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AIYIMA A07 TPA3255 Tear Down

hoverdonkey

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Although I question your presumption -- "a cheap part" my be deficient in "feel," long-term reliability, and/or taper matching between sections, but as long as it's properly functional it won't color "the sound" -- TI's own TPA3255EVM and a number of Chinese-made boards fit that description. As for assembled, ready-to-use TPA3255 power amps, how much are you willing to spend for your preference?

Finished HIFI TPA3255 Class D Power amplifier BTL High Power amp

Noob question - does the audio signal pass through the volume pot as usual with this amp, or does the pot control the gain of amp chips?
 

pma

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Noob question - does the audio signal pass through the volume pot as usual with this amp, or does the pot control the gain of amp chips?

The plot is placed right behind the RCA input connector before the amp circuits. It does not change feedback ratio and thus the feedback gain.
 

jst

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They could have cleaned it but at these prices is not something you expect. It should work fine.

I let the amp run for about 6 minutes driving 20 watts x 2 into 4 ohm load. The heatsink was too hot to touch and temp kept climbing:

AIYIMA A07 TPA3255 Class D Chip Thermal Analysis.jpg


TI specs the chip at 90% efficiency at max power. At 20 watts, it is running around 80% efficient so is producing 8 watts of heat into that little heatsink. With no vent or circulation, I would not deploy this amp for continuous high power use. The junction temp is rated quite high at 150 degrees C though so it is a tough little chip to kill. It has a thermal shutdown of 155 degree C so if it does that, you best not push it remotely that hard.

The two aforementioned electrolytic caps are sitting pretty close to that heatsink. If they not nichicons, they may go first.

And I just bought 48v 5a black brick adapter. OMG should I start to worry one of these days it will eventually explode ? I use it daily for my main source of audio, turning it on the moment I wake up till the moment I sleep, so it's pretty much 10-16h a day, but the volume is at 9 oclock most of the time , 10-11 occasionaly, never at 12+
- Using 32v 5a, the casing is 36.8 °C
- Using 48v 5a, the casing is 39.3 °C (max I ever checked)
It doesn't look like much using higher volt, but that's the shell casing, wonder if the heatsink inside differ much.

I also wonder if the casing also acts as heatsink because it does for LP838 (I saw one dude on youtube saying he almost blew the amp coz he removed the cover not realizing it acts as heatsink too)
 
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trl

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From Amir pics I understand that heatsink is the one from top of the chip, not the bottom case. Max. heatsink temp. can probably reach to 85C, as per TI datasheet (they tested the chip at this temp.):
"Thermal data are obtained with 85°C heat sink temperature using thermal compound with 0.7W/mK thermal conductivity and 2mil thickness".

Max. voltage seems to be 53.5V, so unless your external PSU stays clean at 48V, even when no music is playing, you should be fine.
 
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trl

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I just bought 48v 5a black brick adapter. OMG should I start to worry one of these days it will eventually explode ?
From Amir's test, on 4-Ohms loads, when passing 77W/channel chip's protection kicked in. I would say that the original heatsink (probably thermal paste too) is not up to dissipate heat so well.

Maybe it would be safer to use a 32V/5A PSU for this amplifier when driving 4-Ohms loads.
 
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jst

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From Amir pics I understand that heatsink is the one from top of the chip, not the bottom case. Max. heatsink temp. can probably reach to 85C, as per TI datasheet (they tested the chip at this temp.):
"Thermal data are obtained with 85°C heat sink temperature using thermal compound with 0.7W/mK thermal conductivity and 2mil thickness".

Max. voltage seems to be 53.5V, so unless your external PSU stays clean at 48V, even when no music is playing, you should be fine.
How about the elco/capacitor near the heatsink, amirm said that's a bad placement and the capacitors there will be the one to go first if heat ever gets too high affecting the surrounding.
From Amir's test, on 4-Ohms loads, when passing 77W/channel chip's protection kicked in. I would say that the original heatsink (probably thermal paste too) is not up to dissipate heat so well.

