Weird clipping sound from stacked single coil?

xscaramanga

I've got a pair of DiMarzio stacked single coils in my Strat, and they make a weird and very unpleasant sound if you hit the low E string too hard. The noise is a bit like digital clipping (so much so that I initially thought my AX8 or digital wireless were at fault).

I've taken it to a tech, who is a bit stumped. He checked and double checked all the wiring, and everything should be fine.

Then he got another guitar in for repair that has the same problem (to a lesser extent), also with DiMarzio stacked singles. It's worse on the neck pickup than the middle (and if you swap the pickups round, it's always whatever's in the neck that sounds worse). The E string is worst, but the A string does it a bit too.

Is this a known issue? DiMarzio tech support suggested adjusting the pickup further from the strings. That seems to reduce the problem but not eliminate it. Do other stacked singles suffer from the same problem, or is this particular to DiMarzio's 'Area' pickup design? 

OilCityPickups

I've had Fender 'noiseless' stacks with the same issue. With the Fenders they are not built to be disassembled or messed with, so I have never attempted to work on them ... much like Lace Sensors. Most 'noiseless' SC pickups work on the same principal (bar Lace) in that a single magnet works as say the south pole for the upper coil, and the north pole for the lower coil which is reverse wound. The upper coil does the heavy lifting as far as sound production, with the lower coil being too far away from the strings to contribute much to the sound. This traditionally has the unwanted side effect that in order to get say the same output as a traditional 6k Strat pickup you have to wind the whole pickup to close to 12k as the bottom coil does virtually nothing. This gives the tone curve of a 12k pickup with only half its output. Hence too much compression and smoothed over top end.

Now Area's are quoted at 6.15k which would suggest to me they are not a conventional stack design. Possibly they may be a split humbucker, which is like a P Bass pickup but with both coils placed end to end under the cover. These too suffer from issues, mostly string volume reduction when bending between the two opposing magnetic fields on the 3'rd string ... but it's also tough to get enough wire of the right gauge on the tiny bobbins.

Without any idea which method DiMarzio use, it's hard to work out what might be causing this. It has your friendly local pickup maker a tad foxed too :-) 

Funkfingers

Some of the DiMarzio stacked coil replacement pickups for Stratocaster have a steel screening plate surrounding the upper coil on three sides - rather like the "claw" on a Fender Jaguar pickup. The rod magnet polepieces only pass through the upper bobbin and coil. Thus, the lower coil is purely a dummy for noise-cancelling purposes.

I discovered all of this when I investigated a semi-functional DP116 DiMarzio HS-2. It arrived in the middle position of a HSH shred stick guitar, wired to operate in single coil mode only à la Steve Vai. I soon realised why. The lower coil was broken!

The two plastic bobbins of this pickup are held together with a single cross-headed screw through the underside. If the screw works loose, there could be unwanted resonance.

The published D.C. resistance stat for the DP166 HS-2 is 14.97k. My cruddy old multimeter reads 8.5k for the upper coil alone.

OilCityPickups

Funkfingers said:

Some of the DiMarzio stacked coil replacement pickups for Stratocaster have a steel screening plate surrounding the upper coil on three sides - rather like the "claw" on a Fender Jaguar pickup. The rod magnet polepieces only pass through the upper bobbin and coil. Thus, the lower coil is purely a dummy for noise-cancelling purposes.

I discovered all of this when I investigated a semi-functional DP116 DiMarzio HS-2. It arrived in the middle position of a HSH shred stick guitar, wired to operate in single coil mode only à la Steve Vai. I soon realised why. The lower coil was broken!

The two plastic bobbins of this pickup are held together with a single cross-headed screw through the underside. If the screw works loose, there could be unwanted resonance.

The published D.C. resistance stat for the DP166 HS-2 is 14.97k. My cruddy old multimeter reads 8.5k for the upper coil alone.

That's a common design choice ... ie the lower coil is purely a dummy, and the upper 'claw' adds to the inductance of the top coil. What interests me however is the stated DCR of the 'Area' at 6.15k ... that wouldn't allow for a second inactive coil, and would rather suggest a split humbucking design where each mini coil was just over 3k.

Funkfingers

6.15k could be the nett result of two hugely overwound coils connected in parallel. (Like the dreaded Gibson P100.)

Some Duncan Stack pickups give d.c. resistance readings of ⅔ working coil, ⅓ dummy coil. 

