PE vs Poly wire isolation experiment with sound samples included

[ScottA]

In post # 2 Mr Candy shows images of a table listing DCRs in the mid 7 KHz range and 100 KHz L of about 4.4 H, along with the corresponding frequency response plots. These are typical values for fully assembled humbuckers.

Two humbucker bobbins wound to these specs and connected in series without pole pieces would have significantly lower inductance, less than half that.

For comparison, I've measured (using an Extech, and a Syscomp with a measurement circuit set-up similar to Errede's) an uncovered Duncan '59 at:

R @ 100 Hz (pretty close to DCR): 9070 Ohms
L @ 100 Hz: 4.937 H
F resonant: 6924 Hz

Bobbins alone (no pole pieces or baseplate):

R @ 100 Hz: 8916 Ohms
L @ 100 Hz: 2.256 H
F resonant: 9523 Hz

Duncan reports (for a full pickup):

DCR (bridge): 8130 Ohms
F resonant: 6 KHz

Pretty close to my values above.

What coil is used for what:
For sound samples the following coils were used:
Poly
Coil №3 Poly LS- 83 5000NT(screws)
Coil №5 Poly LS- 83 4900NT(slugs)
PE
Coil №4 PE LS- 83 5000NT(screws)
Coil №6 PE LS-83 4900NT(slugs)

As for coils with 30LS, they were used as test coils to identify the influence
of wire layout in a row on the frequency characteristics.

Spectrograms and Echar of pickups made

PE
[ATTACH=CONFIG]14864[/ATTACH] [ATTACH=CONFIG]14865[/ATTACH]

Poly
[ATTACH=CONFIG]14866[/ATTACH] [ATTACH=CONFIG]14867[/ATTACH]

Materials:

[ATTACH=CONFIG]14868[/ATTACH] [ATTACH=CONFIG]14869[/ATTACH]

To be continued post 3...

[ScottA]

Decreasing the winding capacitance should get the resonance up, I agree. But search the available literature, I haven't seen anyone quoting anything close to that high with this kind of design at these specs.

MrCandy claims to be able to vary the coil capacitance by about a factor of twelve by use of winding techniques. That is, the resonant frequency can vary nearly 3.5 times. This would make unusually high resonant frequencies possible, as well as unusually low ones.

SD does not state the conditions under which the frequencies are measured. I suspect that there may be a length of cable in use. MrCandy incorrectly claims that a 1 Mohm input impedance (even with small capacitance) can significantly affect the resonant frequency, so there might be something strange about his setup. Also, you have to be sure whether he is measureing the coil alone or with slugs in place. There might be somewhat less than a factor of two difference.

[Mike Sulzer]

Decreasing the winding capacitance should get the resonance up, I agree. But search the available literature, I haven't seen anyone quoting anything close to that high with this kind of design at these specs.

Nor have I. He has not explained how he winds very low capacitance coils (his trade secret?). There are well known techniques for doing this, but I do not see how it can be done with pickup bobbins and such small wire.

[MrCandy]

In post # 2 Mr Candy shows images of a table listing DCRs in the mid 7 KHz range and 100 KHz L of about 4.4 H, along with the corresponding frequency response plots. These are typical values for fully assembled humbuckers.

Two humbucker bobbins wound to these specs and connected in series without pole pieces would have significantly lower inductance, less than half that.

For comparison, I've measured (using an Extech, and a Syscomp with a measurement circuit set-up similar to Errede's) an uncovered Duncan '59 at:

R @ 100 Hz (pretty close to DCR): 9070 Ohms
L @ 100 Hz: 4.937 H
F resonant: 6924 Hz

Bobbins alone (no pole pieces or baseplate):

R @ 100 Hz: 8916 Ohms
L @ 100 Hz: 2.256 H
F resonant: 9523 Hz

Duncan reports (for a full pickup):

DCR (bridge): 8130 Ohms
F resonant: 6 KHz

Pretty close to my values above.

It would be nice if you describe in detail how you measure.
1) What are the components of your measuring cable?
2) Do you have IN high Om devider/probe in your measuring cable?

I will illustrate something for you and Mike Sulzer whom we respect for his inquiring mind:

We will take the same pickup here as in the experiment above PE 5000/4900 83LS and we will measure it with different ways:

1) Using active probe in witch IN characteristics are determined by gate of MOSFET, Cig - 2.1 pF and Rin -"tend to infinity"

This spectrogram you can see watching video above.

