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Review and Measurements of Topping DX3Pro DAC and Headphone Amp

Music1969

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Hi @amirm , is the low output impedance (1 ohm measured in this review) across the full audio range of 20 Hz to 20 kHz?
 

Music1969

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I haven't done testing but I'm pretty confident that it is.

Noted. Hopefully amir can confirm.

Do you know what the AKM AK4493EQ chip in the DX3 Pro internally oversamples PCM up to?

To 768 kHz? or to ~1.5 MHz like some ESS chips.

Only asking out of general interest.
 

JohnYang1997

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Zout.PNG
Measured with 8ohm load and no load. 0.1-0.2db difference. I took 2% difference. So 2% * 8ohm is 0.16ohm across the board. Really nice and consistent.
Edit: no i read it wrong. It's lower than 0.1db So 0.1ohm and less.
As the chip topology it's delta-sigma so basically it has to over sampling to a very high frequency. Idk the frequency exactly but you can get hint from the oscillator. I'm not an expert in that regard so I'll leave it as is.
 

JohnYang1997

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Hi, did you end up trying a 25Vdc external power supply?
The output of regular is fixed. Using high voltage makes not difference.
And I saw in the notification maybe you have changed, that power bank will eliminate ground related noise. Actually the smps are double insulated so already no ground noise to pass through. Sure you may try it may still function well. You just won't see improvement.
 

Music1969

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Actually the smps are double insulated so already no ground noise to pass through.

But SMPS's can be sources of AC leakage current? A battery will not?

No AC leakage current 'loops' = no ground loop related issues? (depending on system)
 

JohnYang1997

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But SMPS's can be sources of AC leakage current? A battery will not?
SMPS runs at very high frequency so not a problem. In fact, power bank also has smps in side to make sure the voltage is constant.
There may be some leakage but not an actual concern if the design was complied to safety standard as far as I know.
 

JohnYang1997

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Sure they have switching regulators but they are immune from AC related issues, like leakage current 'loops', unlike SMPS's.
Idk man. I never in my life have seen those. With dx3pro and stock smps, the mains noise is less than -134dbFS. FS = 10V.
 

Music1969

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@JohnYang1997

I see the spec for DX3 Pro states compatibility with 16-300 ohms.

Would 450 ohm impedance headphones present any increase in measured distortion?
 

noel_fs

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Hi, does anyone know how DSD is handled with the headphone output of the DX3 Pro, with digital volume control?

Is DSD converted to PCM?

Maybe you know @amirm or if you have a Topping contact, can they clarify?
I dont know it for a fact, but im quite sure it just does pcm conversion and volume goes from there.
 

Music1969

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SMPS runs at very high frequency so not a problem.

RME just touched on this today:

"There is one weak point, though: the SMPS (power supply). It does not provide full isolation against ground loop noises, even produces its own (leakage current)."

As I mentioned, while battery powerbanks have switching regulators, they do eliminate this 'weak point' of SMPS's that RME discusses - full isolation against ground loops and no leakage currents...

https://www.audiosciencereview.com/...-adi-2-dac-and-headphone-amp.7546/post-198553

A lot of Pro Audio DACs have 12Vdc inputs and sometimes engineers use car batteries to power them, for this reason (immunity to AC related issues).
 

Sinquito

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I am very tempted by the prime day discount, but I am fearing for the issues discussed here and finally I think that I maybe better served by a portable amp like the NX4 DSD or the Xduoo XD-05.
 
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