Mismatched coils

[David Schwab]

I dug out some notes last night I made back in the 70's where I wrote down DC resistance readings on various pickups.

One was my old Hi-A (Bartolini) mini humbucker from about 1976. I noticed I wrote two numbers down, so I got the pickup out and read it.

One coil is 3.33K and the other is 4.52K!

So I guess this stuff has been done for a while now.

Just thought someone might find that interesting.

[kevinT]

I dug out some notes last night I made back in the 70's where I wrote down DC resistance readings on various pickups.

One was my old Hi-A (Bartolini) mini humbucker from about 1976. I noticed I wrote two numbers down, so I got the pickup out and read it.

One coil is 3.33K and the other is 4.52K!

Forgive my poor math skills....what does that equate to with regard to a percentage and what do you think the number of turns of wire difference to be?

[David Schwab]

Forgive my poor math skills....what does that equate to with regard to a percentage and what do you think the number of turns of wire difference to be?

I'm not sure. I have no idea what size wire is used, or the coil sizes ... the pickup is cast in epoxy. This is a very early Bartolini that I bought directly from them when the Hi-A pickups first came out. I'm sure it uses some of the features in his patents, which I think his newer pickups do not. He sometimes used multiple coils linked up. Magnetic viewing film shows two bar poles.

But I was just winding some pickups the other day and got similar results winding one with 1,000 turns less than the other. I was actually doing two different pickups (neck and bridge) and then decided to swap the coils from each to try the mismatched pairs out.

I'm still testing the pickups out, so I haven't decided if I'm going to wire them up that way.

[Zhangliqun]

I'm a big mismatch fan.

[PoorMan]

I'm a big mismatch fan.

+1

[madialex]

The only thing that I cant get around is the size diff in the coils. One is full, the other is about 3/4 full it looks odd to me. That why I went to another method and a smaller offset in the coils, I get the same effect but with less offset.

What are you guys thoughts or what are you doing for that problem? Just curious.

[PoorMan]

The only thing that I cant get around is the size diff in the coils. One is full, the other is about 3/4 full it looks odd to me. That why I went to another method and a smaller offset in the coils, I get the same effect but with less offset.

What are you guys thoughts or what are you doing for that problem? Just curious.

Not an issue for me...but I do less than 1k bias. 1k is a pretty big difference IMO.

[Ruel]

I dug out some notes last night I made back in the 70's where I wrote down DC resistance readings on various pickups.

One was my old Hi-A (Bartolini) mini humbucker from about 1976. I noticed I wrote two numbers down, so I got the pickup out and read it.

One coil is 3.33K and the other is 4.52K!

So I guess this stuff has been done for a while now.

Just thought someone might find that interesting.

With this much mismatch, how is the humbucking effect?

[Zhangliqun]

The only thing that I cant get around is the size diff in the coils. One is full, the other is about 3/4 full it looks odd to me. That why I went to another method and a smaller offset in the coils, I get the same effect but with less offset.

What are you guys thoughts or what are you doing for that problem? Just curious.

It's not a problem if it sounds good.

[David Schwab]

With this much mismatch, how is the humbucking effect?

I thought I posted an answer to this... guess I didn't hit submit!

It's a very quiet pickup. I had it in my '74 Ric 4001 with a sidewinder at the neck, and even with no string ground, the bass was dead quiet. Fully shielded with copper foil.

I read that jazz guitarist Tuck Andress had a custom made Bartolini pickup for his guitar, and he insisted on matched coils. So this must have been a common feature in Hi-A's.

[PoorMan]

It's a very quiet pickup.

This is something I've discovered since I started winding (contrary to printed word research). Empirical evidence has taught me that the coils don't need to be matched as closely as is commonly believed to make for a quiet pickup.

Pickup winding...the black art.

EDIT: EDIT: Ah yes. Now the quote looks right.

[David Schwab]

EDIT: DAMMIT!!! Why did the quote screw up?!?!?! Oh well...

You lost the first bracket and forward slash on the closing quote tag when editing the quote. You can still fix it.

The other thing we don't know about the pickup is if he used different size wire, but the same number of turns, on each coil.

I can see with magnetic viewing film that it has two blade poles, but it might have more than two coils as well. He used to do that with the early pickups as outlined in his two patents.

[Joe Gwinn]

It's a very quiet pickup.

This is something I've discovered since I started winding (contrary to printed word research). Empirical evidence has taught me that the coils don't need to be matched as closely as is commonly believed to make for a quiet pickup.

Pickup winding...the black art.

How well the coils must match was discussed some time ago, so a search of the archives in in order.

The basic point is that a 10 decibel reduction in hum is noticeable, and a 20 decibel reduction is for all practical purposes perfect. So, how close must the coils be for 20 dB?

A humbucker has two coils. Each coil generates a music voltage and a hum voltage. A series-wired humbucker is arranged such that music voltages add while hum voltages subtract, the objective being that the hum voltages exactly cancel. Let us designate the hum voltages as V1 from one coil and V2 from the other.

The formula for decibels given voltages is dB = 20*Log10[V1/V2], so 20 dB implies a voltage ratio of ten. This is the ratio of the difference of hum voltages divided by the sum of hum voltages. So, if the hum voltages are matched to within 10%, the hum reduction will be at least 20 dB.

[PoorMan]

How well the coils must match was discussed some time ago, so a search of the archives in in order.

The basic point is that a 10 decibel reduction in hum is noticeable, and a 20 decibel reduction is for all practical purposes perfect. So, how close must the coils be for 20 dB?

A humbucker has two coils. Each coil generates a music voltage and a hum voltage. A series-wired humbucker is arranged such that music voltages add while hum voltages subtract, the objective being that the hum voltages exactly cancel. Let us designate the hum voltages as V1 from one coil and V2 from the other.

The formula for decibels given voltages is dB = 20*Log10[V1/V2], so 20 dB implies a voltage ratio of ten. This is the ratio of the difference of hum voltages divided by the sum of hum voltages. So, if the hum voltages are matched to within 10%, the hum reduction will be at least 20 dB.

Very interesting stuff, Joe.

[Jim Darr]

I know this is a very old tread, but is has some great input to review and understand.

I personally like a fairly big mismatch between the coils for certain 50’s HB sounds. For a T-Top sound, I go for a more even coil match. Anyway, that is just me. To be honest, I don’t notice that big of a hum difference between the two formulas.