Post by sumgai on Jun 24, 2010 19:00:40 GMT -5
This idea came about as a result of several members wanting to gain a series combination between their two Tele pickups, but didn't want to give up the parallel connection either. The Telecaster 4-way switch to the rescue:
Discussion:
In essence, we have two electrically separate switches that are physically tied to the same control knob. By thinking "outside the box", we can make good use of this fact.
In the vast majority of cases, guitar manufactures large and small follow Leo's first thought - keep it simple. Sometimes that vision actually blinds one to other switching possibilities. For instance, in the "normal" scenario, we switch the pickup hot leads on or off as desired, and leave the ground leads permanently attached to ground. But what if.....
What if we were to switch the ground lead on one of the pickups instead, and leave the hot lead permanently attached to the output line? Would that not let us create a switched (user-controllable) series combo? Why, thank you for asking, and yes indeedy, that's exactly what we can do, as illustrated above. In position 3, the Neck's ground lead is connected to the Bridge's hot lead. Since the Bridge ground lead is still going to ground, and since the Neck's hot lead is already connected to the output line, we now have a series connection between the two pups.
If you'll look at positions 1, 2, and 4, you'll see that they are the standard Neck only, both in parallel, and Bridge only that we're used to. But wait, what's that extra wire in position 4, you ask.
Ah, that's to keep the Neck pup from acting like an antenna, good for picking up all that stray noise hanging around the joint. You know, the very crap we're trying to get rid of by shielding our guitars in the first place! The circuit theory goes something like this:
A vibrating string causes the magnetic field to induce a current in the coil. The coil will have an output on both ends, each end being in opposite phase compared to the other end. If we attach only one end to the output line, we have our antenna. (Ordinarily, as seen in the Bridge pup above, we attach the one end to ground, and indeed, that's an antenna that is "feeding" the noise into shielding.) The magic comes about because of that "out of phase" thing between the two ends. If we feed them both to the same point (the output line in this case), we have effectively shorted the pickup, no? Yep, that's exactly what's happened. Both ends of the coil are tied together, negative cancels positive, so we end up with no output at all from said coil. And that's a good thing.
</Discusson>
Further discussion (aka diatribe):
There is a small school of thought that goes something like this: "Shorted pickups rob tone from the any other pickups selected at the time." The word "extra" also crops up from time to time in that phrase, but the meaning is the same.
And the proper response is "Nope, sorry, no such thing happens". Why not?
Because the pickup is always located in the same vicinity of the vibrating string, whether or not it's selected for output. And that means, the current induced in the coil during string vibration always occurs, whether or not we elect to use that current via the Pickup Selector switch. But wait, that school says "shorted" - isn't there a difference between an unconnected pup and a shorted one? Well, yes, technically there is, but consider (from a layman's point of view): Shorting a coil causes a "backlash" current to be induced at the same time as the "normal" current. Of course this is out of phase, and for real-world purposes, it's of the same magnitude or strength, so the signal is cancelled out. But doesn't that induced current work backwards through the coil, and thus make the magnet work against the strings (thus stealing vibrational energy from the other pups)? After all, it is out of phase, right?
Uh-uh, bunky. Keep considering: if the signal is electrically out of phase, and thus cancelled, what's left over to excite the magnet, and thus the strings? Answer - nada. Now, that's in a perfect world, and in any pickup known to man, nothing is perfect. Thanks to the time it takes for a signal to travel the complete length of a coil (through the wire, not across the physical end-to-end of it), there can be a delay. It would take laboratory-grade instruments to capture and measure this delay, but I'm pretty sure that it's there nonetheless. But at such vanishingly small differences in time, the actual strength of the positive and negative aspects of the two signals is about 10 decimal places to the good, which I'd call close enough for government work, wouldn't you?
</Further discussion>
That's it in a nutshell, but as usual, if there are any questions, let 'em rip!
HTH
sumgai
(EDIT: corrected two bleepin' spelling errors. Sigh.)
Discussion:
In essence, we have two electrically separate switches that are physically tied to the same control knob. By thinking "outside the box", we can make good use of this fact.
In the vast majority of cases, guitar manufactures large and small follow Leo's first thought - keep it simple. Sometimes that vision actually blinds one to other switching possibilities. For instance, in the "normal" scenario, we switch the pickup hot leads on or off as desired, and leave the ground leads permanently attached to ground. But what if.....
What if we were to switch the ground lead on one of the pickups instead, and leave the hot lead permanently attached to the output line? Would that not let us create a switched (user-controllable) series combo? Why, thank you for asking, and yes indeedy, that's exactly what we can do, as illustrated above. In position 3, the Neck's ground lead is connected to the Bridge's hot lead. Since the Bridge ground lead is still going to ground, and since the Neck's hot lead is already connected to the output line, we now have a series connection between the two pups.
If you'll look at positions 1, 2, and 4, you'll see that they are the standard Neck only, both in parallel, and Bridge only that we're used to. But wait, what's that extra wire in position 4, you ask.
Ah, that's to keep the Neck pup from acting like an antenna, good for picking up all that stray noise hanging around the joint. You know, the very crap we're trying to get rid of by shielding our guitars in the first place! The circuit theory goes something like this:
A vibrating string causes the magnetic field to induce a current in the coil. The coil will have an output on both ends, each end being in opposite phase compared to the other end. If we attach only one end to the output line, we have our antenna. (Ordinarily, as seen in the Bridge pup above, we attach the one end to ground, and indeed, that's an antenna that is "feeding" the noise into shielding.) The magic comes about because of that "out of phase" thing between the two ends. If we feed them both to the same point (the output line in this case), we have effectively shorted the pickup, no? Yep, that's exactly what's happened. Both ends of the coil are tied together, negative cancels positive, so we end up with no output at all from said coil. And that's a good thing.
</Discusson>
Further discussion (aka diatribe):
There is a small school of thought that goes something like this: "Shorted pickups rob tone from the any other pickups selected at the time." The word "extra" also crops up from time to time in that phrase, but the meaning is the same.
And the proper response is "Nope, sorry, no such thing happens". Why not?
Because the pickup is always located in the same vicinity of the vibrating string, whether or not it's selected for output. And that means, the current induced in the coil during string vibration always occurs, whether or not we elect to use that current via the Pickup Selector switch. But wait, that school says "shorted" - isn't there a difference between an unconnected pup and a shorted one? Well, yes, technically there is, but consider (from a layman's point of view): Shorting a coil causes a "backlash" current to be induced at the same time as the "normal" current. Of course this is out of phase, and for real-world purposes, it's of the same magnitude or strength, so the signal is cancelled out. But doesn't that induced current work backwards through the coil, and thus make the magnet work against the strings (thus stealing vibrational energy from the other pups)? After all, it is out of phase, right?
Uh-uh, bunky. Keep considering: if the signal is electrically out of phase, and thus cancelled, what's left over to excite the magnet, and thus the strings? Answer - nada. Now, that's in a perfect world, and in any pickup known to man, nothing is perfect. Thanks to the time it takes for a signal to travel the complete length of a coil (through the wire, not across the physical end-to-end of it), there can be a delay. It would take laboratory-grade instruments to capture and measure this delay, but I'm pretty sure that it's there nonetheless. But at such vanishingly small differences in time, the actual strength of the positive and negative aspects of the two signals is about 10 decimal places to the good, which I'd call close enough for government work, wouldn't you?
</Further discussion>
That's it in a nutshell, but as usual, if there are any questions, let 'em rip!
HTH
sumgai
(EDIT: corrected two bleepin' spelling errors. Sigh.)
I'm wondering if it is possible with 2 poles only.
