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WolfX700 Measurement of Topping A90 Headphone Amp

WolfX-700

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#1
This is really a long and memorable vacation ...

Mainly for well-known reasons ... I haven't released any measurements for a long time

Logistics was completely stopped ... R & D and manufacturing were also completely halted ...

God ... this is really a boring holiday ... I have been bored to spend the whole week to adjust one of the equipment I made before (for example, to make the THD+N vs Freq curve of the left and right channels basically the same, and the harmonic components are also consistent);)

For the coronavirus, I was almost 600km away from the center of the outbreak. In terms of government's epidemic prevention measures, in fact, I could hardly find anything to worry about-----Good social order and basically good supply in the supermarket-one thing to complain about is that Coca-Cola in the supermarket near my house is always in short supply:facepalm:


well, let's get back to business……

Before the Spring Festival, I knew that Topping was developing a new headphone amplifier and made an appointment with them for measurement.

The thing was finally mailed to me two days ago (thankfully they started working).

Photo.jpg


Rear.jpg


This is a compact unit. The workmanship is not exquisite, but there is nothing to complain about. Topping's family-style design (the size is the same as D90)

What I like very much is that the Power supply is built-in, making the whole system look simpler (it is always uncomfortable to hang a power adapter outside)

It's a headphone amplifier and preamp integrated product, this design may be very suitable for desktop users? (A small combination of active speakers and headphones)

First I will measure the headphone amplifier part:

I start with a medium gain, 4V input

4VUBDashboard.jpg


8VBALDashboard.jpg


Wow! ... I was a bit shocked ...

I feel that it is not the device under test that restricts the measurement results, but APX555.


In the case of 5V input / UNBAL output, I got 123 SINAD!:oops:

123-2.jpg


This is crazy!o_Oo_Oo_O

For comparison, this is the AP Loopback:

AP.jpg


How does THD + N change with frequency?
FREQ-THD+N-Ratio.jpg

Attention! The bottom of this chart is not 0.0001% as usual, but 0.00001%!

Alright, let's get on the load! See the results under load!
SNR:
SNR.jpg


THD+N vs Level
33R-THD+N-Ratio-vs-Measured-Level.jpg


50R-BAL-THD+N-Ratio-vs-Measured-Level.jpg


I was having difficulty measuring the maximum output ... because the protection circuit is very sensitive, it cuts off all outputs at the moment of overload ...

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.

HP32RMAXdashboard.jpg


The results of the previous test were so crazy that it made me feel boring to release things like frequency response (such a device is almost impossible to have problems in this area)

Relative-Level-(1.jpg


Of course ... Since the volume is adjusted with a potentiometer, there must be some problems with channel balance.But it is said that the final version of the gain will be adjusted to -9 0 9 (the one I got is 0 6 12) should be able to adapt to various headphones.

RMS-Level.jpg



End of headphone amplifier measurement ... output impedance(0.37R):
OI.jpg


Preamp section: As good as the headphone amplifier section!






Update:
I got a retail version from a friend (avoid gold samples)

Simple measurement:
Retail.jpg
 
Last edited:

JohnYang1997

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#8
That's absolutely crazy performance, must be at the limit of what you can measure. What does the AP get in the 50 mV SNR test in loopback mode? Also what's the maximum power output (or voltage swing) into 300 Ohm?
The performance of AP is certainly limiting that particular test. With extra test equipment like low noise preamp between the amp and AP, I would expect about 106dB of SNR at 50mV.
 
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WolfX-700

WolfX-700

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Thread Starter #9

Schackmannen

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#11
The performance of AP is certainly limiting that particular test. With extra test equipment like low noise preamp between the amp and AP, I would expect about 106dB of SNR at 50mV.
Wow, so around only 0.25 uV noise? That's absolutely crazy.

Thank you very much for all the tests you are doing! So maximum unbalanced output power would be around 250 mW then? Also any rough ideas on what it will cost when released?
 
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WolfX-700

WolfX-700

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Thread Starter #13
Wow, so around only 0.25 uV noise? That's absolutely crazy.


Thank you very much for all the tests you are doing! So maximum unbalanced output power would be around 250 mW then? Also any rough ideas on what it will cost when released?
Yes [email protected]

In terms of price, they haven't told me yet ...
 

JohnYang1997

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#14
One thing about the gain setting.
Balanced out will always have 6db extra gain.
So this version is RCA input (XLR input): -6db (0db) 0db (+6db) +6db (+12db)
Final version will have -9db (-3db) 0db (+6db) +9db(+15db).

Also noting the output impedance is a little bit high here. Our measurements showed 0.05Ohm to 0.06ohm for single ended output (hand calculated).
 
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WolfX-700

WolfX-700

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Thread Starter #15
One thing about the gain setting.
Balanced out will always have 6db extra gain.
So this version is RCA input (XLR input): -6db (0db) 0db (+6db) +6db (+12db)
Final version will have -9db (-3db) 0db (+6db) +9db(+15db).

Also noting the output impedance is a little bit high here. Our measurements showed 0.05Ohm to 0.06ohm for single ended output (hand calculated).
0.37R for BAL
 

Fred Jacquot

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#16
One thing about the gain setting.
Balanced out will always have 6db extra gain.
So this version is RCA input (XLR input): -6db (0db) 0db (+6db) +6db (+12db)
Final version will have -9db (-3db) 0db (+6db) +9db(+15db).

Also noting the output impedance is a little bit high here. Our measurements showed 0.05Ohm to 0.06ohm for single ended output (hand calculated).
Is it your baby?
 

Veri

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#19
One thing about the gain setting.
Balanced out will always have 6db extra gain.
So this version is RCA input (XLR input): -6db (0db) 0db (+6db) +6db (+12db)
Final version will have -9db (-3db) 0db (+6db) +9db(+15db).
+15dB on balanced is pretty high lol. But hmm, so no 0dB/unity gain for balanced in final design?
 

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