Question About Seymour Duncan HSH Pickup Scheme

[terryturtle]

Currently I have a Valley Arts California Pro with the following pickup configuration:

N: Seymour Duncan Cool Rails
M: Seymour Duncan Hot Rails
B: Seymour Duncan JB

I want to change this configuration to this one:

N: Seymour Duncan Hot Rails
M: Seymour Duncan Vintage Flat
B: Seymour Duncan JB

Will the Seymour Duncan HSH wiring scheme with auto-split work with this setup? Tried asking them directly, but no response. I basically want a Ibanez JEM wiring setup.

[newey]

TT-

Hello and welcome!

I assume this is the diagram from SD you intend to use:



This should work just fine if both the Hot rails and JB are 4-conductor HBs, which I believe they are (I didn't check that).

The only issue which may arise: Since the diagram is based on 2 identical HBs (the Lil' Humbuckers), and you are using 2 different types (all SD pups but different models), the coils which are split at positions 2 and 4 need to be reverse wound, reverse polarity with respect to the middle pup, in order to ensure that the combinations are hum-cancelling.

The likelihood is that SD's various pickups are all the same in this regard. But you might want to check the polarity on each of the HBs to be sure. Worst-case scenario, you might have to mount one or the other HB 180° from its normal mounting position. If so, you may also have to extend the wires from that pup to reach the controls.

[terryturtle]

Thank you! That diagram is slightly different than the one I saw, but the scheme is dead on what I want. Yes the JB and Hot Rails are 4-wire. Is the middle pickup the right output for such a setup or does it need to be hotter? It's a low type.

[ashcatlt]

Aug 26, 2009 5:52:14 GMT -5 newey said:

Worst-case scenario, you might have to mount one or the other HB 180° from its normal mounting position.

Newey, you know better than that! Didn't we just have a discussion on this topic? Physically turning the HBs won't make any difference at all to the relative signal polarity.

[ChrisK]

The middle pickup will be selected alone or with one coil from either the bridge or neck pickup. These are 6dB lower in output than the full series humbucker configurations.

Try it first and then decide.


If there are signal phasing issues with the selected single coil on the bridge and neck pickups relative to the middle pickup, disconnect the wire from the 5-way lever switch that goes to the back of the volume pot and connect it to the hot terminal on the volume pot.

This will short the other coil on the bridge and neck pickups and effectively select the coil of opposite polarity relative to the middle.

Besides, it's way easier than rotating this space-time-brane instantiation (the entire universe).

[newey]

Ash:

Newey, you know better than that! Didn't we just have a discussion on this topic? Physically turning the HBs won't make any difference at all to the relative signal polarity.

Yes, we did just have that discussion and, yes, I do know better. But I wasn't talking about relative polarity, I was talking about making sure that the inner coils of both the neck and bridge HB are the coils which are RWRP with respect to the middle pup.

As I said, presumably all SD pups are the same in this, but since he's using 2 different SD HBs I thought he should probably double check it.

[terryturtle]

Wouldn't having the middle pickup reverse wound handle the hum cancelling issues?

[ChrisK]

Wouldn't having the middle pickup reverse wound handle the hum canceling issues?

That depends on what it's RWRP with respect to.

A humbucker has coils wound both ways; each of its coils is RWRP relative to the other.

The middle pickup will be RWRP with respect to one of each humbucker's coils; the trick is to determine which one.

[ashcatlt]

Well, the middle pickup will be RW with respect to one of the coils, and RP with respect to one of the coils on each HB. It may not be both RW and RP with either of the coils, when wired using the colors provided.

You need to identify which of the coils are RP (reverse magnetic polarity) from the middle and make sure that these are the ones selected when combined with that same middle. This may require either changing the "order" of the coils in the series structure, or swapping the "output wires" like ChrisK said. I think those are identical solutions.

Then you will have to determine the "winding direction" of these coils and make sure that you wire it up reverse from the middle pickup. If it doesn't work out wired like the picture, it would likely be easier to reverse the one SC rather than both HBs.

[newey]

TT-

To summarize this for you, (at least as I see it):

What Chris, Ash and I are all talking about amounts to the same thing- being absolutely sure that you have the proper coils selected for positions 2 and 4 so that these positions will be a pair of SCs which are hum-cancelling in combination.

But frankly, you really don't need to do all that, at least probably not. The odds are very good, I'd say excellent, that if you wire it up according to the SD diagram it'll work just fine.

Since all the pickups are Seymour D's, the wiring colors on the HBs should be identical. No worries there.

You can assume that the diagram is set up, using the Lil HBs, to be hum-canceling in pos. 2 & 4. If this assumption turns out to be false, they were seriously asleep at the switch at SD when they drew this up.

Since all the pickups are SDs, the chance that they have elected to have a different coil be the RWRP one on the Lil HBs, and have the opposite coil RWRP on your JB and/or hot rails, is at a very low order of probability.

I would expect that if the Vintage Flat you get for the middle is the RWRP version, there is a strong likelihood that it will be RWRP with respect to the innermost coils on both the JB and the Hot Rails, meaning as long as you mind the wire colors properly it should work as advertised.

If it doesn't work correctly, a simple swap of a few wires will set it straight, as ChrisK points out.

In an effort to all be technically correct, we don't want you to lose sight of the fact that you can do this mod easily, and if you do have the "wrong coil" problem, it's easily corrected.

On the other hand, if you want to totally avoid the possibility of having to take it apart again, you can test the coils as we have suggested.

I'd say, wire it up and report back your results. If there is a problem with the hum-canceling positions, we've already diagnosed it and given you the antidote.

[ChrisK]

A presumption would be that the Hot Rails and the JB have identical wiring which may not be true since the SD diagram is for two mini-humbuckers (single coil sized) and a single coil.

However, our Pickup Wire Colors and Polarity post indicates only one wiring scheme for SD 4-wire humbuckers.

Based on this, I would presume that they are wired the same.

The diagram indicates that the slug (north polarity) coil is selected in the bridge plus middle position. I don't see any indication of the standard polarity of SD single coil pickups on their web site, nor am I willing to spend time "fishing" for this information.

A simple test is to briefly place the middle pickup's top pole pieces against the bridge slug coil pole pieces.

If they attract, they are RP with respect to each other and phasing is a simple exercise of swapping the middle pickup wires with each other if needed.

If they repel, then they are not RP with respect to each other and polarity and phasing are then somewhat more complex exercises. If you are willing to use the screw (south) coil on the bridge humbucker, disconnect the wire from the 5-way lever switch that goes to the back of the volume pot and connect it to the hot terminal on the volume pot. This will select the south coils on both the bridge and neck in conjunction with the middle.

You may still need to do the exercise of swapping the middle pickup wires with each other if the combined sound is weak and thin.