Topping DX5II teardown

[Minato]

mine stopped working after less then 2 months. waiting to see if i can get another one but i bought it from china so you never know.
may i ask you how you opened it? i unscrewed 10 screws but it didn't open

But it won't turn on anymore? The screen stays black?

 

[Zamiel]

But it won't turn on anymore? The screen stays black?

yeah. i think the psu is gone or maybe a fuse

 

[chill]

yeah. i think the psu is gone or maybe a fuse

Mine is bricked today too
FW v1.67, same symptoms: black screen, not recognized by Windows via USB.
DFU mode is not shown after power on with the knob pressed.

 

[pma]

Assembly quality, soldering and cleanliness is not nice, it is quite poor. Disappointing.

 

[rocksteady]

@kevin gilmore has the circuit diagram posted here. Here's the full pcb board.


View attachment 467197

First, the digital part


View attachment 467198

You can see the bluetooth module on the top left.
On the middle right is the MS8422N, which is a chip to do routing, replacing LC89058W on earlier topping devices.
The signal then routes to the XMOS for final digital processing (EQ).

On the middle left is the ES9018 DAC. generating analog audio signal and then sending to the synwit processor below.
The Synwit chip will use onboard 12 bit ADC to convert that back to digital signal, and perform the FFT computation.
The FFT bin amplitude will be displayed on the screen as spectrum.

Right side is the I/V module and on the top is the output buffer for RCA using OPA1612.

The power supply is spread across the entire PCB. but below is the main one.

View attachment 467199

Here're the step down converters that generate +/-15V from the switching power supply. There're also mosfets/bjts that control the on/off of the power rails on the top.
the lower right is the headphone protection circuit, by detecting the sum of 4 (2 ch x 2 phase) outputs, so if any transistor fries, it should be able to prevent your headphone from being destroyed.

View attachment 467200

Here you see two I/V boards. Op Amps seem to be OPA1656.
I/V boards are dual sided and the front side can be seen as an improved op amp based on this patent.
once the circuit is simplified to equivalent circuit according to the patent,
what remains is a textbook I/V, identical to op1, r1, r2 and C1 in this article
The back side of the board is just the current source to support the differential pairs on the front side.

Below the I/V boards are the DAC chips and passive output stages.
Topping D50 III has the same board. but DX5 II has twice the I/V.
Each board computes the difference of L+/L-/R+/R- and Ref/2 per DAC.
D50III may omit the Ref/2 or just sum the L/R.

The middle part is particularly interesting. There're multiple transistor pairs. The output of those transistors goes to the I/V board's diff pair input.
So it's the reference voltage for the DAC chip. Based on the transistor counts I am pretty sure it's this patent.
D50 III has the same circuit, by the way. It's safe to assume both devices are designed at the similar time frame (2023).

On the right portion there's +/- 5.8V power rails (half of that shown in the photo), which power the op amps.

In kevin's diagram you can find the transistor pair model.

View attachment 467201

Finally the tiny PCB here is the HP Amp's input and VAS. BJTs are power source, similar to the I/V. The transistor pairs are the input stage (differential pairs).
The input signal is from the bottom motherboard's resistor group, which has the I/V output and HP amp feedback signal, with gain control / mute switches.
The Op Amp (looks like OPA1612) is the VAS. It finally goes to the heat sink on the right (not in the photo) for output.

The output stage is nothing special but a classic class B amplifier. Thanks to the global feedback and tons of compensation it doesn't show any signs of crossover distortion.
The efficiency of the amplifier is also how Topping can cram so much power inside this small box.

"The output stage is nothing special but a classic class B amplifier." You mean class A/B, surely? Otherwise, there would be no Crossover distortion to begin with...

 

[audiofun]

"The output stage is nothing special but a classic class B amplifier." You mean class A/B, surely? Otherwise, there would be no Crossover distortion to begin with...

no. class b. you didn't read the next sentence, did you?

 

[rocksteady]

no. class b. you didn't read the next sentence, did you?

I did read it. "Thanks to the global feedback and tons of compensation it doesn't show any signs of crossover distortion." Perhaps I'm just a Noob, but it was your reference to the lack of Crossover distortion that created confusion in my mind. I always thought that Crossover distortion was a property of Class A/B, specifically. It would seem that I was mistaken.
Thanks for the the Education...

 

[jmdesignz2]

Knock on wood mine is still functioning

 

[audiofun]

I did read it. "Thanks to the global feedback and tons of compensation it doesn't show any signs of crossover distortion." Perhaps I'm just a Noob, but it was your reference to the lack of Crossover distortion that created confusion in my mind. I always thought that Crossover distortion was a property of Class A/B, specifically. It would seem that I was mistaken.
Thanks for the the Education...

View attachment 479913

If you have an op amp to control the class b amplifier, and the feedback is from the output of class b back to op amp input, and if you have compensations to make the circuit stable, then the nonlinearity of the class b will be corrected by the feedback control, and won’t have the crossover distortion class b usually has.

