How much different? The difference at 50% rotation will change depending type of pot you have. On the graphs in that pdf, "B" taper is 50% resistance from either lug to middle at 50% rotation (as you would expect for a linear pot). "A" taper is about 25% from middle-right lugs, and 75% from middle-left lugs. "C" taper is similar at 50% rotation but the the way it changes in the first half-turn is completely different.
Can you sub in a cheap Radio Shack 500K log pot and see if it works? That way at least you can eliminate the pot as the culprit.
Well, i tought i replied to this a couple of days ago, but my net connection has been crappy so i guess it got lost somehow. Anyway, i am now very suspicious of the pots (both Vol and Tone) as i have switched the Cap to a 47nf one and can hear the same evvect on the tone as on the volume, where there is very little change for most of the rotation, then a sudden change right near the end. The thing is, the sudden change occurs at the opposite end of rotation for the tone pot as compared with the volume. i.e., i'm turning the volume pot clockwise and when it's nearly at the end it changes suddenly, but i'm turning the tone pot anticlockwise when the same thing happens.
A couple of things come to mind:
- The pots are definitely 500k audio taper (480k ohms measured between left and right lugs, 120k between middle and right, 460k between middle and left at 50% rotation)
- I changed the cap for an even larger one (220nf) to see if it made any difference, and it didn't. the sudden change still occured in the same place and virtually no change around the rest of the rotation. (i have now replaced the 47nf in the circuit)
- I bought these about 2 years ago (when i first started this project.....it's been a VERY long process), so they have been exposed to dust etc. for that time, altough i have tried to keep them in a clean environment
- I will definitely take at least one of the pots out and test is seperately to se if i can measure a corresponding change in resistance, though i may not get around to it till after christmas
- I can't sub in a cheap radio shack pot as i don't have access to radio shack (i'm in australia) and the local versions (dick smith and jaycar) leave something to be desired
- It seems $10 for a pot is quite high, obviously it's higher than normal but i couldn't find long shaft pots ( which i need as it's a carve top) much cheaper. They are $8 at guitarelectronics.com but their postage prices are much higher. Is there anywhere else they're available cheaper if i do need to replace them (or for future builds)?
Thanks for you help so far everone.