Dual Cathode Resistors

[clyde]

Is there any way to mitigate the "pop" when switching a second one in or out? 

[sluckey]

Is there any way to mitigate the "pop" when switching a second one in or out?

Try putting a big resistor across the switch contacts. Maybe 100K or higher.

[clyde]

No, unfortunately it doesn't seem to do anything, went 10k and lower even.

[shooter]

the further you go down the signal-path, the louder the pop.
are you switching the cathode side or the ground side?


you could do some creative math so you never "break" the path, just parallel a 2nd resistor to = your "new" resistor.

[sluckey]

No, unfortunately it doesn't seem to do anything, went 10k and lower even.

I said maybe 100K or higher. Shooter has a better idea.

There are a few different ways to wire this. Show us exactly how you have your switch connected. Simple schematic.

[clyde]

I am switching the ground side, so resistor is attached to the cathode.  I used my decade box, started with 10M across the switch contacts,going lower until it didn't make any sense anymore.  The second resistor is switched in for a warm gain increase, 2nd stage 6J5.  I could try switching the cathode side.  In any event, it's not harmful but an annoyance. 

[sluckey]

Which switching method are you using (A or B)? Or are you using something else?

[clyde]

"A"  I never thought of using "B", the 2nd resistor half the value of the first, or thereabouts.  It might solve the problem. 

[sluckey]

Is there a bypass cap involved?

[SnickSound]

Is there any way to mitigate the "pop" when switching a second one in or out?

Doing this changes the bias point, I don't know of any way of getting rid of the pop beside pulling a Mesa and muting the amp while switching is happening

[Esquirefreak]

I recently tried switching a preamp triode Rk in parallel with another and could not get rid of the pop. Didn't seem to make any difference with snubber resistors. I suppose that's the nature of switching DC.

/Max

[clyde]

No bypass cap.

[shooter]

what's the end-game you're looking for by on the fly re-bias?

[kagliostro]

From this proposal of Mr. Merlin, see option C



Something to which you can give a try



Franco

[clyde]

what's the end-game you're looking for by on the fly re-bias?

It's a warm gain on the 2nd stage as stated above, not really "on the fly" but noticeable when switched with the amp on.  This is a restomod of a trashed Harmony H194 which has only volume and tone and I'm just trying to get a little more of an expanded tone palette.  The volume has a pull-on cathode cap on the first stage as well.   

[kagliostro]

... It's a warm gain on the 2nd stage as stated above ...

May be something like this ?



Franco

[clyde]

Tres cool, unfortunately I don't have room for a pot, but thank you very much!

[kagliostro]

You are not obliged to use a pot on the faceplate

you can simply use a trimmer to find the right values and then resistor and SPDT switch

Franco

[SnickSound]

You are not obliged to use a pot on the faceplate

you can simply use a trimmer to find the right values and then resistor and SPDT switch

Franco

That brings us back to the original problem though, hard switching the cathode resistor changes the bias point and will always result in a pop.

The LDR is a nice idea, complicated, but nice.

I would probably just try to get what I want a different way

[kagliostro]

Also the pot that feeds the LED can be changed using resistors and a switch


Franco