Review and Measurements of Topping DX3Pro DAC and Headphone Amp

[david99]

So how about organizing to get your unit to me? I prefer to get one from US but a situation like yours where the problem comes and goes is ideal to try to a) replicate and b) see if variations of power/temp will make it worse or better. Happy to pay you for the price of the unit.

By the way I have tried different PSU 12V as I do not have 15V one. And tried to put topping on balcony for 30 mins where was around 0 celsius and then also remove back cover and set my hot air gun to minimum and heated whole unit to about 50 celsius in any case there was not change in behavior it is still stuck in standby. Only thing what is working is settings menu when you hold roller button, and it is also detected on PC. tried to reload firmware but it failed during switching to FW upgrade mode.

 

[yue]

By the way I have tried different PSU 12V as I do not have 15V one. And tried to put topping on balcony for 30 mins where was around 0 celsius and then also remove back cover and set my hot air gun to minimum and heated whole unit to about 50 celsius in any case there was not change in behavior it is still stuck in standby. Only thing what is working is settings menu when you hold roller button, and it is also detected on PC. tried to reload firmware but it failed during switching to FW upgrade mode.

If you have a very long hex key you can open it and take a look at pcb inside to find if there're any loose contact. If not just return it to seller, and let Topping know about this issue.

I wrote Topping an email today, gave them quite a lot of feedback, and also included your video with many others'. I am still waiting for their reply.

 

[Cidious]

Id almost wish I could replicate this myself. But I really don't have any issues with any of my units.

I also really wonder what is causing it and why I don't have any issues on 1808/1812/1901 batches.

I swapped out my LPS for switching brick for a while but nothing bad either.

I went over the PCB with magnifying glasses and except for the weak solder joints on the headphone jack I couldn't really find any weak solder joints.

 

[amirm]

Just want to share an interesting implementation detail and correct you that DX3's volume control, albeit digital, is just software mixing. It's not doing volume control in the analog stage.
There're almost no difference between controlling via operating system volume vs controlling via DX3's hardware volume knob.
Unlike some products I have (such as Loxjie D20) which use dedicated volume control chip (e.g., NJW1194) or digital potentiometers (see JDS's C5 amp implementation), DX3's volume value is set in AK4497 chip.
This was confirmed by my discussion with Topping engineers two days ago.

I explained it was a digital volume control and you "correct" me by saying it is the same thing? How is that a correction? Here is the speck from AKM:

The reason they need to use relays to hide the noise produced by AK4497 is exactly that. If there's a dedicated volume control chip, they could use that instead and avoid "clicking" noise entirely. But there isn't such chip in DX3 Pro. And unfortunately they also chose mechanical relays, which produce noise. I recommended them to change that to silent solid state relays in future batches of production. However they are celebrating Chinese New Year now so there's no future change plan yet.

Solid state relay can reduce performance. There is no free lunch here. As I explained, the digital volume control provides precise channel matching which is very important to people with sensitive IEMs. Relay clicking is not an issue for many people.

 

[amirm]

I went over the PCB with magnifying glasses and except for the weak solder joints on the headphone jack I couldn't really find any weak solder joints.

I did the same on mine and it looked very good. No sign of anything that could cause the reported problems.

 

[david99]

If you have a very long hex key you can open it and take a look at pcb inside to find if there're any loose contact. If not just return it to seller, and let Topping know about this issue.

I wrote Topping an email today, gave them quite a lot of feedback, and also included your video with many others'. I am still waiting for their reply.

So far I do not have that long key, ordered it and waiting for delivery. Yes return to seller is one option but it will take long time it will also cost me shipping to china and what is most important there is no doubt with my luck that replacement unit will break after 3 days again.

 

[yue]

How is that a correction?

Well the first time I read your post I got the misunderstanding that the volume control is done at analog stage via a digital control, either via volume control chip or digital potentiometers, which I believe are the common practices. Such implementation will reduce noise level by not amplifying DAC's noise floor. What I want to clarify is this is not how topping Topping DX3 is implemented.

So here it is not equal for you to compare DX3 with "headphone amplifier using analog volume control" as this is not an equal comparison. What you should compare is DX3 vs DAC w/ system volume control + headphone amplifier with maximum volume, and they are exactly the same.

It's very rare a DAC today does not have system volume control (perhaps the most notable ones are Schiit products). So DX3 Pro is not doing something extraordinary here. Users without DX3 can easily achieve what DX3 has --- just use operating system / disc player mixer and avoid using their amp volume knob.

 

[MusicNBeer]

The quality of the digital volume control can vary so I'd use the DX3 before PC. Worst performance is scale and round prior to analog conversion. Proper performance is to add digital dither (shaped or flat) at level proportional to scaling, then scale, then round.

