Coupling Cap Switch - Pre Charging?

[Chuck H]

+1
I get it. But the challenge is keeping the caps charged while still silencing the pop (before we knew about the mute circuit). So here's another idea. Add a big cap to the end of the string to isolate the switched circuit. Would this work???

[Chuck H]

This isn't a niggle, it's just to further my own education on the matter....

Is the grids DC potential to the cathode relevant to the circuit in post #10??? Or is the grids DC potential to the cathode a seperate issue from it's DC potential to the switched circuit? Provided the tube isn't drawing grid current. Or will there always be some grid current as the nature of tubes?

[tedmich]

Every once in a while the theoretical scientists had their calm discussion interrupted; a disheveled experimentalist lurched through the door of the ivory tower, obviously lost. "Do the damn experiment!" he bellowed, and fell back down the stairs...

[Steve Conner]

Keeping with the stereotypes, he was obviously disheveled because his experiment blew up in his face!

The circuits of posts #5 and #6 both pass the DC offset back to the previous circuit through the resistors. The other circuits don't.

Most classic amps have the DC from the tube grids going onto pot wipers. According to the EE textbooks, this shouldn't be done. But if you modified the circuit to include a DC block cap, you can bet someone would whine that it killed the mojo.

[Enzo]

The grid's relation to the cathode matters in the overall picture, but not to pops from cap switching at the grid. Regardless of the bias on that grid, ie. the voltage to cathode, if you make a step change in the voltage there, it will be amplified.

I suppose the post 16 cap would work, but it is just a way to add something to make post 10 work instead of just doing post 5.

[Chuck H]

I suppose the post 16 cap would work, but it is just a way to add something to make post 10 work instead of just doing post 5.

I don't know why, but I didn't realize that post #5 was charging the caps. I thought that something more like post #10 was needed

Looking now I see it. So the only reason I was trying to make post #10 work was because I knew the OP wanted the caps pre charged before selection.

It's plain as day now. Post #5 is the way to go. Thanks Enzo and Steve.

[Enzo]

The essence of it is the cap remains always connected between the two points and so is always charged. The switch shorts the resistor. Other than the brief charging pulse when power is first applied to the system, there is no current through the resistor, so no voltage is dropped across it. Thus we can short it with impunity. Or with a toggle switch.

[Chuck H]

Thus we can short it with impunity. Or with a toggle switch.

Oh, so I should use a toggle switch then. I was having trouble finding impunity in the Mouser catalog.

[Enzo]

ANother victim of RoHS.