AIYIMA A07 TPA3255 Review (Amplifier)

[Joe Smith]

I am currently running my A07 with the 32v5a brick and with my KEF Q 15.2 speakers, I am normally listening to music in the 10 to 11 o'clock pot range, depending on source. Case never gets warm at all. In a normal size listening room, does not seem like a preamp of any kind would really add anything except as Walter says, noise/distortion.

 

[dr_mick51]

I'm using the 500-2000Hz pink noise method on the tones. This looks like it may work, it says it gives instantaneous and peak values with a meter accuracy: Class 1.0; 0.5%-1.5%.

https://www.amazon.com/Suraielec-Calculator-Protection-Electricity-Electrical/dp/B08GSPLZBN

Just be careful and don't plug many things to it. I saw the terrifying pictures from the reviews. I suspect they overloaded it.

 

[dr_mick51]

I am currently running my A07 with the 32v5a brick and with my KEF Q 15.2 speakers, I am normally listening to music in the 10 to 11 o'clock pot range, depending on source. Case never gets warm at all. In a normal size listening room, does not seem like a preamp of any kind would really add anything except as Walter says, noise/distortion.

Again. That's because we really don't need much power to begin with.
My "recommendation" (i'm not saying is really needed) for those people who want more "power" instead of buying a bigger power supply (which will do little to nothing to increase the output volume with a input signal of 0.2V) it would be better to increase the input signal with a preamp. The amplifier has enough power, the problem is the gain and the input signal(real music) not being high enough.
People use their test tone 1kHz at 2V and get for example 20V rms on the output. 20^2/4=100W with the pot at 100% and they believe that when they play "real music" they are also using 100W, therefore they believe they need a bigger power supply. In reality their input signal is about 0.2V which translates to 6V at maximum volume. 6^2/4=9W.
What they need is an audio signal boost by using a preamp.
Yes, you may say it increases the distortion but I really doubt anybody could be bothered by 0.2% THD at 90DB SPL, that's a distortion of -57db. Which means that only if you play music beyond 57db it will become audible +0.0db, reaching 33db at 90db SPL music, that's "almost" inaudible (or at least to be perceived as bad). In my humble opinion.

And not all distortion is bad or sound bad. Distortion means the output signal is not identical to the input signal. But adding second harmonic distortion with "Tubes" might add something "enjoyable/pleasant" according to some people, including me.

 

[Walter]

Again. That's because we really don't need much power to begin with.
My "recommendation" (i'm not saying is really needed) for those people who want more "power" instead of buying a bigger power supply (which will do little to nothing to increase the output volume with a input signal of 0.2V) it would be better to increase the input signal with a preamp. The amplifier has enough power, the problem is the gain and the input signal(real music) not being high enough.
People use their test tone 1kHz at 2V and get for example 20V rms on the output. 20^2/4=100W with the pot at 100% and they believe that when they play "real music" they are also using 100W, therefore they believe they need a bigger power supply. In reality their input signal is about 0.2V which translates to 6V at maximum volume. 6^2/4=9W.
What they need is an audio signal boost by using a preamp.
Yes, you may say it increases the distortion but I really doubt anybody could be bothered by 0.2% THD at 90DB SPL, that's a distortion of -57db. Which means that only if you play music beyond 57db it will become audible +0.0db, reaching 33db at 90db SPL music, that's "almost" inaudible (or at least to be perceived as bad). In my humble opinion.

And not all distortion is bad or sound bad. Distortion means the output signal is not identical to the input signal. But adding second harmonic distortion with "Tubes" might add something "enjoyable/pleasant" according to some people, including me.

Much/most of the tube gear I've seen tested turned out to have significant amounts of 3rd harmonic distortion, also. Some people like it, others can't hear it, but if you have a clean signal you can add any distortion you want with software. Nothing you can do about it if it is built into the signal chain. And noise is cumulative, so even if the SNR is around 80, which is good for cheap tube gear, it is still adding some noise which will then be amplified, which may or may not be audible or bothersome depending on the situation.

Personally, if I wanted max power/volume out of an A07, I'd use a 48v/9.3A PSU, replace the thermal compound with something better, then mod the case to handle a larger heatsink and/or a fan, as already suggested. A decent quality but not great slow moving 12v 120mm PC case fan would cost about $10 and make very little noise beyond 30cm or so. Running it off a 5v phone charger would ensure it ran at its minimum speed. Might not look too good, depending on your skills and tools, but you could always a fan with RGB if you wanted a tube-like glow.