Yes the dither reduces SNR by up to 3 dB but the noise floor is so low the loss is moot IMO. If the analog noise floor is higher than the digital quantization floor, loss is even less.

 

[yue]

The quality of the digital volume control can vary so I'd use the DX3 before PC. Worst performance is scale and round prior to analog performance. Proper performance is to add digital dither (shaped or flat) at level proportional to scaling, then scale, then round.

Unless using a software mixer, OS send data and volume independently to Dacs. It’s up to the dac itself to decide how to implement volume calculation correctly.

Xu208 and ak4493 use 32 bit for mixing so rounding never happens by default. You maintain the original precision.

Today’s software mixer (core audio for instance) also don’t do rounding and calculate in 32bits field instead of 16bit.

With that said I still believe having dac at max volume and control at analog stage is a better solution. Unfortunately dx3 is not implemented like this.

 

[MusicNBeer]

Good point, I was just about to correct my post with the same thing. While reading the data sheet I realized no dither is even needed since it's a 32 bit DAC. Even better.

 

[MattG]

Here's a presentation by ESS on digital versus analog volume control. Getting a bit old, but it does acknowledge @yue's point, that ultimately analog volume control is best, but well-done digital can get close.

Like most things, my take is that it's a matter of implementation quality, which is a continuum. At the state of the art end, analog wins. But as you back away from the top-notch end, certainly decent digital can be better than mediocre analog. Clearly there is a cost to do analog right, and I suspect it's a hard sell to the accountants for a "budget" device like the DX3 Pro, particularly when you already have it for "free" with the DAC chip. Also, you could always disable the digital volume control by setting it to 0dB, then put a pre-amp between the the DAC and amp.

While we're on the topic, what do higher-end DACs, such as Benchmark or ADI use for volume control?

Amusing anecdote on my experience with this: I had a heavily modified DAC, that I thought sounded fantastic. This is back when my listening was almost entirely nearfield, i.e., tiny amounts of power, low volume. So my volume control---analog---was a simple potentiometer between the DAC and power amp. The volume always stayed under 20% or so. Eventually that DAC and amps got shelved, and I was able to get away from a nearfield setup.

Someone came along and wanted to borrow my DAC. I dusted it off and powered it up to make sure it still worked. But at this point, I no longer had the volume pot on my amp, so I was forced to use digital volume control: specifically, volume control on my PC. Even with the volume "low", it turns out, somewhere along the way my modifications clearly broke something (or I implemented them incorrectly), as there was a non-trivial amount of noise/static coming through, along with the music---basically un-listenable.

Clearly, the volume pot I was previously using, given that I always kept the level so low, was effectively masking the noise.

 

[pejakovic1]

So in the end, is USB or S/PDIF better? I really can't understand that from these posts. @amirm can you chime a light on us by giving us the final answer to this?

 

[Veri]

So in the end, is USB or S/PDIF better? I really can't understand that from these posts. @amirm can you chime a light on us by giving us the final answer to this?

USB has better jitter rejection. In real-life performance, i.e. listening it will not matter... but if you can decide either way, USB is better for this device.

 

[pejakovic1]

USB has better jitter rejection. In real-life performance, i.e. listening it will not matter... but if you can decide either way, USB is better for this device.

Thanks. I'm in a bit of a dilemma with my device. It creates buzz in all active speakers. I suspect some ground problems in it. The moment i plug it in any power grid the buzz starts.

 

[Veri]

Thanks. I'm in a bit of a dilemma with my device. It creates buzz in all active speakers. I suspect some ground problems in it. The moment i plug it in any power grid the buzz starts.

In that case optical s/pdif should be a good way to break any ground loop if it stems from the USB connection

 

[pauze]

Thanks. I'm in a bit of a dilemma with my device. It creates buzz in all active speakers. I suspect some ground problems in it. The moment i plug it in any power grid the buzz starts.

I have the same issue when connecting it directly to my active studio monitors. The buzz disappeared when I connected it to my mixing board, which then feeds the signal over balanced cables to the monitors.

 

[lystor]

Detailed information about AK4493 filters (F1-F6 in DX3 Pro) is available in official AK4493 English Datasheet (attached).

 

[amirm]

@amirm can you chime a light on us by giving us the final answer to this?

Use USB.

 

[pejakovic1]

In that case optical s/pdif should be a good way to break any ground loop if it stems from the USB connection

Tried that, doesn't work...

 

[pejakovic1]

I have the same issue when connecting it directly to my active studio monitors. The buzz disappeared when I connected it to my mixing board, which then feeds the signal over balanced cables to the monitors.

So if you are using a mixing board, which dac gets through? I mean if your mixing board has a dac wont it be pointless to use dx3 pro, sorry for the newbie question.