The Fender Super 55 pickups were side-by-side coils (and plates) but two-con + shield output cable. They vanished very suddenly. Perhaps, something about the Super 55 construction fell foul of somebody else’s patent?

xscaramanga

Update for anyone interested: The tech gave up, put my guitar back together, and refused to charge me, which I think was over generous of him but there you go. He's lowered the pickups to almost flush with the scratchplate, and at that distance, I have to pick as hard as I possibly can to hear any of the unwanted noise, and even then it's much less prominent than it was. The tone is still quite useable.

For the record, the pickups were a Virtual Vintage Heavy Blues 2 neck (DP409, 8.53k) and Injector Neck in the middle position (DP422, 8.56k).

I'll see if I can live with it and how good it sounds through my rig. I have good quality vintage-style true single coils in my other Strats, but I want one noiseless Strat for gigs where vintage pickups are unusable because of dirty power supply or crazy lighting rigs. If these don't do it for me I'll look at alternatives, but I do like the sound they make when they're not farting out.

Thanks @OilCityPickups for generous advice on a competitor's product. I could well end up with some of your custom rails jobbies if these don't work out. Those P90s you wound me are the bomb, by the way!

Alegree

I've worked on Areas before 

As said before, they've got a big steel claw around the top coil. The top coil is wound with most of the DCR, bottom has about 1/3 of the resistance (but has same physical coil volume, so it's definitely wound with less turns of thicker wire). The magnets only past through the top bobbin, with the steel claw making the magnetic field very strong at the top. This doesn't make the bottom coil a dummy coil. The idea that the pole / screw inside a pickup is what picks up the sound is false. What this makes is a top coil wound reasonably with thin wire, and very strong magnetic field, and a bottom coil which is wound very modestly (but enough to buck the majority of the hum) with thick enough wire to not influence the tone too much.

Edit: I concur with the prediction of a resonance issue.

OilCityPickups

Alegree said:

The idea that the pole / screw inside a pickup is what picks up the sound is false. 

Pardon? The pole screw or slug or magnet is the way the magnetic field gets to interact with the string. No pole screw, slug or magnet .. no sound.

Alegree

OilCityPickups said:

Alegree said:

The idea that the pole / screw inside a pickup is what picks up the sound is false. 

Pardon? The pole screw or slug or magnet is the way the magnetic field gets to interact with the string. No pole screw, slug or magnet .. no sound.

No, put a magnet above the string and a dummy coil below and it'll make noise. It's not the magnetic field interference from the pickup. It's the magnetic field of the string inducing a current in the pickup.

OilCityPickups

Alegree said:

OilCityPickups said:

Alegree said:

The idea that the pole / screw inside a pickup is what picks up the sound is false. 

Pardon? The pole screw or slug or magnet is the way the magnetic field gets to interact with the string. No pole screw, slug or magnet .. no sound.

No, put a magnet above the string and a dummy coil below and it'll make noise. It's not the magnetic field interference from the pickup. It's the magnetic field of the string inducing a current in the pickup.

However the magnetic field would not get to string without a magnet or magnetised pole wherever it's situated, The string itself is not magnetic, I know what you are trying to say, but the way you stated it was a little confusing for ordinary punters on here with no technical knowledge :-) Magnetic fields are subject to the inverse square law, so the positioning of the magnet in relation to the string and in turn the positioning of the coil relative to the magnet will determine the eventual output of the coil, dummy or main.

None of this is particularly gallivant to the OPs question, and I would agree with you that it's a resonance issue. Solving that issue is another thing again.

normula1

IIRC, the Virtual Vintages basically ripped of the Kinman design and then to rub salt in the wound tried to patent the idea and stop Kinman selling in the US.

Having said that, I like the set I have which are on the warm side of Strat tone.

Keefy

OilCityPickups said:

... Magnetic fields are subject to the inverse square law, so the positioning of the magnet in relation to the string and in turn the positioning of the coil relative to the magnet will determine the eventual output of the coil, dummy or main.

...

IIRC from my Uni physics course (a very long time ago, I hasten to add), magnetic field strength falls off as a simple inverse of distance, whereas intensity of electromagnetic radiation (which has both an electric field component and a magnetic field component) is proportional to the inverse square of the distance from the source. If you can't sleep, try looking up vector cross products...

/nerd

OilCityPickups

Keefy said:

OilCityPickups said:

... Magnetic fields are subject to the inverse square law, so the positioning of the magnet in relation to the string and in turn the positioning of the coil relative to the magnet will determine the eventual output of the coil, dummy or main.

...

