AIYIMA A07 TPA3255 Review (Amplifier)

[Midnight Audiophile]

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

Not at all. I've got two of them and have run them at that level on a regular basis for over a year. Never had them get hot. It's only drawing about 30w max at that level. The stock power supply is 32v 5 amps (160w) should be fine. I'm going to double-check it in my system just to see if there's any detectable noise. As I said earlier, I'm not an engineer, just trying to be an educated consumer.

 

[Walter]

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.

2V at max input level is 2V, be it test tones or musical peaks. It sounds as if you are talking about average volume, which makes no sense in this context. 80-100 watts into 4 ohms can be achieved with a power supply with only slightly more amperage than stock, as Amir's testing shows. 8 ohms will need more voltage, as well. But in neither case is a preamp needed or relevant. I wish one of the EE audio electronic designers on here, like @pma, @SIY, or @KSTR who can really explain this would chime in about what has been said on the last few pages. And hey, if they say I'm wrong, they can at least explain it in a way that makes sense and I will have learned something.

 

[SIY]

2V at max input level is 2V, be it test tones or musical peaks. It sounds as if you are talking about average volume, which makes no sense in this context. 80-100 watts into 4 ohms can be achieved with a power supply with only slightly more amperage than stock, as Amir's testing shows. 8 ohms will need more voltage, as well. But in neither case is a preamp needed or relevant. I wish one of the EE audio electronic designers on here, like @pma, @SIY, or @KSTR who can really explain this would chime in about what has been said on the last few pages. And hey, if they say I'm wrong, they can at least explain it in a way that makes sense and I will have learned something.

The confusion is between peak voltage (the capability of which will be the same regardless of signal) and RMS voltage (which is VERY dependent on the nature of the signal).

 

[dr_mick51]

2V at max input level is 2V, be it test tones or musical peaks. It sounds as if you are talking about average volume, which makes no sense in this context. 80-100 watts into 4 ohms can be achieved with a power supply with only slightly more amperage than stock, as Amir's testing shows. 8 ohms will need more voltage, as well. But in neither case is a preamp needed or relevant. I wish one of the EE audio electronic designers on here, like @pma, @SIY, or @KSTR who can really explain this would chime in about what has been said on the last few pages. And hey, if they say I'm wrong, they can at least explain it in a way that makes sense and I will have learned something.

I'm sorry, but have measured it?. Test tones have always higher amplitude than real music. Don't tell me that a DAC produces 2V RMS with audio signal(real music). The 2 Volts is the maximum voltage the DAC can produce, usually with test tones at 0db. Music plays at -10db usually(much lower amplitude)
Tell me which audio signal was used by Amir during him maximum power measurements. I'm pretty sure he did not use real music, he used a test tone. Why?. Because real music does not have enough input voltage which multiplied by the amplifier gain produces the output voltage hence power.
I have already explained this before, and showed all the Math so won't do it again.
If one believes that the music input signal voltage is 2V because it's a 2V output DAC, then I suggest that person to measure those voltages. Of course it needs to be an average because music is very dynamic and the best we can do is measure an average.

 

[dr_mick51]

The confusion is between peak voltage (the capability of which will be the same regardless of signal) and RMS voltage (which is VERY dependent on the nature of the signal).

Right. If one was supposed to measure the input signal voltage, what is the right way. Do we measure peak voltage or average over the durations of the song. I don't know, I might be wrong but the average is a more realistic representation of the song, and therefore for me it is the right measurement.
It is for example if I ask you what is your home power consumption. For me the right answer would be the average of the last year( at least 1 year). Because if I tell you my power consumption during the month of July (peak) you might believe that's my consumption all year round, which is not true.
Yes, during music there are peaks, but those are not representative of the whole song. And for those peaks the bulk capacitors provide the energy required. We don't need a bigger power supply because of those peaks.

 

[Midnight Audiophile]

The DAC I'm using (ifi Zen Signature v1) has both 4.2v (balanced) and 2.1v (single-ended) outputs. Right now I'm using the unbalanced out for the A07 and then using a 4.4mm to RCA cable to sent the balanced signal to a Rolls SX95 Dual Subwoofer filter (then to powered subs). Would there be a benefit to switching those around?

 

[dr_mick51]

The DAC I'm using (ifi Zen Signature v1) has both 4.2v (balanced) and 2.1v (single-ended) outputs. Right now I'm using the unbalanced out for the A07 and then using a 4.4mm to RCA cable to sent the balanced signal to a Rolls SX95 Dual Subwoofer filter (then to powered subs). Would there be a benefit to switching those around?

You can't use balanced inputs on the Aiyima as it is now. You will need to bypass the whole preamplifier and invertion section(opamps).
Also, the input signal you have is more than enough to produce the power you need.
The reason for the 2 dual opamps on the Aiyima is to use each opamps to increase the input (I believe, I have not measured how much. If not why 2 opamps then) and the second amplifier from each opamps to create an inverted signal from the first amplifier to create a differential signal to feed the amplifier chip. The TPA3255 is a differential amplifier (not a single ended amplifier) which takes a positive signal and an inverted/negative signal for each channel to achieve higher output voltage. The same concept of balanced outputs/inputs.
The Topping PA5 has the capability of using both Balanced and Single ended inputs. By using the opamps (as in the Aiyima) or completely bypassing them.

