Rochey said:
The digital step size is always the challenge. "Oh,, I can hear a 0.25dB step!"
I have invested too much time into digital controlled analog and digital step size becomes much less relevant when step changes are co-ordinated with zero crossings (zero times anything is zero). Some modern Digital controlled preamps build in the zero crossing circuitry.
Plus, once you start asking digital silicon designers for VCA's, their eyes glaze over.
Actually VCAs are not trivial and the recent THAT VCA technology is a fairly significant achievement. My last exchange with a real silicon designer (admittedly a junior, wet behind the ears field engineer), ground to a halt when we tried to include a basic OTA cell inside a power amp control IC. The kid actually suggested adding emitter degeneration to an OTA input stage to reduce DC offset concerns.
At that point I realized the project was doomed, since the IC guy should know more about ICs than me. .
==========
Back in topic, digital controlled analog is based on the premise that there is some inherent value from operating in the analog domain. While i am an old school analog guy I wish that was true (IMO it isn't), but how many music projects can successfully avoid being digitized (some niche market of hipsters buying analog to analog records?)
Of we accept the ultimate conversion to digital, signal integrity is better preserved by making that conversion as early in the audio path as possible. The economics for operating in the digital domain is even more compelling. Do what floats your boat for DIY, commercial products for a wide market can not ignore cost.
JR
