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If one does not have any grid resistors except the volume control at the preamp tube grid, has anyone tried a grid choke inserted at the volume control ground side?
Follow Ups:
the only place a grid choke could work wrt the volume control is from the wiper to ground.
dave
Dave
Depending on the DC resistance of the choke,cam't it change the effective resistance of the volume pot to where it may not operate as it's supposed to,going from the wiper to ground?
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
For AC the inductance of the choke appears in series with the DCR and the combo becomes part of the load the volume pot needs to drive.
At some low frequency the finite inductance will indeed cause problems but that needs to be analyzed on a case by case situation.
dave
I wire the volume pot signal input to the pot 120K and ground the other side. The wiper is the input to next stage. So, would not the grid choke wire in-between the pot ground end and ground to lift any AC shunting to ground?
No.
If you wire it that way the grid choke will be a frequency dependent impedance in the shunt leg of the voltage divider.
The artip of the series vs the shunt values of a voltage divider determine the attenuation of a pot. If you put a fixed inductance in the ground leg you will mess things up pretty badly.
dave
I think I will not install a grid choke. Thanks Dave.
Edits: 02/02/17
and get rid of the volume pot all together. Possibly something like a switchable signal level autoformer for level control?
Never thought of a transformer as a volume control.
Transformer volume controls have been around for many years now. If you do an internet search, you will find many examples for diy. They are pricey though. I purchased a Stevens and Billington tvc years ago and installed it in my 26 preamp.
might be even better.
Tre'
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