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Post by michaelcbell on Apr 25, 2007 6:00:17 GMT -5
I'm working on yet another schematic (I'm actually building this one... really!) and am having trouble getting everything I want without one of the positions (mid of SSS by itself) leaving a pup hanging from hot (actually, the neg lead of the neck pup, if it matters). How horrid a problem is this and what might I hear once it's all built? Thanks for your help.
-m
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Post by JohnH on Apr 25, 2007 6:20:03 GMT -5
I think the risk is a slight amount of buzzy hum, as the ungrounded free end acts as an antenae. I dont know of anyone really doing an A/B test to be sure. It may be negligible inside a well screened guitar, but avoiding it if possible is a tenet to live by, like eating fish on Friday.
John
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Post by sumgai on Apr 25, 2007 12:59:11 GMT -5
michael, Akshully, I keep everyone honest, watch this....... John, it's not just the "ungrounded free end" that acts like an antenna, it's the whole bloomin' coil.  ::takes off Sherriff's badge:: The debate is not nebulous in that it can be tested, but as John points out, no one here has reported doing so...... yet. I tend to agree with John, inside of a well-shielded instrument, the problem should be negligible. But on the whole, we as a group of Forum Members to like to espouse "Best Practices", and this is one of them.  Like unklmickey says, if you can't avoid it, OK, get on with the project. But if you can avoid it............ HTH sumgai |
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Post by DarKnight on Apr 25, 2007 14:56:38 GMT -5
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Post by wolf on Apr 25, 2007 15:43:15 GMT -5
michaelcbell
I'm guessing you are talking about a single coil as opposed to a humbucker correct?
A single coil can have 2 different kinds of output wiring:
1) 2 wires (the + and — of the coil and a ground "shield" surrounding both wires.
2) 1 wire and 1 ground shield. In this case the pickup manufacturer was cheap and didn't want to spend the extra money for another wire and another connection at the pickup end. The "—" pickup lead and the ground are wired together at the pickup.
Well basically if you have the pickup described in case #2 then it is a very bad idea even in a well-shielded guitar.
If the pickup is the type in case #1, I'd say you'd be fine. (I'm sure some of the purists on this board would disagree with me, but I'd say it would be a minimal problem.)
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Post by JohnH on Apr 25, 2007 21:51:56 GMT -5
A couple of further thoughts:
You can demonstrate the nature, but not the magnitude, of the hanging from hot hum by attaching an aligator clip to the end of a guitar cord. With nothing attached, a good cord plugged into an amp is still fairly quiet. With a short wire attached to the ground (jack barrel), it is no worse, while if attached to the jack tip, (hanging from hot), it buzzes.
Another condition in some of our designs is chain of pups in series, in which some are disabled by shunting. Setting aside whether this causes change in tone, I wonder if this also risks noise, if the shunted coil is then effectively hanging with both its ends to hot? And is that in principle better or worse than a case with just one end of a coil hanging from hot? I don't know, although Ive not noticed this problem in practice.
John
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Post by ChrisK on Apr 25, 2007 22:30:01 GMT -5
I tend to believe that a hanging coil will couple noise and ultra-high frequencies from the vibrating strings, especially if there is any appreciable inter-lead and to ground capacitance (yet another two terminal network.
A humbucker in theory will only couple in ultra-high frequencies from the vibrating strings.
A coil with both ends shorted together should not couple in any more noise (and no signal) than a wire equivalent since shorted is shorted. It may still capacitively couple in some ultra-high frequencies from the vibrating strings, and may well affect the sustain of the strings from the perspective of converting vibrational string energy into a short comprised of the coil's internal impedance.
So, are you in favor of, or opposed to, eating fish on Friday?
(I remember when the Catholic Church in the U.S. abolished the mortal nature of "Phishy Phriday" indiscretions back in the 60's. When I inquired as to whether there was going to be a "catch and release" program for all of those previously incarcerated in Hades on a "meat rap", it was not particularly well received.)
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Post by michaelcbell on Apr 26, 2007 4:55:07 GMT -5
hmm... I think I've figured a way (not quite ideal, but close) to eliminate the hanging hot, but if my pups don't have a seperate ground, then phase might prove to be a noisy endeavor. I thought about sheilding the pups individually since that might help, considering what's going on, but won't that change the tone of the pup pretty significantly?
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