Pickup selector question

Bill Ladd · From: Wilmington, NC, USA

Guys and Gals - I have a Magnum D-10. Stock single coils with a standard three position switch between necks. If I select both necks the tone is greatly changed. Kinda like having a wah pedal half open or a coil tap on a humbucker. It seems more prominent on the C6 neck, but both necks are affected. (On my '54 Fender dual 8, the selector switch simply seems to drop the output slightly in the middle position).

Is this normal? Might my pickups be wired out of phase?

My new gig has a few songs where I rapidly move from one neck to the other. Otherwise it wouldn't be a big deal.

Thanks.

John Swain · From: Winchester, Va

All 15 D-10's I've owned lost volume and tone when both pickups are on, I think it's normal!

Rick Barnhart · From: Arizona, USA

My D-10 is the same way, and it's normal. I think the switches are known as "ON-on-ON" As I understand it, the middle selection basically splits the full signal and halves it between the two pick ups.
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Clinesmith consoles D-8/6 5 pedal, D-8 3 pedal & A25 Frypan, Pettingill Teardrop, & P8 Deluxe.

Jon Light · From: Saugerties, NY

Bill--with my new product, the 2pup (sorry for the scent of spam), there is the option to have both on, in-phase and both on out-of-phase. The difference in volume and in tone--as you describe, sort of comb filtering--is distinct and extreme in the out of phase position and a lot more pronounced than in the in-phase position. If you are up to the task, reversing the wires of one pickup at the switch would be a worthwhile diagnostic.

edited to add: and you may find that it just is what it is.

Bill Ladd · From: Wilmington, NC, USA

Thanks John. (How are you by the way? That Patsy gig we spoke about turned out to be a huge waste of time) Kinda thought that but wanted to make sure.

Hmm, now that I think about it, it does make sense. On a two-pickup six-string, having both pickups on probably cuts the output of each, but still still gives slightly more overall output than either pickup by itself.

Any electronics gurus want to comment? Is there a way to make it better with caps or whatnot?

Michael Hummel · From: Ottawa, Ontario, Canada

I'm a long-time 6-string player, and an Electronic Engineer. I haven't been playing pedal steel for very long, but I can give a short technical summary of what is going on.

If two pickups are on the same neck, and therefore under the same set of strings, when they are both ON the polarity relationship DOES matter.

If the two pickups are on separate necks, the polarity relationship DOES NOT matter.

[Side note: many people inappropriately use the term "phase reversal" when they mean "polarity reversal", but that's another story for another time Cool

]

So, in your situation, having the switch in the "Both ON" position puts the pickup underneath the "active" strings in parallel with an inactive pickup. The inactive pickup does not add any signal, but its impedance is now in parallel with the active pickup, changing the apparent source impedance looking into the amplifier. This impedance has a loading and filtering effect on the signal coming from the active pickup, changing the tone.

I have exactly the same situation happening on my Sho-Bud D10, except the C6 pickup is single-coil, and the E9 pickup is humbucking. The single-coil pickup has a lower impedance so when I switch both on while playing the E9 neck, I can hear a huge difference in the tone.

The only way I can think of to get around this is to install a (not too simple) circuit that would be like having a buffer pedal for each pickup before the switch that selects which pickup is sent to the jack. That way each pickup is isolated from the other's loading effect. Hey, there's an idea for a new PSG product...

Hope this helps.
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MSA Classic 5+4
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Jon Light · From: Saugerties, NY

Michael--I should know that. I just walked right through that stop sign. Of course two pups on two different necks will not interact in a frequency cancellation sort of way. Dope slap.
Bill--our conversation was re: Jimmy Nations. Don't know about no Patsy gig.

Bill Ladd · From: Wilmington, NC, USA

Thanks Michael! I'm an electrician, not an engineer, but what you say makes total sense to me. How could a single pickup ('cause that's what we have - one pickup on each neck) be out of polarity with anything at all?

I also was aware of the difference between phase and polarity but, in fact, used the incorrect terminology.

