If I am using for example Frank's 6sn7 line stage and its grid resistor is 1M and it has a input control of 100K what is the impedance of this? Wouldn't the impedance change with different volume settings?
What about figuring the impedance of the line stage section in my phone preamp that has a grid resistor of 221k but has a volume control after the input tube with a resistance of 100k?
What about figuring the impedance of the line stage section in my phone preamp that has a grid resistor of 221k but has a volume control after the input tube with a resistance of 100k?
Since the grid resistor on the second line stage is 221K and there isn't a volume control until after the tube then wouldn't that impedance be 221K?
phono preamp need more gain
Refer to post 12 for the phono preamp schematic that I am mentioning in the second part of my post #1.
Refer to post 12 for the phono preamp schematic that I am mentioning in the second part of my post #1.
Yes, it would.
About 90.9k at full volume and 100k at zero volume.
It can be calculated as x+(100k-x)*1M/(100k-x+1M), where x is the resistance of the "upper" part of the pot (from the input to the wiper).
Still 221k. The input impedance of the tube itself can be considered roughly infinite, so the volume control pot is "isolated" from the input.
So the input impedance which is 221K stays the same and since the volume control is on the other side of the tube it has no effect on the impedance?
So in a perfect world if I wanted to use a line stage with more gain than the original one in the Mapletree 4A Phono preamp I have I would throw things off unless its impedance was also 221K?
So in a perfect world if I wanted to use a line stage with more gain than the original one in the Mapletree 4A Phono preamp I have I would throw things off unless its impedance was also 221K?