Review and Measurements of Topping DX3Pro DAC and Headphone Amp

[Krunok]

..when back in the box it will be a little better.

Will it? Not that I see many RF stuff on your measurements. Not that such thin case can block many RF stuff either.

 

[eziitis]

Will it? Not that I see many RF stuff on your measurements. Not that such thin case can block many RF stuff either.

well, since it went little worse when I took it out, I would expect the opposite thing may happen as well ....
on the other hand all my diy dacs measure better when boxed.

 

[eziitis]

now listening "Sultans of Swing" I can say that Mark Knopfler has become overly sibilant (what of course he is not) and in general, this thing has exaggerated highs and some deficit in the midrange. lows also might be more resolute. opamp rolling or filter recalculation hardly will be an optimal solution. actually, I like OPA1612 very much, but not in such a silly position serving 2 mono dacs. better they would use only one dac and FDAs for each channel followed by a summing opamp. would increase the price a little, but unfortunately, the designer has been under heavy influence of the datasheet schematics

 

[777]

What kind of piece is this ? Perhaps voltage regulator, from 5,3v to 5.0v ?

 

[Pavel]

What kind of piece is this ? Perhaps voltage regulator, from 5,3v to 5.0v ?

Yes it is LDO

 

[777]

Did you know something about it ?

 

[finneybear]

I do. How about you? Have you read the paper this came from? And the reason those two graphs are higher than the rest???

You can find the paper here:

https://www.interstatemarketing.com/Papers/TechArticles/Tant-Niobium/tantbench.pdf

Studer used niobium oxide caps for signal coupling in their master reel deck such as A820, A810, A807 back to 30 years ago. Nobody complained about their sound quality.

The two bad ones are MLCC, multi-layer ceramic, caps. They are fairly bad at audio frequencies yet for very high HF, they are superior. Piezo effect kills their sound.

 

[amirm]

You can find the paper here:

I have the paper already and read it. The only two caps that did worse where due to piezoelectric effect/acoustic interference. It has nothing to do with the current arguments. Or any superiority of different caps. The write-up is also very poorly done with little detail as to why the distortion is as bad as it is to start with.

Please don't throw data at the membership hoping they don't understand it or no one knows how to get the rest of the data.

 

[finneybear]

The dc-dc module is actually smaller than the space for the 2 tps dc switcher. This is a higher quality one from Murata in mouser.

https://www.mouser.com/ProductDetail/Murata-Power-Solutions/NMA1515SC?qs=sGAEpiMZZMvGsmoEFRKS8Kn8hpQIdAem/1LMX04mJrk=

I have seem a dip to smd socket with cog cap solder accross the +/- pin. This is one of the opamp tweaks that improve the sound.
If I do this, I would use a audio ecap and solder one of the leg directly on the socket and the other to the board.

Topping had an initial offer of the D70 but ended without further news.
https://www.aliexpress.com/item/Top...-Decoder-December-20-Arrival/32959667114.html

The ak4497 would be more difficult to implement correctly and more demanding on the power supply.

You can play with battery power directly to the digital circuit. Trust me, it will be a revelation. The lifepo4 battery output 3.2-3v and you can easily tap it directly. Just using the battery on the clock will bring improvement.

Thanks for the link to Murata part. Have you ever tried it? It can only do 1w though.

Some SOIC/DIP adapters would put silver mica across the +- lines but this may not work all the time.
Another concern is the feedback loop. The adapter will pull the line too long. I like SMD parts much better. Easier to work with, too.

This weekend I will replace the XOs. Probably add a 1.5A 15V linear power supply later then that will be it. I will be done with DX3. This thing already sounds much better than most $1k DACs. The machine has been running non-stop for over 60 hours now. Solid stable. The sound keeps getting better and better. Warm and smooth. Lovely vocals. The biggest steal in 2019!

I have read some early feedback on Topping's D70, pretty much in line with what I heard from DX3.
After looking into DX7, most likely I will skip D70 - I see the same bad 100uf SMD caps again.

This one seems to be a good candidate. The implementation looks good, at least it follows whatever 4497 datasheet asks for, the four big caps around 4497 are good. The output stage looks correct. The major issue I can see is those DIP OPs. SOIC is much better.

 

[finneybear]

I have the paper already and read it. The only two caps that did worse where due to piezoelectric effect/acoustic interference. It has nothing to do with the current arguments. Or any superiority of different caps. The write-up is also very poorly done with little detail as to why the distortion is as bad as it is to start with.

Please don't throw data at the membership hoping they don't understand it or no one knows how to get the rest of the data.

