| Author |
Topic: Hum cancellation on twin-neck |
Ian Rae
From:
Redditch, England
|
Posted 26 Mar 2014 3:21 pm |
|
On a D10 with single-coil pickups, is there any appreciable hum cancellation if both pickups are selected and switched out of phase? Thought I'd ask before I went to the trouble of rewiring to find out.
_________________
Make sleeping dogs tell the truth!
Homebuilt keyless U12 7x5, Excel keyless U12 8x8, Williams keyless U12 7x8, Telonics rack and 15" cabs |
|
|
|
Chris Lucker
From:
Los Angeles, California USA
|
Posted 26 Mar 2014 3:45 pm
|
|
On a Bigsby, adjacent pickups are reverse wound for hum cancellation. While Bigsby pickups are not wound with the same number of turns -- it varies depending upon the proposed tuning for that neck -- the pickups are somewhat hum canceling.
_________________
Chris Lucker
Red Bellies, Bigsbys and a lot of other guitars. |
|
|
|
Ian Rae
From:
Redditch, England
|
Posted 27 Mar 2014 11:33 am
|
|
"Somewhat hum canceling" is encouraging, at least better than a flat "no"!
It hadn't occurred to me that pickups might be wound differently for different tunings - why? Mine measure 9710 and 9740 ohms at DC - is that a big enough variation to be intentional? It's about 0.3% so could be normal manufacturing tolerance.
_________________
Make sleeping dogs tell the truth!
Homebuilt keyless U12 7x5, Excel keyless U12 8x8, Williams keyless U12 7x8, Telonics rack and 15" cabs |
|
|
|
Chris Lucker
From:
Los Angeles, California USA
|
Posted 27 Mar 2014 4:24 pm
|
|
On an Emmons, and certainly on other guitars, you have, for simplicity sake, stronger pickups on the fat string C6 neck than on the thin string E9 neck. That is oversimplifying the differences in the pickups.
The 705 pickup used to be suggested for E9 necks and 805 for C6 neck.
Bigsby would wind to different pickups differently for the E6, E13 and A6 necks.
Despite guys thinking that because the Bigsby pickup winder shows number of winds for different pickups, it is simply not what Bigsby did.
_________________
Chris Lucker
Red Bellies, Bigsbys and a lot of other guitars. |
|
|
|
Ian Rae
From:
Redditch, England
|
Posted 12 Apr 2014 6:59 am
|
|
I finally got round to trying one pickup out of phase, but I've been foiled for the moment. Each pickup has three wires, and one is grounded to the changer and the endplate. One of the others is grounded too, so I can't reverse the phase without shorting everything out.
If the connection to the changer and endplate is just for safety, I suppose I could lift it temporarily in the interests of experimentation. Or am I missing something?
_________________
Make sleeping dogs tell the truth!
Homebuilt keyless U12 7x5, Excel keyless U12 8x8, Williams keyless U12 7x8, Telonics rack and 15" cabs |
|
|
|
Craig Baker
From:
Eatonton, Georgia, USA - R.I.P.
|
Posted 12 Apr 2014 8:51 am Phase Cancellation
|
|
Ian,
In order for maximum cancellation, the signal level from the pickup coils needs to be equal and of opposite phase. In addition, the coils need to be in close proximity to each other, and properly oriented.
Please let us know your results.
Sincerely,
Craig Baker 706-485-8792
cmbakerelectronics@gmail.com
C.M. Baker Electronics
P.O. Box 3965
Eatonton, GA 31024
_________________
"Make America Great Again". . . The Only Country With Dream After Its Name. |
|
|
|
Chris Lucker
From:
Los Angeles, California USA
|
Posted 12 Apr 2014 6:13 pm
|
|
Yes, I did not mean to imply that on Bigsbys there is maximum cancellation, by any means. It is noticeable, but not maximum. And the field on a Bigsby is pretty wide. It is well outside the blade or the poles because of what is going on underneath.
