Interleaved windings?

[soundmasterg]

Well I for one would be interested in their impressions of the difference in sound in a pickup like that. Hopefully you'll remember to post about it when you get the results!

[DrStrangelove]

Gaglio Pickups and bifilar windings

Gaglio Pickups has a patent for interleaved windings: US 6476309B2.
From a friend's personal communication with Gaglio's biz manager, I see
that their 2002 patent is a starting point from several designs, PAF-style,
stacked humbucker, J-bass, and mini-bucker among them.

Gaglio's site has little info, however, and I am unwilling to include their
more interesting promotional email without permission. Their english
is only serviceable.

You all (as in David Schwab and Joe Gwinn) talked about the Gaglio patent
in January. Joe listed a patent application but the actual patent was
granted in 2002. It's a product and they want both buyers and investors.

-drh

[soundmasterg]

It figures that someone would have patented it. I wonder if it is enforceable since interleaving windings has been done forever in transformers and is a well known technique? I'm more interested in the sound difference anyway....

[DrStrangelove]

RTFP

It figures that someone would have patented it. I wonder if it is enforceable since interleaving windings has been done forever in transformers and is a well known technique? I'm more interested in the sound difference anyway....

The 2002 patent is only a starting point and shows an elaboration over simple bifilar windings. Gaglio has a few reasonable-looking pups over at the site at http://www.gagliopickups.com/products.html.

Get the US 6476309B2 patent at www.pat2pdf.org and see what they are so proud of. The PDF doc is about ~275k.

-drh

[Gagliopickups]

Gaglio Fantasma Pickups

Good morning to all of you. I'm Claudio from Roma Italy I represent the Gaglio pickups company.I casually stumbled upon your forum whilst surfing the net : I don't mean to intrude on your talks or anything but I'm at your disposition to answer any questions on our products.We've got a few guitarists who are using our pickups .John Scofield (unofficially of course).
We are just about to start distribution in the states and we are with Erica Monty in Canada at www.brianmonty.com .
Sorry but the English is limited all orthographic corrections are welcome.
Cheers Claudio,Roma.

[R.G.]

Interleaved windings on output transformers are used to reduce the leakage inductance between the two windings. It increases capacitive coupling between the windings.

However, sectional winding of inductors reduces the self capacitance. It's used in RF inductors. I think a pickup wound in side-by-side sections would be noticeably brighter.

By sections I mean winding more than one side-by-side section in the coil area. Self-supporting sections would be nice but just a fin of paper to separate them would be OK too.

[peskywinnets]

Old thread I know, but today I knocked up a small bobbin out of scrap blue cast acrylic (ahem, it won't win any beauty prizes!) & then wound it bifilar style using 0.1mm wire ...it came in at about about 95 ohms per coil 'leg' (therefore 190 Ohms in total end to end)

I will be hooking it up to a 'balanced' (breadboarded) differential amplifier over the next night or so - I'm quite hopeful that'll sound reasonable!

[Rick Turner]

I was winding Litz wire pickups in 1990 using 7 strands of 44 gauge wire in a slow rope twist. They're a bitch to wind, and the turns count is pretty low, and the DCR quite low. As I recall, I was going to about 1/6th the normal number of turns you'd expect on a typical bobbin, but the DCR was about 1/10th. I did Strat, Tele, P-Bass, J-bass, humbuckers, and Guild Starfire (Hagstrom) pickups. They sound great, though, and what was interesting was the low end response which could best be described as being very tight. I preamped some of them, and my friend Dan Schwartz ran one of his through a mic preamp in a recording studio; that one was a Guild Starfire (Hagstrom) pickup. Sounded fantastic. Don't know what effect this might have as prior art on any patents, but that was 20 year ago, and yes, I did sell some.

[peskywinnets]

Well, I got around to hooking it tonight (using a two stage differential amp made up out of 3 x TL072s) - even with very old (dead) strings on my test guitar it's sounds very 'full bandwith'. And as Rick has just pointed out ...there's something about the low end through a distorted amp sim - it struck me as being less muddy vs a high impedance pickup.

I'm quite impressed. But what has really knocked me out is the lack of noise (that'll be the common mode rejection going on -my first real experience with it ...& I'm sold!).

Probably put some new strings on my test guitar & have a dabble for a night or two!

Told you it was ugly.... (pointless going for aesthetics when you're just having a bit of a dabble)



(it's the close blue lump - disregard the other dual coil further up the guitar - that's a DIY sustainer)

At only 6mm tall, 9mm wide - with M4 steel 'grub screws' + neos on the bottom. It slides under the strings and sticks to the body....so no routing needed.

[David King]

I guess I don't see how you could have CMR when all the magnets are going the same way and it isn't a stack? Are you sure the low noise isn't just a result of low impedance?

Rick, The litz wire is only supposed to have an effect above audio frequencies. What you have then would be equivalent to a 39 AWG single strand, (or something like that) unless the capacitance changes somehow. That said Audiophools have been selling Litz speaker wire forever.