 

[Midnight Audiophile]

Personally, if I wanted max power/volume out of an A07, I'd use a 48v/9.3A PS

I'm not an engineer, just trying to be an educated consumer. From what I've gleaned from various forums, 48v is pushing to much voltage, and 32-36v is a good operating range. The large caps in my A07 are 50v. The A07 has NE5532 op amps stock, those have a max supply voltage on the spec sheet of 44v (rec. 30v if I'm reading it correctly). This is a quote from another forum from the dude that heads up TI's op amp department. He's speaking about the OPA1656 but I think the gist is relevant:

 

[dr_mick51]

I'm not an engineer, just trying to be an educated consumer. From what I've gleaned from various forums, 48v is pushing to much voltage, and 32-36v is a good operating range. The large caps in my A07 are 50v. The A07 has NE5532 op amps stock, those have a max supply voltage on the spec sheet of 44v (rec. 30v if I'm reading it correctly). This is a quote from another forum from the dude that heads up TI's op amp department. He's speaking about the OPA1656 but I think the gist is relevant:
View attachment 224602

Don't worry, the opamps are fed through a 12 volts regulator. They don't take the whole DC input voltage. But it is true that there is no real benefit on using 48V power supplies. 32-36V and more than 5A is more than enough. The issue is not PS power or voltage, it is the input signal voltage. Boost your input signal and you will have plenty of output power.


Also. I need to mention that the Aiyima A07 has multiple revisions. Some of them use a Post-Filter Feedback (PFFB) to try to reduce distortion but also causes the Gain to be reduced, which means less output power for the same input signal. It has nothing to do with power supply voltage/power.

 

[Midnight Audiophile]

Also. I need to mention that the Aiyima A07 has multiple revisions. Some of them use a Post-Filter Feedback (PFFB) to try to reduce distortion but also causes the Gain to be reduced, which means less output power for the same input signal. It has nothing to do with power supply voltage/power.

Do you know if they fixed the reversed channels on the 3.5mm aux. out on the newest version?

 

[dr_mick51]

Do you know if they fixed the reversed channels on the 3.5mm aux. out on the newest version?

No idea. But you can always use RCA split or Y cables to connect a subwoofer if you want/need.

 

[Midnight Audiophile]

No idea. But you can always use RCA split or Y cables to connect a subwoofer if you want/need.

Yeah, no problem running subs off of it with a splitter, I just had to find out the hard way that they were reversed when I used it as a stereo pass-through.

 

[Walter]

I'm not an engineer, just trying to be an educated consumer. From what I've gleaned from various forums, 48v is pushing to much voltage, and 32-36v is a good operating range. The large caps in my A07 are 50v. The A07 has NE5532 op amps stock, those have a max supply voltage on the spec sheet of 44v (rec. 30v if I'm reading it correctly). This is a quote from another forum from the dude that heads up TI's op amp department. He's speaking about the OPA1656 but I think the gist is relevant:
View attachment 224602

Yes, it is my understanding that the 50v caps are the weak point. One of the adjustable units that will allow reducing the voltage by 5% is probably advisable if you don't want to upgrade the caps. While they are theoretically fine, that is getting really close to the limit. I know some people have used this amp with 48v supplies for extended periods, but only with improved cooling of one type or another.

 

[Walter]

Don't worry, the opamps are fed through a 12 volts regulator. They don't take the whole DC input voltage. But it is true that there is no real benefit on using 48V power supplies. 32-36V and more than 5A is more than enough. The issue is not PS power or voltage, it is the input signal voltage. Boost your input signal and you will have plenty of output power.


Also. I need to mention that the Aiyima A07 has multiple revisions. Some of them use a Post-Filter Feedback (PFFB) to try to reduce distortion but also causes the Gain to be reduced, which means less output power for the same input signal. It has nothing to do with power supply voltage/power.

Power and gain are not the same thing. Assuming sufficient current, a 100 watt amp with 20 dB gain has the same power as a 100 watt Amp with 29 dB gain--100 watts. It will have the same ability to control speaker movement and will possibly be better with speakers that are considered difficult loads. It just won't get as loud, again assuming that both amps have enough current. I think that might be the point you are trying to make, but it might confuse people the way it was worded. It is also worth noting that once you reach the max input level required for full power, applying more voltage using a preamp will make no difference whatsoever, other than possibly overloading the input circuitry. I'm not sure what the required level is for the TPA3255, but I would guess around 1v or less, and almost certainly not more than 2v.

 

[trungdtmc]

Think if using 48v+, i must also notice this 22uf 50v cap besides 2 PVDD caps

 

[dr_mick51]

Power and gain are not the same thing. Assuming sufficient current, a 100 watt amp with 20 dB gain has the same power as a 100 watt Amp with 29 dB gain--100 watts. It will have the same ability to control speaker movement and will possibly be better with speakers that are considered difficult loads. It just won't get as loud, again assuming that both amps have enough current. I think that might be the point you are trying to make, but it might confuse people the way it was worded. It is also worth noting that once you reach the max input level required for full power, applying more voltage using a preamp will make no difference whatsoever, other than possibly overloading the input circuitry. I'm not sure what the required level is for the TPA3255, but I would guess around 1v or less, and almost certainly not more than 2v.

