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AIYIMA A07 TPA3255 Review (Amplifier)

Synergy,

Thanks for that.

I‘m running the A04@32V and the 07@48V.

FWIW, I have the tops removed from both amps and must say that the A04 seems to run noticeably cooler than the 07. After cranking the 04 for 30 minutes, the heatsink is barely warm to the touch.

Perhaps one might conclude that total wattage shouldn’t be the deciding factor between these amps.
 
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The TPA3251 can also operate at a slightly higher PWM frame rate frequency (600kHz) than the TPA3255 (450kHz).

This is an incorrect information. From the TI datasheet you will read

1610440213157.png


And AIYIMA A07 TPA3255 operates at 600kHz carrier frequency

AIYIMA_A07_FR_4ohm.png


Please check before you write an info like this.
 
How do I reconcile @pma 's FR measurements with Amir's (linked below)? I can see there's a difference in the unit used in the 2 charts, as well as a difference in the load presented, but my technical knowledge ends there. What are the likely real world implications?

My measurement and the one that you posted are in a complete agreement, but remember that it is only about 4 ohm resistor load.
Because the A07 and any other class D with the same topology uses the output LC filter, the frequency response differs with load impedance. Again, this is the simplest electrical engineering knowledge, however, you need it to be able to think about audio. Without load at the LC filter output, there is a high peak at cut-off frequency, because LC acts as a resonant circuit. Resistor makes damping and depending on ratio between R and rt(L/C), the filter is optimally damped, underdamped or overdamped. Depending on load resistor value the LC filter response looks like this

1610441585252.png


This is only a part of the story, for a pure resistor as a load. With the real speaker, which is a complex load (Z = R + jX), the story becomes much more complicated, as you can see in my thread.
 
This is an incorrect information. From the TI datasheet you will read

View attachment 105533

And AIYIMA A07 TPA3255 operates at 600kHz carrier frequency.......Please check before you write an info like this.

Ok, sorry they seem to have the same frequency rate.

I was quoting the Nominal value.

It looks like someone goofed up TPA3251 datasheet, since Nominal should define the same typical parameters for the same test conditions. Someone flipped the numbers on the TPA3251 datasheet incorrectly.

Capture.JPG
 
My measurement and the one that you posted are in a complete agreement, but remember that it is only about 4 ohm resistor load.
Because the A07 and any other class D with the same topology uses the output LC filter, the frequency response differs with load impedance. Again, this is the simplest electrical engineering knowledge, however, you need it to be able to think about audio. Without load at the LC filter output, there is a high peak at cut-off frequency, because LC acts as a resonant circuit. Resistor makes damping and depending on ratio between R and rt(L/C), the filter is optimally damped, underdamped or overdamped. Depending on load resistor value the LC filter response looks like this
......
This is only a part of the story, for a pure resistor as a load. With the real speaker, which is a complex load (Z = R + jX), the story becomes much more complicated, as you can see in my thread.

This is also a motivation for powered speakers, such as the JBL 305P (too bad about the hiss) with a built in amplifier, where the impedance or equalized response can be properly matched between the amplifier and speaker/network. For Class D amplifier applications, the load speaker crossover network may need optimization to tame the input impedance.
 
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Here , working on the TPA3255. My 3 revision of the PCB. Yes better than -100 Sinad already achieved .
Are you going to make a power only amplifier version so they can be used with pre amplifiers, active loudspeaker controllers ie DEQX etc ? This would sell by the truck load these horrible cheapest integrated amplifiers are rubbish, people talking about buying a couple a year as good value for money you have to be kidding . Happy to pay for a high Sinad quality product so my active loudspeaker can be used to there potential
 
Sorry I did not get you. We will release this as an mono amplifier in a box. No volume control on board
 
I plugged the Aiyima at my place tonight, on DIY speakers (broadband Visaton B200 corrected with EQ) instead of the AD18. I use that pair of speakers to watch movies. The AD18 makes very little hiss in the speakers, almost inexistant even few centimeters away.

The Aiyima seems more powerful and sounded good (I couldn't detect any difference with the AD18 at the low volume used). BUT there was more hiss. I ended up plugging the AD18 back.

See the two graphs: I think it shows that AD18 has lower noise at low volume.

1610827099628.png


1610827114806.png


0.02% THD = -74 dB
 
See the two graphs: I think it shows that AD18 has lower noise at low volume.

Yes, but linearity (THD/amplitude) of AD18 is worse and strange, the power is lower and clipping looks awful. And the power supply used in the measurement of A07 was inadequate to measure the available power, I measured much higher power.

A07_4562_thdampl_1_6kHz_RCfilter__50VunregPSU.png
 
Sorry I did not get you. We will release this as an mono amplifier in a box. No volume control on board

That sounds like something I would buy. Built-in power supply or external brick? And if an external brick, any chance you can offer a single one with two paralleled plugs + enough power for a stereo pair?
 
Yes, but linearity (THD/amplitude) of AD18 is worse and strange, the power is lower and clipping looks awful. And the power supply used in the measurement of A07 was inadequate to measure the available power, I measured much higher power.

View attachment 106528
My comment was about noise only, which matters in my use case.
 
I got my old Wharfedale Diamonds 8.4 (“6Ohm, “20-150W amp required”) out of the closet, and am running them with A07 (with 48V 3A, 3-prong Amazon brick) for a few days. Sounds fantastic - plenty of power for a mid-size room. No hum/buzz whatsoever. Amp is warm to a touch, but barely. The setup is very responsive to Roon‘s DSP tweaking...

Bottom line - liking it (thinking of the second one)!
 
So I pulled the trigger in the A07. $55 for both the amp and 32V power supply. Now that it is delivered, first impression is the volume knob feels a little cheap. I cranked up the volume with nothing playing, it is silent. No hissing. No thuds when powering on/off
 
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So I pulled the trigger in the A07. $55 for both the amp and 32V power supply. Now that it is delivered, first impression is the volume knob feels a little cheap. I usually wouldn't mind feeling the friction when turning it but it squeaks. Anyone have experience on fixing or improving this ?
I just leave my A04 vol at ~12 o'clock and use digital volume control. I hope Aiyima comes up with versions of the A07 & A04 where the knob is ditched altogether..
 
I personally did my own PSU for my Aiyima A04 updated amp, I am using a 35V TZT LLC PSU + AC Filter, works fine (next step = I will probably update some caps)

300W (continuous / 600W peak)
35V / 8.5A
Low ripple less than 150mv
Conversion efficiency: Max 98%
96*96*38mm



 
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I personally did my own PSU for my Aiyima A04 updated amp, I am using a 35V TZT LLC PSU + AC Filter, works fine (next step = I will probably update some caps)

300W (continuous / 600W peak)
35V / 8.5A
Low ripple less than 150mv
Conversion efficiency: Max 98%
96*96*38mm

Looks good. Nice insulated crimp terminals. Have you measured the ripple? It may be better than specified, like this:

1611039822265.png
 
I just measured it @34v but I am not equiped to measure the ripple....I shared the one from manufacturer but should be nice to measure it you are right )
 
I just leave my A04 vol at ~12 o'clock and use digital volume control. I hope Aiyima comes up with versions of the A07 & A04 where the knob is ditched altogether..

Was able to pull the knob off and lubricate it. Works well enough.
 
I got mine today. Two surprises:

1. There was no power unit included with the amp
2. It came straight to me without customs
 
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