[Rick Turner]

David, I totally understand the logic of what you're saying, and I did indeed do all the calculations re. equivalent wire gauge. I do not have an explanation of why the low end of the pickups is so good. I did spend an afternoon with exotic cable guru George Cardas who happens to be a bass player and who thought the pickups sounded splendid. His theory re. the tightened up low end was that group delay...essentially phase response...had been improved. He certainly heard it as I did...as a tightening of the low end. Of course I expected an improvement in the top end as the self resonance of these is way above 20 K.

Also I agree re. your comments re. low noise. Bi, tri, or whatever you do with multiple parallel windings will do nothing for magnetically induced hum. Electrostatic noise will be lower as a result of the source...the pickup...now being lower impedance.

I still have several spools of the wire. I'll have to try another go-round with it when I'm not dealing with two out of my three luthiers being out sick or on paternity leave.

[peskywinnets]

I guess I don't see how you could have CMR when all the magnets are going the same way and it isn't a stack? Are you sure the low noise isn't just a result of low impedance?

When I say common mode rejection above - I'm not referring to the pickup signal or hum (the pickup doesn't buck hum) but with respect to noise rejection/cancellation that's being introduced with the amplification.

If I use traditional coil with say 200 windings of 0.1mm wire and feed the two connections into a single stage opamp amp...the output signal is noisy (as seen on a scope ....& heard). This is because with just 200 windings the pickup output is so low, that the signal is right down in amongst the noise floor - so obviously, when I ampliify the signal up (to get it to a useable level) the noise floor gets amplified up too ......result = Hiss City, Arizona. (ok, so this could be reduced a bit with a nicer psu, better shielding using discreet vs opamp etc)

However, if I now use a bifilar wound coil, with the same 200 windings, but wound as follows

'100 turns - Centre Tap -100 turns ' (+ve, com,-ve)

... & then connect it to opamp circuit configured as an instrumentation amplifier (well, after all I am feeding it with an instrument ) , there now ain't any noise to speak of on the output of the preamp output......it's severely reduced the electrical noise (& not just a little bit reduced - but more like, erhm, WTF! gone!!). And that's using the same noisy PSU, the same average opamps, the same screening arrangements - in other words, it's very forgiving!

[Joe Gwinn]

However, if I now use a bifilar wound coil, with the same 200 windings, but wound as follows

'100 turns - Centre Tap -100 turns ' (+ve, com,-ve)

... & then connect it to opamp circuit configured as an instrumentation amplifier (well, after all I am feeding it with an instrument ) , there now ain't any noise to speak of on the output of the preamp output......it's severely reduced the electrical noise (& not just a little bit reduced - but more like, erhm, WTF! gone!!). And that's using the same noisy PSU, the same average opamps, the same screening arrangements - in other words, it's very forgiving!

It's a standard approach, and any reasonable opamp type should achieve at least 50 dB of common-mode rejection at audio frequencies. What remains will be the opamp's own hiss contribution.

Actually, you can do the same thing without the center tap. Just connect a 10 Kohm resistor from either end of the coil to ground, to keep the common-mode voltage within the opamp's capabilities. Or, use two 10K resistors to ground, one per coil end, if one 10K resistor unbalances things unduly, allowing too much common-mode noise to leak through. Although the resistance of a 200 turn coil can be made low enough to not unbalance things too badly.

[peskywinnets]

It's a standard approach, and any reasonable opamp type should achieve at least 50 dB of common-mode rejection at audio frequencies. What remains will be the opamp's own hiss contribution.

I wasn't suggesting it was unique - or that I'd stumbled upon something novel - just a reveleation to me!

And for all it might be a standard approach within electronics in general, there really is cack all info about wrt to doing this type of thing with pickups (not much related info on thius very forum...I guess cos you you need a centre tapped pickup to dabble!) - this application note is where I got the inspiration/circuit from - http://www.intersil.com/data/an/an1298.pdf, but this fellow Brit is getting good results from a similar setup Pre-Amplifier For Balanced Magnetic Guitar Pickup « joebrown.org.uk ).

And having dabbled with several low impedance pickups with opamps operating unbalanced...I'm happy to report that a bifilar/instrumentation config certainly slams all other low impedance combos wrt s/n ratio.

But I'll certainly the way you mentioned a bash! (I'm presuming you mean a standard 'two wire' pickup into an instrumentation amplifier?)

[David King]

Rick, thanks for the clarification. It makes no sense but if your ears heard it, that should be good enough for me. I've seen twisted Litz OFC wire on Ebay before so maybe I can grab a spool and mess with it.

Pesky,
Thanks for the links, that's very helpful.
Joe, thanks as well.
So the CMR rejects everything but induced noise in the pickup and preamp self-noise and that's a 50dB drop vs a single ended coil and op-amp?
We all know that mics can be very quiet, especially if they cost some bucks. Why not just just plug a low impedance (150 Ohm) humbucker into a mic preamp or sound desk mic input via balanced XLR and call it good? (I'm lazy around PCB creation.)