Input sensitivity switch?
Moderators: pompeiisneaks, Colossal
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Input sensitivity switch?
I want to switch input grid stopper resistor in my diy amp.
Originally, it was 68K. I want to switch it 33K by add 68K parallel.
I measured it after installed a resistor and a switch. It was measured as 68K / 33K as desired.
However, when I turned on the amplifier and operated the switch, I could not feel any change.
I installed it like below. Theoretically, I do not think there is anything different from the high / low inputs commonly used in vintage amplifiers and why does not it work?
Please let me know if you have any problems with switching in this way.
Originally, it was 68K. I want to switch it 33K by add 68K parallel.
I measured it after installed a resistor and a switch. It was measured as 68K / 33K as desired.
However, when I turned on the amplifier and operated the switch, I could not feel any change.
I installed it like below. Theoretically, I do not think there is anything different from the high / low inputs commonly used in vintage amplifiers and why does not it work?
Please let me know if you have any problems with switching in this way.
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Re: Input sensitivity switch?
There is a difference from your wiring in the vintage amps. For example in a Twin Reverb AB763,it is essentially dividing the signal to ground with the 2 68K resistors when you plug into the #2 jack.
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Bryan
Bryan
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Re: Input sensitivity switch?
Oh, you're right!
Then, is the result like this?
Then, is the result like this?
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- Littlewyan
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Re: Input sensitivity switch?
Not quite. When you plug into the low sensitivity input on a Marshall 1987 or Marshall 1959 (I think most Fenders are the same) the wiring puts the 68K to ground after the grid leak resistor forming a voltage divider.
http://drtube.com/schematics/marshall/1959-01-60-02.pdf
Here is a nice clear schematic so you can see how the input wiring works.
http://drtube.com/schematics/marshall/1959-01-60-02.pdf
Here is a nice clear schematic so you can see how the input wiring works.
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Re: Input sensitivity switch?
Is it right?
Can I operate it with DPDT switch? I want to make it with DPDT push-pull potentiometer.You do not have the required permissions to view the files attached to this post.
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Re: Input sensitivity switch?
Dose it function?
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- Littlewyan
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Re: Input sensitivity switch?
No that will put the 68K to ground before the grid stopper, it needs to come after it. Sorry I don't have time at the moment to draw anything up for you
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Re: Input sensitivity switch?
Maybe this is right. But there seems to be a loud pop noise.
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- Colossal
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Re: Input sensitivity switch?
How about this? In the High position there is 68k || 68k for 34k/1M. In the Low position there is 68k / 68k.
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Re: Input sensitivity switch?
Oh, you re genius! Thanks!