Topping A90 Discrete (A90D) - Teardown and personal thoughts

[kevin gilmore]

this was the schematic of the nfca module as used in the eha5. so the 90d may be slightly different as it probably does not have the 18khz filter.
and the volume pot is replaced by a discrete relay attenuator. high res pictures posted elsewhere. too big to fit here.

 

[mrjayviper]

Everything is straight forward, but after taking off the back plate you will need to figure out a way to easily disconnect the two ribbon cables coming from the rotary knob and display.

Worst part is to get the two screws from the front plate off, given that you'll need a very long and very thin screwdriver (the one from iFixIT is shorter and thicker, even with the longer adapter included).

Chances to damage the ribbon cables and/or to not be able to put everything back are quite high, so I strongly don't encourage anyone to teardown this device!

BTW, why drilling the top case for? I measured quite low temps on top, even after driving at insane levels two planars at the same time the temps were like around 40C. My Matrix HPA-3B was hitting 60C when I was driving two planars for testing.

thanks for the reply. my worry is those 2 ribbon cables. removal might be easy but putting it back is my worry.

 

[trl]

Putting back the ribbons can be easily done from front side, given that you will need to remove the front plate anyway. So worst part now would be figuring out a way to place back the two screws in the corresponding locations from the front plate. Worst case scenario is to not be able to fix back the front plate (fix the feont plate with a couple of small scoth tape pieces).

However, if you can find a long enough and very thin screwdriver you should be able to place those two tiny screws back. I was using the iFixit screwdriver + the 150 mm Flex Extension and it was a PIA to put back those two inner screws, so anything longer and thinner than that would be way better for this job.

 

[mrjayviper]

Putting back the ribbons can be easily done from front side, given that you will need to remove the front plate anyway. So worst part now would be figuring out a way to place back the two screws in the corresponding locations from the front plate. Worst case scenario is to not be able to fix back the front plate (fix the feont plate with a couple of small scoth tape pieces).

However, if you can find a long enough and very thin screwdriver you should be able to place those two tiny screws back. I was using the iFixit screwdriver + the 150 mm Flex Extension and it was a PIA to put back those two inner screws, so anything longer and thinner than that would be way better for this job.

do you still have the amp in "pieces"? can you please take a pic of the front pieces and the front pcb just to give me an idea on what's involved in putting it all back together?

thanks again!

 

[trl]

The headamp has been assembled back a few hours after I had it disassembled for this teardown review, but you can look on the first page and check the pics with the temperature measurements and you can clearly see there the front panel and the top of the PCB with the two ribbon cables connected.

 

[Music1969]

Any teardown of Topping A70 Pro coming @trl ?

I believe it is even better amp, and cheaper !

See here: 8 minutes ago

 

[audiofun]

Any teardown of Topping A70 Pro coming @trl ?

I believe it is even better amp, and cheaper !

See here: 8 minutes ago

I would like to see a teardown too. but even with that we may still have limited knowledge, as the main parts are sealed in modules. I lost interest in buying (and teardowning) topping products after they transitioned to use those modules. To me this is a stupid move --- causing a lot of product issues, and not enough to prevent competitors learning their designs.
I would say they have similar technology, both use PBSS305 as output transistors. but unlike the complex discrete circuit here, A70 Pro sealed module is perhaps just using op amps.

 

[trl]

Any teardown of Topping A70 Pro coming @trl ?

I believe it is even better amp, and cheaper !

See here: 8 minutes ago

The A70 Pro seems to have capsulated T'ang-ku modules, while A90 has capsulated NFCA modules, like the ones used in the DX9 below (which are naked and not capsulated):

​

However, you can check https://www.audiosciencereview.com/forum/index.php?threads/topping-a70-pro-hp-preamp-review.44636/ and also the graph published by Amir as well:

​

I suppose that the newly developed T'ang-ku modules are still Nested Feedback Composite Amplifier type, but more details can also be found here: https://www.tpdz.net/productinfo/1009982.html. Perhaps @JohnYang1997 would like to share more with us or perhaps to update https://www.audiosciencereview.com/forum/index.php?threads/topping-a70-pro-hp-preamp-review.44636/ with a few inside pics?