DiMarzio DP154, (the DLX+ Bridge), Surprise Coil Readings

[Drak]

I've had several DiMarzio P-90 HB's in the drawer for years, probably over 10-15 years.
So I had a project in mind for one or two which might involve coil splitting so I decided to ohm them out.

I have three of what I 'think' are DP164 DLX90's (discontinued) that all ohm out right around 10k.
They all have hex-head adjustable poles.
One coil is slightly over 5k, the other slightly under 5k, like ~4.5k and ~5.5k, for all three of them.
So there's that for a reference toehold in the sand.

I also have two DP162's, which are the DLX+ Necks.
Advertised resistance is 13.8k.
These had slightly unbalanced coils, ~7.6k and ~5.8k, both of them.

Then, this is the surprise and why I posted this thread, simply because there's very little info out there on them.

The DP154, the DLX+ bridge, gave me quite a surprise.
Advertised resistance is 17.28k.
It measured 12.2k (red/black/north) and 5.6k (white/green/south).
Wowza, what a difference.

Could you imagine someone coil tapping this thing with no idea what coil was doing what?
I don't know the whole line, or if there are others with this big of a coil differential.
Just thought I would post my findings, as I know these aren't very popular items and so very little info out there on them.
I would assume they were going for a more narrow sensing window (primary coil)
With the secondary coil doing nothing except acting as a 'shadow coil' to allow the HB'ing effect.
Or something...just guessing really.

[Cynical]

Wildly mismatched coils are kind of par for the course with DiMarzio. They've even got a (now-expired) patent on using different gauges of wire in each coil in a humbucker.

[freefrog]

Could you imagine someone coil tapping this thing with no idea what coil was doing what?
I don't know the whole line, or if there are others with this big of a coil differential.
Just thought I would post my findings, as I know these aren't very popular items and so very little info out there on them.
I would assume they were going for a more narrow sensing window (primary coil)
With the secondary coil doing nothing except acting as a 'shadow coil' to allow the HB'ing effect.
Or something...just guessing really.

I can certainly imagine coil tapping a Dual-Resonance DiMarzio since I've done here more than once.

No, there's not a strong coil while the other would be weak: they have roughly the same strenght and their sound differs mostly because of their different positions under the strings. :-)

As stated above by Cynical, what explains the difference of DCR is the thickness of the wire used: for example, the 12k coil of a DLX+b is wound with much thinner wire than the other coil...

Both have EXACTLY the same inductance: 2.25H per coil.

But as implied by the principle of Dual-resonance, they resonate @ different frequencies (and have different Q factors).

Below is the electrically induced resonance of each coil when a DLX is splitted. In this screenshot, one coil resonates @ 4320hz and the other @ 4085hz...
Pink line is the 12k coil alone.
Red line is the 12k coil in HB mode.
Black and green lines are the lower resistance coil (5.3k in this case), in split and HB modes.



And below is the DLX played in chords, neck posittion (yes, iI know it's a bridge model: it has been intentionally mounted in neck position). Blue line is the 5.6k coil. Red line is the 12k coil. Light grey line is the whole HB.



Now, let's just memorize this fact: DCR has NOTHING to do with output level.

What defines the output level of a magnetic transducer? Its inductance + magnetic field.

Pickups makers list DCR only because most people haven't the gear to measure inductance and because inductance rises with DCR all other things being equal. But if the wire gauge changes, "other things" are no more equal.

FWIW. the usual wordy attempt to share.

[freefrog]

Damn, can't edit the message above without receiving an error message.

So, the mistakes or imprecisions in this hasty answer above will remain as a probable proof that I shouldn't post early in the morning before a busy working day.

To complete what I was explaining about the pickup pictured in my previous reply: it's indeed a P90 sized DiMarzio DLX+b, whose coils measure respectively 12k and 5.3k at normal ambient temperature (total DCR in this case: 17.3k, close to published DM specs).

And its inductance in full humbucker mode is 5.15 Henry. It's more than twice the 2.25H of each coil separately because of "mutual inductance"...

The screenshot involving the pickup played in chords illustrates how the output level varies with inductance: adding 2.9H brings approximatively +6dB on fundamental notes.

Regarding single coilish tones: in split mode the 5.3k coil would be closer to a Fender SC thx to its higher Q factor, higher pitched resonant frequency and to the tonal effect of these features: "better" harmonics...

FWIW. These P90 sized DM's are not outstanding tonally but they are versatile when wired in an optimal way...

[freefrog]

Never two without three...

My first answer lacked of nuance.

Actually, there's a relation between DCR and output...

... but it might be counterintuitive.

If two pickups or coils with the same inductance and magnetic field are played, the strongest electrically will be... the one with the lowest resistance (!). That's why the resonant peak of the 5.3k above is several dB higher than the Rz of the 12k coil in my first screenshot above : the 6.7k added to the second coil are just "useless" resistance, since they don't contribute to higher inductance. So, these added 6.7k act a bit like a volume pot turned down a tiny wee bit.

What makes the 12k coil as strong as the 5.3k coil when chords are played is the lower Q factor of the 12k side: its power is not "focused" in its resonant peak so it compensates a bit its slighly weaker electrical output level.

FWIW - another nerdy contribution.

[Drak]

FWIW - another nerdy contribution.

You can super-nerd out on me anytime, Thanks very much for ALL that information, most appreciated.