AIYIMA A07 TPA3255 Review (Amplifier)

[Piero]

I'm new on this forum, so first of all: hi everybody, thank you in advance for your help... and sorry for my poor English!

To better explain my question, I need to start from the beginning.

Last year (during the first covid lockdown, dreaming about the BIG party I'll organize when all this will be finished...) I decided to realize a cheap PA amplifier. On Amazon I took a small module equipped with a TDA7498e (~30$) and a cheap switching power supply 36VDC 10A (for LED strips/stepping motors, ~35$). The results was REALLY a surprise for me (...I'm too old to trust such a small heatsink): that amplifier can output 22 Veff@1KHz to an 8ohm load (60W), both channels driven. And the sound... is not so bad.
A few weeks ago, tidying up my garage, I found a couple of VU meters and a box (originally used for a preamplifier/electronic crossover) and I decided to (try to) rise the bar in terms of power, using a TPA3255 power amplifier (the "classic" PCB, with 2 x 4700uF big capacitors) and a 48VDC 12.5A power supply. Unfortunately:
- the first amplifier module was faulty (short on the power input);
- the second has shown a behaviour that I have considered as a problem: the right channel goes in OLP -and shuts down- too early (at least IMO). Fault active, OTW inactive... reset required (that means: cycle power, NOT reccomended during a party ).
I've checked the TPA3255's datasheet. Since the OC_ADJ resistor value on that pcb is 22K (that means: protection strategy=CB3C, OC threshold=17.0A) and my loudspeakers' impedance is 8ohm, I think that the OLP shoudn't activate at all; so I've assumed the second module as faulty too, and decided to try another kind of module. So, I've ordered an Aiyima A07 in order to disassemble it and use the bare PCB.
Eventually, here are my questions.
1 - Can you confirm that FAULT and CLIP_OTW signals have no visible feedback (LEDs) on this amplifier?
2 - Did anybody check the OC_ADJ resistor on this amplifier's PCB?
3 - On the review you wrote "...the higher voltage power supply does better with 8 ohm load where we become voltage limited", and the max output power you have reached is 61W @ 48VDC. But: what do you mean with "voltage limited"? In other words: (48VDC - Vfet) / 1.414 ... the expected output voltage should be around 32Veff, that means ~130W @ 8ohm. Where am I wrong? And again: what happens over 61W? Did the OLP activate, did the amplifier shut down, did the power supply shut down? And what's next to resume?

Again, thank you for your help. The Aiyima will arrive on Monday, any information will be very useful to me.

Regards

 

[AdamG]

Welcome Aboard @Piero.

 

[lithoc]

I'm new on this forum, so first of all: hi everybody, thank you in advance for your help... and sorry for my poor English!

To better explain my question, I need to start from the beginning.

Last year (during the first covid lockdown, dreaming about the BIG party I'll organize when all this will be finished...) I decided to realize a cheap PA amplifier. On Amazon I took a small module equipped with a TDA7498e (~30$) and a cheap switching power supply 36VDC 10A (for LED strips/stepping motors, ~35$). The results was REALLY a surprise for me (...I'm too old to trust such a small heatsink): that amplifier can output 22 Veff@1KHz to an 8ohm load (60W), both channels driven. And the sound... is not so bad.
A few weeks ago, tidying up my garage, I found a couple of VU meters and a box (originally used for a preamplifier/electronic crossover) and I decided to (try to) rise the bar in terms of power, using a TPA3255 power amplifier (the "classic" PCB, with 2 x 4700uF big capacitors) and a 48VDC 12.5A power supply. Unfortunately:
- the first amplifier module was faulty (short on the power input);
- the second has shown a behaviour that I have considered as a problem: the right channel goes in OLP -and shuts down- too early (at least IMO). Fault active, OTW inactive... reset required (that means: cycle power, NOT reccomended during a party ).
I've checked the TPA3255's datasheet. Since the OC_ADJ resistor value on that pcb is 22K (that means: protection strategy=CB3C, OC threshold=17.0A) and my loudspeakers' impedance is 8ohm, I think that the OLP shoudn't activate at all; so I've assumed the second module as faulty too, and decided to try another kind of module. So, I've ordered an Aiyima A07 in order to disassemble it and use the bare PCB.
Eventually, here are my questions.
1 - Can you confirm that FAULT and CLIP_OTW signals have no visible feedback (LEDs) on this amplifier?
2 - Did anybody check the OC_ADJ resistor on this amplifier's PCB?
3 - On the review you wrote "...the higher voltage power supply does better with 8 ohm load where we become voltage limited", and the max output power you have reached is 61W @ 48VDC. But: what do you mean with "voltage limited"? In other words: (48VDC - Vfet) / 1.414 ... the expected output voltage should be around 32Veff, that means ~130W @ 8ohm. Where am I wrong? And again: what happens over 61W? Did the OLP activate, did the amplifier shut down, did the power supply shut down? And what's next to resume?

