Pot wiring variations - same or different function?

[cdlynch]

I'm trying to do hybrid Jazz/Ric electronics for a cheap SX short scale Jazz knock-off. It combines the passive resistor mixing of early Jazz designs with 15K instead of 220K, but with a toggle switch to switch the Bridge pickup from the resistor mixer going to the Tip of a TRS jack to its own output on the Ring. The bridge also has a toggle switch for a Ric style HPF.

From studying countless posts here and elsewhere, between standard Gibson, Fender, and Ric circuits, I couldn't find an explicit description of the electrical differences between different pot wiring schemes. The three layout diagrams I attached show three variations. I'm an amateur, and to me these wirings all look like they should do the same job of bleeding signal to ground the same way just through different methods.

If I'm wrong, can anyone tell me the electrical differences and the consequences in function and tone?

@line6man has given me enormously helpful feedback in the past, and I THINK I'm smarter as a result, but this should be a test of that, and hopefully a learning experience.

Pickup to wiper:


Wiper as output:


Mixture, Ric-ish


FWIW I upgraded the tuners and I'll be putting in DiMarzio Area J split coils. Waste of money and time for SX? Wasting time and money is my hobby, who are you to judge?

 

[SharpCat]

Pickup to wiper, the pickup output gets shorted to ground at the low end of volume. Wiper as output, the pot acts as a voltage divider, but the pickup continues to see the full 250K resistance. Basically the slope of the volume cut will vary.

Ric-ish changes the tone pot slope.

 

[fig]

...can anyone tell me the electrical differences and the consequences in function and tone?

The TL;DR version - use the Pickup to Wiper (top) circuit.

The 'bring a drink and snack' version...

The Pickup to Wiper (top) and Mixture, Ric-ish (bottom) are the same circuit. The only difference you're seeing are how the Tone Controls are wired. There's four common ways a Tone Control can be wired. All four ways act exactly the same, so it doesn't matter which tone pot wiring method you use. Installer's choice. All else in the top and bottom circuits are the same.

Here's the four common ways a tone control can be wired, along with their 'Noise Attenuation' mods (with the +). The mod is a jumper wire to the regularly un-used tone pot lug. You used this mod in the Mixture, Ric-ish circuit. Anyway, the four common connection schemes and their associated Noise Attenuation mods.:

Pickup to Wiper (top) Tone Controls are wired like A.
Mixture, Ric-ish (bottom) Tone Controls are wired like D+ (noise attenuation mod jumper between lugs 2 and 3).

You should forget (but up to you) Wiper as output (middle). That's because when the two outputs eventually meet back together (at the resistors), turning either volume pot will control both pickups. In other words, each volume pot becomes a Master Volume pot. Wiper arms as outputs in a parallel circuit are avoided by almost everyone.

Yes, you have two 15kΩ resistors, but they are too small to provide much isolation between the two volume pot wiper arms. If you turn one volume off, the remaining pickup will be at a low volume, even with it's volume control at 10. Probably don't want that to happen. The only way to fix that Master Volume issue is by providing much more isolation between the wiper arms. This means installing the large 250kΩ resistors, like original Fenders, which would mean a large volume decrease everywhere. Personally, I wouldn't bother with the middle circuit, but it's up to you.

Regarding the top and bottom circuits and the 15kΩ resistors, they will remove remove some mid-scoop when both volume pots are at 10. So, if you don't like mid-scoop with volumes maxxed, keep the resistors. If you like mid-scoop with volumes maxxed, like for poppin' and slappin' da bass, remove the resistors and connect the short red wire to both switch terminals where the resistors were connected to.

Between the top and bottom circuits, both of which are the same, I'd use the top one because of the simpler tone control wiring (Pickup to Wiper for the win!). The cap and pot can be located together. The bottom circuit needs the cap strung between the volume and tone pots. Don't forget to add the 'scratch/pop noise attenuator' jumper between lugs 2 and 3 (A+ in my drawing).

Whew!...

 

[cdlynch]

Thanks @SharpCat and @fig !! This is beyond what I hoped for!

I’m still not sure how the differences cause those specific outcomes, but I can use this as a guide while trying to learn more. Dang, I hope it doesn’t involve math…

In the meantime I’m confident to move forward with the first layout plus the noise reduction mod, which I never knew about before. One tiny jump, why doesn’t everyone do this?

As for the resistor values, I read a few TB posts discussing how the original values were too high, and that 15K was enough for reasonable control separation. They’re easy to swap so I’ll start at 15K and increase if I feel like it’s needed. I’m fine with reduced scoop in general, though if can be nice with a pick too.

 

[SharpCat]

For the resistors, get some of these:

Ten turn pots. This one is a 50K. They're tiny, and you can adjust them with that brass screw. I think I paid $18 for a box full of various values on the big A.

 

[cdlynch]

Ten turn pots

It's funny, I DID look for those, but I was only looking for dual gang versions because I'm too lazy to set two pots, and when I couldn't find any (probably because it'd be too hard for them to match for the whole range?) I instantly gave up, fell over on the couch, and slept for a week.

You have inspired me, I'll do some better browsing!

 

[fig]

I’m still not sure how the differences cause those specific outcomes... Dang, I hope it doesn’t involve math…

Math? We don't need no stinking math.

The following drawing removes tone controls, resistors, and switches for clarity and are irrelevant to the point of showing why using the wiper as an output of two parallel volume pots isn't used.

Wiper as output - When either volume control is used, it controls the entire output of both pickups. For example, you dial the Brdg Vol back to 6, then the entire output to the jack is dialed back to 6 (yes, even the Neck output). As shown in the drawing, with extreme settings (Neck 10/Brdg 0), you will lose the entire volume of the bass. The Brdg Vol at 0 sends the Neck output directly to ground thru the Brdg volume pot ground.

Pickup to wiper - This is the only way to keep the volume controls independent from each other. For example, you dial the Brdg Vol back to 6, only the Brdg volume gets reduced. Neck volume stays wherever it was set. As shown in the drawing with extreme settings (Neck 10/Brdg 0), the full Neck volume (10) goes to the jack, Brdg is off.

Hope this is helpful.

BTW, the multi-turn small trim potentiometers that @SharpCat mentioned to replace your two 15kΩ resistors are a great idea. I use to use the heck outta those back when I was anal about tweaking my sound. You can go thru a bunch of resistance settings in minutes instead of breaking out the soldering iron to swap out resistors. Once you find what you like, they're small enough to stash inside the control cavity. Set 'em and forget 'em. Plus, in his example, there's an infinite number of resistance values between 0Ω and 50kΩ. Fixed resistors don't come in an infinite variety of values. Trim pots are small, convenient, and time saving, but they're not necessary.

 

[cdlynch]

Hope this is helpful.

Oh man, it sure is. I was WAY too zoomed in on each pot, but this breaks it down perfectly.

Now as a Masshole I have to say, "Dawn breaks over Marblehead."

 

[fig]

@cdlynch, glad you had your website listed. Just listened to In Between and really enjoyed it. My type of music when I'm in a certain mood. The singer's voice fit perfectly.

 

[cdlynch]

@cdlynch, glad you had your website listed. Just listened to In Between and really enjoyed it. My type of music when I'm in a certain mood. The singer's voice fit perfectly.

Hey, thanks for checking it out, it means a lot that you took a random chance on us! Glad it hit the mood of the moment. Perhaps our other moods will match more moments