Comparison Audacity 2.1.2 with 2.1.3_CKZ (modified by Carsten Karpowitz)

Prerequisite:

Unfortunately Audacity doesn't allow to expand vertically more than shown here. But it's enough for this purpose.

With MME you get dithered 16 bit signals only (but 192 kHz are processed without resampling). With WASAPI on my PC 24 bit work up to 48 kHz only.

The test equipment I use is a special digital audio sine wave generator where I can generate very flexibly and reproducibly signals in way that I even can predict each bit in the signal so that I can check in a signal chain whether this signal is transmitted or recorded bit-precise or changed in any way. (Enlarged photo at the end of the article.)

The audio interface DA2USB is a USB Audio Class 1 and USB Audio Class 2 interface, which, of course, under Windows works in Audio Class 1 only. It is described at http://www.beis.de/Elektronik/DA2USB/DA2USB.html. BTW, the firmware for the DA2USB is written by Carsten Karpowitz, too.

Audacity 2.1.2, 96/24: The 16 bit quantization levels (= +/- 30ยต) are clearly visible. The signal is dithered by anything - I don't know.

Audacity 2.1.3_CKZ, 96/24: The same signal, resulting in a perfect sine wave, clearly more than 16 bit, no dithering

Audacity 2.1.3_CKZ, 192/24: Again a perfect sine wave, but 16 bit only (the maximum for USB Audio Class 1 @ 192 kHz), no dithering. The signal is not symmetrical to zero because the LSBits from the generator are simply truncated.

Audacity 2.1.3_CKZ, 192/16: The same perfect sine wave with 16 bit only and no dithering. The signal is symmetrical to zero because the LSBits are rounded to 16 bit by the generator.

Audacity 2.1.3_CKZ, 96/24, but 100 Hz: Perfect sine wave, 24 bit. Just to show the nice sine wave below 16 bit.

Photo of the Test Equipment:

(Click to enlarge)