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Old 30th January 2012, 02:59 PM   #1
JoshuaK is offline JoshuaK  United States
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Question Pickup wiring/inductance/output questions

Hello all,

I'm brand new to this site [and these forums].

I would have posted these questions in a "Guitar"-site forum/thread, but the scope of my inquiry includes possible voltage/impedance/hazard issues [not sure, which is why I ask], which may be more suited to this particular forum since the range of topics therein is broad. I hope some of you can offer advice and information!

For starters: I know nearly-next-to-nothing when it comes to guitar control circuits, and I know even less when it comes to power requirements/amp connection/safe operation/basic signal transfer no-go's.

I can look at a basic guitar control schematic, wire it up, and troubleshoot from there [be it an active or passive circuit, though my main experience is with passive electric guitars]. However, when it comes to the more advanced wide variations of components, the effect they have on the signal, and WHY and HOW it all works [or doesn't work], it's above my current level of comprehension - I'm sure that an investment in literature on the subject and future projects [trial-and-error] will be of great value.

...and when it comes to amps, just common-sense stuff: ensuring that everything power-related is safe and stable, all connections are correct, and that the amp powers up and the controls work fine. That's it - very little knowledge of hi-/lo-z, voltage requirements, speaker/wiring issues, troubleshooting, or anything that requires opening up the amp section. Again, literature and projects will assist in expanding my knowledge.

In short: I'm an absolute novice - nothing more than a so-called "garage rocker" with almost-basic modding/electronics experience who wishes to acquire greater knowledge - therefore, if I ask questions that warrant an eye-roll, this is why. Please forgive me, thanks-in-advance, and let the eye-rolls commence.

Again, hello to all, and thanks for your help!
---
[MODS: if I've posted this in the wrong place, I apologize - please relocate.]

My project:

I'm currently building a Hohner-clavinet-type instrument. The mechanics, sound, and basic layout and idea are the same, but still a far cry from the original overall design. It's an experiment, and I wanted to see if it could be done with the materials I have on-hand. [For more information on the clavinet, please see this Wikipedia entry: Clavinet - Wikipedia, the free encyclopedia]

The original design called for an active pickup-control circuit, powered by a single 9-volt battery. Some models had an internal speaker, but most were able to connect to an external amplifier via 1/4" output. It was essentially an electric guitar controlled by a keyboard - 60 separate string vibrations translated by a single wide pickup, sent through control circuit, and out to the amp/speaker.

My design, however, is going to be entirely passive, just to keep it simple. Since I can't find a wide-enough passive pickup [12", give-or-take], I purchased 6 "hot-rail"-style single-coil-sized humbuckers, and plan to have them arrayed side-by-side [with slight angle/overlap] to cover the entire range of strings. Here's the catch - all of them need to be active at the same time, essentially acting as one giant pickup. This would require one of two wiring schemes: series or parallel.

I've performed some mild searching over the internet, trying to gather info on if/how this would even work, and what the end result would be. The only basic effects that I have learned about would be thus: series wiring would result in multiplied inductance and resistance, and parallel wiring would result in divided inductance and resistance. I'm referring to this article: How Series And Parallel Wiring Sounds And Why | Guitar Wiring - bottom paragraph.

Just to make for easier understanding, here's the circuit [signal path, from pickups to output]:
- six blade pickups [11.5k each]
- 5-way super switch
- volume and tone controls
- output

The pickups are equipped with four-conductor wiring, for coil switching/phase options. My initial design was to wire all the designated pickup leads together [green with green, red with red, etc.] into a single lead wire for each color, and then to the switch - basically, it would be parallel wiring in this case [I think]. The switch would then allow me to select between series/parallel/in-phase/out-of-phase/single coil sounds. [This diagram/schematic is what I'm referring to: Guitar Wiring Diagram 1 Humbucker/1 Volume/1 Tone/5-Way Lever Switch]

Since I have no clue as to how I would wire these pickups in series [in this situation], I will wire them in parallel with each other, as outlined above.

