Rerurn to Romy the Cat's Site
In the Forum: Analog Playback
In the Thread: The last phonocorrector: “End of Life" Phonostage
Post Subject: EAR834p how does RIAA feedback work?Posted by AlexBerger on: 3/8/2021
Hi Romy,
I read about EAR834p modifications in number of forums. And I never found any explanation how does RIAA feedback work.Only from you I heard about Miller capacity that used in this RIAA.I tried to do my calculations and as I understand the Miller capacity is a function of gain and it should be different on different frequencies because the gain is not constant. So, it make it even more tricky for calculation. I don't understand which gain I need take in account open loop gain or closed loop gain.
I was wrong in my previous post. The feedback should work in this circuit on low frequencies. As result output impedance is much smaller then I calculated before.
But I was right about the trick with huge cathode capacity. It works! If you can do a fixed bias - it is the best. But if you can't (because schematic) or don't want (too lazy to adjust fix bias) huge capacitors make "fixed bias" sound. How does it technically works. Maybe it works, because, extra big capacitors move a cathode bias phase hump around 1-5Hz to lower frequencies. But the more obvious explanation is - huge capacitors makes cathode to ground impedance very small at hearable low frequencies.
Regards,Alex
Rerurn to Romy the Cat's Site