_________________
Chris Lucker
Red Bellies, Bigsbys and a lot of other guitars. |
|
|
|
Jim Palenscar
From:
Oceanside, Calif, USA
|
Posted 13 Apr 2014 7:23 am
|
|
| I know several studio guys who utilize this attribute when recording and put a towel over the C6th neck- it does work. |
|
|
|
Lane Gray
From:
Topeka, KS
|
Posted 13 Apr 2014 7:28 am
|
|
I've not noticed MUCH hum cancellation, but I ALWAYS run both necks open because of the faux coil tap sound.
_________________
2 pedal steels, a lapStrat, and an 8-string Dobro (and 3 ukes)
More amps than guitars, and not many effects |
|
|
|
Bob Hoffnar
From:
Austin, Tx
|
Posted 13 Apr 2014 7:30 am
|
|
I have done what Jim is talking about also but I wonder if the partial reduction in hum has as much to do with the lowering of output as phase cancelation.
_________________
Bob |
|
|
|
Ian Rae
From:
Redditch, England
|
Posted 15 Apr 2014 11:11 am
|
|
Well, I finally got round to trying it for myself, and yes, it works (to the following extent):-
(No volume pedal in circuit.) Using the amplifier itself as a source of induced hum right near the pickup end of the guitar, there is noticeable cancellation in the order of what I judge to be about 20dB but it's still there. But if I put the amp in a sensible place, like within arm's reach of the head end, the difference is much more - with the amp at normal volume it goes from unusable to barely audible. My theory to explain this is that the more distant the source, the more similar the field created at the two pickups and the greater the cancellation.
I did this in the garage where there are nasty fluorescent lights, and the buzz from them was not diminished. I want to do more experiments on orientation when I have time. Meanwhile, in my practice room which is cramped so I'm closer than I'd like to be to both the amp and the PC, I'm enjoying the new-found peace.
_________________
Make sleeping dogs tell the truth!
Homebuilt keyless U12 7x5, Excel keyless U12 8x8, Williams keyless U12 7x8, Telonics rack and 15" cabs |
|
|
|
Tom Gorr
From:
Three Hills, Alberta
|
Posted 15 Apr 2014 12:29 pm
|
|
| I've never investigated pickup wiring in any detail - but was curious if there is a tonal difference when wiring the pickups this way as there may be other signal interactions between the pickups, impedence changes, etc., inductive filtering, or whatever ? |
|
|
|
Ian Rae
From:
Redditch, England
|
Posted 15 Apr 2014 1:39 pm
|
|
Tom, it's very subjective because the ear has too short a memory to compare, but I think I prefer the sound of two pickups in parallel (that's how they happen to be - it was easier). Lane alludes to this above, but his mention of a coil tap suggests series connection. I've no idea what the impedances of my pickups or amp inputs are!
_________________
Make sleeping dogs tell the truth!
Homebuilt keyless U12 7x5, Excel keyless U12 8x8, Williams keyless U12 7x8, Telonics rack and 15" cabs |
|
|
|
Lane Gray
From:
Topeka, KS
|
Posted 15 Apr 2014 4:55 pm
|
|
Ian, they're in parallel. I think it sounds tapped because the pickup sees both the output AND the other pickup, cutting the output by some fraction that I don't know how to calculate.
_________________
2 pedal steels, a lapStrat, and an 8-string Dobro (and 3 ukes)
More amps than guitars, and not many effects |
|
|
|
Craig Baker
From:
Eatonton, Georgia, USA - R.I.P.
|
Posted 15 Apr 2014 6:17 pm
|
|
Bob Hoffnar brings up an interesting point. Regardless of the phase involved, when you load one pickup coil with another. . . along with an overall reduction in output, you also roll off more of the low frequencies than any other portion of the spectrum. This would no doubt result in an "apparent" loss of hum. While in reality, all low frequencies would be somewhat attenuated.
