miallen
New Member
- Joined
- Apr 12, 2015
- Messages
- 18
- Reaction score
- 1
I'm building a kit and I want to add a post PI master volume. I was thinking of just replacing the pull-down resistors with a dual 250K pot. But it seems there is an "Improved" method that adds a dual 1M pot and 1u caps in front of the pull-down resistors.
However it is not obvious to me why this method is "Improved". If the point is only to eliminate DC on the wiper so that it doesn't make a scratchy noise when turning the pot, I don't think I care. There should be very little grid current and not a lot of amplification at that point so I don't suspect the scratchy noise would be that bad. Can someone speak to this?
Also, it seems to me if you add a big 1u cap in series with the grid and the grid start drawing current when overdriven (aka grid current limiting), those caps are going to charge up (aka bias excursion) and you'll get a bias shift that would totally change sag dynamics. Right?
I know this has been covered a hundred times but I can't seem to find a really good technical explanation about the different PPIMV implementations.
However it is not obvious to me why this method is "Improved". If the point is only to eliminate DC on the wiper so that it doesn't make a scratchy noise when turning the pot, I don't think I care. There should be very little grid current and not a lot of amplification at that point so I don't suspect the scratchy noise would be that bad. Can someone speak to this?
Also, it seems to me if you add a big 1u cap in series with the grid and the grid start drawing current when overdriven (aka grid current limiting), those caps are going to charge up (aka bias excursion) and you'll get a bias shift that would totally change sag dynamics. Right?
I know this has been covered a hundred times but I can't seem to find a really good technical explanation about the different PPIMV implementations.