IIRC from my Uni physics course (a very long time ago, I hasten to add), magnetic field strength falls off as a simple inverse of distance, whereas intensity of electromagnetic radiation (which has both an electric field component and a magnetic field component) is proportional to the inverse square of the distance from the source. If you can't sleep, try looking up vector cross products...

/nerd

Very probably correct ... still falls off mind ... that's why lowering your pickups changes your tone and lowers your pickup's output.

Philly_Q

Funkfingers said:

The Fender Super 55 pickups were side-by-side coils (and plates) but two-con + shield output cable. They vanished very suddenly. Perhaps, something about the Super 55 construction fell foul of somebody else’s patent?

After reading Ash's first post on this thread I spent about 20 minutes thinking "what were those funny Fender pickups with an S shape on the cover, I remember something about the G string losing volume on bends...".

Couldn't find anything.  Then 3 posts later you mentioned them. 

OilCityPickups

Philly_Q said:

Funkfingers said:

The Fender Super 55 pickups were side-by-side coils (and plates) but two-con + shield output cable. They vanished very suddenly. Perhaps, something about the Super 55 construction fell foul of somebody else’s patent?

After reading Ash's first post on this thread I spent about 20 minutes thinking "what were those funny Fender pickups with an S shape on the cover, I remember something about the G string losing volume on bends...".

Couldn't find anything.  Then 3 posts later you mentioned them. 

The Super 55s vanished quickly because the idea doesn't work well unless you can overlap the coils as in a P Bass. I made a few prototype split single Tele pickups and the idea works okay for bridge pickups where the string doesn't move much in a bend. Where it comes seriously unstuck is for Strat neck pickups where the string excursion can be quite large on the third string. It's a huge shame, as the Split single sounds far more like a conventional single coil than a stack or rails design.

These are from Curtis Novak and by all accounts are very good.

Alegree

OilCityPickups said:

Alegree said:

OilCityPickups said:

Alegree said:

The idea that the pole / screw inside a pickup is what picks up the sound is false. 

Pardon? The pole screw or slug or magnet is the way the magnetic field gets to interact with the string. No pole screw, slug or magnet .. no sound.

No, put a magnet above the string and a dummy coil below and it'll make noise. It's not the magnetic field interference from the pickup. It's the magnetic field of the string inducing a current in the pickup.

However the magnetic field would not get to string without a magnet or magnetised pole wherever it's situated, The string itself is not magnetic, I know what you are trying to say, but the way you stated it was a little confusing for ordinary punters on here with no technical knowledge :-) Magnetic fields are subject to the inverse square law, so the positioning of the magnet in relation to the string and in turn the positioning of the coil relative to the magnet will determine the eventual output of the coil, dummy or main.

None of this is particularly gallivant to the OPs question, and I would agree with you that it's a resonance issue. Solving that issue is another thing again.

After the string has been magnetised by the permanent magnet (where ever it may be) the string is the magnetic field that the coil picks up. The position of the coil in relation to the magnet has no relevance in a test if the string can be magnetised to similar saturation from two different magnet locations. The string is magnetised in Areas regardless of there not being a magnetic core in the second coil. This means the lower coil will produce noise (albeit not a lot).

Philly_Q

Yes, I remember seeing those on Curtis Novak's website many years ago.  It's an appealing design.

Also reminds me of the "domino" pickups on PRS EGs, made by Fralin I think.  And G&L's Z coils.  Like a P-Bass pickup for guitar.  Not particularly attractive to look at, though.

CasperCaster

Firstly, let me say that I have absolutely no idea how the various noiseless pickups work, or the function of their various components. However, I had previously heard that some Dimarzio designs were 'inspired' by Kinmans, and that this included a metal 'claw' inside the pickup. I didn't realise it was a steel claw intended to increase inductance (like a Tele bridge pickup?).

Funkfingers

Alegree said:
This doesn't make the bottom coil a dummy coil.

I stand corrected.

Alegree said:

put a magnet above the string and a dummy coil below and it'll make noise.

This is how the old Rickenbacker “horseshoe” pickups work.

OilCityPickups

Funkfingers said:

Alegree said:
This doesn't make the bottom coil a dummy coil.

I stand corrected.

Alegree said:

put a magnet above the string and a dummy coil below and it'll make noise.

This is how the old Rickenbacker “horseshoe” pickups work.

And some old lap steel pickups like Supro/Valco

grungebob

I’ve had the HS2 in many a guitar and never had any issues. It’s one of my favourite pickups.