Switching It Up

printer2

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S1c and S1d operation is not clear to me when cascaded triodes work opposite phase? Also isn't the S1D fifth contact on S1?
S1d is a mistake, a leftover from the shuffled around circuit. Should be no switch. Almost like not seeing the elephant in the room. S1c changes the signal path from Plexi to 2203/4. I see a problem when I get rid of S1d. I will return.

This is better. And better yet.

D7Pi9Ws.png
 
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andrewRneumann

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I believe that protection diode needs to be flipped.

When S1b is in the depicted position, you have three parallel grid leak paths. One 10M (which doesn’t do much), the standard 470K, and another 470k going through the upper volume pot. You are going to attenuate more signal there than you probably want?
 

printer2

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I believe that protection diode needs to be flipped.

When S1b is in the depicted position, you have three parallel grid leak paths. One 10M (which doesn’t do much), the standard 470K, and another 470k going through the upper volume pot. You are going to attenuate more signal there than you probably want?
Sigh, thinking Mosfet. I have been distracted today. Thank you, fixed it.
 

andrewRneumann

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The Normal Plexi channel input jack doesn't shunt to ground. That will buzz when nothing is plugged into it and S1 is thrown to the Plexi mode. Add another pole?

I'm following this closely--hope it works out well! I want to do something like this in front of the power amp I've cooked up.
 
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printer2

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The Normal Plexi channel input jack doesn't shunt to ground. That will buzz when nothing is plugged into it and S1 is thrown to the Plexi mode. Add another pole?

I'm following this closely--hope it works out well! I want to do something like this in front of the power amp I've cooked up.
I noticed that the previous iteration have not decided what to do yet. I may have to sacrifice something for it.

Done for now. I think this is my lease objectionable fix. I never cared much how volume bypass capacitors work. The 2.2nF can be moved and should still cut bass.

1qL9n86.png
 
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Lynxtrap

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Adding to @andrewRneumann 's comment about the triple grid leaks, the signal level going into the 3rd stage might be affected by the Normal channel's volume pot. Alternatively, I haven't had enough coffee today. Anyhow the effect would not be huge. Disregarding the pot, the net resistance to ground would be 230k. Adding the full 1M resistance of the pot makes it 345k.
 

printer2

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Adding to @andrewRneumann 's comment about the triple grid leaks, the signal level going into the 3rd stage might be affected by the Normal channel's volume pot. Alternatively, I haven't had enough coffee today. Anyhow the effect would not be huge. Disregarding the pot, the net resistance to ground would be 230k. Adding the full 1M resistance of the pot makes it 345k.
NO,NO! You are right and reminded me what I was going to do but got distracted by something else and forgot. The other switch position. I think this might be it.

ktsCc3U.png


Now to decide if it is worth the bother than the originating circuit without the plexi position. made a couple of changes to it.

NiO9aRB.png
 
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