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Post by JohnH on Aug 28, 2012 5:24:49 GMT -5
Here's an idea for a humbucker module, to get series, parallel, north or south coils with just a single switch pole, and the tone pot:  As shown, the tone pot transitions from single to series to series with tone muted. Change the switch and it does parallel, to other single to single with tone muted. I think it might have some use with an LP configuration using pp pots. I already have my one wired with the series to single control on the tone knob, and it works quite nicely. This would be a way iof adding parallel tones too. cheers John |
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Post by reTrEaD on Aug 28, 2012 10:19:49 GMT -5
The heart of this is an interesting twist on 'binary switching'. I find it helpful to concentrate the wiper to bottom terminal of the tone pot, almost like a SPST switch. This helps me visualize the overall switching structure.
The SPDT allows two modes. In one position it creates a series link. In the other it enables the Blue coil (the Red coil hangs from hot).
In the Blue coil mode, rotating the wiper away from the tone cap 'blends' the bottom of the Red coil to ground. (Parallel)
In the series mode, rotating the wiper away from the tone cap gradually shunts the Blue coil. (Red coil only)
There's a price to be paid for economy. But as long as those costs are understood and accepted, one might opt for economy. The "treble cut" function is only available in the series and Blue coil only modes. Going from parallel to series, a switch needs to be flipped and the pot rotated toward the center of its resistance. This requires a bit more dexterity than flipping two switches.
Also worth considering is the type of pot and the connections to the element. An audio taper with the treble cut function at the (normal) counter-clockwise end, would have an abrupt 'blend' function. If we put the treble cut at the clockwise end, the 'blend' will be smooth but the treble cut will be abrupt. A linear pot would seem a reasonable compromise. Neither blend nor treble cut will be fully optimized, but neither function will be severely abrupt. Choices are.
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Post by JohnH on Aug 28, 2012 18:47:37 GMT -5
When I've played with parts of this type of circuit before, bypassing a series coil or adding resistance to a coil in parallel, Ive found that it only takes a few k of pot to make the main audible amount of transition to turn a two-coil sound into the single. My pickups tend to be not super hot (like 8k for a humbucker), but the main change is all over in about 20k of the pot.
So, to get a pot arranged in order to be able to play with the variations of transistion in a controllable way, I found it really needs the low-taper end of a log pot, and even a linear pot is too quick. This makes it hard to have useful variation control combined with a tone control that is also easy to set.
So my choice would be to use the steep end of a normal tone pot, so that the tone control function happens as normal towards the shallow end. The two-coil to single transitions then happen very quickly, just with a small pot turn. It doesnt offer the transition tones but it is very positive for going from two to one, and its not too critical how much of a small turn is made.
John
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Post by sumgai on Aug 29, 2012 0:53:58 GMT -5
John,
Recall that we've discussed messing around with a pot's taper by adding external resistors across the three terminals. By starting with a larger value pot, and shunting that with a pair of resistors totaling to the same value as the pot, but not of identical values, you can come up with some 'interesting' results.
5spice it first if you want, but me, I'd just bust out the alligator clips and the junk box, then have at it! ;D
sumgai
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Post by reTrEaD on Aug 29, 2012 7:56:04 GMT -5
I'm just shooting from the hip, but I suspect there is nothing you can do with external resistors that will get you closer to the kind of taper you would want for this application. External resistors will likely take you farther away.
The ideal taper for this application would have a slow change in resistance at both ends of the rotation and a rapid change in the middle.
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Post by sumgai on Aug 29, 2012 9:31:46 GMT -5
The ideal taper for this application would have a slow change in resistance at both ends of the rotation and a rapid change in the middle. That's easy - use a dual-gang pot of equal values, but with one taper reversed as compared to the other. Putting both segments in parallel may work as desired, or one may still feel a twitch, a sort of spastic movement of the hand as it inches towards a junk box with lots of spare resistors and such....  |
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Post by JohnH on Aug 29, 2012 22:50:24 GMT -5
I’m thinking the ideal version of this pot would be a lower valued pot, ie 250 or 300k instead of 500k, log taper (or better: antilog) – so that the 1-to-2 coil transitions can get the flattest taper. Then remove a section of track in the middle to make a no-load zone. This would be the default position, preferably with a detent, then roll one way to move to single or parallel, and the other to mute the tone.
If the no-load area is too bright, a 470k resistor will fix it.
Detented pots are hard to find, and hard to take apart if you find them. I'm thinking of an external added detent system, based on something projecting under the knob, running across an oversized washer with a small groove in it
John
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Post by newey on Aug 30, 2012 22:03:48 GMT -5
If you can do that mod, and have it work properly, please send me two of them (two, in case I fry one while soldering it). Because I'm pretty sure I couldn't pull that off myself- not on a pot. . .  I'm sure other Nutz will want theirs as well. Could be a cottage industry! |
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Post by JohnH on Aug 31, 2012 3:40:08 GMT -5
The detent idea, I dont know if I can pull it off either!
But that part of the idea does not actually involve doing anything to the pot. Theres a wide washer, about the diameter of the knob, to go under the nut on the surface of the guitar, with a shallow radial groove.
The knob would need to be a solid type, maybe aluminium, with a hole in the base, parallel to the shaft, near to the edge. In that hole goes a stick with a spring or something resilient. This stick projects below the knob and presses and runs around the washer, encountering a small glitch at the groove, to create the detent feel.. A better version would have a ball bearing spring loaded into the knob base.
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Post by reTrEaD on Sept 2, 2012 14:04:38 GMT -5
Since the knob is integral to this idea, the more common spit-shaft pots wouldn't work as easily. I think a solid shaft with a set-screw knob would be easier to work with.
The spring assembly would be held in place with the same nut that fixes the pot to the panel. The spring assembly itself would resemble the detent mechanism in a rotary or lever switch. It would push a ball bearing up against the bottom flat of the knob.
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