102 pages of indescribable ... Oh man, what a ride it was... Anyway... Ordered the E30 2 days ago from Audiophonics, should be arriving today.
I'm really wondering why Topping chose the 2 MCU design? They clearly can modify the code of the Xmos code themselves if they can release a inversion fix within 2 days of reporting the "issue". The Xmos is a very capable CPU, it should have been no problem whatsoever to also have it control the dac, screen, remote and buttons.
BTW, regarding digital volume control. One thing nobody mentioned here is dithering. Instead of throwing away bits, when you lower the volume, what actually happens is that dithering is used to preserve some of the resolution by adding a bit of random (or noise shaped) noise and "encoding" the rounding errors from the attenuation into them. It's not magic, and you raise the noise floor tiny bit, but it will preserve waveform quite well. Best dithering uses noise shaping to push the noise up in frequency, and therefore making it inaudible. the perceived noise is then not even raised, but you do retain more resolution. Since a 24 bit DAC optimally has about 20 to 21 bit of actual content in them, one can easily use 1 tot 4 bits for dithering.
Obligatory cat image:
This is how it works on images with only a 1 bit. If you have a LCD screen, chances are you've been looking at a dithered for years. Most screens are only actually 6 bit per color, and are dithered to 8.. or 8 is dithered to 10 bit. Did you ever notice the noise?
DSD is also just a form of dithering btw. If you look at the SNR vs frequency graphs of a DSD signal you'll clearly see that the dithering noise is pushed far up in frequency.