Sorry Doc for stealing your phrase.
"There's been a lot of talk (maybe, maybe too much talk)" about digital on this forum lately. And as I decided to take the plunge (again), I've been studying a lot (as if I didn't have more productive things to do).
Here's my learnings, conclusions and decisions:
When digital audio is converted to analog there's a series of phantom signals, identical to the original one, occurring at half the sample rate and another one at each multiple of it. In the case of redbook the first sits at 22.05khz.
The original redbook players had very steep "brickwall" filters above 20khz to eliminate those in the analog domain. Steep filters are complicated and have problems (mostly phase related) so Philips started "upsampling" to push the aliases higher on the spectrum and adding digital filters, thus messing with the signal and creating digital artifacts. Everyone followed. (Delta sigma).
At some point the diy community started experimenting with filterless dacs without upsampling (r2r) or filters. And it sounded better! Of course there's the aliases but even those are better than the stupid digital manipulation of the signal.
It's clear to me that nos MUST be better. The question is how to deal with the aliases. Some people use mild filters, others use transformers (steep filters without the extra circuit), and yet others do nothing.
For my current digital experiment I'll use WE 755A than don't reach aliasing frequencies. Still I think those images can impact the circuits so I'll try removing them.
My plan is comparing a totl Audio Note kit (NOS filterless with two sets of transformers in the audio path) with the upcoming BH dac (current iteration has only a first order filter). And try both dacs with a couple of additional sets of MQ transformers (input and output of the preamp) as well as 1st order pllxo before the pre and before the amps. and play getting those in and out of the circuit.
I may be crazy (but it just may be a lunatic you're looking for).
Saludos
