Volume taper

oleoleo2

Member
2008-08-03 8:50 pm
Hi Diyaudio forum.

I am trying to build a guitar distortion fx. On some part of the amplifier circuit I have a JFET amp-circuit with a 100KA pot at the output to control the volume. The pot leads the signal to ground when it is turned. I am not very satisfies with the way the taper feels. It is like it turns the volume up a lot in the beginning and the gets more and more passive. As I understand the 'A' means that it is logarithmic? Have tried with linear pot's to, it is almost the same. I suppose this must be a problem a lot of others run into? How do I solve this?

Kind regards,

oleoleo2
 
It depends on how old the pot is. "A" used to mean linear, but now means log (what committee dreamt that up?). See Potentiometers (Beginners' Guide to Pots).

You could try measuring the resistance at half-travel. If half the total it is a linear pot. If 10-20% of the total it is a log pot. Of course, you can connect a log pot the wrong way round (and there are anti-log pots too).
 

wakibaki

Banned
2008-01-08 11:51 pm
Replace it with a 100k linear pot and a 15k resistor as on this page: ESP - A Better Volume Control. Or use the existing pot if you can determine that it's linear. The first thing to try is setting the pot to half-way and measuring for 50k. If you don't get 50k then swap the outside connections on the pot and see how that works. If you do get 50K then try the dodge with the 15k connected to the wiper and ground

w
 

oleoleo2

Member
2008-08-03 8:50 pm
It depends on how old the pot is. "A" used to mean linear, but now means log (what committee dreamt that up?). See Potentiometers (Beginners' Guide to Pots).

You could try measuring the resistance at half-travel. If half the total it is a linear pot. If 10-20% of the total it is a log pot. Of course, you can connect a log pot the wrong way round (and there are anti-log pots too).

Well it seems like it's a linear pot then as I get 50R halfway (thanks for the "trick" funny I never though of that :))
 

oleoleo2

Member
2008-08-03 8:50 pm
Replace it with a 100k linear pot and a 15k resistor as on this page: ESP - A Better Volume Control. Or use the existing pot if you can determine that it's linear. The first thing to try is setting the pot to half-way and measuring for 50k. If you don't get 50k then swap the outside connections on the pot and see how that works. If you do get 50K then try the dodge with the 15k connected to the wiper and ground

w

Thanks a million! This seems to the trick!