Rob, can I ask your thoughts on the distortions in digital audio itself - I think you touched on it before when you mentioned the idea of brain burn-in i.e. that the brain has to accommodate to the new types of distortions that have been introduced as a result of digital audio?
It seems to me that the introduction of digital audio have allowed new distortions to be created due to the fact that mathematical processing can be inaccurate in so many new ways that introduce new distortions which were never encountered before in the natural world of vibrating bodies
The sampling and recreating the original analogue signal without timing errors has been an extremely interesting problem for me over the last 3 years - mostly in the appreciation that extremely small timing errors can have a profound effect subjectively. What we are doing with ADC then back to DAC can be summarised:
Analogue continuous signal > Sampled data (ADC)> analogue continuous signal (DAC)
What I (and the rest of the engineering community) have failed to appreciate is how sensitive we are to very small errors in the reconstruction process. Mathematically its simple - we simply need an infinite tap length FIR filter with a sinc impulse response that also infinitely over-samples at the same time, then we will perfectly recover the original analogue signal in the ADC.
In practice, I do not know (for certain) how many taps are needed, and how much oversampling is needed - that said, I have made a lot of progress in this area, but I do not know how much further we can take it. It's one of the very interesting things I hope to learn from the Davina ADC project when I will be able to go from 768k, down to 48k, back up to analogue, and then appreciate how much losses we really get, and how to minimise them.
Very interesting times ahead!
Rob