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Post by kaustinwright on Jul 28, 2015 23:30:09 GMT -5
Wouldn't adding a resistor to the dummy coil increase the impedance of the coil even further? I could heat the coil's wax and unwind a good amount until it perfectly matches the impedance of the others. Would this be a good idea if it works out?
Or I could consider winding my own coil to perfectly match with a spool of 43 AWG for about 15 bucks.
also, I am able to mod my push pull pots to no load if necessary
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Post by JohnH on Jul 29, 2015 8:22:51 GMT -5
Wouldn't adding a resistor to the dummy coil increase the impedance of the coil even further? I could heat the coil's wax and unwind a good amount until it perfectly matches the impedance of the others. Would this be a good idea if it works out? Or I could consider winding my own coil to perfectly match with a spool of 43 AWG for about 15 bucks. also, I am able to mod my push pull pots to no load if necessary A resistor in parallel will decrease resistance. You cant directly pick what it should be. Its not really a matter of just matching resistance. I'm thinking you may wire a spare pot temporarily and turn it to minimise hum for your most critical combination. Then measure it and pick a fixed resistor. The blender will be very dramatic with the phase switch engaged, as pickups cancel each other more or less - could be interesting. Ill do more diagrams as soon as I can
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Post by kaustinwright on Jul 29, 2015 10:55:03 GMT -5
What taper should I use on this spare pot. 500K right? that way I can dial in more values.
So the resistor stops some of the signal from entering the dummy in the first place, reducing the amount of signal that eventually flows to the output?
I could bypass the tone pot (500K) using it as the variable resistor for the dummy for now, then when I measure the value i like that cancels the most hum, ill put the same fixed value resistor in parallel, and wire the tone pot to the circuit.
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Post by JohnH on Jul 29, 2015 15:21:00 GMT -5
you can use any pot for this temporary testing, but the tone pot should be OK if you don't have any spare ones lying around. Log would be best. Even before wiring up, you could try something: Just connect one of the pickups to a guitar cord tip and ground and hear the hum with a bit of gain on the amp. Then do it with the dummy coil and see if you can tell if it is a louder hum or not. Then you could try putting them in series, and hopefully you will hear a difference in hum. Reverse one coil and try again. Such a test will be a bit inconclusive since youll get extra hum from the bare wires, but we might learn something.
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Post by kaustinwright on Jul 30, 2015 14:39:17 GMT -5
I also have a telecaster neck pickup that measures in at less resistance than my coils.. about 3.58k (ohm)
(my strat's coils are ±3.6k) would it be smarter to make a dummy from this value or the higher half humbucker coil? (because it is a lesser value than my pickups)
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Post by JohnH on Jul 30, 2015 15:58:31 GMT -5
I dont know which will work better for the dummy coil. I suggest start with the 1/2 humbucker to save save the tele pickup. Youll be testing this on the bench once its wired up, before putting it all back in the guitar so you can try options then.
I started sketching out the wiring. Its a rats nest! So it will need a clear diagram to follow.
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Post by kaustinwright on Jul 30, 2015 16:16:02 GMT -5
pup1.wav (751 KB) I will gladly get the neat diagram drawn up as soon as I see the rat nest! I have disassembled the tele pickup, and it seems to have caused even more hum (even when reversing phase of dummy) than the single alone. I attatched a 500k pot in parallel and the noise dropped when I had the pot cranked all the way up. I recorded the noise difference . Noise as soon as the coil is introduced, and a slight drop when it's taken away and wired normally. 1st sound is normal, other 2 are with dummy in then out of phase no matter how I wire it, there's more noise with the coil
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Post by JohnH on Jul 31, 2015 21:59:39 GMT -5
Im not sure what was happening with your tests. It could be just the noise due to it being exposed outside of the guitar. But anyway, assuming there is something that will work, here is the design! Id be grateful if somebody could check a setting or two before it gets built. John
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Post by kaustinwright on Aug 1, 2015 13:31:25 GMT -5
THANK YOU!
Awesome diagram, it should be a piece of cake to wire up with the clarity. I can't tell you how much I appreciate it, I'll let you know as soon as I get it off the bench.
Still trying to decide on the best placement for the dummy coil (under pickguard, or in spring cavity)
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Post by JohnH on Aug 1, 2015 15:09:35 GMT -5
Thanks and you are welcome. Im really curious to find out how this one will go! There are good sound combos to be had there, and we will see how well the dummy coil can be made to work (suggest keep options for placement until tested). I think for orientating the dummy, the main important thing is that its axis is parallel to that of the main coils. Ie, the direction of the pole pieces in the pickups coming out of the face of the guitar would be parallel to that of the dummy, if it still had pole pieces. Then it will be sensing the same field of hum as the others. If you have the cavity empty, then that may be a good place to put it so you can get to it, including testing resistors etc, with the guitar all closed up from the pick guard.
We also cant tell which way round its wires should be connected. To reverse the hum from it, you can either swap wires or you can flip the coil physically as if it were upside down in a guitar.
I haven't shown any resistor across the dummy - to be added if one is found to be helpful.
If I was building it, I think Id use bare solid wire to string together the various lugs within the superswitch, then the other wires from switch to pots using insulated, then coil wires last.
If this works, the wiring shown can be adapted to make the hum cancelling and or output active. It would require a 1 transistor preamp circuit (see jfet preamps in the schematic section) - but that is a further chapter.
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Post by kaustinwright on Aug 1, 2015 20:15:32 GMT -5
My guitar is shielded like crazy in the spring cavity, as well as the cavities and faceplate. I was thinking about the dummy, and having it in a shielded cavity might not be a good idea right? It will not pickup the same signal (as the single coils) due to the grounded cage around it, so it will not pickup the frequencies (out of phase) to remove from the single coils. Should I place it in a "non-shielded" area of the pick guard instead of the rear cavity?
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Post by JohnH on Aug 1, 2015 21:59:25 GMT -5
My guitar is shielded like crazy in the spring cavity, as well as the cavities and faceplate. I was thinking about the dummy, and having it in a shielded cavity might not be a good idea right? It will not pickup the same signal (as the single coils) due to the grounded cage around it, so it will not pickup the frequencies (out of phase) to remove from the single coils. Should I place it in a "non-shielded" area of the pick guard instead of the rear cavity? I really don't know, I haven't tried it myself. But I think the shielding will do a lot to reduce high frequency mains 'buzz', but doesn't not do much for the fundamental 'hum'. So it may still work well in the cavity.
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