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WolfX700 Measurement of Topping A90 Headphone Amp

JohnYang1997

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Ok. Wasn't gonna do this. But I have the mood. So,
I went up and measure the actual performance of A90 without load.
The best THD+N that we can measure with AP(noise and THD individually) at 5.4Vrms: 0.0000243%
noise residue of AP input 850nV.

The best performance that we can measure with aid of the noise amplifier (also noise and THD individually) at 5.4Vrms: 0.0000206%

Screenshot_20200312-214132.jpg
(the one that clipped earlier is A90, using unbalanced output)

Some calculation formula I used: (put into Google to verify the result)
Best we can measure:
sqrt((4.8475e-7)^2+(10^-6)^2)/5.4
With AP only:
sqrt((850*10^-9)^2+(10^-6)^2)/5.4

850nV is residue of AP
0.48uV are measured with volume at full with input shorted.

Also we managed to reduce the interference in our lab. So we got the most accurate SNR for 50mV: 105dB (closer to my expectation of 106dB).
Screenshot_20200312-214029.jpg
 
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JohnYang1997

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Idk why but I'm not able to upload pictures today. So I'll update when it's good.
EDIT: It says I don't have the correct extension. So I screenshot the graphs and updated to the above post.
 
Last edited:

JohnYang1997

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If I only take the 2nd and 3rd harmonics from AP(which is actually more realistic) I'll get even better number.
Result is 0.0000153% THD+N (closer to the opa1612's spec)
Formula
sqrt((4.8475e-7)^2+(300e-9)^2+(250e-9)^2)/5.4
-7d73e86ed7bec81.jpg
 

YSC

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Really looking nice, but may I ask what's the rated output power?
 

Matias

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Really looking nice, but may I ask what's the rated output power?
Wolf wrote it there:
"I got a maximum output of 6.5W with 33R (BAL Out) in dashboard mode!

In this case, SINAD is still as high as 110db."
 

Marutks

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When are they going to start to sell the A90? Does it work well with IEMs? No hiss on low gain?
 

JohnYang1997

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When are they going to start to sell the A90? Does it work well with IEMs? No hiss on low gain?
This is probably the lowest noise headamp on the market. The 50mV SNR is at least 2 times better than the current best offerings and it's a few times better than any amp utilizing THX technology. There will be no hiss on low mid or high gain. (if the input is shorted or volume tuned down).
 

Rigel

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When are they going to start to sell the A90?

I also join the first question. Is there any forecast when the sale of the A90 will start?
Being pre-production, I guess it won't take long.

Thank you.
 

Rigel

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Probably depends a lot on how the situation with the virus develops.

Yes, most likely. My country is in a state of alarm.
Hopefully it will be solved soon and we will get something positive out of so much misfortune, preparing ourselves better for the future.
Encourage all the injured.
 

xema

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Could you pls measure it's xlr outputs, as a preamp?
Im curious about it's preamp performance.;)
 

YSC

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One more noob question: any measurement on channel crosstalk in the headphone amp section?
 
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