2) Using passive devider/probe Rin - 1M


3) Using coaxial 3 foot cable without devider/probe( I think you measured this way.)


We assume SD measures the third way


On the attached photo we can see BNC connector with pins connected

[MrCandy]

How were the sound clips recorded ?

Sound clips were recorded like that:

+ TC Electronic audio interface and GENELEC monitors.
Mastering was made without effects and EQ.

[MrCandy]

I don't tell clients the offset. The point is 100 turns offset is nearly nothing tonally. I just know from experience that 100 turns at the end of the coil is going to come to around .7K in resistance +/- based upon wire diameter and or turn per layer count. I wind everything in a room that I keep at 74 degrees F year round and since I mic the wire and am familiar with the materials, a resistance reading for each coil right of the machine is useful. You might be surprised to know that I take QC very seriously which is actually why I see problem with the wire diameter as it relates to this test.

Sorry for misunderstanding, language barriers you know
In the experimental pickups we show here namely PE and Poly 100 turns offset will do nearly nothing tonally.
Because coils AFC is very close. But this pickups will sound with the clothespin on the nose anyway.
The fact is that 100 turns offset can affect on sound pretty much but in other circumstances

[MrCandy]

What I think is a valid experiment, is that you can compare 5k TPL of each.
If This size is typical for his wire, and the other is typical for that particular brand of PE.
It does demonstrate the diff, between 2 wires.
I wonder what brand of wire the Mojo PE is.
I have a 6 pound roll of MWS, that was made by REA, and on the spool it says 1.61 Ohm per foot.
I don't have a micrometer so I don't know the size.
A full spool of My PE wire is always low in DCR compared to my other wires.
He's already done all the work.
So we might as well have fun with the experiment, and see how it turns out, and go from there.
Terry

Could your please measure it and tell us 10footDCR/temperature of your PE.
You dont really need a micrometer to understand bare copper D.
If your PE copper D will be close to our POLY copper D then you can help us
with more appropriate experiment.
We can offer you an exchange 1:2.
We will send you 12 lb of our POLY(42AWG or 43AWG of your choice or 42AWG and 43AWG both 12 lb total) and you will send us 6 lb of your PE if you agree of course.

[MrCandy]

Yes, and the coil will be a different size, and sound different.

Unfortunately this test is flawed and is not a test of poly vs. PE, but is instead a test of wire diameter.

Wind a coil with 42, and then 43, and see if they don't sound different in the same way as in this test.

Because of that, I say it's #2. I liked #1 the best.

Please check this.

[JGundry]

Mr. Candy,

It is very easy to get a large variety of Poly wire. I would be more interested in you offering PE wire that was not from the two known sources here in the USA.

[Mike Sulzer]

I will illustrate something for you and Mike Sulzer whom we respect for his inquiring mind:

We will take the same pickup....

I believe that you are referring to our discussion concerning how much the resonance of a coil (no cores) shifts when you load it with the 1 Meg ohm input impedance of a measuring instrument. What you have shown here is the measurement for a whole pickup, which is a different matter. We can discuss that if you wish, but let's first look at a measurement of a coil to complement the calculation I showed you earlier. (If I remember correctly, I predicted about 20 Hz shift for a certain set of parameters.)

The coil is about 3.5 K ohm #43, on a humbucker bobbin. It is driven with random noise through a very small driver coil. The current through the coil is monitored by measuring the voltage across a resistor in series with the coil. This is one input to a cross-spectral measurement. The coil is connected to a very high input impedance buffer, the output of which is the other input to the cross spectral analysis. The spectrum is measured with and without a 1 Meg resistor across it. The results are scaled by 1/f so that we are looking at the response of the coil circuit.

The difference in frequency between the two peaks is 11 Hz.

The two spectra are shown here:


edit: I connected 460 pf across the coil to lower the resonance; otherwise it would be too high for the sampling rate.

[MrCandy]

I believe that you are referring to our discussion concerning how much the resonance of a coil (no cores) shifts when you load it with the 1 Meg ohm input impedance of a measuring instrument. What you have shown here is the measurement for a whole pickup, which is a different matter. We can discuss that if you wish, but let's first look at a measurement of a coil to complement the calculation I showed you earlier. (If I remember correctly, I predicted about 20 Hz shift for a certain set of parameters.)

