Short wiring paths, capacitance and parts?

[stubhead]

I know that most all diagrams and instructions will tell you to make your wiring paths as short as possible, because every little bit of extra wiring the (passive) pickup magnets have to push signal through is adding resistance or capacitance. And, I know a lot of people (me) usually leave a bit of extra wire on the pickup leads, because we're liable to change our minds a lot.  :dontknow:

BUT: if you look at a regular-sized CTS or Alpha potentiometer, in comparison to their equal-quality "mini" pots, it looks like there's at least twice as much iron in the big ones. Now the outside cases are always "ground" but even inside them, the wipers and discs are larger - why would they make them that big otherwise? I can foresee the point that the larger ones "ought to" wear longer because there's... what - a bit more goo* on the wiper & rotor? But unless you're a heavy-duty Van Halen/Morse little fingerer volume sweller, how often do we really WEAR OUT a pot? Most of the failure is from damage, banging on the shaft or pouring beer into them. And there are now all these pots with a tiny square box on the bottom, the box is usually not much bigger that the shaft of the thing (Bournes is one maker).

I can't find any data (HA HA HA - right! Actual DATA about electric guitar performance? gimme some of what he's smoking!) that details the difference in resistance between, say, a CTS full-size vs. CTS mini pot. It may be there somewhere in the Mouser catalog, but good god. Does anybody know anything about this? And/or, what is the actual output effect of leaving an extra 5" of wire on a pickup - vintage output and/or flamethrowers?


*(forgive my overly-technical vocabulary here)

 

[Cagey]

Reducing signal path length in guitars isn't so much about resistance - not at all, really - it's about picking up noise. You can have perfectly balanced humbuckers and still end up with a pretty noisy guitar by not shielding the 4" or 5" line from the controls to the output jack.

As for the pots, it has to do with heat dissipation. What you're calling the "regular" sized pot is a 2 watt part. The "mini" pots are usually 1/4 or 1/2 watt parts. In all cases, they're grossly oversized electrically for the duty they're asked to perform, as we're only controlling millivolts at milliamps in guitars, which only make for milliwatts. But, if we used properly sized pots, they wouldn't last a day. The higher wattage parts have the same resistance, but they're mechanically much more robust, which allows for the beer and beatings.

 

[Jumble Jumble]

Actually, 1 mV and 1mA gives you 1 µW (microwatt), so it's even more ridiculous.

As for a difference of resistance - well, tolerances aside, a 500K pot is 500K, regardless of physical size.

 

[Dan025]

the cable capacitance is way more than any other componant. the combined capacitance of all other parts is not likely to be any where near in propotion to the cable unless you have specialty cables like George L's or some type of twisted pair or other audiophile cable.

the resistance is marginal. i mean the pickup is like half a mile of wire that is only about the thickness of a hair or sheet of paper. a few inches of 16 gage will have so little resistance you won't be able to accurately measure it.

as cagey said, short leads is good practice to keep the area that can pickup noise as low as possible. the size of the pots matters very little. the size may have a litle to due iwth heat disapation and watts rating. problems only come with cheap parts that can use inferior materials like die cast pot metal and cheaper resistive elements that have less longevity and may have appoximated tapers that use two different linear tapers that meet in the middle to sorta kinda get an audio taper but not really.

 

[stubhead]

I got to thinking all this a while back so I ordered up a little selection or stuff via the 'bay - you can never have too many parts, right? And CTS and Alpha both make "mini" pots that look to be exactly the same materials and quality as their bigger pots. Only, they cost less than half-as-much because any part that can be marketed as the Secret Mojo Part for a guitar gets overpriced. I believe the only longevity issue that would arise is simply in material fatigue of the contact strip and wiper from a whole pantsload of back&forth - which isn't a real big aspect of playing, for me. I'm just going through one of those periods where I want to TRY things instead of thinking that I know the "correct" info from reading it.

Like, everyone "knows" that you use linear pots for tone and audio pots for volume, except, Fender uses linear for everything and Gibson uses audio for everything. So while you can read the difference between them being stated very authoritatively - the two most prominent makers disagree with it, and more importantly you haven't been listening to music made on guitars that use different pots, not often at least. That kind of knowledge is worse than being ignorant, it's willfully stupid.

 

[Cagey]

The longevity issue relative to size is real, but it is as you say - it depends on how abusive you are and/or how much use they get. If you rarely use the pots, they're not going to see much wear. And generally speaking, they don't deteriorate much on their own simply by existing. Your worry would be more along the lines of contamination, which would make them scratchy or present dropouts.

I've never been aware of Fender/Gibson having a deliberate disconnect as far as which taper to use on their pots. It seems to have been more a case of their using whatever they can buy the cheapest at the time. Fender's notorious for this, which is why we still see cloth-insulated wire. They got mountains of surplus of it for next to nothing after WWII, and now everybody thinks it's part of the guitar's mojo.

If you wanted to use the Right Thing, then you'd have log (audio) taper pots for the volume, and linear taper pots for the tone. But, that's too complicated for them. Engineering, Purchasing, Production and Test would have to keep track of more, train more, test more, etc. and there just isn't enough rebellion from the user base to get worked up about. Most kids will take what they get with a guitar, and call it The Best simply because it's different and they don't know any better, so it's exactly as it should be - delicious! It's like the old drill sergeant said: Worst piece of ass I ever had was GREAT!

 

[bagman67]

It's like the old drill sergeant said: Worst piece of ass I ever had was GREAT!

You had Sgt. Jackson for boot camp, too?

 

[Cagey]

Not sure. I think his name was "Sir!"

 

[bagman67]

So yours was in the Marines.  You don't call Army drill instructors "Sir."  They'll come back at you with "SIR!?!?!  Don't call ME 'sir,' boy, I work for a living!  Now drop and give me twenty!!!"

 

[Cagey]

Dunno. Most of the language was NSFW.

 

[bagman67]

YEah, they're technically not allowed to do that anymore.  A rule honored more in the breach, etc., etc., but it's there anyway.

 

[Cagey]

Well, "they" in this case would have been my father, who was immune to such direction. But, that's another story that's also NSFW.