Again, thank you for your help. The Aiyima will arrive on Monday, any information will be very useful to me.

Regards

Amir is using 48v 3a power adapter during the test. I believe the power adapter shutdown due to protection . I'm using 48v 3a and during very very high volume. The power adapter will shutdown


Your 48v 12a definitely put out more power but I guest you will have overheating and reliability issues .

 

[sefril]

I was already in bed when I found your post.
As I read the text again today, did you connect a 24V power supply to the Topping D3 with a 15V power supply voltage? Did D3 break? That's too dangerous.

Most DC plugs have a positive electrode at the center pin. Polarity is usually shown on the power supply body.

The problem is your A07, but I've had the same symptom of not turning on with other TPA3255 amplifiers. The cause was poor quality of the power switch. From that experience I suggest to you.
Repeat ON-OFF of the power switch about 100 times quickly. That may improve it.

Thanks, Toku. Unfortunately i already tried your suggestion and the amplifier still doesn’t work. I already bought another power supply (this time is 48v 3a) and still doesn’t work. I guess tomorrow i’ll try to bring this amplifier to the amplifier service center.

 

[AdamG]

Thanks, Toku. Unfortunately i already tried your suggestion and the amplifier still doesn’t work. I already bought another power supply (this time is 48v 3a) and still doesn’t work. I guess tomorrow i’ll try to bring this amplifier to the amplifier service center.

Welcome Aboard @sefril.

 

[Raindog123]

tomorrow i’ll try to bring this amplifier to the amplifier service center.

Good luck! And please let us know the outcome. There was one other similar report before...

 

[Head_Unit]

OK just got one of these, haven't connected yet (oops speaker wire is at another house, d'oh!). Thanks so much @amirm for actual testing, I needed something small but wanted more than like 13 watts. So many little Class D's out there claiming a lot more watts than what they really can, or are dirty.

 

[Toku]

I'm new on this forum, so first of all: hi everybody, thank you in advance for your help... and sorry for my poor English!

To better explain my question, I need to start from the beginning.

