Review and Measurements of Topping DX3Pro DAC and Headphone Amp

[splkn]

I simulated the headphone circuit is normal work as below.
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Output waveform:
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When the diode (DL2) is broken.
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The output waveform is Negative.
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There are a lot of mistakes on your scheme. In the event of a fault, there was a constant current in the headphones of 10 V. Please simulate a short-circuit of the diode after correcting the circuit

 

[fljoe]

Even if the Topping engineers isolate the problem .. what is our recourse here ... free replacement of broken DX3Pro with a fixed DX3Pro?

 

[yue]

Even if the Topping engineers isolate the problem .. what is our recourse here ... free replacement of broken DX3Pro with a fixed DX3Pro?

good question! I believe a recall of all units is necessary given large amount of people experienced quite a lot of issues, and in worst cases the issue could damage your unit, your headphones, and your hearings. but that’s never going to happen on those cheap Chinese products.

It’s 2019 and some manufacturers still cannot design simple headphone amplifiers correctly, given almost no limitation of unit size and budgets (compare it with apple’s dongles), and their product can still win the highest recommendations on this forum, with a lot of praise of their technical excellence— how ironic it is!

Today good designs are all open source, such as the khadas tone board or the objective 2 amplifier. However the Chi-Fi products are neither willing to learn nor copy from those reference designs. They boasts their products with dual ES9038 Pro/ dual AK4493, while they can’t even reach single ES9038Pro or single AK4490 product performance (such as RME ADI dac or Tone board, oppo Sonica DAC). Moreover they cannot even do the basics right and produced quite a lot of safety and reliability issues.

The forum members are so patiently troubleshooting issues for those manufacturers, and discussing about purchasing extra power supplies to make the unit run more stable. Let me make it clear here — Those manufacturers do not deserve the kindness.


If you still have warranty, return it to your seller. That’s my advice. And avoid buying Topping products just like avoid buying Schiit products in the future. In my opinion Topping is just another version of Schiit., and in terms of customer support and warranties they are even worse than Schiit.

If they don’t recall all units I won’t buy anything from them again in my entire life.

 

[simonchretien]

This is clearly not the case. Mine stop producing sound in the middle of a finale coda, which by no means it cannot detect the music.
Other people experienced the shutdown and are not able to turn it back on.

Yep, one of the shutdowns of my unit was when I was working and listening to music. The others were during the night with and without music playing.

 

[simonchretien]

Incidentally my unit just shut off for the 4th time now. Frequency about once per 3 weeks. So now I can fully agree that we can cross PSU from our list, as I was using Meanwell GS25A15-P1J (15V, 1.66A) since the beginning of this month. Also no other remotes in sight.
I guess one possibility is remote is faulty and sends signal to power off on it's own, but I would really doubt it. I'm connecting dx3 pro to APC ups, maybe that is a factor too, but frankly if anything this should be a positive since it regulates power somewhat (it's standard offline back-ups).

I tried mine on my AVR UPS, and from a separate power bar, makes no difference on shutdowns.

 

[simonchretien]

Even if the Topping engineers isolate the problem .. what is our recourse here ... free replacement of broken DX3Pro with a fixed DX3Pro?

The main problem with this is that they didnt want my unit back, I have to go through the ebay seller which has a rip-off of 20% on returns, plus the insane shipping to china of course. Anyway, that's my mistake, was my first buying experience directly from china, let's say this is the last one.

 

[John Hammond]

In my Dx3Pro the bias current it is 0.0075V/4.7ohm=1.6mA on each channel, left and right.

I measured the presumably "good" left channel of my unit and am seeing the same. This seems like a reasonable bias current for transistors of this package size.

 

[amirm]

If the DX3-Pro circuit is same as Heres's an example of an extremely similar circuit. Maybe the diode was broken which is for controlling to turn off the BJT.

The diodes are there to bias the transistor to get it into conduction zone.

 

[John Hammond]

If the DX3-Pro circuit is same as Heres's an example of an extremely similar circuit. Maybe the diode was broken which is for controlling to turn off the BJT.