 

[dr_mick51]

I think we all can agree on two or three things:
We don't use/need as much power as we thought.
We don't need a preamp (if a decent DAC is used) to reach enough output power (because of the first statement) to satisfy our listening sessions.
Amplifier power, peak or average it's a combination of many factors which together determine the output power: power supply voltage and current, input signal RMS voltage, amplifier chip, amplifier gain, speaker impedance and more ...which in reality don't matter much because we don't use/need all that power in first place(first statement).

Don't we agree? Let's enjoy our Aiyima amplifier.

 

[Midnight Audiophile]

You can't use balanced inputs on the Aiyima as it is now.

Right on. The 4.4mm to RCA cable I'm using for the Sub Filter makes it unbalanced as I understand it.

 

[Midnight Audiophile]

Don't we agree? Let's enjoy our Aiyima amplifier.

I appreciate Amir, you and everyone's help in understanding some of the technical aspects. Manufactures such as Aiyima are now marketing products like the A07 with different op amps and power supplies you can choose. For the average consumer it's good to have even just a basic understanding of these different aspects to make an informed purchase decision.

 

[Walter]

The confusion is between peak voltage (the capability of which will be the same regardless of signal) and RMS voltage (which is VERY dependent on the nature of the signal).

Agreed. No confusion on my part about that. The point I have made is that if a DAC or other source can output 2V (continuous test tone or musical peak) and the amplifier requires 2V or less to reach maximum power, then adding a preamp will not help to produce more power or volume. Is that correct? (Referring specifically to a class D Amp with a switching power supply,although I believe it would apply regardless of the topology.)

 

[dr_mick51]

Agreed. No confusion on my part about that. The point I have made is that if a DAC or other source can output 2V (continuous test tone or musical peak) and the amplifier requires 2V or less to reach maximum power, then adding a preamp will not help to produce more power or volume. Is that correct? (Referring specifically to a class D Amp with a switching power supply,although I believe it would apply regardless of the topology.)

My friend. It is not hard to measure your RCA output voltage. Please play some music and tell me how much voltage you measure. Then play a test tone and report the voltage as well.
If you want max power at playing test tones, then your statement is correct. If your amplifier sensitivity is 2V then by playing a 2V test tone you will get maximum power from the amplifier. But it won't reach the same power (average) while playing music(because your signal will be way less than 2V).
Now, you mentioned musical peak. Yes you might reach max power during a 0.5seconds peak. It does not mean your amplifier is running at that output all the time (during the song). I prefer to measure average continuous power. It's more representative.
I already took the measurements myself on a 1V(max) USB dongle DAC (Apple USB C). A 1kHz test tone reached 1.03V, while a music signal(Alice in Chains - Rooster) measured 0.4V in average. You can try to use a louder track of your taste. I doubt you will get a music track which produces 2V as your test tone did. No matter how loud it is.
I fed each signal to the Aiyima amplifier and measured different power outputs at the same volume pot position(using resistors instead of speakers of course, I don't want to become deaf) by measuring voltage and current.
In the end maximizing your amplifier is not important. I doubt you will need that amount of power.
But my point is you will get different power output(average) by using a test tone and by using real music. That's a fact.

 

[SIY]

Agreed. No confusion on my part about that. The point I have made is that if a DAC or other source can output 2V (continuous test tone or musical peak) and the amplifier requires 2V or less to reach maximum power, then adding a preamp will not help to produce more power or volume. Is that correct? (Referring specifically to a class D Amp with a switching power supply,although I believe it would apply regardless of the topology.)

Adding a preamp will provide more gain and (up until the amp clips) more volume at a given volume control setting.

output 2V (continuous test tone or musical peak)

Those are very different things, so the number is not necessarily comparable. As soon as you say "2V" instead of "2VRMS" or "2V(peak)" the confusion is likely to start. With digital systems, it makes much more sense to specify something like "FS = 2V" or whatever FS actually is, then you can back into things like RMS for a sine wave.

 

[Walter]

Adding a preamp will provide more gain and (up until the amp clips) more volume at a given volume control setting.

That is obvious. However, the max volume without clipping will still be the same, correct? It will just be reached at a lower volume control setting?

Note: This being ASR, I assumed we were not willing to push the amp to the point of audible distortion. If we remove that constraint, I can see where a preamp might provide increased volume in some cases.

