I have played with pkane's Multitone tool this afternoon and the current version runs extremely stable with my setup.
--> Thank you so much
@pkane !
Setup was DAC(USB input, 48kS, Dither 24bit) - APU(notch 1kHz, Gain 26dB) - ADCiso(Range 3v5, 192kS, Mono).
The APU notch was in place because the ADC otherwise makes a distince hump itself.
Multitone:
I took the default THD-vs-Level test and just modified the FFT length to 1M.
I did load Ivan's calibration for the APU notch 1kHz, 192kS (APU_1kHz_26dB_192kS.cal)
The graphs are plotted along the
measured level. (next time I would try to plot them along drive level)
Measured DUTs:
SMSL D-6s (1x ES9039q2m)
SMSL DO400 (1x ES9039Pro)
SMSL PO100AK (1x AK4493, USB-bus-powered)
1) D-6s, L, Vol: 99 (Dithering at 20bit did not make a difference)
2) D-6s, L, Vol: 95 (just slightly shifted)
3) D-6s, L, Vol: 58 (just shifted)
4) D-6s, R, Vol: 95 (hump is smaller)
5) DO400, L, Vol: 0dB
6) DO400, R, Vol: 0dB
7) PO100AK, L
8) PO100AK, R
9) D-6s, L, Spectrum @ -50dBFS
10) D-6s, L, Spectrum @ -40dBFS
11) D-6s, L, Spectrum @ -20dBFS
Can someone falsify or confirm this strange behavior I observed on the SMSL D-6s (1x ES9039q2m)?
(It should suffice to measure the spectrum of a 1kHz sine wave at -40dBFS and -50dBFS)
--> Is this just my unit or is this the typical behavior of the ES9039q2m?
--> Is my measurement flawed?
The DO400 and even the tiny bus powered PO100 (1x AK4493) were very well behaved.
EDIT: Just to avoid any misunderstanding - yes it surely is inaudible.