The coil is about 3.5 K ohm #43, on a humbucker bobbin. It is driven with random noise through a very small driver coil. The current through the coil is monitored by measuring the voltage across a resistor in series with the coil. This is one input to a cross-spectral measurement. The coil is connected to a very high input impedance buffer, the output of which is the other input to the cross spectral analysis. The spectrum is measured with and without a 1 Meg resistor across it. The results are scaled by 1/f so that we are looking at the response of the coil circuit.

The difference in frequency between the two peaks is 11 Hz.

The two spectra are shown here:
[ATTACH=CONFIG]14995[/ATTACH]

edit: I connected 460 pf across the coil to lower the resonance; otherwise it would be too high for the sampling rate.

Hi Mike

I want ro remind you what exactly started this discussion anyway:
In "Machine vs Hand" theme you pointed that passive probe 10M Rin is too high and also you mention that 1M probe will be enough.
I ve showed you some measurements on that using few measuring methods. 1Mom passive probe was not exactly correct.

I ve took 5000 NT coil 42AWG PE (this unwaxed air coil was used for attemt to create dark horse PE clone for POLY from the experiment above(unlucky one)
and measure this coil for public exapmle using different measuring methods.
I will not try to argue that active probe with 1M parallel will measure correct(the difference will be only in amplitude values), but this statement is not affect passive probe with 1M.
Active probes are little publicly available, if you use passive probes 10M is the best available choice.

1)Active probe


2)Active probe and driver coil


3)Passive probe 10M driver coil


4)Passive probe 1M driver coil


Continue at post 2...

[MrCandy]

5) Driver coil coaxial cable 3foot


Also some addition information on this issue is available here

[Mike Sulzer]

Hi Mike

I ve showed you some measurements on that using few measuring methods. 1Mom passive probe was not exactly correct.

Forgive me if I am missing some of what you intend, but one thing that I think is important is that you have shown two basic types of measurements: 1. impedance measurements, which show the pickup impedance, or actually the pickup impedance in parallel with a 1 Meg resistor, and 2. response measurements, which use a driver, and the pickup operates into an impedance of near infinity, 10 Meg, or 1 Meg.

There should be a close relationship between the two kinds of measurements because the driver coil induces a signal in the coil and the response to this signal is a function of the coil impedance. However, we have to be careful in order to get a good correspondence. In particular, the comparison between the impedance measurement with 1 Meg and the driver with 1 Meg should be nearly the same. I want to describe one possible reason for the the difference that you measure.

Here is a measurement that I made last week that I believe that is relevant. Unlike the one I posted earlier that was one coil with no cores, this one is a humbucker pickup, two coils in series and with cores. Both these factors tend to increase the differences between the measurements I made with a very high input impedance buffer on the one hand, and with a 1 meg input impedance on the other. The first does this because the impedance of the system is doubled with respect to the resistor, and the second because the cores lower the Q and broaden the bandwidth and alter the shape of the curve.

The measurement is shown here:

I have scaled the measurement by 1/f because this compensates for the increase in response due to the law of magnetic induction. (Note that the y axis scale on this plot is amplitude, not power. In the plot in the previous post it was incorrectly labeled as power.) This response has the typical shape of a steel cored humbucker, falling to the middle frequencies, but still rising to a peak. This is only possible because the load placed on the pickup inductance by the eddy currents is equivalent to a resistor with value rising with frequency in series with the leakage inductance. That is, the effective load on the pickup coil is much higher at high frequencies than low frequencies.

The difference in the frequencies of the peaks with and without the 1 Meg resistor is about 165 Hz. The question is this: how much would this change if one did not scale by 1/f. I tried this, and the answer is that the difference change to about 330 Hz, about a factor of two. If we want to measure the response of the circuit, we need to excite it with equal power at all frequencies, or compensate after the measurement.

I do not think that you are scaling by 1/f in your response measurements. I am suggesting that this could make your impedance and response measurements agree more closely.

[Mike Sulzer]

One more comment on the previous post:

Even correcting for the response of the pickup coil to the driver coil, I would not expect its response and the impedance measurement to match exactly at the peak for low Q. After all, they are very different at low frequencies. The impedance measurement decreases towards low frequencies approaching the coil resistance, while the response measurement is almost flat. The difference should decrease towards the higher frequencies, but they should not be exactly the same.

[marku52]

One thing that concerns me, in some of the pictures I have seen with the driven coil/sensed coil measurements, the one coil simply sits on top of the other. This would allow capacitive coupling between the two coils to add error.

When I do driven/sensed coil measurements, I put a sheet of grounded nickle silver between the 2 coils to eliminate capacitive coupling.