Here are my questions:
1.] Since the pickups will be wired in parallel, what would be the end result?:
  • Would the resistance be reduced to a mere 1/6th of that of a single pickup?
  • Would this result in low impedance, and if so, would it be a bad thing in terms of voltage or anything else?
  • If the aforementioned electrical properties are diminished, how would this affect the output - meaning, is there any possible shock/damage hazard?
  • If the impedance is low, does this mean that I am now required to plug into a "low-z" input, or even a specific type of amplifier?
  • What would the sound be like - accentuated high frequencies?
  • Would the "gain" of the pickups be diminished as well? I understand that this may affect how outboard effects will operate, as well as preamp gain and overdrive.
2.] GROUNDING. This is a big one! Since I will not be touching the strings with my hands, as with a guitar, the whole "touching-strings-electrical-grounding-buzz" won't be a factor, so-to-speak. BUT, how would I SAFELY ground the circuit? Would it be grounded to the bridge/strings as on a guitar, or would I have to ground it somewhere else?

3.] All things considered, is there any shock/damage hazard in regards to my parallel-wiring design?

4.] Is there a way to wire four-conductor-wire pickups in series in this situation?
  • If so, how would it be wired?
  • Would the combined resistance be too high to be usable as a guitar signal?
  • Would the pickup impedance also be higher, and would I then need to be cautious as to what I plug into, amp-wise?
  • Is there any shock/damage hazard with THIS scheme?
  • Would I still be able to use the super switch for phase/coil options?
5.] Is there ANYTHING ELSE that I have not outlined, or forgotten, or need to know?

I intend to play this keyboard instrument as I would a guitar - meaning, I designed it to be usable with guitar effects units, guitar amplifiers, etc. As far as an amp/speaker cab goes: the range of notes/frequencies isn't too far from that of an 8-string electric guitar, so I don't see too much of an obstacle in that regard. My main concerns deal with actually wiring the thing, and making sure that it's perfectly safe for me [and others] to use as we would an electric guitar - to be able to plug into any amp [big or small] and effect unit.

Thanks much to all of you for your time, effort, and information regarding this project of mine.

- Joshua K.
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Old 30th January 2012, 04:06 PM   #2
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Hi Joshua,
to attempt to answer some of your questions...

1 - the resistance of the pickups will be lowered, yes: this always happens with parallel resistors.
- I'm not sure how the sound will be affected by paralleling the pickups, but I know that putting them in series means increased series inductance, giving a warmer sound. Perhaps having them in parallel will retain the sound of one pickup.
2 - I'd follow normal guitar procedure: the strings are earthed, usually via the bridge (you earth the bridge, that the strings rest on. This earths the strings, too).
3 - I don't think so, but would wait for someone else to chime in before going for it: there are others here with far more experience than me.

With regards to wiring the whole thing: I'd try putting all the coils on screw terminals, then its easy to try different configurations: I can't tell you what sounds good.

It might be worth reading up on the factors that affect the sound of a pickup: the combination of inductance and capacitance (between the windings) means you get a tuned electrical circuit, with a resonant peak somewhere in the operating range. Note that humbucking pickups have more windings than single coil, so the high frequency response is affected (the peak in output occurs lower down the frequency range).
Series/parallel arrangements would alter the position of this peak, but I would expect it to be safe to try different arrangements to find a sound you like.

Chris
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Old 30th January 2012, 06:04 PM   #3
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As I recall the Rhoads pianos used a series-parallel arrangement. 6 or 8 pickups (one for each key) in series and groups of those in parallel. Back in the 70's I remember seeing a pickup system for a Grand Piano that used a powered mixer. Each pickup was about 8 inches long and clamped to a bar that was clamped across the strings. It took the road crew about 2 hours to get it set up and working properly. Not sure how Hammond tone wheel organs work but each pickup must go thru the contacts on each key. There are about 10 switch contacts on each key. Basically one for each draw bar.
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Old 30th January 2012, 10:36 PM   #4
Minion is offline Minion  Canada
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Wiring in Paralell would lower the impedance and have a higher output current
Wiring in series would increase the output impedance and increase the output voltage ....

You pickups have a 11.5k impedance , with a 6 pickups in paralell that is less than 2k output impedance ......
In series it is about 70k ......

if the next piece of equipment in the chain has a input impedance of say 47k then you will get a lot of signal and tone loss from the series connected pickups but not with the Paralell setup .......
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Old 31st January 2012, 02:05 AM   #5
JoshuaK is offline JoshuaK  United States
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Thanks to all for the replies and input - I appreciate it greatly.

From what you have put forth, I suppose there really isn't too much of a risk in what I'm doing [so far]. I believe that was my main concern - any possibility of somehow "shorting" or "overloading" the signal path with however much of whatever element, and setting myself up for a most unpleasant surprise. IF there's anything that I should be wary/aware of, PLEASE post it - I'd like to know!

I suppose that I will have to forge ahead and find out for certain what works and what does not, soundwise. It seems like familiar terrain but it's still a foreign land, so I'll undoubtedly have more questions as I go on.

Thanks to all of you around the globe, for your information and help. God bless you all.

- Joshua K.
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Old 31st January 2012, 06:32 AM   #6
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From the point of view of the pickups, you'll be fine: they have enough internal resistance to ensure they won't cook even when short-circuited.

Chris
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Old 31st January 2012, 06:59 AM   #7
cbdb is offline cbdb  Canada
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If these pic ups are in parallel (or series for that matter) they will load each other down, and decrease the output (each pick up is both a source and a load) and increase the noise. Dont know how much of a problem that will be.
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Old 31st January 2012, 12:17 PM   #8
JoshuaK is offline JoshuaK  United States
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Quote:
Originally Posted by chris661
From the point of view of the pickups, you'll be fine: they have enough internal resistance to ensure they won't cook even when short-circuited.
This is good to know.

Quote:
Originally Posted by cbdb
If these pic ups are in parallel (or series for that matter) they will load each other down, and decrease the output (each pick up is both a source and a load) and increase the noise. Dont know how much of a problem that will be.
...and this is also good to know. I would like it to be as quiet as possible. I wonder, then, if there's any way to wire pairs of pickups in series and then have the pairs wired together in parallel, [roughly] like so:

Pairs of pickups-in-series
[down to]
Pairs wired together as one [parallel to each other]
[down to]
The switch.

Three pairs of series-wired pickups [with each pickup wired to the other in series] wired in parallel. So, on the first step, the resistance and impedance is multiplied for each pair. On the second step, the sum of the multiplied values is then divided by the parallel wiring. [Something tells me I have that wrong.]

Or, would this not make a difference at all, since the greater multiplied values would be divided to a greater degree? I'm currently not privy to the calculations required to figure this out.

I'd like to avoid the noise as much as possible, and possibly retain more output as well, but avoid garnering excessive resistance/impedance. If I could take just one pickup, strrrrretch it out to make it wide enough for the strings, and retain all the original properties, it would be great.
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Old 31st January 2012, 06:36 PM   #9
cbdb is offline cbdb  Canada
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Quote:
hree pairs of series-wired pickups [with each pickup wired to the other in series] wired in parallel. So, on the first step, the resistance and impedance is multiplied for each pair. On the second step, the sum of the multiplied values is then divided by the parallel wiring. [Something tells me I have that wrong.]
This will "restore" the output impedance but I am not sure it will help much with the loading effect. Imagine one string playing makeing only one pick-up put out signal (dosnt happen with guitars), and all the other pick-ups are just loads (13k resistors)

There are other concerns (unless I missed something) Guitar pickups are designed for 6 strings, trying to add strings will make there relative levels different. (look at the pick up, you can usually see where the strings go.)

The wiring on the humbuckers (in/out phase) is what effects the sound (and the hum rejection) the most. To use this you need a super switch for each humbucker.

The best way might be trial and error. Start with one pick-up see what works, add another pick up. Make sure you have a very high impedance input. (the instrument input on a guitar amp). Keep us posted.
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Old 31st January 2012, 10:37 PM   #10
JoshuaK is offline JoshuaK  United States
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Quote:
Originally Posted by cbdb View Post
There are other concerns (unless I missed something) Guitar pickups are designed for 6 strings, trying to add strings will make there relative levels different. (look at the pick up, you can usually see where the strings go.)
...
The best way might be trial and error. Start with one pick-up see what works, add another pick up. Make sure you have a very high impedance input. (the instrument input on a guitar amp). Keep us posted.
The pickups I'm using are Asian-made copies of Seymour Duncan 'Hot Rails' - blade polepieces span the entire string spread, with no gaps. So regardless if the string spacing is 1mm or 2 inches, it should pick up the string vibrations between the ends of the blades.

When you advise that I use a high-impedance input: is that just-in-case [like extra "headroom", so-to-speak], or would I still be better off seeking a hi-z input even if I wired them all in parallel and had a combined low impedance sum of +/- 2k? Forgive me if this is basic stuff I should know.
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