 

[Walter]

If you want max power at playing test tones, then your statement is correct. If your amplifier sensitivity is 2V then by playing a 2V test tone you will get maximum power from the amplifier. But it won't reach the same power (average) while playing music(because your signal will be way less than 2V).
Now, you mentioned musical peak. Yes you might reach max power during a 0.5seconds peak. It does not mean your amplifier is running at that output all the time (during the song). I prefer to measure average continuous power. It's more representative.
I already took the measurements myself on a 1V(max) USB dongle DAC (Apple USB C). A 1kHz test tone reached 1.03V, while a music signal(Alice in Chains - Rooster) measured 0.4V in average. You can try to use a louder track of your taste. I doubt you will get a music track which produces 2V as your test tone did. No matter how loud it is.
I fed each signal to the Aiyima amplifier and measured different power outputs at the same volume pot position(using resistors instead of speakers of course, I don't want to become deaf) by measuring voltage and current.
In the end maximizing your amplifier is not important. I doubt you will need that amount of power.
But my point is you will get different power output(average) by using a test tone and by using real music. That's a fact.

I can't see why anyone cares about the position of the volume pot. In fact, you generally want to be able to use nearly the full range. I'm only referring to max, unclipped volume. If you use a preamp to push your AVERAGE voltage level up to the maximum input level the amp requires to reach full power, by definition you will be clipping the hell out of the peaks. So yes, it will be subjectively louder but sound like utter crap. So I stand by my statement that a tube preamp is not the better way to increase power, and will expand it to say it is not a better way to increase volume, even if your DAC has an extremely low output level like some dongles. In that case, buy something like
https://www.audiosciencereview.com/forum/index.php?threads/fx-audio-dac-sq3-review.27239/ that was recently on sale for $55. If it's a phono preamp not a DAC, then buy a $20 CD player.

Also, while I'm not sure of the value for a TPA3255, many class D amps reach full power at well under 2V input. If the amp requires almost exactly what the sources maxes out at, and if the music has no OdBFS peaks, then in that very unusual circumstance a preamp will provide a little increased volume without clipping.

 

[SIY]

That is obvious. However, the max volume without clipping will still be the same, correct? It will just be reached at a lower volume control setting?

Yes, exactly.

 

[dr_mick51]

That is obvious. However, the max volume without clipping will still be the same, correct? It will just be reached at a lower volume control setting?

Note: This being ASR, I assumed we were not willing to push the amp to the point of audible distortion. If we remove that constraint, I can see where a preamp might provide increased volume in some cases.

For example. If you want to produce 5W output power there are infinite combinations of Input signal voltage and Volume pot position, right?
Many reviews on this website use a 29db Gain, which requires 0.16V (in average) and whatever position on the pot which reaches 5W (4.47V rms output swing at 4ohms), which depends on the Amplifier gain, right?
But if you use 1V input signal to produce the same 4.47V rms output swing which translates to 5W at 4ohms, then your amplifier Gain will be lower. Does it matter? Hell yeah.

Let's use the Aiyima A300 as an example:
using RCA:

and using XLR at the same voltage:

Just a little SINAD increase mostly because of a noise reduction due to the balanced inputs.

But if we increase the input signal:

We get a considerable improvement. Don't you think?.
And the lower the gain(higher input) at the same 5W, the Higher the SINAD because the amplifier needs to "work" less hard.

If we keep increasing the input signal we get lower and lower distortion.

Now you see the importance of the input signal and why using a good preamp is good for the amplifier. For example I use the SMSL SH-6 headphone amp and preamp which is able to produce up to 6V or 7V rms with music signal(not test tone). By the way, we were never able to see that review on this website even thou Amir has had it since last December.

This is a science based website, and I'm using your science to make a point.

What would the Aiyima A07 measurements be if a lower gain is used(higher input signal) as used on the Topping PA5 (0.5V vs 0.157V): 10db Lower Gain

I'm not saying it will reach the same performance. I'm just saying it will be better that what was measured before, probable 3-4DB higher SINAD. And the lower the Gain the better.

 

[dr_mick51]

Another nice example of an Amplifier which improved a lot by reducing Gain (increasing input signal):
Loxjie A30
At 0.16V:

At 1.9V:

Do the input signal and Gain matter? It's up to you to decide. I'm just providing evidence.

 

[Walter]

Now YOU are the one relying on test tones! Sure, if you want to maximize SINAD or any other spec at one specific wattage, you can vary the input level until you get the amplifier operating at its sweet spot for that measurement. But as soon as you play music that all goes out the window. However, you can continue to write whatever you want. I'm done on this topic. I still maintain that using a preamp for any reason other than having a very low level analog source will measurably and perhaps audibly degrade the sound in most cases, especially if it uses tubes. Anyone who understands math and basic electronics can read the conversation and decide for themselves what they want to do. Enjoy the music.

 

[dr_mick51]

Now YOU are the one relying on test tones! Sure, if you want to maximize SINAD or any other spec at one specific wattage, you can vary the input level until you get the amplifier operating at its sweet spot for that measurement. But as soon as you play music that all goes out the window. However, you can continue to write whatever you want. I'm done on this topic. I still maintain that using a preamp for any reason other than having a very low level analog source will measurably and perhaps audibly degrade the sound in most cases, especially if it uses tubes. Anyone who understands math and basic electronics can read the conversation and decide for themselves what they want to do. Enjoy the music.

You are right. Everything has been shown and said already. People are smart to realize and decide by themselves what they want to do.

I'll keep enjoying my setup and my music in the meantime.