amplifier. Many think differently but for me it remains an absurd risk, I know

There are a lot of all-in-one unit out there like those offering from topping/SMSL having both DAC and preamp in one unit, but yea more devices and links between the source and speakers, the higher the risk, not to mention the risk of introducing more/higher noise floor, and more chances for things to go wrong.

 

[Talisman]

There are a lot of all-in-one unit out there like those offering from topping/SMSL having both DAC and preamp in one unit, but yea more devices and links between the source and speakers, the higher the risk, not to mention the risk of introducing more/higher noise floor, and more chances for things to go wrong.

I would never want to connect a power amp to something that doesn't have an analogue volume control, especially when using very powerful amplifiers, even more so with companies whose quality control has not always proven to be their strong point.
The risk of blowing up the speakers or my hearing or my children's hearing keeps me very far from this choice

 

[Xcaliber]

I would never want to connect a power amp to something that doesn't have an analogue volume control, especially when using very powerful amplifiers, even more so with companies whose quality control has not always proven to be their strong point.
The risk of blowing up the speakers or my hearing or my children's hearing keeps me very far from this choice

even bigger risk when the power amps don't have any gain control.

 

[hmt]

The safest approach is not to use a DAC as a preamp directed to a power amplifier. Many think differently but for me it remains an absurd risk, I know

Also some DACs present some pops and stuff when changing sample rates. That's why a 130db SINAD DAC is some typical ASR product. It measures nice in one metric but has little use since it just a DAC. Not a pre amp, not a Headphone amp and not a PEQ. That's why I find those kind of products really boring and too much engineered to a forum audience. I would rather have a powered amp with a DAC, PEQ and headphone amp with a SINAD of 90 on my desk that 4 one trick ponies with sky high SINAD values. Similar things seem to happen with the chip amps. Optimized too much for forum appeal.

 

[Talisman]

Also some DACs present some pops and stuff when changing sample rates. That's why a 130db SINAD DAC is some typical ASR product. It measures nice in one metric but has little use since it just a DAC. Not a pre amp, not a Headphone amp and not a PEQ. That's why I find those kind of products really boring and too much engineered to a forum audience. I would rather have a powered amp with a DAC, PEQ and headphone amp with a SINAD of 90 on my desk that 4 one trick ponies with sky high SINAD values. Similar things seem to happen with the chip amps. Optimized too much for forum appeal.

I don't understand what you're raving about, this discussion has absolutely nothing to do with what I said.

 

[hmt]

It has to some point. Manufacturers from China developing products to appeal ASR protocols. In case of DACs the results is no real use case. In case of the chip amps it is overblown SIAND and power ratings.

 

[Xcaliber]

Speaking of preamps, is there any good preamp with decent remote control under $1K worth considering? majority of the preamp from topping are kind of trash, in these day and age you'd think they do away with the 1980s IR remote that require direct line of sight to work.

 

[EddNog]

Speaking of preamps, is there any good preamp with decent remote control under $1K worth considering? majority of the preamp from topping are kind of trash, in these day and age you'd think they do away with the 1980s IR remote that require direct line of sight to work.

I’m using Gustard’s H16 as my preamp and the remote is freakin’ fantastic! It is IR, but you don’t need to be a military sniper for it to register. General direction is enough and quite long reach.

-Ed

 

[staticV3]

majority of the preamp from topping are kind of trash, in these day and age you'd think they do away with the 1980s IR remote that require direct line of sight to work.

Looks like they're switching to Bluetooth remotes for future products.

 

[hmt]

Speaking of preamps, is there any good preamp with decent remote control under $1K worth considering? majority of the preamp from topping are kind of trash, in these day and age you'd think they do away with the 1980s IR remote that require direct line of sight to work.

Nice would be also when it has a PEQ and headphone amp. I dont bother having extra devices for this purpose on my desk.

 

[EddNog]

Nice would be also when it has a PEQ and headphone amp. I dont bother having extra devices for this purpose on my desk.

My source, a HiBy R6 Pro II DAP, which I use as a desktop streamer (remote controlled using my tablet via HiBy’s HiByCast app), has a fully customizable global parametric EQ. I use it for room correction.

It goes without saying that it has an integrated headphone amp, but it doesn’t put out as much power as my preamp (the Gustard H16), which I use instead during late night listening when the kids are asleep and I can’t play my loudspeakers.

-Ed

 

[nvidia_7]

I saw a lot of people suggesting to set the gain/volume at MAX on these TPA amps, then adjust the volume from the source/DAC/preamp afterward?

I don't know about you but when and if your DAC or preamp have a hiccup, the amp will be going full tilt suddenly and be sending max power straight to your speakers, worst case scenario...enough distortion to blow the speakers, worst case scenario...it may cause permanent damage to your hearing.

Personally, I do it the other way around like how we tune and setup car audio back in the days:

1)set the gain on amplifier to the lowest level in the beginning
2)play a full spectrum sine wave sweep, on loop
3)slowly turn up the volume on the source/preamp/DAC to about 90%, leave the last 10% as headroom, if at this point your speaker is playing loudly, then back down the volume control and skip step 4 below and leave the gain on the amp at the lowest gain, if not...proceed to step 4.
4)then turn up the gain on the amplifier slowly, to a level as loud as you deemed appropriate (or could tolerate), without clipping the amp or hearing ANY audible or measureable distortion, then back down the gain a notch.
5)turn the main volume from source/preamp/DAC back down to a sane level
6)only use the main source/DAC/Preamp as volume control, and leave the gain control on the amp alone.