I know what Power is, and I know what Gain is. The difference between a 100W output with 20dB gain vs 100W output with 29db gain is the on the first one your input signal needs to be almost 3 times higher to reach the same 100W(4ohms speakers?) So, Power=Voltage^2/Z (I know this method is not very accurate because Impedance changes with Frequency, but let's assume 4ohms) How much output voltage (don't confuse with DC input voltage) swing we need to produce 100W output power? (100W*4ohms)^(1/2)=V =>V= 20V rms.

I used this website to convert db Gain to Voltage Gain:
http://www.muzique.com/schem/gain.htm

First scenario:
20db Gain= 10x voltage ratio => 10= Vout/Vin => Vin=20V/10 = 2V
On the other scenario:
29db = 28.18x voltage ratio => 28.18 = Vout/Vin => Vin=20V/28.18 = 0.709V
Now you know the importance of Input signal voltage and Gain on an amplifier.

What do you think will happen if you feed a 0.2Vrms Audio(from real music, not pure tones) signal to both amplifiers?

On the first amplifier:
Gain=10=Vout/Vin => 10= Vout/0.2V => Vout=2Vrms. P=V^2/Z => P=2^2 / 4 = 1W
On the second amplifier:
Gain = 28.18 = Vout/Vin => 28.18=Vout/0.2V =>Vout=5.636Vrms. P=V^2/Z => P = 5.636^2/4 = 7.94W.

Remember how Amir used 0.157V and the Volume pot at 3 o' clock to reach 5W?
29.125db Gain = 28.59 Voltage Gain. Then, (0.157*28.59)^2 / 4 = 5.0369W.
29.216dB Gain = 28.89 Voltage Gain. Then, (0.157*28.89)^2 / 4 = 5.1432W.
It cannot get more accurate than that:

At maximum volume on the pot it would reach aprox 8W.

So you will ask how did he reach:

Well, he just increased the input signal to 2Vrms from his signal generator and used the volume pot to control output power until the amplifier clipped.

See the importance of the input signal? Of course there are other factors: DC input voltage is important because it dictates how much output voltage swing the amplifier can reach. Current is important because there is no power without current. Input voltage noise and ripple is important to reach low THD+N levels on the amplifier. Power supply output capacitors (capacitance) are important because it determines how much instant peak power the power supply can provide. Etc....

I mean, people can do whatever they please. If they want to buy a 1GW power supply then go on. But if your input signal remains the same (low) you won't see a benefit.

Again, my first question is how much output power are you really using from your amplifier. Did you measure it? If you tell me ok, I'm using 80-100W and I want more power, ok. In that case it is really power what is limiting you. But if you tell me that your power is 1-5Watts, then the power supply is not the limiting factor. In that case just increase the input signal voltage and you will get plenty of extra power.

 

[dr_mick51]

Power and gain are not the same thing. Assuming sufficient current, a 100 watt amp with 20 dB gain has the same power as a 100 watt Amp with 29 dB gain--100 watts. It will have the same ability to control speaker movement and will possibly be better with speakers that are considered difficult loads. It just won't get as loud, again assuming that both amps have enough current. I think that might be the point you are trying to make, but it might confuse people the way it was worded. It is also worth noting that once you reach the max input level required for full power, applying more voltage using a preamp will make no difference whatsoever, other than possibly overloading the input circuitry. I'm not sure what the required level is for the TPA3255, but I would guess around 1v or less, and almost certainly not more than 2v.

I forgot to mention, 100W output is 100W power no matter what "Gain" the amplifier has. It only dictates how much input signal it requires to reach the same amount of Power/Output Voltage. One does not get/feel louder than the other, both have the same power, output swing, damping factor and same loudness if using the same speakers.

Please, measure your output power(with music), and your input signal voltage (if possible, an average or max) and then we can continue having this conversation with evidence and measurements. I might be wrong, you might be wrong, both might be wrong, both might be right. Let's see.

I hope to hear your findings. I think we can achieve something important here. There are too many Myths regarding power on amplifiers.

I measured with an oscilloscope an audio coming from a cheap USB DAC and it was on average 0.422Vrms or 1.05Vp-p.
If I measure a 1kHz Sinewave test tone I get 1.03Vrms and 2.85Vp-p. That's 2.44x higher input voltage which represents 2.44^2= 5.95 more output Power on the amplifier at the same volume pot position,.
Test tones are used to calculate maximum possible power from amplifier. But we listen to music not test tone. At least I do.

The question is not how much power your amplifier can provide. The question is how much do you really use.

