How do i turn a 5KB pot into a 5KC rev log?

[pete_g]

I made a ZVEX super hard on and realised that it has a reverse log 5 k pot.
What value resistor can i put on the lugs to turn it into one?
Would it go on the lugs 1&3?
I also have a 100k C rev log pot so if I can use that what value resistor would I use?
Thanks.

[duck_arse]

you can't. to end up with a C5k, you need to start with something like B25k or B50k. you can use a C100k pot as a C100k pot, I don't believe the tapering resistors works on C or A tapers.

there are currently two taper-resistor-calculator threads open, have a wee search. also, "the secret life of pots" at geofex, and there is another similar page at ESP.

[Kipper4]

Why not use a A5k and wire it back to front?

[Kevin Mitchell]

Answers are all over the place! Why create a thread on something covered over and over again...

You probably shouldn't sub a rev log with a log or vice-versa. If you know the difference between the two then you'd understand that you could - but shouldn't.

A 5k linear pot would be fine.

To answer your question on adjusting tapers;
A good thread to read

Also if you really would like to get into it, read the Secret Life of Pots at Geofex.

Why not use a A5k and wire it back to front?

Reversed control....

[Kipper4]

Depends if you think it's an issue.

[Kevin Mitchell]

Depends if you think it's an issue.

I suppose it would be ideal if one side of the control is considerably sensitive. This is usually the case with most LFO speed controls (when rev log is the best option). In that case, I'd compromise with a type A pot wired backwards. Until the right one comes in!

Otherwise, type B fits the bill.

To note... The more you taper (modify a pots resistance limit) the less usable the sweep becomes. So 100k tapered down to 5k will leave you with very little range to work with. At 12o'clock you'd be at the middle of the taper sweep but the end of the 5k resistance would be limited and no longer relevant with full rotations. So it would be stuck at 5k for most of the turn.

Hope that made sense!

[Kipper4]

Fair enough.

[pete_g]

So you think a B5K is fine?
I suppose it just means that it just takes it until about 3/4 to start distorting instead of early on in the sweep?
Does that alter any high frequencies, do they appear more later on in the sweep?
Reason I'm asking is because mine doesn't have much sparkle until it start to get to around 3/4 and starts distorting.
Thanks.

[nocentelli]

The sparkle and the gain level are inextricably linked, but in inverse proportions. As the source resistance is decreased by the pot being turned "up", the gain increases but the input impedance decreases. So at 5k there is no gain boost but the impedance is very high so all of the natural sparkle/treble of your guitar is preserved. The impedance lowers as the gain goes up which helps prevent it being ice-picky trebly when boosted (plus the distortion adds some upper harmonics). I'm guessing you are just noticing the still-relatively-high input impedance more at higher levels. The taper of the pot will only alter how far you need to rotate the pot to get the sound you want, it does not affect the characteristics of the sound of the circuit itself.

[Kevin Mitchell]

If the control is more sensitive at the end of the resistance sweep (you say at 3/4 with linear) then that would imply a rev log would  be the same at maybe half the turn. The point of a rev log is so there's more usable range at the higher rotations.

Pots work the same and the type doesn't change the resistance sweep. Only how the pot interacts. Log types have a slow resistance sweep towards low settings and is more bunched up at higher settings. The opposite with rev with the slow sweep in the high. Linear is an even sweep all throughout. I'd draw a graph to make more sense of this but I'm lazy. There should be drawings all over if you need visual aid

[DavidRavenMoon]

You can get them here

http://www.mammothelectronics.com/Alpha-Potentiometer-p/200-100-c.htm

[pete_g]

Thanks for all the help.
BTW the Super Hard On brings a bass amp to life in the studio