Paging the Frog Man

[Chistopher]

I was doing research into how Lace Sensor designs some of their pickups, most notably the D3 and Alumitone series. The way I understand the Alumitone is that when you "split" it you are actually disabling one of the secondaries of the little transformer they put in there. This has the interesting effect of making it so there is a wrong way to split it. When you wire it up, you are supposed to ground the split wire and lift the ground wire instead of just ground the split wire.

For those who don't know what I'm talking about, when you ground the red/white link on an SD pickup, the north coil has a hot and ground, so you can hear it, but the south coil has two grounds, so you can't hear it. What I'm referring to would be the equivalent of grounding the white wire and lifting the green wire. This leaves the north coil with a hot and a ground, and the south coil with nothing. The conventional wisdom says this makes no differences, but I can't think of one person who has experimented with it.

Now I'm assuming the reason you aren't supposed to leave the other coil attached in the Alumitone is because the Alumitone is a transformer based design, allowing eddies to goof around in a disabled coil would, through the principle of mutual inductance, inadvertently effect the performance of the other coil of the transformer?

I assume all this is such a big deal because of the high current / low voltage nature of the Alumitones and the more tightly coupled nature of the secondary coils relative to a standard humbucker, but is their reason to think that the eddies of a shorted coil effect the performance of the active coil in a traditional split humbucker?

 

[freefrog]

If the question is for me: I've no lab data about the Alumitone's and I currently lack of free time to think twice about the whole thing... But I know for a fact that aluminium is one of the biggest sources of Foucault currents in presence of a magnetic field. Hope it contributes to answer... More later if time permits. Work is waiting me right now. :-/

 

[Chistopher]

I definitely understand. I'll have to setup a little rig to test it.

 

[freefrog]

is their reason to think that the eddies of a shorted coil effect the performance of the active coil in a traditional split humbucker?

Let's try to reply in a more efficient way than in my first post above...

IME: it depends on the pickup and its specs... BUT various kinds of coupling effect (magnetic, capacitive) can certainly be noticed between a split coil and the unused one with a traditional humbucker.

Below is a pic with the smallest coupling effects measured here between split coil and unused one, wired in 4 different ways.

Some of my data show bigger changes - and even dramatic ones in some (not necessarily typical) cases.

Now, the tonal consequences of such differences generally remain subtle. ;-)

FWIW. Hope I'm not totally off topic this time. And HTH.

 

[Chistopher]

Interesting, I'll definitely have to setup a rig to test it out myself. What traits do pickups that tend to have greater differences have?

 

[freefrog]

What traits do pickups that tend to have greater differences have?

Frequency response with "stairsteps" beyond main resonant peak and/or lower pitched resonance, both depending on how the unused coil is wired (or not).

 

[htrd]

Hope it helps

https://guitarnuts2.proboards.com/thread/7769/damping-caused-unused-splitting-humbucker

 

[freefrog]

All contributions are welcome IMHO but in the topic on Guitarnutz, the post 22 was misunderstood -since its author didn't precise that he was showing the separate frequency responses of humbucker coils in series...

...And my experience / experiments of these last 20 years disagree with how this post 22 was commented : secondary peaks exhibited by humbuckers don't "disappear with load" and are actually / factually responsible of noticeable differences in the harmonics of many humbuckers. In some specific cases, they can even be painful for the ears through a bright amp / cab (Fender Twin, Roland JC120), especially once the bright swicht enabled.

I've worked with / for a pickups maker on this issue and shared what I could share about that in a dedicated topic about inner capacitance on the music-electronics forum... Sadly, It didn't prevent people to keep claiming that a few dozens of pF from a pickup and its wires are drowned in the way bigger capacitance of a guitar cable. It's in fact not true at all since a low parasitic capacitance before pots defines how these controls reshape the resonance once lowered. It also gives clearly different transients, faster, with more amplitude (which can also be painful to hear because too crisp, too bright: that's what users disliked without knowing it in hand wound humbuckers like Skatterbrane's, for instance).

 

[htrd]

Sadly, It didn't prevent people to keep claiming that a few dozens of pF from a pickup and its wires are drowned in the way bigger capacitance of a guitar cable. It's in fact not true at all since a low parasitic capacitance before pots defines how these controls reshape the resonance once lowered. It also gives clearly different transients, faster, with more amplitude (which can also be painful to hear because too crisp, too bright: that's what users disliked without knowing it in hand wound humbuckers like Skatterbrane's, for instance).

That correlates with my experience with Lundgren Black Heaven humbuckers. Measured capacitance is rather low for the humbucker, 90-97pF at 100kHz (6 and 7 string versions) with baseplate attached (58-65pF without shielding wire), but while the difference with the more conventional 120-150pF pickups is not significant if we a measuring them with the generic cable and its ~500pF, soundwise it is extremely clear and sparkly. Longer cable with additional capacitance can't compensate for this crispness. Sometimes people rely too much on the simplified LCR model of the pickup ignoring their ears.