Maybe it would be safer to use a 32V/5A PSU for this amplifier when driving 4-Ohms loads.
I'm using 8ohm speakers, so is it safe even at 48v/5A ? I never crank the volume up too high, even at 9 o'clock already loud enough for me. Most Ppl on youtube videos using it at 12+ , one vid I found even max it but he's using laptop adapter, 19.5v iirc. Is increasing volume too high will add more load to adapter ?

btw, do you know how to bridge Aiyima A07 ? Does it involve modding the inside or just jumpering things at the backpanel ?
 

trl

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How about the elco/capacitor near the heatsink, amirm said that's a bad placement and the capacitors there will be the one to go first if heat ever gets too high affecting the surrounding.
There's nothing you can do about those caps, this is how the PCB was designed. However, if these caps are really Nichicon RZ-series, then you should be OK for many years from now.

I'm using 8ohm speakers, so is it safe even at 48v/5A ?
I think so, yes.

btw, do you know how to bridge Aiyima A07 ? Does it involve modding the inside or just jumpering things at the backpanel ?
Not sure if John's answer is what you're looking for: https://www.audiosciencereview.com/...255-review-amplifier.18984/page-2#post-621694.
 
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jst

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trl

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TPA3255_BTL.png



TPA3255_PBTL.png

I don't know if under the heatsink there's one chip running BTL or two chips running PBTL, but given the price and the output power measured by Amir I'm guessing it's one chip setup to run in BTL mode. Given the above two pics (taken from TI's datasheet) and the output filter passive components values recommended by TI in the datasheet, I would say that out of the box this amp may not be safe to run in PBTL mono mode.

If you have two of these amplifiers and two power supplies and you know an EE that can modify them a little bit, according to TI's recommendations from above, you may give it a try and let us know if these amplifiers are running stable in operation in PBTL mode. However, per https://e2e.ti.com/support/audio-gr...43807/an-encrease-power-output-on-amp-tpa3255 thread while running this chip in PBTL will not increase voltage output, but only current, which may suffice for low-impedance speakers, if more power is needed.

However, perhaps @pma or @JohnYang1997 may have a different opinion and a better explanation too. Thanks!​
 
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somebodyelse

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How about the elco/capacitor near the heatsink, amirm said that's a bad placement and the capacitors there will be the one to go first if heat ever gets too high affecting the surrounding.
If you look at the layout guidelines in the datasheet you'll see this is actually following TI's recommendations:
Note T1: PVDD decoupling bulk capacitors should be as close as possible to the PVDD and GND_X pins, the heat
sink sets the distance. Wide traces should be routed on the top layer with direct connection to the pins and without
going through vias. No vias or traces should be blocking the current path.
This is because a low impedance path to the power supply is required to achieve the chip's potential performance. I don't think there are any measurements in the datasheet to show this, but it has been commented on by some designing boards for them at diyaudio. The designer has to balance audio performance, design life and component cost.
 

trl

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"10.2.1.2.1 Decoupling Capacitor Recommendations In order to design an amplifier that has robust performance, passes regulatory requirements, and exhibits good audio performance, good quality decoupling capacitors should be used. In practice, X7R should be used in this application" - source: https://www.ti.com/lit/ds/symlink/tpa3255.pdf.

The PVDD decoupling caps are the small ones with a value of 1uF, not the big ones. The big ones seem to be called "PVDD Capacitors" and keeping these elcos away from the heat dissipated by the heatsink may improve elcos operating life. However, if these caps are indeed original Nichicon @105C I would say everything's fine in this application for several years of home-use.

What intrigues me now is the 50V rated for the PVDD Nichicon electrolytic capacitors; that means that a 48V external PSU may be too close to max. voltage these caps can handle. Perhaps an oscilloscope needs to be used to measure the RMS and peak-to-peak voltage across these caps.
 

trl

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BTW, seems that the evaluation module might have the big PVDD elcos pretty close to the heatsink too (not seen on the picture, but have a look at the soldering points), but these two caps are placed on the backside of the PCB, so heat coming from the heatsink is not an issue:

TPA3255EVM_SPL.JPG


TPA3255EVM_top.png


TPA3255EVM_bottom.png


TPA3255_PVDD.png

The two big PVDD electrolytic caps from TI's EVM are 4700 uF / 80V, while A07's caps are rated at only 50V, hence my concern that using 48V/5A external power supply might not be a good idea.

 

somebodyelse

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See section 12.2 Layout Examples in the same datasheet in the notes beneath each of figures 38 to 40. I believe 'bulk capacitors' in the quote refers to the electrolytics, and that the small decoupling caps are covered by the next note:
Note T2: Close decoupling of PVDD with low impedance X7R ceramic capacitors is placed under the heat sink and
close to the pins.
I'm with you on the rest. I almost mentioned the EVM putting things on the flip side, and the possibility of using the case as heatsink, but thought it was a bit out of scope.
 