Class a/b eliminates such distortion by biasing at the cost of slightly lower efficiency

 

[Mario1969]

Mine is bricked today too
FW v1.67, same symptoms: black screen, not recognized by Windows via USB.
DFU mode is not shown after power on with the knob pressed.

What did you do with the device? Did you send it back to TOPPING?

 

[dimon0869]

Mine is bricked today too
FW v1.67, same symptoms: black screen, not recognized by Windows via USB.
DFU mode is not shown after power on with the knob pressed.

I had exactly the same issue, but with firmware 1.39 and after only two hours of use. I turned it off and it wouldn't turn back on. I sent it to Moscow for repairs, but instead of fixing it, they made excuses like the processor was faulty, saying repairs weren't cost-effective and that I'd be better off buying a new device. Now I've sent it to a repair shop in my city, and the verdict is the same: either the processor or just the firmware itself. We've requested the firmware from the manufacturer twice, and two months have passed, with still no response. Overall, I'm not thrilled with Topping or their technical support, and I've lost any desire to buy their products again.

 

[Zamiel]

Received a refound and bought another one, this time from a shop in europe. i hope this one lasts

 

[SnakeLord]

I had exactly the same issue, but with firmware 1.39 and after only two hours of use. I turned it off and it wouldn't turn back on. I sent it to Moscow for repairs, but instead of fixing it, they made excuses like the processor was faulty, saying repairs weren't cost-effective and that I'd be better off buying a new device. Now I've sent it to a repair shop in my city, and the verdict is the same: either the processor or just the firmware itself. We've requested the firmware from the manufacturer twice, and two months have passed, with still no response. Overall, I'm not thrilled with Topping or their technical support, and I've lost any desire to buy their products again.

This makes no sense.

Why dont you just send your device to the shop where you have bought it from to get it either replaced or repaired as an warranty case? Instead of sending it to some random repair shops and then wondering that it makes no sense for those to repair an 300$ fully integrated device as the repair costs would be pretty much the same if not more.
And since it was already opened the warranty should have voided by now anyways.

Did you got your device directly from the manufacturer (Topping) or why do you expect them to take responsability for technical support in your case?
Just imagine how many resources Topping would need if they had to take care of all the Audiophile issues around the world...

 

[sokE]

Well, there goes mine... Bricked. Already sent an e-mail to Apos, just waiting on a reply. I had no clue this was even a thing. I just got mine end of August, and it worked till last night. Fun!!!!

 

[Mario1969]

Well, there goes mine... Bricked. Already sent an e-mail to Apos, just waiting on a reply. I had no clue this was even a thing. I just got mine end of August, and it worked till last night. Fun!!!!

It's sad to read this. From what I understand here on the forum, this is the fourth or fifth unit. Maybe it's a faulty batch. I'm starting to wonder when mine will die.

 

[sokE]

This is sad to read. From what I know, yours is the fourth. Maybe it's a faulty series. I'm starting to wonder when mine will die.

Actually I have a good news update and some info for the forum. I was on 1.72 firmware. I was able to get the screen to turn on in fw update mode and updated to new firmware 1.76. Guess what though? 1.72 doesn't even exist on the website anymore so I guess it was also defective like the older firmware mentioned on here. Topping needs to get their firmware game in check.

 

[Power Pop 23]

It's sad to read this. From what I understand here on the forum, this is the fourth or fifth unit. Maybe it's a faulty batch. I'm starting to wonder when mine will die.

Sad indeed. I relegated my still-working Topping PA5 amplifier to a secondary location rather than wonder if today was the day it was going to fail.

@Kal Rubinson wrote a thoughtful footnote to his review of the Topping DM-7 in Stereophile:

Footnote 1: It seems to me that Topping has emphasized making a high-quality product at the lowest possible cost, with the expectation that there will be little need for extended warranty support. The basic warranty is only one year, and internet purchases may require shipping to China for warranty repairs or replacement. While none of my Topping devices have failed, buyers need to assess their personal tolerance for dealing with the possibility.

I sometimes wish ASR members would be required to acknowledge they have read and understand the above footnote before reading an ASR review of gear from Topping Audio or an audio manufacturer with a similar business model.

 

[Mario1969]

Actually I have a good news update and some info for the forum. I was on 1.72 firmware. I was able to get the screen to turn on in fw update mode and updated to new firmware 1.76. Guess what though? 1.72 doesn't even exist on the website anymore so I guess it was also defective like the older firmware mentioned on here. Topping needs to get their firmware game in check.

that's a good sign ..the patient will live

 

[jmdesignz2]

Well, there goes mine... Bricked. Already sent an e-mail to Apos, just waiting on a reply. I had no clue this was even a thing. I just got mine end of August, and it worked till last night. Fun!!!!

What were the symptoms? What firmware

 

[sokE]

that's a good sign ..the patient will live

Haha yes the patient is alive and kicking again thankfully!