Voltage Mode Pre and Post Filter Feedback

[hermanv]

Although digital errors, delays, non symetry and errors introduced by the filter are all real and non-trivial. There may be alternate solutions besides an analog feedback loop.

Many of those digital errors are effectively time offsets and can be compensated for in other ways. The filter is a different problem but passive components that can handle the currents and frequencies involved might be big but otherwise not impossible to obtain.

I'm not saying that an all digital approach is superior. I am asking, if we think outside the box are there approaches that should be considered?

For example an all digital approach brings up the perenial problem of digital volume control, we don't want to truncate any bits (by most accounts there aren't enough bits now) so one idea would be to vary the voltage on the digital output stage. This would change the volume (yea, I know, its an analog approach) without any DSP or arithematic units in the signal chain.

It may even be a way to add feedback without a DSP.

Using an active comb filter to get an error signal from the speaker drive signal is not hard, a passive comb filter for the speaker output is not practical. I think a comb filter recovers the maximum analog component with minimum absolute or differential delays.

Most of this is just thinking out loud, there may be some substance in there but I sure don't guarantee it.