Using 500K potentiameters with single coil pickups?

[tobijohn]

The answer is probably obvious, but I've always been conceptually challenged when it comes to electronics. Traditionally, 250k pots are used for single coils other than P90s and 500K pots are used for humbuckers and P90s (Gibson sometimes used or uses 300K pots, I've read).

However, if you used a 500k tone pot with a single coil and turned it back half way, would you get the same effect of a wide open 250k pot ?

Also what's the effect of a 500k volume pot on a single coil pickup?

TIA

[Rollin Hand]

It has nothing to do with volume. The 250K pot is not the same as a 500K pot at half. 500K is more open and bright.

Using a 500K on a single coil could make it more bright and ice-picky. Or it could brighten a dark pickup.

By the same token, some people use a 250K pot with a Duncan JB to tame the high end a little.

[mozz]

Here's my take. Included is a old Gibson wiring diagram. 50's and modern wiring are a bit different.

Consider your pickup as a coil with x amount of resistance, also throw in some x amount of winding capacitance. It has a peak at a certain frequency. It's usually pretty narrow and sharp. Real ice picky. Once you thrown in the wire resistance and the wire capacitance, it becomes more tame, fatter, lazy, broad, not as ice picky. A pot across that tames it even more. No tone controls for now. Picture below.

blog_pick-up-frequency-response-300x218.jpg (13.49 KiB) Viewed 6151 times

Place that peak to the left it moves the peak to a lower frequency, or right for a higher freq. Add some resistance in parallel and the peak is not as sharp but is broader. May sound dull and lifeless if you go too much. By too much i mean lower resistance, such as 50k would really mush/blanket it.

accircuits-acp240.gif (11.01 KiB) Viewed 6151 times

So, your pot is always in parallel with the pickup. That is going to dampen it. Your wiper of the vol pot is going to your output, that adjusts your level but doesn't effect the parallel resistance across the pickup. Now your guitar cable has a bunch of capacitance, that is in parallel with the pickup. Makes a big difference. You can try 500k pots across a single coil and use a 30 ft guitar cord. Some of those coily cords Hendrix used to use will really tame a strat.

Here's the effect of the the control on the peak.

1 more thing, a 500k pot will get you more output voltage, in theory , more dynamic range from soft to quiet.

Gibson diagram.

[mozz]

If you have a scatterwound/handwound pickup, it has less capacitance. You have a sharp peak. But you can tame it, lower it, broaden it. First thing i noticed when i started winding single coils was the tone knob was really working, not just bright or dull. If you have a near perfect machine wound pickup, it already has a broader fatter peak, and if it's too extreme, there is nothing you can do to make it peaky again. You can see how a no load pot really brings the peak up.

The Gibson studio i just bought had 300k pots, which actually measured at 270k. Swapping out to 500k pots made a very noticeable difference. I can lower the pickups because i have more output and lower pickups means increased sustain. It all really ties in together, you should actually swap out pots before pickup changes but most people do all at once and your ear goes "Wow" I really like these pickups.

[Partscaster]

Made me try to remember about adding cheap resistor to modify higher pot value.

quote from another forum:
"All you have to do is to wire a 470k (closest to 500k) resistor across the pot, i.e. connected to lug 1 and 3. You can use crocodile clips for a quick test.

The equivalent resistor of the 500k pot and a 470k resistor in parallel will be 242k (with 10 to 20% tolerance), close enough to 250k. The taper will be altered, you might like that or not, depending on the original taper."
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I hope that is correct.

[andrewsrea]

if you used a 500k tone pot with a single coil and turned it back half way, would you get the same effect of a wide open 250k pot ?

Not the same, even with a liner-taper pot. As @mozz explained, the pot value will change the resonant frequency of the pickup.

If you take a B500K (linear) pot and solder a 500K resistor between lugs #1 (ground) & #3 (pickup lead), you'll get a 250K pot with a taper that is a little different than linear.

Also what's the effect of a 500k volume pot on a single coil pickup?

Brighter on '10', and a quick 'darkening' when you roll the volume off using an audio-taper. A 500K tone pot will also change the resonant frequency and have less treble dampening, to which you can always keep the tone rolled-off a bit to achieve the dampening (removing harsh, spikey treble).

Here is what I've been liking lately:
Strat single coils & Firebird pickupss: Gibson 300K linear taper for the volume (I have a bunch which are really around 275K), CTS 250K audio taper for the tones, (1) for the middle & neck pickup and (1) to tame the bridge pickup. Tone caps I typically use are 0.015uF for middle-neck tone and 0.022uF for the bridge.

Tele single coils: CTS 250K audio taper for the volume & CTS 250K audio taper for the tone. I like a 0.022uF to 0.033uF for a Tele, depending on the overt brightness of the guitar and in specific reference to the neck pickup. I like a clear and airy neck pickup and a sizzily (but not strident) bridge pickup. Sometimes I'll insert a 47pF to 180pF capacitor from the pickup lead on the 3-way switch to ground, to tame a harsh Tele bridge pickup. I like to combine components in a way that I avoid treble-bleeds on Teles.

Note: I typically wind my pickups to naturally be twangy, chimey and airy, but not harsh, which saves me from having to resort to such measures.

P-90's: Gibson 300K linear for volume and CTS 500K audio taper for tone, or a CTS 250K audio if you are after more of a mid-range push. Tone caps again depend on the guitar and pickups, but 0.015uF, 0.022uF or 0.033uF are safe bets. I like my P-90's 'bouncy-chimey' vs. mid-range heavy.

PAF to Strong (up to 12K DCR) Humbuckers: CTS 500K audio taper for both volume and tone, with 0.015 (neck) and 0.022 (bridge) tone caps. Typically, a 250pF + 200K series resistor Treble Bleed, if it darkens too much between '7' & '9' on the volume.

Very pushy (> 12K DCR) Humbuckers: I find these to be the hardest to set up, especially if the bridge is heavy and the neck is PA-ish. Sometimes CTS 1M or CTS 500K audio taper for volume and CTS 500K audio taper for tone. A 0.015 (neck) and 0.022 (bridge) tone caps. A Treble-bleed is typically required, and I don't have a one-size solution. This is usually ttrial and error for me.

Alpha pots are not bad (I use them exclusively in my pedals). I was on a Bourns kick for 10 years as I liked the audio taper, but found I was killing them in about a year of normal playing, thus I stopped using them due to reliability. I liked the Emerson CTS, but can't find them any longer.

I use the full extent of the volume knob when I play and have been wanting to try 'VIPots' for volume controls, which are supposedly exactly to 50's specs (about $22 bucks each after shipping). I know from my 1951 Gibson ES125, the taper is different, but I can't tell you if it is a preferred difference as I never used that guitar electrically in a band performance situation.