Bill Ladd · From: Wilmington, NC, USA

Jon Light · From: Saugerties, NY

Michael--would it be accurate to say that if you reverse the polarity of the second pickup on a single neck you are putting it out of phase with the first pickup? I'd like to understand this if you've got the inclination to explain. I hate to think that I am describing it incorrectly in my product literature.

Michael Hummel · From: Ottawa, Ontario, Canada

Hi Jon:

Well, the common expression (I use it too) among guitar folks is "out of phase". There's nothing wrong with that as most everybody knows what the intention is.

In engineering terms, phase is a continuous variable, which can vary anywhere from negative infinity to positive infinity (in practical terms we usually limit the value from 0 to 360 degrees as it just repeats if the values get bigger). So, if the phase difference between two signals is, say 160 degrees (not 180 degrees), are they "out of phase" or not? Probably not, but we can't say for sure.

Polarity, on the other hand, is a discrete variable with only two possible values. Think of the wires going to a power outlet, usually white and black. Hopefully you have the polarity wired correctly to your outlet instead of backwards!

So...in pickup terms...because two pickups on a single neck cannot occupy the same physical space, and therefore do not output the exact same signal, how can you possibly talk about signal phase when the two signals are different?

Again, this is engineering semantics. I might have failed one of my engineering courses for using the wrong term, but I don't think anyone will bitch about it in your product literature.

Smile

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MSA Classic 5+4
Too many 6-strings and amps to list

Rick Barnhart · From: Arizona, USA

Bill, maybe you should just practice throwin' the switch a little quicker...seems like a way simpler solution. Winking

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Clinesmith consoles D-8/6 5 pedal, D-8 3 pedal & A25 Frypan, Pettingill Teardrop, & P8 Deluxe.

Bill Ladd · From: Wilmington, NC, USA

Jon Light · From: Saugerties, NY

I actually understood that perfectly. As my second pickup is moveable, I guess the phase is infinitely variable. I'm satisfied that my use of the word is acceptable but now I'm better armed if anyone wishes to confront me with an argument (my defense being 'guilty, with an explanation'.
Thanks for taking the time.

Michael Hummel · From: Ottawa, Ontario, Canada

Glad to help. I can't tell you how happy it makes me to offer some small contribution to the forum.

I've been bugging folks to help me with my beginner questions about learning to play the pedal steel, and people have been SO helpful and giving of information.

Earlier today I was asking someone why some people had 9 or more knee levers...I think we need to add an extra knee lever connected to the pickup switch for Bill !
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MSA Classic 5+4
Too many 6-strings and amps to list

Lane Gray · From: Topeka, KS

I've noticed a drop in signal strength and a change in tone that I like. even when I have no intention of using the other neck, I leave both necks hot. with 250 watts of amplifier, I don't believe they lost power is missed much, and I like that sound better
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2 pedal steels, a lapStrat, and an 8-string Dobro (and 3 ukes)
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Bill Ladd · From: Wilmington, NC, USA

Michael Hummel · From: Ottawa, Ontario, Canada

Lane:

I think I like the sound of my guitar better with the switch on both necks too...except sometimes I get lazy and scrape my watchband across the C6 strings! Not a pretty sound.
_________________
MSA Classic 5+4
Too many 6-strings and amps to list

Bill Ladd · From: Wilmington, NC, USA

Ron Pruter · From: Arizona, USA

Bill,
It sure sounds like"out of Phase " to me. Here's how I check it. Find an old ohm meter with a needled meter scale rather than a digital one. Connect it up with both pick ups on. Tap one pick up along the top, with the side of a metal screwdriver. The needle will bounce, ever so slightly to the right or left. Take note which way. Then tap the other PU. It should bounce the same direction as the first. If not , just reverse the two leads on one of the pick ups and you'll be in bussiness . Ron
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Doug Palmer · From: Greensboro, North Carolina, USA

Assuming you have a double neck guitar with both pick-ups reading 20K ohms each. If you put the neck selector in the middle position you'll get a 10K ohm reading. It will have a thinner sound.
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Bill Ladd · From: Wilmington, NC, USA

Doug and Ron -- All my meters are digital so I can't do the polarity test until I find an analog. I will do the overall resistance test and see what I get.

Thanks fellas!

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