I just changed the grid resistor value from 500r to 2k on a 12b4a preamp build.
I now have to advance the volume pot significantly to reach a normal listening volume.
I have never made such a large change in grid resistor on any project...
Is this to be expected?
I now have to advance the volume pot significantly to reach a normal listening volume.
I have never made such a large change in grid resistor on any project...
Is this to be expected?
The grid stopper resistor (series with the grid) is usually 500R to 10k. It should not cause the symptom you described.
The grid leak resistor, however is between the grid and ground (its hot side placed before the grid leak). The usual value is 100k to 1M. 2k is extremely low, it will shunt most of the audio signal.
The grid leak resistor, however is between the grid and ground (its hot side placed before the grid leak). The usual value is 100k to 1M. 2k is extremely low, it will shunt most of the audio signal.
If it is the leak resistor, not the stopper, and the value was 500k instead of 500R, changed to 2k, that'll do what you say.
As also mentioned above by @Icsaszar.
Of course a schematic would help, if not asking too much.
Jan
As also mentioned above by @Icsaszar.
Of course a schematic would help, if not asking too much.
Jan
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You must have done something unnoticed. Changing a stopper from 500R to 2k will not change the volume.
I guess a schematic is asking too much?
Even saying 'Changed trouble shooting noise' is a nonsensical sentence.
This'll drag on for days as everything is speculation.
Good luck guys!
Jan
I guess a schematic is asking too much?
Even saying 'Changed trouble shooting noise' is a nonsensical sentence.
This'll drag on for days as everything is speculation.
Good luck guys!
Jan
Changing a stopper from 500R to 2k will not change the volume.
Thatsvwhat I'm looking for no more no less....
Thanks veveryone.
Nothing to look at here movev along 😊
Thatsvwhat I'm looking for no more no less....
Thanks veveryone.
Nothing to look at here movev along 😊
The knob rotation angle of a 500 Ohm pot does not equal the knob rotation of a 2000 Ohm pot, when . . .
One is a Linear Taper pot
And one is an Audio Taper or Log Taper pot.
Are the tapers of the pots the same?
Rotate both pots to 50% of rotation.
Measure the ratio of wiper to ground, versus top to ground.
Suppose one measures wiper to ground 250 Ohms, and top to ground 500 Ohms,
Or wiper to ground 1k Ohm, and top to ground 2k Ohms,
Those are Linear pots.
If one of the ratios is not 50% Resistance with the pot at mid rotation,
chances are one of those pots are either Audio Taper, or Log taper.
At 100% rotation (full volume setting of each pot) the preamp should have the same gain.
One is a Linear Taper pot
And one is an Audio Taper or Log Taper pot.
Are the tapers of the pots the same?
Rotate both pots to 50% of rotation.
Measure the ratio of wiper to ground, versus top to ground.
Suppose one measures wiper to ground 250 Ohms, and top to ground 500 Ohms,
Or wiper to ground 1k Ohm, and top to ground 2k Ohms,
Those are Linear pots.
If one of the ratios is not 50% Resistance with the pot at mid rotation,
chances are one of those pots are either Audio Taper, or Log taper.
At 100% rotation (full volume setting of each pot) the preamp should have the same gain.