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    Review and Measurements of Topping DX3Pro DAC and Headphone Amp

    Just got in touch with the company's validation lab which has a few APx525. I think I will just have them to do a test on DX3. This is more convenient to me.
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    Review and Measurements of Topping DX3Pro DAC and Headphone Amp

    The design goal of LPF is different. It's actually to make square wave less squarish. Topping engineers chose standard X4 sampling frequency, around 178KHz, as the roll off point. 4493's datasheet suggests any FC point from 120K to 170K is good. For DSD, 4493 even has a LPF inserted internally...
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    Review and Measurements of Topping DX3Pro DAC and Headphone Amp

    I stopped by here once a day or sometimes once a few days. Is posting all replies in one shot a big problem to you?
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    Review and Measurements of Topping DX3Pro DAC and Headphone Amp

    Mmm.... you are confused with two different things. For the capacitors, I was answering to people who claimed all capacitors have the same performance. The THD talk is a follow up discussion between Amir and me. For the mod of DX3, what I was doing is mainly to resolve the stability problem. I...
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    Review and Measurements of Topping DX3Pro DAC and Headphone Amp

    Datasheet calls for at least 470uf here. Designers at least should follow what datasheet says. Topping uses 100uf here to save money.
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    Review and Measurements of Topping DX3Pro DAC and Headphone Amp

    There are a lot of over 100KHz upsampling and switching noises coming out of DAC and they will have to be removed by LPF. LPF has long been a design challenge for DAC.
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    Review and Measurements of Topping DX3Pro DAC and Headphone Amp

    And you have another headphone amp stage. The non-linearity of the impedance/distortion is the real problem.
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    Review and Measurements of Topping DX3Pro DAC and Headphone Amp

    As I have mentioned, it is a good idea for Amir to do the measurements for a consistent result, not that I do not have AP to do test. And I can predict the result will be pretty much aligned with what other people have got - much less noise spikes, etc. I plan to swap the XO for lower phase...
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    Review and Measurements of Topping DX3Pro DAC and Headphone Amp

    It is not the amount of THD, it is the shape of the curve. After signal going through the cap, the distortion amplitude changes among different frequencies. The impedance curve is another important factor, too. Then after the cap, if the signal gets amplification, the THD will go up again. This...
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    Review and Measurements of Topping DX3Pro DAC and Headphone Amp

    The paper stated that there's a 80.5db total gain. You have to deduct the values by 80.5db. The general shape of the curves look right to me. Have seen those in too many reports.
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    Review and Measurements of Topping DX3Pro DAC and Headphone Amp

    Yep, the 100uf value used in DX3 is bad, too. 4493 is suffering with all the ripples.
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    Review and Measurements of Topping DX3Pro DAC and Headphone Amp

    signal integrity wise, it is much better. shorter feedback path as there are a lot of HF signals going through. Go ahead check out the layout guidelines in those high performance OPs datasheets
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    Review and Measurements of Topping DX3Pro DAC and Headphone Amp

    In this case, you need 16V or 25V cap. 10uf is fine here. If you want something better, you can use solid polymers, as what I had done.
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    Review and Measurements of Topping DX3Pro DAC and Headphone Amp

    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.
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    Review and Measurements of Topping DX3Pro DAC and Headphone Amp

    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.
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    Review and Measurements of Topping DX3Pro DAC and Headphone Amp

    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.
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    Review and Measurements of Topping DX3Pro DAC and Headphone Amp

    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...
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    Review and Measurements of Topping DX3Pro DAC and Headphone Amp

    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...
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    Review and Measurements of Topping DX3Pro DAC and Headphone Amp

    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.
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