Review and Measurements of Topping DX3Pro DAC and Headphone Amp

[finneybear]

It wasn't that hard for my (no-name, Chinese) DAC to reach 98 C on hot days, so...
Btw, max operational temperature for AK4493 is 85 C. It probably won't burn at this level, but may fail to operate properly, I assume.

Now you have got me all interested. How do you now the chip reached 98C? If the chip surface reached 98C, the junction temp would be much higher than that. Were you running the chip at 1GHz or had it generate 1 amp output?

So what DAC is it? I think it had made a world record as the hottest DAC in the world. LOL

 

[finneybear]

I offer another option. Disable capacitors only on one set of outputs. Leaving connected all sets of outputs.

This will work but the whole purpose is to get rid of the coupling caps.

Now talking about paralleling DAC chips. When you parallel two DAC chips together, some random noises will get canceled. Though there is one catch more than that - the switching noises. There are many fast moving switches in a DAC and they can generate a lot of short voltage spikes. Those switching spikes are a big challenge to remove.

For a current output DAC, when you parallel two DACs together, the music signal current gets doubled, and due to minor phase difference between the DACs, the number of switching spikes are also doubled but spreading out so practically, the signal ratio between music signal and switching noises is improved by ~3db.

Paralleling voltage output DAC such as AK4493 is not as beneficial. Personally I would not bother with using both sets of outputs.

 

[777]

Did you measure it at the exit from the topping? Or in front of capacitors?

In front of capacitors of course. After capacitors the dc voltage is 0 volts. Every AK4493 has 4 output ports. Two of them are positive and are in parallel, the rest are negative in parallel too. One negative with one positive form one pair, with the same dc voltage (150mV for example) on both. The other pair, positive with negative, have the same 250mV( for example) on each it.

So, if you shunt all the caps, then you will have positive1 with 150mV dc and positive2 with 250mV dc, both in parallel. After that the voltage could be only one. So, the difference between 250mV and 150mV will be divided at the resistance between them and will be result a current. So, there could not be the same two ports, positive or negative type, in parallel without a capacitors between them, or a limiter resistors.

AK4493 isn't output current chip DAC, is a voltage output chip DAC.

 

[splkn]

DX3 has two 4493 running in mono-mono mode. To save two extra OPs, each 4493 is for one channel and the two sets of outputs per chip are summed together to drive one OP. To do the summing, the coupling capacitors are required because there can be DC offset between the two SCFs.

Are you afraid that the reverse current, in our case the current from the potential of 100 mV, can damage 4493? Can we install diodes instead of capacitors to prevent this?

 

[MacDac]

Now you have got me all interested. How do you now the chip reached 98C? If the chip surface reached 98C, the junction temp would be much higher than that. Were you running the chip at 1GHz or had it generate 1 amp output?

So what DAC is it? I think it had made a world record as the hottest DAC in the world. LOL

I'd rather have the hottest girl, but I can't afford such an expense, I'm affraid.

I measured the AK4490 surface temperature with a (K-Type) thermocouple connected to a digital multimeter.
DAC looks like this:

 

[777]

Are you afraid that the reverse current, in our case the current from the potential of 100 mV, can damage 4493? Can we install diodes instead of capacitors to prevent this?

In series with capacitors there are 1k42 ohm resistors. So, between the outputs of the ak4493 there is a equivalent resistor of 2k84 ohm. The dc current between outputs of ak4493 will be around a 0.000035 A. It is big ? It is small ? I don't know. I suppose it is small if we look at internal heat but maybe it is big if we looking at the distortion.

 

[scibry]

Just wanted to throw out there that my personal DX3Pro died a hard death as other members have said, total lack of output. The support from topping would be "below average" at best.

 

[Cidious]

I've got parts rolling in.

Kemet KO-CAP 100uf that fit perfectly for the DAC output.
Some transformers to play with

More caps coming in. I follow up to Finnybear's advice. Still waiting for the polymer radials and the Panasonics for the digital input.

It's spring festival here.. I tried to persuade many shops to still send me some with the last open shipping company. but it's difficult

 

[Cidious]

Just wanted to throw out there that my personal DX3Pro died a hard death as other members have said, total lack of output. The support from topping would be "below average" at best.

I experienced the opposite.. I communicate with them through Taobao... and They've send me spare parts and helped me out on a lot of things... I'm on the other end of the spectrum.. a fan...

 

[splkn]

Kemet KO-CAP 100uf that fit perfectly for the DAC output.

Place two removed 33 μF capacitors in place of the 10 μF capacitors on the opa1612 power line. + -10v.

 

[splkn]

Just wanted to throw out there that my personal DX3Pro died a hard death as other members have said, total lack of output. The support from topping would be "below average" at best.

What kind of power supply did you use?

 

[y845133y]

Today, My DX3-pro's headphone port has some noise and the output sound is abnormal. I check the headphone connector's ground pin is a bad connection on the PCB ground. I re-solder all of the ground pin. Then it can work normal now.

 

[kprog]

I like dx3, for being all in one, and very beautiful. Also it seems to have power to have very high volume in my dt990pro 250 ohm.
But it seems that they are all breaking up little by little, I'm afraid of that ...
I'm in a big doubt, buy DX3 .. or buy Atom + khadas or d10 topping .. This set would be more expensive, and less attractive ...

 

[simonchretien]

I experienced the opposite.. I communicate with them through Taobao... and They've send me spare parts and helped me out on a lot of things... I'm on the other end of the spectrum.. a fan...

Naw its just horrible, 2 email zero reply in over week.

 

[Cidious]

Naw its just horrible, 2 email zero reply in over week.

Why don't you get taobao ? I'll give you the link to the shop they will respond within a few minutes

 

[Cidious]

Today, My DX3-pro's headphone port has some noise and the output sound is abnormal. I check the headphone connector's ground pin is a bad connection on the PCB ground. I re-solder all of the ground pin. Then it can work normal now.

View attachment 20956View attachment 20957

Damn I just looked at my boards and I also need to give it a little dot of solder... there is barely anything on it.

 

[gypsygib]

Naw its just horrible, 2 email zero reply in over week.

I just sent my second email today about getting a working remote (yes, the battery is in correctly), haven't had a reply to my first email sent 7 days ago. The customer service seems very poor at Topping.

 

[Sangram]

Sorry that I confuse you a bit. I was talking about very little DC current. The current is really not a big deal to the beefy transformer.
As for DC voltage, remember tube amp has long been using output transformers? That is mighty DC voltage.

Re tube amps:

SE transformers have gapped cores to be able handle DC.

Push-pull transformers operate in full diff mode, with same voltage at two ends of the winding, resulting in net zero voltage across transformer.

Small signal transformers will saturate with as little as 40mV offset.

You really need to know what you're talking about when dishing out advice. I'm not the one who's confused. Your post on mono mode is simply wrong too. Even voltage out DACs have theoretical benefits when used properly. Go read a few datasheets and application notes to refresh your knowledge please. Not trying to be rude, but you're simply wrong on a number of things.

 

[Veri]

Some transformers to play with

What kind of transformers are those?

 

[chrisliuboy]

Just wanted to throw out there that my personal DX3Pro died a hard death as other members have said, total lack of output. The support from topping would be "below average" at best.

Just curios, some suspect DX3pro can't handle hot working temps, could I ask do you live in a rather warm state?