Those curves are valid measurement data. The main focus is to show the different curves among tantalum and electrolytic, etc. The small gaps look deceiving here due to the scaling to accommodate the poorly performed MLCC.

 

[amirm]

Those curves are valid measurement data. The main focus is to show the different curves among tantalum and electrolytic, etc. The small gaps look deceiving here due to the scaling to accommodate the poorly performed MLCC.

They are not valid data when you cut off even the label under the graph let alone the link to the paper. The piezoelectric effects are known and nothing new. The focus of the paper is also on acoustic interference from what I can gather. It certainly has no bearing on headphone listening.

 

[finneybear]

it sounds pretty good indeed.... not matching yet my heavy es9028pro box, but... velvet sound you know
since there is no way how to objectively forward listening impressions (whatever you think about that), i took the liberty to measure 192/24 1khz sinewave, which should show the things if done right.

4493 has an internal LPF kick in at DSD mode hence you get a much cleaner result with DSD. The harmonic pattern at DSD, large second harmony, low 3rd, etc, says a lot.

On the board, right beside the power plug socket, there is a ground pin which will touch the enclosure to provide a valid shielding.

 

[finneybear]

They are not valid data when you cut off even the label under the graph let alone the link to the paper. The piezoelectric effects are known and nothing new. The focus of the paper is also on acoustic interference from what I can gather. It certainly has no bearing on headphone listening.

I have seen similar measurement datum on different cap types on many other places. The curves here are pretty consistent with other results. Cant see why you would declare them as invalid?

The paper is about the usage of caps as signal coupling devices. acoustic interference is one thing which matters.

As for the headphone amp performance? DX3 use electrolytic caps as coupling devices already. The discussion is whether the stock electrolytic caps are good enough? This has nothing to do with the paper. I brought up the curves simply for people who claimed all caps perform the same.

 

[finneybear]

now listening "Sultans of Swing" I can say that Mark Knopfler has become overly sibilant (what of course he is not) and in general, this thing has exaggerated highs and some deficit in the midrange. lows also might be more resolute. opamp rolling or filter recalculation hardly will be an optimal solution. actually, I like OPA1612 very much, but not in such a silly position serving 2 mono dacs. better they would use only one dac and FDAs for each channel followed by a summing opamp. would increase the price a little, but unfortunately, the designer has been under heavy influence of the datasheet schematics

No. the implementation in DX3 has diverted from the datasheet reference a lot. This is the problem.

To get full and rich bass, you will have to remove those coupling caps.

 

[finneybear]

Did you know something about it ?

Yes, this is another problem in DX3.

 

[eziitis]

I doubt whether the capacitor rolling will be any good here. their choice depends on many factors including the regulators utilized. I have not yet scrutinized how exactly secondary regulation is organized, but for instance, one can not just put a top-notch 10uF cap on the LP5907 output, if it is designed to work with 1uF ceramic. secondly, for audio the primary importance in a LOW and FLAT PS output impedance over all frequency range, the task that IMHO is beyond the selection of capacitors only...

 

[Veri]

To get full and rich bass, you will have to remove those coupling caps.

Says who though, there is a little too much of purely empirical advice going on here, especially by you finneybear really..

I mean these mods are fun to look at, but for the average viewer stumbling on this 156p thread I don't think this is of the essence really.

 

[finneybear]

I doubt whether the capacitor rolling will be any good here. their choice depends on many factors including the regulators utilized. I have not yet scrutinized how exactly secondary regulation is organized, but for instance, one can not just put a top-notch 10uF cap on the LP5907 output, if it is designed to work with 1uF ceramic. secondly, for audio the primary importance in a LOW and FLAT PS output impedance over all frequency range, the task that IMHO is beyond the selection of capacitors only...

The only value change I did are the main power cap and the four analog power caps for 4493( I used 470uf and you made them to 2200uf), other values are the same.

 

[finneybear]

Says who though, there is a little too much of purely empirical advice going on here, especially by you finneybear really..

I mean these mods are fun to look at, but for the average viewer stumbling on this 156p thread I don't think this is of the essence really.

Removing coupling caps is to go back to follow datasheet's recommendation. It is also validated by people who have been working with other AKM devices. It's not my own idea.

 

[splkn]

You meant the 4493 output coupling cap, size 3216? You only need voltage rating 6.3v there. 47uf nobium oxide is the largest I can find. Dont use tantalum there. If you want strong full bass, no coupling will be the way to go.

No, I meant capacitors for power OPA1612.