Humbucking Inductor to reduce HUM

[rogeryu_ph]

 R.G. Quote
"Try to get/buy/make a humbucking inductor; this is a second identical inductor electrically in series but mechanically inverted right next to the existing one. Hum cancels, signal adds."

R.G.
How to do this or how to configure the two inductor say position of each other? I made my wah using  audio output transformer as per your column on technology of wah but not satisfied with only one but I used two then I  seried both on the primary : This is how I made it.

"The circuit input is on 1st transformer primary A pin then I cut the B pin which is the center tap then the C pin output connect to the 2nd transformer primary A pin also no center tap then the C pin output  back to the to the circuit"
http://i186.photobucket.com/albums/x139/rogeryu_ph/PICT0291.jpg
http://i186.photobucket.com/albums/x139/rogeryu_ph/InsideTwinductor.jpg
http://i186.photobucket.com/albums/x139/rogeryu_ph/SeriesTwinInductor.jpg
http://i186.photobucket.com/albums/x139/rogeryu_ph/WahTwinductor.jpg


I like this wah and very much satisfied but the issue of hum is there, if I could do humbucking both the inductor as per your advised maybe this might be my solution co'z i'm already using two inductor!
I can not visualized this "mechanically inverted right next to the existing one" so that I could do this. icon_cry
Maybe a sketch would be a very big help. Thanks in advance R.G.
Roger

[birt]

maybe you could use an audio transformer that has a center tap. that's 2 inductors in series, but i don't know if that will be inverted mechanically

[Jobet]

I guess what he means is that the coils should be counter-rotated e.g. the inductor you put in series must be phase-reversed from the original inductor i.e. if the original inductor is wound counter-clockwise, the humbucking inductor should be clockwise. This is the simple principle of a humbucking pickup, and operates in the way that any common signals picked up by both coils will be phase-reversed and hence will cancel each other.

One more attempt. Say if you have two identical inductors (say audio transformers) and you're looking at the leads from left to right (1-left, 2-right). Wire the second inductor such that its "2" is also connected to the "2" of the original inductor. This puts the add-on inductor in a phase-reversed configuration wrt the original inductor. Again this assumes that both your inductors are identical to the letter.

[R.G.]

Actually, I think this is easy in your case. I don't have the stuff to do this experiment, but maybe you can try it and tell us how it works.

You have two transformers that are theoretically identical, and you have them mounted side by side. It should be possible to mount them so the primaries are both on the same side. Transformer windings have a polarity. This depends on which is the start wire of the winding and which is the end wire, and whether the wire is wound on the bobbin clockwise or counter clockwise. For the purposes of this explanation, let's assume that your transformers have both primary leads on the side facing us, and that the leftmost wire is the start wire, the rightmost wire is the end wire. If we hook the two windings up with the end of the first transformer connected to the start of the second, then the inductance is doubled because the two are in series. Inside each core, the magnetic field go the same direction round the core if the input signals are equal, which they are.

The external M-field affects both cores equally, and induces a voltage in each coil. Since the coils are identical, the resulting hum voltage adds.

However, what happens if we put the incoming signal into the start of the first transformer, and connect the end of both transformer windings together, taking the signal from the start of the second transformer?

The signal still sees two inductances in series, and so the wah effect is not changed. However, the INTERNAL field from the audio signal goes in the opposite direction in each coil. This is important because the EXTERNAL M-field is still in the same direction in both cores. The hum which is induced is the same mechanical direction, but the electrical coils which produce the voltage are hooked up backwards. The hum voltage across the total transformer windings 1 and 2 should be equal in size but opposite in direction - it cancels.

So - swap the start/finish leads of one primary. I think the hum will cancel IF it is magnetically induced hum the cores are picking up. This will do nothing for grounding hum.

[rogeryu_ph]

Yes, both audio transformer are the same. I series both the primary and both cut the middle lead using only the outside both primary leads on the side facing us. Just as you describe the leftmost wire is the start wire, the rightmost wire is the end wire which I hook to the start of the second transformer.

This show you my present configuration and your suggested configuration
http://i186.photobucket.com/albums/x139/rogeryu_ph/SeriesTransformer.jpg

Hope I get you right.

Thanks R.G. btw also to you Birt and Jobet
Roger

[JHS]

Just only adding a hum cancelling coil will reduce the gain and alter the sound of a wah, PU. ect. a lot.

You can put the additional coil in series or parallel, but however you have to re-calculate the values for both coils to achieve the same sound generated by a single inductor.

If hum is your only problem, I recommend to swap the platic bottom plate of the wah for a 1mm metal plate to achieve a better shielding of the circuit.

JHS

[R.G.]

Just only adding a hum cancelling coil will reduce the gain and alter the sound of a wah, PU. ect. a lot.

It will indeed if you add more inductance by just putting in a hum cancelling coil.

You can put the additional coil in series or parallel, but however you have to re-calculate the values for both coils to achieve the same sound generated by a single inductor.

However, roger said that he already uses two identical coils and likes the sound of them. So there are already two coils to play with - adding another one is not needed.

[rogeryu_ph]

Yes JHS, I'm already using two audio transformer pls see hyperlink on the top of this thread. That why I call it TWINDUCTOR. Here is the sound clip sorry for the video not clear.
http://www.youtube.com/watch?v=3W9OCZ_W42c

R.G. I'll try to swap just the wiring as you suggested, this coming Christmas season i'm on vacation so I got lot of time to do it then I get back to you.

Thanks
Roger

[rogeryu_ph]

R.G. I just get back from holiday. I did your suggestion it reduces into about 50 percent not zero hum compared before now I can live with it.. No changes to sound still the same like before, but sure i'm glad that I reconfigure it now.

Many thanks and more power to you!
Roger