Last year (during the first covid lockdown, dreaming about the BIG party I'll organize when all this will be finished...) I decided to realize a cheap PA amplifier. On Amazon I took a small module equipped with a TDA7498e (~30$) and a cheap switching power supply 36VDC 10A (for LED strips/stepping motors, ~35$). The results was REALLY a surprise for me (...I'm too old to trust such a small heatsink): that amplifier can output 22 Veff@1KHz to an 8ohm load (60W), both channels driven. And the sound... is not so bad.
A few weeks ago, tidying up my garage, I found a couple of VU meters and a box (originally used for a preamplifier/electronic crossover) and I decided to (try to) rise the bar in terms of power, using a TPA3255 power amplifier (the "classic" PCB, with 2 x 4700uF big capacitors) and a 48VDC 12.5A power supply. Unfortunately:
- the first amplifier module was faulty (short on the power input);
- the second has shown a behaviour that I have considered as a problem: the right channel goes in OLP -and shuts down- too early (at least IMO). Fault active, OTW inactive... reset required (that means: cycle power, NOT reccomended during a party ).
I've checked the TPA3255's datasheet. Since the OC_ADJ resistor value on that pcb is 22K (that means: protection strategy=CB3C, OC threshold=17.0A) and my loudspeakers' impedance is 8ohm, I think that the OLP shoudn't activate at all; so I've assumed the second module as faulty too, and decided to try another kind of module. So, I've ordered an Aiyima A07 in order to disassemble it and use the bare PCB.
Eventually, here are my questions.
1 - Can you confirm that FAULT and CLIP_OTW signals have no visible feedback (LEDs) on this amplifier?
2 - Did anybody check the OC_ADJ resistor on this amplifier's PCB?
3 - On the review you wrote "...the higher voltage power supply does better with 8 ohm load where we become voltage limited", and the max output power you have reached is 61W @ 48VDC. But: what do you mean with "voltage limited"? In other words: (48VDC - Vfet) / 1.414 ... the expected output voltage should be around 32Veff, that means ~130W @ 8ohm. Where am I wrong? And again: what happens over 61W? Did the OLP activate, did the amplifier shut down, did the power supply shut down? And what's next to resume?

Again, thank you for your help. The Aiyima will arrive on Monday, any information will be very useful to me.

Regards

Which product was your first TPA3255 amp?
Among the TPA3255 amplifier products, I know one that works as you pointed out. They have the wrong circuit design.

I use two AIYIMA A07, but there is no indicator LED for FAULT and CLIP_OTW. However, the operation at high volume is very stable. The power supply voltage can operate at 48V, but the withstand voltage of the decoupling capacitor of the power supply line of A07 is only 50V, and continuous use at 48V is dangerous. I have lowered it to 42V by the voltage regulation volume.

The output power displayed by a Chinese audio amplifier such as the A07 is not a value that can actually be output. The displayed output power is the maximum value listed in the IC chip manufacturer's data sheet. It seems that such labeling is allowed in the business customs of Chinese society.

 

[Piero]

Thank you for your reply, Toku.
In the attached image you can see the design of my first & second amplifiers. Don't ask me the manifacturer... anyway, I have no way to choose one, instead of another.
About the wrong design: see the second image. There's also a problem with some resistors' value... or with the printings on the PCB

the operation at high volume is very stable

That's what I need. Also, I hope that the overall output power will be higher than the TDA7498e's one... and that the reason for shutdown -in case- will be the OTP instead of the OLP. No problem with fans, in my scenario

Thank you again

Regards

 

[Toku]

Thank you for your reply, Toku.
In the attached image you can see the design of my first & second amplifiers. Don't ask me the manifacturer... anyway, I have no way to choose one, instead of another.
About the wrong design: see the second image. There's also a problem with some resistors' value... or with the printings on the PCB


That's what I need. Also, I hope that the overall output power will be higher than the TDA7498e's one... and that the reason for shutdown -in case- will be the OTP instead of the OLP. No problem with fans, in my scenario

Thank you again

RegardsView attachment 125939View attachment 125940

I expected your amp to be this product. The expectation was a perfect hit.
I bought two of the same amp boards over two years ago and suffered from exactly the same symptoms as you. If I continued to use it after that, it started to generate noise and I gave up using this amp board.
This amp board has undergone several modifications and is still on sale. As far as I know, there are four types. However, it seems that the problems from the initial model have not been improved at all.

 

[sefril]

Welcome Aboard @sefril.

Thank you Mr Adam the moderator.

Good luck! And please let us know the outcome. There was one other similar report before...

Okay, here’s the report. Turns out that my amplifier has a problem in the DC power socket. The repairman (is it the correct name? Lol) test the amplifier by bypassing the DC socket and it works. He told me to bring my power supply for further test tomorrow (yeah, i forgot to give the power supply to him today).

btw, is it hard to replace the DC power socket? I already ordered the replacement (doesn’t even cost 1US$). If it’s not hard to replace then i’ll ask the repairman to replace it. Thanks.

