Review and Measurements of Topping DX3Pro DAC and Headphone Amp

[Pavel]

I assume that the problem of the sleep mode is the initial reset (initialization) scheme.
A more powerful Meanwell produces more current when it is turned on, and the reset circuit is activated. Weak power supply units do not provide a sharp rise in voltage and the initialization circuit does not work.

Added 4700uF to output LM317 and DX3 also stably started.
In general, one problem has become less.

 

[gypsygib]

Does anyone have an intermittent hum or noise in the headphones when on high gain mode with both RCAs plugged in?

I'm experiencing a strange issue where I hear a faint hum or ring only in high gain and only if both left and right RCA are plugged in. If I remove either the left or right RCA the noise goes away. The noise is still present even if I unplug the speakers from the outlet. If I switch to line out there's no noise and if I don't use high gain there's no noise. Only on high gain with both RCA's plugged with it set to output through headphone.

I've tried with multiple headphones and on two PC and the hum/ring is still there. It's not very loud but if you listen, it's definitely there.

 

[Pavel]

After my tweaking, I got the following result:

Before the improvements, the measurements were as follows:

 

[Veri]

A whopping 1,26 SNR / 0.0001% THD 'gain' well, you didn't break anything either so I still have to applaud your efforts

More modders should measure their stuff rather than go by their "ear".

 

[Pavel]

A whopping 1,26 SNR / 0.0001% THD 'gain'

Look not at measured weights but at a forest of high-frequency harmonics.
My EMU-0204 does not measure better.
They didn't let me sleep. Now they are not.

 

[777]

Pavel, can you measure again for a 50hz frequency ?

 

[Pavel]

Pavel, can you measure again for a 50hz frequency ?

I do not understand what you want to see there. There are still two main harmonics...

 

[chrisliuboy]

If you dont care about getting the lowest THD number, even the old timer OPA2134 will give you a more balanced sound.

Thanks~ Will try to mod if got any chance.

 

[777]

I do not understand what you want to see there. There are still two main harmonics...

View attachment 22272

Thank you.

 

[pacman]

WTF is wrong with this forum, never saw so many freaks and weirdos reunited in just one thread

Do you people actually listen music on your gear or just waste your entire life staring at charts and numbers on internet?

 

[amirm]

WTF is wrong with this forum, never saw so many freaks and weirdos reunited in just one thread

Do you people actually listen music on your gear or just waste your entire life staring at charts and numbers on internet?

Let's not get personal please.

 

[Veri]

Do you people actually listen music on your gear or just waste your entire life staring at charts and numbers on internet?

/r/inclusiveor

 

[Pavel]

WTF is wrong with this forum, never saw so many freaks and weirdos reunited in just one thread
Do you people actually listen music on your gear or just waste your entire life staring at charts and numbers on internet?

Objective measurements are the only information that can be published on the Internet.
Your subjective opinions about sound do not have absolute authority.
High-quality sound can be only from the device that meets the minimum requirements of HI-FI. If the device does not maintain these standards, then there is no point in wasting your time and attention on it.

 

[NTomokawa]

WTF is wrong with this forum, never saw so many freaks and weirdos reunited in just one thread

Do you people actually listen music on your gear or just waste your entire life staring at charts and numbers on internet?

Here's a thought, pal: How about you don't come into our home and insult us for what we like?

Ignored.

 

[Jestercow]

WTF is wrong with this forum, never saw so many freaks and weirdos reunited in just one thread

Do you people actually listen music on your gear or just waste your entire life staring at charts and numbers on internet?

Looks like someone stayed logged in on a public computer lol

 

[david99]

Thank you all for your findings, opinions, modings opinions it is really very interesting reading for me and I think for rest of the forum as well. It would be nice once situation will settle down to publish let's say some tutorial for moding of DX3 Pro let's say maybe for most important mods which will influence listening experience most.

 

[finneybear]

The answer is OPA1622. Read this : https://e2e.ti.com/support/amplifiers/f/14/t/518233

OPA1622 does not have the right package. It is basically a slower version of OPA1612. 1622 has even lower THD for certain frequencies and has a warm sound. It is interesting to see different design goals would lead to very different sound for pretty much the same design.

 

[finneybear]

Fortunately, thanks to the simultaneous output through mpd server very simple comparison - just change the input from USB to BT and instantly plays the selected source - even the two inputs are led by itself. Despite the AKG 702 absolutely no qualitative change (Aptx-HD automatically convert everything to 48 kHz according to the display). BGVP DMG and FiiO FH5 absolutely the same quality - a bit of bass with Bluetooth, a volume of about 2 dB. But both IEM shuffle the AKG 702 with detail and submit the bass component of the song. I do not even talk about comfort. I still own the Etymotic HF5, but despite the mass of enthusiasts and their own SpinFit tip I do not consider them a measure. For years I played a double bass behind me and Etymotic just does not know.
I note that I have 59 year old ears 40 years old with headphones with medium volume of all genres except trash metal and similar rumors).
t a moderate volume).

Thanks for sharing the experiences. It is good to know that AptX-HD works well. I do not have bluetooth 5.0 device at the moment. Will have to try it someday!

Interesting that people are still listening to This Mortal Coil! Blood is very good for listening test.

 

[finneybear]

I got a steady and repeatable problem.
DX3 is not initialized with a 15V line power supply (LM317) - the standby point is lit. But you can adjust the settings.
With the Meanwell MES30A-4P1J power supply, it works stably.

The problem is those stock caps are not very good. Their capacitance value drops fast when frequency goes up or temp arises, etc.
At certain point, the voltage would drop due to lack of current reserve then you will run into hang-up or all kinds of problems.
It also depends on various scenarios - run temperature, whether you are in bad luck to have a very bad cap for the MCU, etc.

Increasing the cap value means it will take a while to charge them up during the power on process. The MCU may see the system's voltage is not up yet hence directly goes to the stand by mode. In this case, you need a PS which can charge those bigger caps faster.

I am thinking about just keeping the same cap value. As far as I am using solid polymer caps at 100uf/25V, they can still remove those HF noises very effectively. The 25V rating will have high ripple current, then at the same time, 100uf is easier to drive for the power supply.

Main concern now is 4493 datasheet is calling for 470uf for the analog power. Not sure whether it is OK for the analog section of 4493 to power up late. Otherwise I will have to reduce it to 220uf to see how it goes.

Will switch to linear power supply, LT1085 based, 3A output, just to be safe.

 

[finneybear]

Thanks~ Will try to mod if got any chance.

Based on what friends learned from AKM4497, OPA1624 and MUSES 8920 are good matching for it.
Teac uses MUSES 8820 in their AKM4497 based streamer.

OPA2134 is very similar to OPA1624 when the latter is a newer design.