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jst

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What intrigues me now is the 50V rated for the PVDD Nichicon electrolytic capacitors; that means that a 48V external PSU may be too close to max. voltage these caps can handle. Perhaps an oscilloscope needs to be used to measure the RMS and peak-to-peak voltage across these caps.
Does dc voltage vary wildly ? 2v is 4% from 48v, so it has that for tolerance before max 50, and probably the elco also has a few % tolerance after 50.

I'm too obsessed with watt when buying it and forgot about the advice to lower it by a notch down from max volt which shld be 42, it's really hard to find brick adapter with high amperage, all I can find was 5A unless the industrial one which looks dangerous.

If you look at the layout guidelines in the datasheet you'll see this is actually following TI's recommendations:
If the amp follows recommendation so it shld be able to run at 300Watt x2 = 600 watt ?

Now here's another product with 2 x 350 watt @8ohm. (The brand is Ashley, model PA350, it's probably imported and rebranded for local here in Indonesia). Aiyima A07 300 watt x2 would be using the elco at 1000µF x4 =4000µF, while this amp, rated 350 watt (only differ by 50 watt) but the elco is much higher at 6800x4 =27200 µF. What's the difference using this vs aiyima 300 watt x2 ? they're both outputing 2x300 watt and 2x350 watt , at 8 ohm, only differ by 50 watt per ch. Can Aiyima be as powerful as the Ashley with 27200 µF elco ? I dont know much about EE and electrical components but I read that elco is like reservoir for power.

Screenshot_439.jpg



Here's the look of what's inside the amp
Screenshot_441.jpg


power supply is 60v with 10 A =600 watt psu. If I use 48v x 6.4A x2 that would also be more or less 600 watt psu.
Screenshot_442.jpg
 

jst

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The two big PVDD electrolytic caps from TI's EVM are 4700 uF / 80V, while A07's caps are rated at only 50V, hence my concern that using 48V/5A external power supply might not be a good idea.
I've been using it for a few days now, always on for more or less 12h, so far nothing worrying, one time it produced short blue spark on the dc jack because i plugged in the dc jack while the adapter was plugged in wall socket (amp was off though) I was shocked I thought it's done for but all good.

Oh and, this guy commented on youtube aiyima a07 vid, that's also the reason I bought this 48v 5a lol.
Screenshot_443.jpg




I forgot one thing, this is a mass produced black brick adapter from China, it's real output probably less than 5A , dunno about the v, but for ampere it usually is lower than spec. Like if it's labeled 10A then real output probably only 5A, so 5A probably only 3A or cmiiw if anyone ever tested a brick adapter. The weight of this adapter 48v 5a is only 450 gram, even that is with its iec cable.

I've seen aiyima a07 being cranked up the volume to one o'clock, and one video cranked it up to MAX (but he's using 19v 6A, is it safe to crank up to 12 o'clock with 48v 5a ? 9-10 o'clock is already loud though, but I'm curious.
 
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trl

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jst

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@jst, pma was able to achieve 170W/4Ohms with this amplifier, but here's something: https://www.audiosciencereview.com/...2-and-opa2134-option.19155/page-2#post-639061. Using 48V PSU and loud music playing may damage the amplifier. Short term burst are fine, but in a long term you may need to use a lower voltage rated power supply )perhaps 44V max.).
He suggested to use this with 32v 5a, but guess I'll have to take the risk coz 48v 5A sounds more powerful and aiyima page recommends even 48v 7.5a. I'll keep an eye for 44v 7.5A though.

Damn, using 48v5a, 10 oclock volume and the heat went up to 40.0 °C. Guess I'll have to stick to 32v5a
 
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bravomail

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found couple of vids on TPA3255 amps. In Russian, but u can watch measurements. Or turn subtitles?
1 vid on audio quality, low noise on low signal. impressive and coming close to Hypex nCore territory.
2 vid on how much power u will get. close to 280watts. he used 48V 20A PSU :) cooling solution needed.


 
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Walter

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He suggested to use this with 32v 5a, but guess I'll have to take the risk coz 48v 5A sounds more powerful and aiyima page recommends even 48v 7.5a. I'll keep an eye for 44v 7.5A though.

Damn, using 48v5a, 10 oclock volume and the heat went up to 40.0 °C. Guess I'll have to stick to 32v5a
40C is not hot at all!
 
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