Amazing Budget Amplifier Find: AIYIMA A07 TPA3255 Video Review

[Keith Conroy]

Thread on loans here.

Info on donations here.

Thank You So Much for your input !

 

[Steamrolly]

Is it based on the same chip?

No the Fosi Audio amp shown is based on a TDA7498E chip which is the same chip used in the Topping PA3.

 

[Koeitje]

At around 12 minutes, the distortion of class D amplifiers is stated to be "messy" in that the distortion varies at different frequencies. Is this part of the reason or rationale of preferring (or assuming to prefer) class A over class D?

It depends on the class D amplifier, NCore and Purifi don't have these issues.

 

[carsknivesbeer]

It depends on the class D amplifier, NCore and Purifi don't have these issues.

So class A does not have this problem and is this part of the argument people have against class D in general?

 

[restorer-john]

So class A does not have this problem and is this part of the argument people have against class D in general?

Class A and Class AB amplifiers are also not immune to THD rising vs frequency. Class A and AB also generally have increased distortion as the load impedance drops. No amplifiers are perfect and some are considerably worse than others.

Traditionally, Class Ds have been a mess at high frequencies, much worse than other topologies. The situation is improving for sure, but with testing bandwidths reduced in order to prevent issues with out of band content and analyzers, THD numbers are not remotely comparable to the many decades of full bandwidth THD numbers we have grown used to with traditional amplifiers.

 

[Bruce Morgen]

Class A and Class AB amplifiers are also not immune to THD rising vs frequency. Class A and AB also generally have increased distortion as the load impedance drops. No amplifiers are perfect and some are considerably worse than others.

Traditionally, Class Ds have been a mess at high frequencies, much worse than other topologies. The situation is improving for sure, but with testing bandwidths reduced in order to prevent issues with out of band content and analyzers, THD numbers are not remotely comparable to the many decades of full bandwidth THD numbers we have grown used to with traditional amplifiers.

Like me, I think you may remember the days when top tier amp designers went to great lengths to minimize transient intermodulation distortion (TIM) by maximizing slew rate and extending high frequency response far beyond audibility. The mammoth Sansui AU-X1 integrated amp was spectacular in that respect, as were some Kenwood and Pioneer products from that era, but there was a lot of skepticism about the audible benefits of that sort of exotic circuitry -- and TIM is rarely even mentioned nowadays. As for THD numbers not being comparable between Class D and the older topologies, that may well be true -- but I can testify that my A07s (I own four and use three of them in my 6.1 desktop/nearfield system, driven by a vintage Yamaha DSP-1/DSR-100) are subjectively better performers than the highly touted, Nelson Pass designed Adcom GFA-535 I swore by back in its late 20th century heyday.

 

[Koeitje]

So class A does not have this problem and is this part of the argument people have against class D in general?

Depends on the design. The worst tested amplifier in this site is a DIY Class A amplifier. I wouldn't be surprised if there are more terrible class A amplifiers out there. I don't see the point in saying that class D is bad because of these low budget amplifiers. If you do that you might as well say class A is also bad. There does seem to be some obsession with out of the audio band performance for amplifiers. I don't know what is that about.

 

[rockyb]

@amirm: given the conversations about different wall warts or external power supplies, have you considered including another test that substituted a lab power supply (ideally linear) to eliminate any switching noise? That way those who wanted the ultimate performance could address that source of noise with better power supplies. Amplifiers like this might be addressed with three motorcycle batteries in series as a way to determine if the search for a better power supply is worth the time and expense.

 

[amirm]

My lab supply doesn't have enough current for power amplifiers unfortunately.

 

[MondoAudio]

@amirm, thanks for this review. I own one of these amps and use it as my go-to bench amp to test speakers and drive DIY projects. Truth is, I enjoy it! Nonetheless it's nice to see objective validation.

 

[Berguezinho]

Excellent video and analysis ! What i miss and feel here with TPA 3251 is that seems ok with pure 4 ohms resistive loads ! Real, hard passive crossovers , seems to dim a lot the highs (i have a Focal TC120 TDX2 in my monitor with Seas 6,5 mid) and sure i listen the difference ... Can you comment this , please ? Andreas

 

[conuss]

I own one of these amps and use it as my go-to bench amp to test speakers and drive DIY projects. Truth is, I enjoy it! Nonetheless it's nice to see objective validation.

In your DIY project process, have you noticed a specific attenuator model in this amplifier? If you didn't attach importance to its quality, then I would be very surprised. What is the specific model and how do you assess the quality of this volume control? Does it need replacement?

 

[Ismapics]

On sale for Prime Day. https://www.amazon.com/AIYIMA-A07-T...+D&psr=PDAY&qid=1624374492&s=prime-day&sr=1-3

 

[Sonny1]

Amir, your YouTube channel has become my favorite. I know the videos are time consuming but they are so well done. Looking forward to seeing more. I’ve learned so much and appreciate the effort you put into the videos. Great stuff!

 

[carlmart]

You all have probably seen the review of the AIYIMA A07 here but for YouTube audience, they asked for budget finds so I thought I do a video on that:

Text review: https://www.audiosciencereview.com/...ds/aiyima-a07-tpa3255-review-amplifier.18984/

Teardown: https://www.audiosciencereview.com/forum/index.php?threads/aiyima-a07-tpa3255-tear-down.19020/

My congratulations on a very clearly explained test on what figures represent on the amplifier, and everything else.

There's an easy thing I would recommend to anyone buying any of these class D amplifiers, probably whichever the chip is. Unscrew the heatsink, clean the thermal grease, which might probably be dry (that happened to on a Breezy Audio amp), and replace with the white thermal grease you can buy for a few dollars. Just a thin even layer all around the chip. That should improve heat dissipation a lot!

You can always try to find another heatsink that is longer, or taller, though taller would make impossible using the box top cover, except if you cut a hole around the heatsink fins.

Another thing you could try is using a small fan, though that may make noise.

Replacing the grease can be done by anybody. For the rest you need some more experience in DIY mods.

Space will probably not allow it, but you could move the large "Nichicon" caps below the pcb and increase their size at the same time, to 2200uF or higher. The higher the better. Or you could move toe caps with wires to the vacant space below (on the internal pcb picture that was shown) and lie the caps horizontally, which would also allow higher capacity caps. You have to add two 100nF film capacitors to the pads you took the caps from.

Some people in DIYAudio have modified many other parts, but these things I described are things that demand little work. Once again, this should be done by people that have electronics DIY experience.

Well, just my five cents.