volume taper

[jadeharp]

i built a vibrolux clone a while back. Everything works fine, and no real complaints, but the volume control from 1 to 2 is almost nothing, but just a hair past 2 is too loud. It has a 1M audio taper pot. what can I do to make this more gradual.

[maxkracht]

Try adding a resistor between the center lug and ground on the volume pot. Maybe around 220k?

http://www.geofex.com/article_folders/p ... tscret.htm

[pdf64]

I don't think such a resistor will help the smoothness of the slope at the CCW end.
I suggest to buy a better pot, or fit a master volume.
These are stage amps, not intended for low sound levels.

[maxkracht]

I don't think such a resistor will help the smoothness of the slope at the CCW end.
I suggest to buy a better pot, or fit a master volume.

Could you explain why it wouldn't work? I agree that a pot with a better taper would be preferred, and if there is a defect in the pot It wouldn't correct it, but it is easy to try if the op has a suitable resistor. I have used tapering resistors successfully in the past.

[pdf64]

I don't think such a resistor will help the smoothness of the slope at the CCW end.
I suggest to buy a better pot, or fit a master volume.

Could you explain why it wouldn't work? ...

The taper modification idea is most effective in the middle range of the pots rotation.

the volume control from 1 to 2 is almost nothing, but just a hair past 2 is too loud.

'1' is full CCW, so 1 to 2 will be the CCW track end pad.
Just a degree past that and the volume has shot up too much.
But from the schematic representation on the Geofex page, the R2 section of the track (between the wiper and CCW end pad) will still be a low resistance, eg 10k.
Whatever reasonable R3 value is connected there, it's not going to bring it down to a level eg 1k that's needed for a smoother taper coming off the end pad.
eg even R3 at 100k is only going to bring the total effective R2 to 9k.

[maxkracht]

Thanks. My assumption was adding more taper to an already tapered pot would be an improvement. Small changes in the early part of the rotation are still changes. Whether that is enough is subjective, but your're probably right that might not be enough.

[Roe]

CTS audio pots usually have a 10% taper nominally, whereas alpha has 15+%. But pots vary quite a bit, reading higher or lower than the specs often

[pdf64]

CTS audio pots usually have a 10% taper nominally, whereas alpha has 15+%. But pots vary quite a bit, reading higher or lower than the specs often

In reality, I suspect that the extra large CCW end pad on CTS pots results in the actual track taper slope (ie once the wiper reaches the resistive track) being as steep as Alpha's 15%.
And having so much of the available rotation given over to that oversized end pad makes using CTS pots rather irritating.

[cdemike]

Although it won't change the taper, you could get more usable range out of the pot by adding a resistor in series with it prior to the pot, basically changing the ratio in the voltage divider formed by the pot. I'd choose the value by marking the range of the pot's travel where it goes from too quiet to too loud and add the value closest to the resistance between the input lug and the wiper when it's too loud.