At least on my failed channel, there's no issue with the biasing diodes - these have all tested as good with approximately a 0.55V diode drop. The fault is in the PNP transistor which has failed to a short from collector to emitter.

 

[John Hammond]

I did some additional experimentation with my unit last night and didn't find anything conclusive as to why some users have seen their headphone amp stages die. I ran some swept sine tones through the working left channel of my unit into a variety of resistive and headphone loads and didn't see any stability issues on an oscilloscope, and current through the headphone amplifier output transistors seemed completely reasonable. It's possible Topping built with a bad batch of transistors?

For my unit, I don't want to deal with the return shipping to China (and likely restocking fee) just to possibly receive another unit that may have the same design and/or part quality flaw. Under the theory that there is some issue in the quality of the headphone amp output transistors Topping used, I'll probably try to find something footprint and spec compatible on Digikey and swap them in to see if I can bring my amp back to life. I'll keep this thread updated.

 

[yue]

I did some additional experimentation with my unit last night and didn't find anything conclusive as to why some users have seen their headphone amp stages die. I ran some swept sine tones through the working left channel of my unit into a variety of resistive and headphone loads and didn't see any stability issues on an oscilloscope, and current through the headphone amplifier output transistors seemed completely reasonable. It's possible Topping built with a bad batch of transistors?

For my unit, I don't want to deal with the return shipping to China (and likely restocking fee) just to possibly receive another unit that may have the same design and/or part quality flaw. Under the theory that there is some issue in the quality of the headphone amp output transistors Topping used, I'll probably try to find something footprint and spec compatible on Digikey and swap them in to see if I can bring my amp back to life. I'll keep this thread updated.

Topping is silently working on a redesign of DX3 Pro. they will silently refresh the product with the new design.

This is bad news for existing customers because you will just be ignored.

I understand you don't want return shipping to china and a restocking fee. So make good use of your right to leave seller a poor review, and aski Topping to recall all DX3 Pros. My recommendation.

 

[PorchSong]

So, do you think they will 'dump' existing designs on Massdrop? I see they JUST started another drop on this unit when the last one was only a couple weeks ago.

Yue, any indication when the 'redesign' will be out?

 

[JohnBooty]

Under the theory that there is some issue in the quality of the headphone amp output transistors Topping used

I am not a person with any electrical engineering chops whatsoever, but this certainly seems most likely to me.

If it was a design problem, you wouldn't see some units (like Amir's original unit) being seemingly bulletproof while others fail. Also if there was anything obviously flawed about the design I suspect somebody would have pointed it out by now. Topping says they're doing a "redesign" but I'm guessing it's a minor revision.

And based on your unit (admittedly, a sample size of one) it doesn't look like there was a quality control issue with the way the unit was assembled.

 

[yue]

So, do you think they will 'dump' existing designs on Massdrop? I see they JUST started another drop on this unit when the last one was only a couple weeks ago.

The one on sell on massdrop was manufactured before that, and indeed it is of a new design --- you'll notice they replaced the LED display. Because they already manufactured it, they will of course sell it.

Yue, any indication when the 'redesign' will be out?

No but I assume it takes months.

 

[kukocz]

Maybe I missed something but could you please tell me where Topping announced they're working on redesign of DX3 Pro?

 

[yue]

Topping says they're doing a "redesign" but I'm guessing it's a minor revision.

According to Topping, it's not a minor revision. It's not clear whether they'll imrpove the amp stage but power circuit and relays will all be replaced.

If it was a design problem, you wouldn't see some units (like Amir's original unit) being seemingly bulletproof while others fail.

The mysterious thing is all failed units failed differently. And some failed units are rock solid under other people's hands.

 

[777]

My unit after almost two months works perfectly. I abuse it every day. I was soldering and desoldering tens of pieces and no one problem. My unit is solid like a rock. Today I was rise up the bias current of the headphones amplifier from 1.5mA to 12mA and no problem. Everything was like a book.

