I have made a some measurements with a DANIU ADS1013D. As many other reviews have stated the analog bandwidth is about 25 MHz. You will get a signal at higher frequencies but the amplitude will not be accurate. Besides this limitation is quite good product for this kind of money.
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It is capable to export waveform data to files but I haven't found any source of information describing the format. I was able to extract some data from the files to make FFTs. Single tone a low frequency signal looks pretty nice.
When feeding dual tones at high an low frequency at the same time the higher frequency get folded in as a result of low sampling rate.