 

[Walter]

Amir has a good post about determining how much power you really need. I'm simply addressing the issue of what I personally would do if I wanted to maximize the power of an A07, as I already stated. Not stated explicitly, but I'd also be sure to use a DAC that had at least 2v max output, as the vast majority of tested desktop DACs do. Personally, I'd probably be fine with the stock 32/5 PSU, and I'd definitely prefer the improved performance of PFFB over the higher gain without it for most uses, but I can see scenarios where more power and more gain might be preferable.

 

[dr_mick51]

Amir has a good post about determining how much power you really need. I'm simply addressing the issue of what I personally would do if I wanted to maximize the power of an A07, as I already stated. Not stated explicitly, but I'd also be sure to use a DAC that had at least 2v max output, as the vast majority of tested desktop DACs do. Personally, I'd probably be fine with the stock 32/5 PSU, and I'd definitely prefer the improved performance of PFFB over the higher gain without it for most uses, but I can see scenarios where more power and more gain might be preferable.

Ok. You need to remember DACs have 2Vrms output if "Test tones" are used. As I mentioned earlier , on real music the signal is 2.5 times lower, which might or might not be enough to squeeze all the power from amplifier(at least not loud enough for music).
Now you say you prefer the PFFB version which makes things worst. The gain is reduced by almost 10db which will required even higher input signal. I've seen online post from people complaining because the amplifier with PFFB is not loud enough even with a 2V DAC, well. I wonder why.

Aiyima even provided instructions on how to remove the PFFB, and the person who did it said the amplifier is much better now.

I just want to clarify that for me it does not matter. 1W is enough for my usage and application. But some people want 80-100W. And it won't work for them, not without a preamp to increase the input signal.

 

[Midnight Audiophile]

So I got my watt-meter and hooked it to my Drok PS (48w 10a adjustable) and A07. I set my PS to 32v and it's pulling 7w with no music playing and DAC and amp pots at 0.

I've got the A07 connected to Dali Spektor 2s and I cranked up AC/DC's "Shoot to Thrill" to around 93 - 97 Db at my listening position (42" triangle). The amp is hitting between 19 - 28w on the meter. I didn't want to push the speakers any louder but they did fine at that level. Good deal! *Note: At normal listening levels between 84 - 88 Db, I'm seeing it stay around 7.5w. So minus 7w at 0 volume, it's pulling about an additional 0.5w.

I'll test the Drok against the stock 32v 5a PS that comes with the A07 to see if there's any difference in noise. The Drok runs dead silent and I've not had its fan come on yet.

 

[dr_mick51]

So I got my watt-meter and hooked it to my Drok PS (48w 10a adjustable) and A07. I set my PS to 32v and it's pulling 7w with no music playing and DAC and amp pots at 0.

View attachment 225519

I've got the A07 connected to Dali Spektor 2s and I cranked up AC/DC's "Shoot to Thrill" to around 93 - 97 Db at my listening position (42" triangle). The amp is hitting between 19 - 28w on the meter. I didn't want to push the speakers any louder but they did fine at that level. Good deal! *Note: At normal listening levels between 84 - 88 Db, I'm seeing it stay around 7.5w. So minus 7w at 0 volume, it's pulling about an additional 0.5w.

View attachment 225521

I'll test the Drok against the stock 32v 5a PS that comes with the A07 to see if there's any difference in noise. The Drok runs dead silent and I've not had its fan come on yet.

Nice. That's how it is tested.

It makes total sense. The Dali Spektor have a 84db/W/m sensitivity. If you are measuring at 42inches=106.6cm, per channel:
84db 1W
87db 2W
90db 4W
93db 8W
96db 16W

Just a couple of questions: what was the volume pot position when you ran the test? And, did you have any trouble with your neighbors?

 

[Midnight Audiophile]

Nice. That's how it is tested.

It makes total sense. The Dali Spektor have a 84db/W/m sensitivity. If you are measuring at 42inches=106.6cm, per channel:
84db 1W
87db 2W
90db 4W
93db 8W
96db 16W

Just a couple of questions: what was the volume pot position when you ran the test? And, did you have any trouble with your neighbors?

lol. I don't know about the neighbors, they are fairly close. My system is in a den that was a garage years ago so I've got a concrete floor under carpet. I didn't have my subs on for the test. There's one window in the den and it faces the neighbor's house. I've got an Audimute isole absorption sheet covering that window.

On the pots, I have an ifi Zen Signature DAC that I use the preamp analog volume control for the system, had it about 1 o'clock, and then the pot on the A07 at about 1 o'clock also. I run a 6.5" sub under the coffee table my system is on, and then a 8" slimline sub directly under the LP. I run about an 11 Db bass bump that starts at 220 and is 3 Db down at 30 Hz. Sounds good when it's dialed in. A slimline sub coupled to your couch is better than roses on your piano imo : )

 

[wave]

Thanks for the detailed post with numbers. Did the A07 get too hot during 96db output?