Roscoe Primrose wrote:
What sources does he think are putting anything out above 30kHz anyway? What's a 30kHz filter do if there's nothing up there anyway? Any changes he's hearing from the 30kHz filter are more likely due to phase shift below 20kHz as a result of the filter.
Roscoe
Actually RFI/EMI "saddles up" and rides along with the audio, LP playback can have ringing out past 30-kHz., and digital playback ultrasonic artifacts also can cause issues such as "fogging" and limiting inner detail.
The "old school" designers played that game that Paul talks about such as Syd Smith (Radiocraftsman/Marantz) along with the Heathkit guys that did the same thing. I am sure there were others.
I've noted where others close down the feedback loop to provide a low-pass function.