 

[abdo123]

btw, is it hard to replace the DC power socket? I already ordered the replacement (doesn’t even cost 1US$). If it’s not hard to replace then i’ll ask the repairman to replace it. Thanks.

do you have a soldering machine? if not it's better to let the repairman handle it. it should be very little work.

 

[Raindog123]

@sefril Have you tried contacting Aiyima? After you explain them your situation, they might even send you a new unit without asking/waiting for return of this faulty one. They are still at the point of building their reputation, so seem to care about customers and publicity.

 

[Piero]

I expected your amp to be this product. The expectation was a perfect hit.
I bought two of the same amp boards over two years ago and suffered from exactly the same symptoms as you. If I continued to use it after that, it started to generate noise and I gave up using this amp board.
This amp board has undergone several modifications and is still on sale. As far as I know, there are four types. However, it seems that the problems from the initial model have not been improved at all.

I agree. This kind of board has some problems... and not only at circuit's design level, imo.
The seller left me the first amplifier (the burnt one, to save the return costs), so I could take a look. Well... just talking about the heatsink: the IC side is totally flat. They had to use a very thick termal pad, because other components -liying under the heatsink- are as high as the IC (maybe more...); anyway, using just two bare screws to keep the heatsink, the thermal transmission is surely bad... and it's really hard not to create problems to other components, such as those 1uF capacitors (...look at the hole in the red circle... )
To enhance the heat dissipation I have modified the heatsink, using a small alluminium brick and a couple of springs + longer screws. One more thermal interface, but thermal paste instead of pad (plus, a safe distance from PCB's components). Hope it will be useful on Aiyima's PCB too.

...the withstand voltage of the decoupling capacitor of the power supply line of A07 is only 50V, and continuous use at 48V is dangerous. I have lowered it to 42V by the voltage regulation

Yes, I've seen on Amazon's pictures. 1000uF 50V. Texas Instruments suggests 1000uF 80V, at least.
I would like to make it work @45VDC... maybe, bypassing the polarity protection diode that seems to be on the PCB.
What's your opinion about -possibly- changing those capacitors...? And what about (trying to) obtain a connection to OTW, FAULT and RESET pins? Too dangerous...?

Thank you again for your help

Regards

 

[sefril]

do you have a soldering machine? if not it's better to let the repairman handle it. it should be very little work.

Yeah, he’s the one that replace the socket. Thanks for the suggestion.

@sefril Have you tried contacting Aiyima? After you explain them your situation, they might even send you a new unit without asking/waiting for return of this faulty one. They are still at the point of building their reputation, so seem to care about customers and publicity.

already contact Aiyima through the platform where i bought the amplifier. I don’t expect much though.

btw, new problem arise after i set up the amplifier in my home. Here is my system: laptop - USB cable - Topping D3 - RCA cable - Aiyima A07 - speaker cable - Heco Interior Reflex speaker (old school, 90’s speaker with 4 ohm 60-90 watt).

when i put the max volume in my laptop and only turn the volume a little on A07, the left speaker is very dominant (loud) compared to the right speaker. When i use half volume in the laptop and turn up volume in A07, the right speaker sounds a little bit louder than before (the left speaker not as dominant as before). Is it because the volume potentiometer is broken? Or i need to test with another speaker or speaker cable?

I almost gave up this amplifier and searching for another amplifier instead Lol.

 

[pma]

The potentiometer used has very low quality and L-R balance of resistances is worst at the beginning (lowest volume). And every piece will be a bit different.

 

[abdo123]

The potentiometer used has very low quality and L-R balance of resistances is worst at the beginning (lowest volume). And every piece will be a bit different.

can you bypass it?

 

[pma]

Yes, but the gain would be too high then for most purposes.

 

[phoenixsong]

Yes, but the gain would be too high then for most purposes.

Unless a preamp is involved, but that defeats the low cost of this unit, wouldn't it?

 

[abdo123]

Yes, but the gain would be too high then for most purposes.

Is it simple to do? I'm planing to use a MiniDSP for volume control anyway.

I would very much appreciate if you would share how to bypass it with us.