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

This is really a long and memorable vacation ...Mainly for well-known reasons ... I haven't released any measurements for a long timeLogistics 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 supplywell, 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).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 inputWow! ... 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!This is crazy!For comparison, this is the AP Loopback:How does THD + N change with frequency?Alright, let's get on the load! See the results under load!SNR:THD+N vs LevelI 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.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)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.End of headphone amplifier measurement ... output impedance（0.37R):Preamp section: As good as the headphone amplifier section!Update:I got a retail version from a friend (avoid gold samples)Simple measurement: