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Electronics wizards - series/parallel pickups - how/why?

S

stradivarius151

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Jan 18, 2014
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#1
Hi all,

I've been thinking about getting some form of Jazz Bass for some time now, and thinking about immediately modding to push-pull pots, one for series/parallel and one for phase. I get that series and parallel sound different, and I get what each sounds like, but I'd like to know why.

What is the scientific/electrical reason that pickups sound different when connected in series/parallel? Go into as much detail and/or scary science words as necessary, I've seen 'em all before.

Thanks!
 
#3
True, but I want more. What about the harmonics and overtones? I know they get simply summed when in series (which about doubles the total output, yadda yadda), but what happens in parallel? Clearly some harmonics cancel, to some degree, because the sound is different, but what is the mechanism that causes that cancellation due to the way they're connected.
 
#5
The resonant peak of two coils in parallel is typically almost an octave higher than when the same coils are in series.

Also the height of that peak is usually much lower in series. This is due to the higher impedence as others have said, and the load of the pots. In fact, often the peak disappears altogether and you have a simple roll-off. That's why series sounds much warmer.

FWIW, if you buffer the coils directly with a high Z (1Meg or greater), and also adjust the gain so both series and parallel have the same perceived output, the difference is usually very subtle.
 
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#6
RobbieK said:
The resonant peak of two coils in parallel is typically almost an octave higher than when the same coils are in series.

Also the height of that peak is usually much lower in series. This is due to the higher impedence as others have said, and the load of the pots. In fact, often the peak disappears altogether and you have a simple roll-off. That's why series sounds much warmer.

FWIW, if you buffer the coils directly with a high Z (1Meg or greater), and also adjust the gain so both series and parallel have the same perceived output, the difference is usually very subtle.
Click to expand...
That's it... like tuning an R/C circuit. The following is a guy talking about tuning old radios, but the principal is essentially the same:
Tuned circuits
 
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#7
vickerekes said:
In simple english, you generally get a hotter signal in series... more punch, but not as transparent a sound (harmonics/overtones, etc.).
Electrically, you've got a higher impedance, capacitance, and more resistance (statically).
How's that?
Click to expand...
Also, the loose some high end in series. The 2 halves of a P pickup are reverse would to cancel noise and wired in series for a bigger, fatter but darker sound.
I wire all my Jazz basses with an S-1 series/parallel switch for bigger pallet of tones. This is a good thing for Jazz basses but useless on a P bass.
 
#8
stradivarius151 said:
...one for phase.
Click to expand...
Please, forget about putting a phase switch in your bass. It adds complexity and is, in my opinion, completely useless. The out-of-phase sound is extremely weak and thin, imaging playing 'bass' through a telephone. Too little bass and too little output to bother with, IMO. Use a treble booster or EQ pedal if you need a super-trebly special-effect tone.
 
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#10
Not to hijack the thread, but anyone care to comment about mid scoop and how the distance between the coils changes the tone and why?

Two J pickups right together is basically a humbucker and the pair, when both are on, lose a bit of highs vs a single coil. Spread them apart like on a J bass and it becomes a mid scoop instead of a high cut. Spread them even further apart (put one right by the neck heel) and (I think) you get a much lower frequency mid scoop than in the J bass orientation (a sound I happen to love). As to why, I have not a clue.
 
#11
stradivarius151 said:
Hi all,

I've been thinking about getting some form of Jazz Bass for some time now, and thinking about immediately modding to push-pull pots, one for series/parallel and one for phase.

Thanks!
Click to expand...

I did exactly that with my first bass and had the same sort of curiosity and thirst to learn. TB is great for that. Have fun!!
 
#12
While this doesn't answer your question, I can tell you that I added a series/parallel switch to my jazz about 6-7 years ago, and it is *always* in series mode. Sometimes I'll switch it back to compare, and there is just no question that I prefer the series setting 100%.

HOWEVER .... I tried the same on a recently acquired fretless jazz, and did not like the series sound at all.

Just some food for thought.
 
#13
Doner Designs said:
Not to hijack the thread, but anyone care to comment about mid scoop and how the distance between the coils changes the tone and why?

Two J pickups right together is basically a humbucker and the pair, when both are on, lose a bit of highs vs a single coil. Spread them apart like on a J bass and it becomes a mid scoop instead of a high cut. Spread them even further apart (put one right by the neck heel) and (I think) you get a much lower frequency mid scoop than in the J bass orientation (a sound I happen to love). As to why, I have not a clue.
Click to expand...

Response Effects of Guitar Pickup Position and Width

Response Effects of Guitar Pickup Mixing

This is neat :

Guitar Pickup Response Demonstration

You can watch the frequency curve as you move pickups around.
 
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#14
stradivarius151 said:
Hi all,

I've been thinking about getting some form of Jazz Bass for some time now, and thinking about immediately modding to push-pull pots, one for series/parallel and one for phase. I get that series and parallel sound different, and I get what each sounds like, but I'd like to know why.

What is the scientific/electrical reason that pickups sound different when connected in series/parallel? Go into as much detail and/or scary science words as necessary, I've seen 'em all before.

Thanks!
Click to expand...

When you wire two pickups in series the resistance sums. More resistance tends to mean less highs.

Combined resistance in parallel follows 1/R1 + 1/R2 = 1/R vs. series R1 + R2 = R. If you know a little math, you can see that in series wiring the R value will be higher. This moves your resonant peak back, and cuts some highs. Of course this is an AC circuit, not DC and there are other factors to consider. Ignore this for the next section, that's just to partially explain one perceived difference in series vs. parallel, namely, loss of highs.

When two coils are wired in parallel (and at the same volume) they each individually lose output due to insertion loss, winding up at something like 1/4 the output of series wiring when mixed together. Human ears don't perceive sound in a linear fashion so it doesn't sound 1/4 as quiet, but we can notice it's quieter.

When two coils are wired in series, it's just forwarding the signal along through the pickups each in turn.

You can experiment with parallel coils using a Jazz bass' volume knobs. Roll the volume down a little on one pickup, leave the other full on and you get some output back.
 
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#17
Why not just throw a 4x3 rotary switch wired for [neck/both-series/both-parallel/bridge] where the first volume knob is, and use the second volume and tone as masters and be done with it? Then you can hear for yourself and switch it back and forth anytime you want it. :)
 
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#18
I wire all of the Jazz basses I build or refurbish with a DPDT for series/paralell

On the Squier vintage modified fretless Jazz that went through here the difference was significant.

On my other 4 string warmoth with Bill Laurence pickups the difference was audible but subtle.

My current build is with barolini pickups same wiring so when I get that bolted together I will post again
 
#19
I won't get into the why - but an example of a difference I noticed ...
I have a PJ that I set to series. (all passive) When it was parallel and you switched to both pickups, there was always a volume drop compared to either pickup solo. When wired series there is a boost in volume when both pickups are selected compared to either pickup solo.
 
#20
When it was parallel and you switched to both pickups, there was always a volume drop compared to either pickup solo.
Click to expand...

It doesn't have to be this way. If you get a hot J and an underwound P, and also set the J close to the strings, so that the output of both is very close, you will usually get much less of a drop. It also pays to have pickups of similar impedence.

When wired series there is a boost in volume
Click to expand...

This, as just about everyone so far on this thread has said, is entirely normal. Typically around 6dB is the perceived volume jump. (Well for the lows and mids anyway.)
 

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