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500K-W POT VS 500K-D POT?

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Never heard of the W pot. The D pot, I have seen on Cort made Ibanez's and always in the tone position. I even bought a few for other guitars since I LOVE the taper of it. It actually does something around the 7 mark on the dial. How strange is that?

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The D Type have a shaft shaped like a D having a flat spot for the knob. Some knobs press on and some have a set screw that tightens to the flat spot. 

The D pot is likely designed for a Hi Fi, stereo or some similar audio amplifier pot that requires a linear potentiometer instead of an audio type often used in guitars.  The overall Value is the same but the way the audio tapers down are quite different.   There are reverse taper pots for special applications too.  If you have an ohm meter you can connect it to the middle and one of the end legs then set the pot half way. If its a linear pot it should read about 250K at the half way point.  If its a guitar pot it likely reads less because the taper is non linear.  

 

Not sure what the W is.  It may be a unique manufactures code. If its a spline shaft I can see the w as a description for that.     

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You do sometimes find linear pots in guitars, usually as tone pots, but they're not as common as logarithmic pots. Some folks prefer them as volume pots but that's up to your ears.

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14 hours ago, DeepEnd said:

You do sometimes find linear pots in guitars, usually as tone pots, but they're not as common as logarithmic pots. Some folks prefer them as volume pots but that's up to your ears.

I've never seen Linear and audio pots in a factory build like that unless it has active electronics.  You can purposely add them if its something you want depending on the pedals, pickups and amps being used. 

Back when I was a kid just learning this stuff I used to Cannibalize old electronic gear, especially TV and Hi Fi stuff for parts.  I learned early on pots were designed for different signal strengths of gain staging and substituting the wrong ones can do some nasty things. A pot attenuating a line level signal between a preamp and power amp for example are almost always linear. The signal is usually above volt and the impedance is often low so the resistive pad can be linear without sucking tone from the signal and it sounds normal to the ears.  The weak output of a pickup is only a tenth of what a preamplified signal is the tapering is added to accommodate both the Haas effect and the Fletcher Munson curve of the ears as low volume levels are ramped up. 

You can add a bleeder cap you can further change how the volume vs tone changes as you turn down.  Some pickups like Humbuckers can take a quick dip in volume going from 10 to 8 on a volume knob and loose half their volume.  Dialing up the right amount of overdrive from the guitar can be very glitchy depending on the gear being used.  Changing the taper can be one way of changing how gradually the drive or volume tapers down and adding a bleeder can help maintain the brightness of the signal, even when the volume is nearly off. 

Typically I wouldn't advise using a linear pot for pickup attenuation unless the pickups are active.  What happens is the volume goes from zero to 90% when the pot is turned from 0 to 1 and the rest of the range from 1 to 10 only varies the volume by maybe 10%.  That's pretty much unusable in my book.  Its pretty much like using a switch to cut the volume off. 

The wrong pot value for a pickup can make you think the taper is wrong too.  I've used 1 & 2 Meg pots on single coil pickups and they taper much like a linear pot or a pot with a bleeder cap does on a pickup. The volume can remain high till its turned nearly off then it takes a big dip at the end and practically switches off.  Again, that might be just what you need for some gear.  Fuzz pedals for example might benefit from this because their built in pots often ramp the gain up within a small percentage of rotation. Having an input signal that is less tapered can take advantage of that 10% change and spread its effect out over a longer rotation. 

The Dallas Arbiter Treble booster was another glitchy pedal designed to overdrive the first gain stage of an amp. If you used the volume on the pedal itself it would create all kinds of crackle and jumps in volume as the pot is turned due to the higher voltages passing through the pot. This is why most are set to a fixed level and set on top of the amp instead of used like a normal  stomp box then the gain levels are varied using the guitar volume instead of the knob on the box.  Different guitar pot tapers can change how that pedals gains up the signal and how much Frequency response it has at those levels. 

There are some rule of thumb formulas used when designing circuits which do have a foundation in physics for this involving impedance and gain staging,  but guitar players have been breaking those rules since the first player cranked his guitar into saturation. Many of the components like pickups were built by ear instead of with a slide rule and other components like pots and amplifiers came from either the telephone or radio industries and simply adapted so what gives you high fidelity is rarely what a player wants.

The player often prefers something unique or just the opposite for good clean sound which shoots holes in many of the formulas you'd normally use so my advice is find a junk guitar for $25 and use it for experimentation. make sure its something that has easy access to the electronics cavity then buy a bunch of inexpensive parts on eBay including switches, pots, caps, and pickups and go to town trying out all the different wiring possibilities.  It can be a whole lot of fun and it removes the mystery surrounding allot of this stuff when you have the hands on experience actually using it. 

 

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3 hours ago, WRGKMC said:

I've never seen Linear and audio pots in a factory build like that unless it has active electronics.  You can purposely add them if its something you want depending on the pedals, pickups and amps being used. 

Pretty sure Gibson has done it that way for years.

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On ‎1‎/‎10‎/‎2020 at 1:34 PM, DeepEnd said:

Pretty sure Gibson has done it that way for years.

Just the opposite in many cases actually, they used allot of 300K linear pots for most guitars with a P90/single coil pickups but not exclusively.  Firebird III's with three P90's used 500K Audio. My guess is the third pickup increased the impedance enough where they needed to raise the volume pot resistance to maintain signal strength. 

Some of the volume pots were as low as 100K linear on some of their vintage guitars.  Back in the day they weren't particularly interested in getting any kind of overdrive from an amp. Electronics were strictly a matter of matching the clean acoustic tone on most instruments without any distortion.  Add to that many 300K pots can have at least a 20% variance so you could easily have 60K ohm difference either way making a 300K pot reading closer to a 240 or 360K depending on the batches made.  it can change over time as carbon wears off too. 

Gibson did build some oddball stuff over the years and I wouldn't be surprised what you might find in one of their signature custom builds or even some of their newest builds. The LP Pro and recording model uses a 1K linear pot for treble and 2.5K linear for bass, but they also use oddball pickup impedance plus an output transformer.  It uses low impedance output transformers so you can plug in a balanced cable and play through a PA/mixer direct.    If you can think it up they've likely tried it at one time or another, they did allot alot of experimentation trying to find the best tone vs cost.  I was reading about their modern stuff using multi tapped pickups but couldn't find that link again.     You can dig through their archives is you want here.  http://archive.gibson.com/Service/Tech/Schematics/   Its has mostly contemporary and popular vintage models, but it isn't complete. 

I spent years going through most of them looking for new wiring ideas and you'll find most new Gibson's use 500K Audio pots throughout for both tone and volume.  same with Epiphone.  

 

 

 

Edited by WRGKMC

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