 

[yue]

Maybe I missed something but could you please tell me where Topping announced they're working on redesign of DX3 Pro?

Topping told me via email that they plan to change many parts of existing circuit.

I know to normal customers it may sounds weird but all manufactures (Topping, JDS, SMSL included ) change their pcb and components without notice regularly. Almost every batch they produce could have some differences.

Manufactures revise their boards a lot of times in each batch and zero customer noticed that. SMSL did that quite often in the past but the worst thing they experienced was Amir announced one of their revisions of SMSL SU-8 as "version 2", it cost them a lot of money as many existing customers return their "version 1" devices (and in fact there're many versions of "version 1"). That's also part of the reason they posted tutorial on how to change V1 devices to V2, just to avoid you returning to them.

With this bad example, you can now understand why manufactures never inform customers even when most times the changes leads to product improvements in later versions.

Earliest version of JDS atom has right and left channel swapped and they manually rewire them. That pcb bug was fixed in a later version of PCB without notice as well.

In short, modifying pcb/components between each production batch without informing customers is not news to manufacturers. Such change may lead to performance differences, and Amir's review can only measure performance of only one batch of a product. Bear that in mind when you read his reviews, and what you end up in your hand may be a different device.

 

[noel_fs]

Topping told me via email that they plan to change many parts of existing circuit.

I know to normal customers it may sounds weird but all manufactures (Topping, JDS, SMSL included ) change their pcb and components without notice regularly. Almost every batch they produce could have some differences.

Manufactures revise their boards a lot of times in each batch before that and zero customer noticed that. SMSL did that quite often in the past but the worst thing they experienced was Amir announced one of their revisions of SMSL SU-8 as "version 2", it cost them a lot of money as many existing customers return their v1 devices. That's also part of the reason why they posted tutorial on how to change V1 devices to V2.

With this bad example, you can now understand why manufactures never inform customers even when most times the changes leads to product improvements in later versions.

Earliest version of JDS atom has right and left channel swapped and they manually rewire them. That pcb bug was fixed in a later version of PCB without notice as well.

In short, modifying pcb/components between each production batch without informing customers is not news to manufacturers. Such change may lead to performance differences, and Amir's review can only measure performance of only one batch of a product. Bear that in mind when you read his reviews, and what you end up in your hand may be a different device.

Even tho for the most part you are not wrong, you just fucking love drama. Get over yourself. Yes, its a shame that some early adopters of the product got fucked. But hey, do you have something comparable for the same price point with similar specs and features? Guess what, no, there is nothing like this. So, yes, some of the very first customers will get fails, but its your right to know what are you buying. Myself had and issue with my unit and had to return it and im not that angry. As long as i dont have to pay the shipping back cost im fine since paypal does for me. Thats what everybody should have done, get some insurance before gambling instead of blaming at a company that tries to sell quality products for decent prices.

 

[yue]

Even tho for the most part you are not wrong, you just fucking love drama. Get over yourself. Yes, its a shame that some early adopters of the product got fucked. But hey, do you have something comparable for the same price point with similar specs and features? Guess what, no, there is nothing like this. So, yes, some of the very first customers will get fails, but its your right to know what are you buying. Myself had and issue with my unit and had to return it and im not that angry. As long as i dont have to pay the shipping back cost im fine since paypal does for me. Thats what everybody should have done, get some insurance before gambling instead of blaming at a company that tries to sell quality products for decent prices.

The top priorities for a product is safety and reliability. There's no point to buy a $200 device if it has large chance of failure and may damage your equipment and hearing, even if performance test show it has the highest level of transparency. For a unit stopped working from time to time, plugging my headphone directly to computer is a far better choice.

Samsung galaxy 7 was a great device. It performs super well, and the design was just amazing. But because of faulty batteries it ends up with a recall.

When selling a product, safety issue is the danger zone that no manufacturer can cross. Topping DX3 Pro crossed that line, so that's beyond my toleration level.