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AIYIMA A07 TPA3255 Tear Down

amirm

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This is a teardown of the AIYIMA A07 TPA3255 Class D Amplifier I just reviewed. I gave it high marks for very low distortion at extremely low budget price. Question was raised on the revision of the board and thermal characteristics of the unit so here we are.

I was very pleased to see the PCB having silk screen markings for all surface mount parts:

AIYIMA A07 TPA3255 Class D Chip Teardown.jpg


The business end, i.e. TI TPA3255 IC is buried under that gold color heatsink. To the left we have some power supply circuits and input buffers made up of common NE5532 opamps. To the right we have reservoir capacitors and output filtering. Speaking of those caps, I was very surprised to see them having the top capacitor brand, Nichicon:
AIYIMA A07 TPA3255 Class D Chip Teardown Nichicon Capacitor.jpg


Someone should do the forensics and tell us if they are the real deal or fakes.

Soldering job on speaker terminals and such is acceptable.

The back side shows smudges and imprints of other boards:


AIYIMA A07 TPA3255 Class D Chip Teardown PCB.jpg


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.

Conclusions
Sans the pedigree of the caps, I really don't see corners being cut here given the target market and very low cost of the unit. It could have been much worse than it is. With power supply being external, safety risks lay there, not inside this amp. The metal enclosure should contain any fires and such in that unlikely event.

So not bad!

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DuncanTodd

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Thanks Amir.
I have the A04, and I know that one for sure had a few builds. I don't have the right screwdriver to open it and see which one I got lol.
 

DuncanTodd

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I hear you. :) This one had very nice, threaded hex screws and was very easy to open and put back together.
Heh, nice.
Non of the 10-12 options I have here fits and I'm too cheap to buy one just to open and close it once ;)
 

Bruce Morgen

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How about the "pedigree" of the NE5532s? I'm interested because there are apparently lots of penny-priced counterfeits out there that must be a temptation to manufacturers of bargain-priced gear.

Another thing that ought to be brought out is that the channels of the 3.5mm input jacks are reversed from the de facto standard of tip=L and ring=R.
 

whazzup

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Someone should do the forensics and tell us if they are the real deal or fakes.

How about the "pedigree" of the NE5532s? I'm interested because there are apparently lots of penny-priced counterfeits out there that must be a temptation to manufacturers of bargain-priced gear.

Ask the manufacturer? Will they go on the record and vouch for their amps not using any counterfeit components? ;)
 
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YSC

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In light of the caps is both a surprise and a sign to any manufacturers that at al cost you should be able to use these great brands and not cut a few dollars off
 

DuncanTodd

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How about the "pedigree" of the NE5532s? I'm interested because there are apparently lots of penny-priced counterfeits out there that must be a temptation to manufacturers of bargain-priced gear.
Over at a Nordic DIY forum a tech guy tested it and found it to seem fine. You never can truly know they are all alike.
 

pma

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Thanks for this analysis, @amirm . The board looks exactly as at Amazon photos. After I receive my piece I will check if NE5532 are genuine parts, as I heard some doubts. They are in sockets so it will be easy. I also have some concerns to operate the unit at higher continuos power, as I normally do as a test procedure.
 

pavuol

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Excellent, than you.

Some more information from TPA3255 datasheet:

Absolute Maximum Ratings : Tj 150°C [Overtemperature error at I/O protection signalling]
Recommended Operating Conditions : Tj 125°C [Overtemperature warning at IO protection signalling]
Thermal metric data - obtained with 85°C heat sink temp.
Datasheet audio measurements - @ TC = 75°C

BTL power vs. temp.:
2021-01-02 11_20_31-TPA3255 315-W Stereo, 600-W Mono PurePath™ Ultra-HD Analog-Input datasheet...jpg


So if I get it right, ideal temp. is =<75C, max. recommended is 125C with even some "reserve" up to 150C ?
And active cooling would mostly help with better reliability & life expectancy rather then significant power increase?
 
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Matias

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Those opamps look like they are mounted on a socket, right? If so one can change and roll opamps. Some better ones are not that expensive, a few dollars each.

Dual opamps

AD823, AD823AN, AD8066, AD8620, AD712, AD827, C4570, JRC4556AD, JRC4580, JRC5532, JRC5532D, JRC5532, LF353, LM4562, LME49860, LM833N, LME49720, MUSES8920, NE5532, NEC4520, NEC4570, NJM2068D, NJM2114, NJM2214D, NJM4558, NJM4558D, NJM4560, NJM5532, NJM4558P, OP275, OPA1612, OPA2277PA, OPA2132, OPA2134, OPA2604, JRC4558, RC4558D, RC4558P, TL052, TL072.
 
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PeteL

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Someone should do the forensics and tell us if they are the real deal or fakes.

/
It's a 35 cents part in quantity, there are two. maybe I'm a bit naive, but there are many places to save money elsewhere. I am more curious about the Blue ones, film capacitors are actually expensive, and of course they wouldn't have gone for the high quality WIMA there, and in the end they are actually in the signal path. Do you see any markings?
 

pma

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I am more curious about the Blue ones, film capacitors are actually expensive, and of course they wouldn't have gone for the high quality WIMA there, and in the end they are actually in the signal path. Do you see any markings?

They are in the output LC filter that is tuned at some 45kHz/-3dB. I don't think these capacitors might be audible. However, they have to accommodate high dv/dt.
 

Matias

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PeteL

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They are in the output LC filter that is tuned at some 45kHz/-3dB. I don't think these capacitors might be audible.
I don't think it's audible neither, I'm just wondering what are the cheap options for this purpose.
edit: It could be EPCOS/TDK from the color, but they are not that cheap neither.
 
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PeteL

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Thanks for this analysis, @amirm . The board looks exactly as at Amazon photos. After I receive my piece I will check if NE5532 are genuine parts, as I heard some doubts. They are in sockets so it will be easy. I also have some concerns to operate the unit at higher continuos power, as I normally do as a test procedure.
Honestly, I don't think that a manufacturer that would be willing to put counterfeit parts to save a few cents would have cared to put it in a socket for people to easily assert their fraud...
 

DuncanTodd

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Those opamps look like they are sitting in a socket, right? If so one can change and roll opamps. Some better ones are not that expensive, a few dollars each.

Dual opamps

AD823, AD823AN, AD8066, AD8620, AD712, AD827, C4570, JRC4556AD, JRC4580, JRC5532, JRC5532D, JRC5532, LF353, LM4562, LME49860, LM833N, LME49720, MUSES8920, NE5532, NEC4520, NEC4570, NJM2068D, NJM2114, NJM2214D, NJM4558, NJM4558D, NJM4560, NJM5532, NJM4558P, OP275, OPA1612, OPA2277PA, OPA2132, OPA2134, OPA2604, JRC4558, RC4558D, RC4558P, TL052, TL072.
It was experimented to some degree already. LM4562 and a couple of the OPA ones were prefered over the shipped one, likely on subjective basis though. a DIY forum or two did a lot of modifications on this unit and others.
 
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