Series vs. Parallel. Can someone please explain?

[axekicker]

I'm kinda embarrassed to ask, but I'm not sure I understand what the difference is. Between the two. What's the tonal difference? Thanks. There's so much discussion about it on the boards and I'd like to understand what's being discussed.

[newey]

We could toss around a bunch of adjectives, saying for instance that parallel is a "thinner", "brighter", "lower output" sound, while series is "beefier", "higher output", etc. But such descriptors don't help much.

The best way to discern the difference is with your ears. Page down to the "Sound Samples" part of the board, there are several examples of series/parallel combos there, using various different pickups and/or coils.

If we're talking about putting 2 separate pickups in parallel or series, as opposed to the 2 coils of a HB, you know what 2 pickups in parallel sound like- like pretty much every stock guitar you've ever heard. 2 single coils in parallel? Listen to a Strat. 2 HBs in parallel? An LP.

For two pickups in series, again, check the sound samples.

[axekicker]

Thanks for that. So the second position on the strat switch and the middle positing on a les paul are parallel i.e. when both pups are on? I'm trying to visually understand what's going on.

[newey]

So the second position on the strat switch and the middle positing on a les paul are parallel i.e. when both pups are on? I'm trying to visually understand what's going on.

Yes.

For a visual, wolf's site has a good drawing of 3 pups in parallel versus series:

www.1728.com/guitar.htm

(page down a bit to find it).

Basically, just think of it this way: In parallel, the "hot" leads of 2 (or more) pickups all connect together, and the "not hot" leads likewise all connect together.

In series, the pickups are "daisy-chained", one to another. The "hot" lead of the first one in the chain goes out to "hot", the "not hot" lead of the last one goes to ground, and in between, they are connected together, "hot" to "not". In series, the signal goes through each pickup in the chain before going out.

[Yew]

In parallel, both pickups feed to the utput, in series, one pickup goes through the other.. im wondering if which way you wired them would have an effect though ( bridge first, or neck first) unless they dont work like that..

[JohnH]

It’s an interesting subject, that can get rather technical. Admirable restraint has been shown so far!

I think there are a few aspects worth having more explanation for.

Why is series louder than parallel?

In series, the signals from two coils get added together, whereas in parallel, they could be thought more of being averaged. An analogy can be made with 1.5V battery cells. If you put two in series, the voltages add to make 3V, but in parallel, it is still 1.5V.

Why do they sound different?

There’s two reasons

1. To some extent, the two coils or pickups will be picking up the same signal from the string. If they had exactly the same signal, and if they were connected directly to a high impedance input via very short cable, they will sound the same, just series will be louder. A difference will occur however in most guitars, due to the loading of the pots, and the cable capacitance. This is due mainly to the fact that the coils have inductance. When combined in series, the inductance is 2x that of one coil, where in parallel it is ½x that of one coil. A signal source with higher inductance (such as coils in series), when loaded by resistance (the pots) and capacitance (the cable), will have less high frequency response than one with a lower inductance.

Hence parallel-wired coils will have lower output, but relatively more high frequencies than the same in series.

Another related subtlety, the inductance and cable capacitance result in a resonance, with a peak in response in the high treble. With greater inductance as in series wiring, this peak is at a lower frequency.

2. But also, to some extent, two coils will pick up different signals, particularly if they are spaced apart. With series wiring, both contributions get added. But with parallel wiring, one pickup that may be detecting a harmonic that is not picked up by the other, will be loaded by the second coil, partly suppressing that different signal component. Hence there is an interaction where differences are suppressed. There has been some discussion as to whether it is a good idea to reduce this interaction by adding a resistance to each coil, a matter of personal choice (not IMO).

Where do single coils fit in?
Based on Factor 1 above, a single coil, with its 1x coil inductance, would be expected to be brighter than a series combination, but less bright than a parallel combo. But it may in fact be brighter and more edgy than a parallel combo, due to Factor 2, since there is no other coil loading it to suppress differences, which tend to be in the high harmonics.

Does it make a difference which order coils in series are wired?
No, not unless there are switching for coil taps involved etc

I’ll stop there!
cheers
John