Newbie Impedance question

[bob_h81@yahoo.com]

Hi Guys,

I'm new here, so make fun of me if you need to, but I'm just here to learn. In fact, today is my first day here. What a great find you guys are.
I'm interested in opinions of my findings on a new pickup I've just wound.
I used a Fluke LCR meter because it's the only one I had access to. My Extech 380193 will be here in a few days. (thank you amazon.)

Here goes:

Inductance: 20.27 mh

Capacitance: 1239.2 (1khz) nf

Resistance: 161.5 ohms

What, if anything, can be said about this?
According to my frequency formula, the resonant frequency is somewhere around .10042 hz.
Somewhat below normal hearing range, I think.

Anywho, please take the time to weigh in on this. I'm open to all comments and questions.
Oh yeah, I slapped it in my '72 strat.....doesn't make a sound.


Thanks,
Bob.

[SonnyW]

If it is a normal passive type strat pickup it should have something like these readings:
Inductance: 2 - 3 henry
Capacitance @ 1kHz: 8-10 nf
DC Resistance: 5 - 6 k ohms.

Unless you are working on an active design, it sounds like possibly some shorted turns, but need more info, such as number of turns etc..

[bob_h81@yahoo.com]

Thanks Sonny,

After reading a few dozen posts here, I realize I need to read a few dozen more.
I don't know what an 'active' design is, let alone how to make one. I'm assuming it would use some sort of pre-amp, no?
I wish I could tell you more, as in I wished I had counted the turns. I'll strip it off and count next time, but only after I've gleaned all I can from this experience.
Please, tell me more about the 'etc' part. What else would you want to know?
I've used litz wire, 10 strand/46 ga. and wound as much as it would take. Litz wire works good in other coils, maybe not so much in guitars....Oh well, I had to try it.
I just spent the last 5 minutes at your website. Pretty danged amazing. I'll need to spend more time there.
I've checked the numbers of the P/U I removed from the strat. Pretty much in line with the numbers you gave me.
Don't be afraid to point me in a direction.

Thanks,
Bob.

[nickb]

I'm pretty sure you can't measure the p/u parameters using an LCR meter. They are designed to measure the value of one type of component at a time. In a p/u you have more than one and this confuses an LCR meter and so gives misleading results. You need to use a network analyzer.

As for it not working in your Stat, check the DC resistance with an ohmmeter, it should be in the Kohm range. If not, then Sonny's suggestion is likely correct - you have shorted turns. If the resistance is OK, then you likely mis-wired the pickup into your stat.

[nickb]

No, Litz wire in not suitable. It's designed for high performance RF coils. You need lots of turns. Litz wire is too large a diameter.

[SonnyW]

By the way, welcome to the forum.

I don't know much about the effect of using litz wire. It is my understanding that the benefits of that type of coil construction are more useful in the lower RF range. I would guess that 10 strand 46 litz wire should give you something in the neighborhood of 1/10 of the number of turns, that a normal strat pickup would have. Since the inductance will vary as the square of the number of turns, this is going to give a whole lot less inductance. A typical strat pickup is wound with #42 gauge single wire. Also 10 conductors in parallel are going to have much less DC resistance than a single wire would have. The biggest factor that determines the output and the character of a given pickup is inductance. The more inductance, the more output, and the darker the tone.

The active designs do use preamps and thus need less inductance.

The etc part, or other things that would affect the design are wire gauge, number of turns, coil dimensions (such as distance between the upper and lower fiber flatwork), type of wire insulation, magnet alloys.

I would say to try winding it with #42 wire. Things that can be varied in the winding are the number of turns, tension, and to a less extent the spacing between the flatwork. Different wire insulations make for different amounts of capacitance and tones. Vintage style strat pickups used heavy formvar insulated wire. More modern designs use single insulated poly or plain enamel. There is a lot of information here on the forum to peruse through on the effects of various combinations.

[bbsailor]

Hi Guys,

I'm new here, so make fun of me if you need to, but I'm just here to learn. In fact, today is my first day here. What a great find you guys are.
I'm interested in opinions of my findings on a new pickup I've just wound.
I used a Fluke LCR meter because it's the only one I had access to. My Extech 380193 will be here in a few days. (thank you amazon.)

Here goes:

Inductance: 20.27 mh

Capacitance: 1239.2 (1khz) nf

Resistance: 161.5 ohms

What, if anything, can be said about this?
According to my frequency formula, the resonant frequency is somewhere around .10042 hz.
Somewhat below normal hearing range, I think.

Anywho, please take the time to weigh in on this. I'm open to all comments and questions.
Oh yeah, I slapped it in my '72 strat.....doesn't make a sound.


Thanks,
Bob.

Bob,

Welcome to the forum.

Rick Turner reported about using litz wire for making pickups with some interesting results. Search on his name on this forum.

Your 10/46 Litz wire is equal to AWG36 with an OD of .009 inches. I guess that you have about 700 to 750 turns of wire on the bobbin. You will need a matching transformer such as P/N 42TM117-RC (1K to 50K) from Mouser Electronics (do a web search). This is a small transformer and will fit inside the control compartment. You can only mix this low impedance pickup with other high impedance pickups after going through the matching transformer, otherwise make all the pickups low impedance and rewire the guitar like the Les Paul Recording Guitar with a 2.5K volume pot. Then, put a microphone matching transformer at the amplifier end to boost the low impedance output of the guitar back up to a high impedance level with a Shure A95U transformer. Use a stereo jack with balanced line (2 conductor shielded mic cable) with an XLR connector on the amp end with pin 1 being the sleeve or ground, pin 2 being the tip and pin 3 being the ring on the guitar end.

You cannot measure the capacitance of the pickup with an LCR meter. You must use an audio generator feeding the pickup through a 1M ohm resistor and observe the voltage across the pickup to see the resonance frequency. Then, knowing the pickup inductance, you can calculate the effective coil capacitance. Most high impedance pickups resonant between 3KHz to 5KHz mainly due to the cable capacitance being in parallel with the pickup output. Cable capacitance dwarfs the smaller pickup coil self capacitance, but it all adds up.

The Extech LCR will be a valuable tool for making guitar pickups and experimenting.

Provide more details about your project so other folks can jump in and provide input.

Learning by doing. Let the fun begin!

Joseph Rogowski