Best regards,
Craig Baker 706-485-8792
cmbakerelectronics@gmail.com
C.M. Baker Electronics
P.O. Box 3965
Eatonton, GA 31024
_________________
"Make America Great Again". . . The Only Country With Dream After Its Name. |
|
|
|
Ian Rae
From:
Redditch, England
|
Posted 16 Apr 2014 3:36 am
|
|
So maybe the sound we think we're preferring is just the result of a bit of simple bass roll-off? Nothing wrong with that.
_________________
Make sleeping dogs tell the truth!
Homebuilt keyless U12 7x5, Excel keyless U12 8x8, Williams keyless U12 7x8, Telonics rack and 15" cabs |
|
|
|
Bob Hoffnar
From:
Austin, Tx
|
Posted 16 Apr 2014 4:47 am
|
|
I'm thinking the reduction in volume that happens when 2 pickups are active might result in the perception that the lows are rolled off.
_________________
Bob |
|
|
|
Michael Hummel
From:
Ottawa, Ontario, Canada
|
Posted 16 Apr 2014 8:51 am
|
|
I'd like to remind everyone that when you flip the wires of one pickup around, you are wiring it to have opposite polarity (not phase; phase is a continuous property and therefore can't have an "opposite").
I know it doesn't make any difference to what we're talking about here...but I couldn't help myself (you can take the lad out of engineering, but you can't take...)
Also, if you think about it in circuit terms, the pickup not being excited by strings looks like an inductor and resistor in parallel with your volume pedal input. Having an inductor across the signal wire like that will affect the frequency response and roll off the low end. (We all know a capacitor across the signal wire rolls off the high end.)
Cheers,
Mike
_________________
MSA Classic 5+4
Too many 6-strings and amps to list |
|
|
|
Craig Baker
From:
Eatonton, Georgia, USA - R.I.P.
|
Posted 16 Apr 2014 2:41 pm
|
|
Michael Hummel wrote:
| Quote: |
"Having an inductor across the signal wire like that will affect the frequency response and roll off the low end."
Are you sure about that Michael? I said that last week and everybody argued with me
Sincerely,
Craig Baker 706-485-8792
cmbakerelectronics@gmail.com
C.M. Baker Electronics
P.O. Box 3965
Eatonton, GA 31024
|
_________________
"Make America Great Again". . . The Only Country With Dream After Its Name. |
|
|
|
Stephen Cowell
From:
Round Rock, Texas, USA
|
Posted 16 Apr 2014 10:00 pm
|
|
A capacitor in series rolls off the low end.
A capacitor in parallel rolls off the high end.
An inductor in series rolls off the high end.
An inductor in parallel rolls off the low end.
A pickup is more like an R/C circuit, since it has both capacitance (between the windings) and inductance (through the windings). Therefore, it has a characteristic peak frequency that it will pass... so it's more like a mid-pass thing, it will tend to take away near its resonant frequency. Since its brother pickup also has a resonant peak around that frequency the result is normally to flatten the response and attenuate the signal.
_________________
Too much junk to list... always getting more. |
|
|
|
Michael Hummel
From:
Ottawa, Ontario, Canada
|
Posted 17 Apr 2014 7:56 am
|
|
Good point, Stephen. I just know on my steel if I leave the pickup selector on "both" the low end seems to be rolled off. However, that could be because the C6 pickup is single-coil and the E9 pickup is a humbucker.
Mike
_________________
MSA Classic 5+4
Too many 6-strings and amps to list |
|
|
|
Ian Rae
From:
Redditch, England
|
Posted 17 Apr 2014 12:17 pm
|
|
Thanks, guys, for all your comments and theories. To pursue this any further, I should brush up the circuit theory I had when I was a student but haven't used for 40 years (use it or lose it  ).
Most pickup manufacturers quote DC resistance, which is easy to measure anyway. How many quote inductance?
_________________
Make sleeping dogs tell the truth!
Homebuilt keyless U12 7x5, Excel keyless U12 8x8, Williams keyless U12 7x8, Telonics rack and 15" cabs |
|
|
|
