which pots?

[lordsonic66]

Hi guys, still learning....anyway can someone tell me what kind of pots to use generally in stomp boxes, I'm working from fuzz vero layouts which gives me numbers i.e 1 meg, 50k etc....but do I use linear, log or audio taper? Or does it depend on the pedal type? Any help much appreciated guys

[petemoore]

  GEO: Secret life of Pots...
  Audio taper has a curvy line showing how the one resistance [between wiper and outside lug] increases, and the other resistance decreases [between wiper and other outside lug], as the shaft is turned.
  With linear taper it's a straight line, and you get numbers like 10% / 90%, or 50/50, 60/40...
  For many volume pot arrangements, the wiper [output] is a balance between Gnd. [which is called 0.0vdc for this discussion] and whatever signal voltage at the input lug. You can swap the input and output lugs and the only change is the same effect, except the pot is turned the opposite direction.
  Audio pots [used for the volume scheme described] have that 'wierd' off balance taper to compensate for how our ears percieve amplitudes. You can use a linear pot here, but all the change in level will tend to be 'scrunched up' at one end of the potshaft's rotational range.
  The same thing is true if you use an audio taper for something that calls for linear or other 'wierd taper' [smallbear sells a 'Fuzzface gain' pot, special taper spreads the gain range over the shaft rotational limits], but the control will probably [depends on..what it depends on] be scrunched into about 10% of the potshaft twist-range.

[lordsonic66]

thanks Pete, still slightly confused....only just beginning to get into stompbox building. So are you saying all of these types will work, but linear is most suitable? Sorry for being dumb, this is the vero I am going to attempt,   http://www.aronnelson.com/gallery/main.php/v/DRAGONFLY-LAYOUTS_0/album18/album144/album109/these should be linear? Or would any work in theory? thanks Sonic

[valdiorn]

Link doesn't work, but I'm guessing it's this one?
http://www.aronnelson.com/gallery/main.php/v/Renegadrian/dragonfly+blue+plate+special.gif.html

Pots depend on the project. Every pot that's used in a schematic or layout is usually labeled with the correct size (and a different size can drastically change the sound!). Some pots are labeled Audio, Log or A, such as 100k A  or 100k Audio, in the case of this dragonfly vero layout it says 500k Audio, which means it's a logarithmic/audio pot.

PS: If still confused, please read this: http://www.geofex.com/article_folders/potsecrets/potscret.htm

[lordsonic66]

thanks again, actually it's the orpheum fuzz which doesn't specify what type of pots, quite a few of these vero's don't specify, I guess I need to read up about it, in the meantime maybe someone could help me out with this one, I have all the parts, just not sure about the pots, thanks again people.

[petemoore]

  a 10k pot should have just <10k [usually more than about 8k8] between the wiper and each outside lug, every resistance value between the pots measured value and 0.0k can be found when dialing the potshaft, from a lug on either side of the wiper.
  An audio pot'll make a 'scrunched up' R sweep, 90% or so of the range may be near one end of the shaft travel.
  Imagine a line from lower left to upper right on a graphic representation of the shaft position relationship to R value measured as potshaft is swept across it's range...that'd be a linear pot.
  Now imagine that line was a rope, and it sagged...not much change in resistance [< about 10% of total] from 0.0k until the last bit of travel...non-linear, it jumps all of a sudden at one end, or put another way, it has 'tapered resistance'.

[MohiZ]

If the pot taper isn't specified, I'd go ahead and use linear. EXCEPT for these applications the typical taper is log: volume, gain. If you get it wrong, the worst thing that can happen is the control isn't particularly responsive or the usable settings are crammed up on a small portion of the pot travel.

[head_spaz]

Linear pots have a LINEAR taper, where the mid-point in its rotation is also the mid-point of its resistance.
Audio pots, are LOGARITHMIC, where the resistance curve is exponential in taper. At mid-point rotation, it may measure only 10-20% of its total resistance, with the remaining percentage of resistance crammed together near one end of its rotation. Which end depends on whether it's a normal or reversed audio taper.

The human ear detects loudness as logarithmic, where you would have to exponentially increase the volume to detect the difference.
The ear is much more discerning when it comes to detecting frequency variations.

So, in a nutshell, audio taper pots are best suited for volume controls... and linear pots are typically better for tone and balance.
But basically, the only difference in the pots is the rotational curve. They are interchangeable electrically... but the rotational differences would be remarkably different than what one might anticipate. For instance, using an audio pot as a balance control would be awkward, as you'd have to dial it way off center to acheive a center balance.

[biggy boy]

Just took a look at the diagram for the Orpheum in Dragonfly's gallery. Your second link didn't work eather.
The tone is 1Meg Linear
The volume is 100K log

[lordsonic66]

thanks guys I am enlightened, but how could you tell from the vero which pots to use? Thanks again, if this works, I'll let you know. I got into this because someone sold me a broken shin-ie fuzz on ebay, the guy said it was 90% working. When i got it I found it to be only 10% working and making motorboarding sounds with a very weak fuzz, absolutely useless. A friend with some electronics experience encouraged me to buy some components after looking at a schematic and then vero board, 2 attempts later and a mountain of solder, the bloody thing still wont work! Anyway thought I'd try a different fuzz from scratch, I am slowly reading about electronics, but hated maths and physics at school, so find it hard to get to grips with some of the principles but I'll get there, cheers!!!!!