That's a much a safer approach for me personally, to prevent the amp accidentally go full tilt. At normal listening level, you shouldn't need the full power output from these TPA3255 amps unless you're powering huge towers, with listening position at well over 15ft away, and in a very large room, if that's the case you'd need a more powerful amp.

You would need some SERIOUS speakers with some SERIOUS power to damage your hearing in the amount of time that it would take you to turn off a system that played at max volume suddenly, or even the response of covering your ears. Speakers don't have infinite volume with power, many start to have large amounts of compression before even reaching 100dB at normal listening distances. Maybe if you were in a professional cinema with speakers that were designed to output 105dB with no sweat, sure a sudden massive surge might produce the 120dB+ of SPL required to do immediate damage but even then, not sure if those speakers could handle that without compression and then blowing.

But on that note, ever been to fireworks show? Thats 130dB+. Ever driven by road construction with someone using a jack hammer or other heavy equipment? Thats 130dB+. To get to those levels of loudness requires a lot more than consumer level speakers with consumer level electronics. That is the reason you see people in the car audio world using 4+ subwoofers. They can get the first one to an uncompressed 90-100dB, they add a second one to get an additional 6dB, and then each one after the second one is only netting them 3dB more of SPL. To go from 100dB to 106dB takes twice the amount of power, and to go from 106dB to 112dB takes another doubling of that and so on.

The amplifier knob is not a volume knob. It's controlling gain and the correct way to set it is to match it with your input source's input voltage. You do not adjust it by ear. You adjust it by math and measurements. If an amp has a gain of 20dB and a max output of 200w at 4 ohms, you would first calculate what the output voltage is at 200w with a 4ohm load. To do that use the equation: watts x resistance = sqrt(x). In this case 200 x 4 = sqrt(800) = 28.284. So, it takes 28.284 volts of amp output to reach max rated power at 4ohms.

You now need to know how many input volts coming from the preamp, dac, whatever you have connected that is supplying the analog signal to the amp, is required to now reach that 28.284 voltage of output power. We know the gain of the amp (20dB), and we know the max output voltage (28.284). So with that information we use the formula: gain = 20xlog(output voltage/input voltage). In this example it would be 20 = 20xlog(28.284/x) = 2.83, so we need 2.83 volts of input to get the max rated output of the amp. If your input source has an output voltage of 2.83 volts, then great you are done. If not, you can either decrease/increase the input voltage if you have the ability to do so, or you can decrease/increase the gain if you have the ability to do so, in order to match them. By match I mean you can never go past the rated output voltage and go into clipping, which is what will damage speakers much more easily than over powering them. An overpowered sine wave will make a speaker unhappy, but a square wave of any power (clipping), will destroy it. Setting gain by ear is dangerous because you may well be going into clipping by just going off of volume. You could set the gain of the amp as low as you want, but if the input source has a high enough voltage it will still go into clipping.

Below is a graph illustrating compression on a large 18" subwoofer, the Dayton UM18. This is a subwoofer that is designed for serious output and power handling. As you can see, at 71 volts (1200w/4ohms) it is reaching 115dB. Nearly doubling that power to 89 volts (2000 watts/4ohms) you only see a 1dB increase. Why? The speaker has reached maximum compression. More power wont equal more volume. If you used two of these, supplying a whopping 2400w of power, you still "only" get 121dB of output power. You would need to add 3 more subwoofers, making for a total of 5 18" subwoofer at 1200w a piece (6kw of power, thats 50 amps at 120v), to get to immediate hearing damage jack hammer levels. However do remember that although listening to levels even at 85-90dB or so wont cause immediate hearing damage, it will cause damage over time. So to summarize, treating the amps gain knob as a volume control in fear of damaging speakers or hearing, is irrational and actually the reverse of what you are worried about. If you were truly worried about damaging speakers, you would set the gain as noted above.

 

[howard416]

I keep seeing that amplifier knobs control gain. I would like to see one such knob that actually does that, rather than the usual voltage divider that attenuates input signal

 

[EddNog]

I keep seeing that amplifier knobs control gain. I would like to see one such knob that actually does that, rather than the usual voltage divider that attenuates input signal

The PS Audio GCC series control amps were, in fact, variable gain power amplifiers.

-Ed

 

[nvidia_7]

I keep seeing that amplifier knobs control gain. I would like to see one such knob that actually does that, rather than the usual voltage divider that attenuates input signal

In practical use it does. Attenuating input voltage is a lot less complex than directly changing the amplifiers gain, and has the exact same outcome. Input voltage and output gain are directly related.

 

[howard416]

OK, I guess as long we are all OK with calling input attenuators gain controls, and *definitely* not volume knobs.

"Exact same outcome" is another one of those things that you might want to mean one thing, but then someone else doesn't see it the same way. For example, a Class D amp vs a Class AB amp, both audibly transparent, are practically the same thing, since the outcome is the same, right?