So what exactly is needed to make this graph?

[belwar]

I've been looking into documenting some of changes that I make when designing a new pickup.. I love statistics, and charts like the one below just blow my mind.. LOVE IT. Problem is I have no idea how to make these!

Can someone tell me what is involved with making one, what tools are needed, and or a process? The existing tools I have are a a good Fluke DMM, Extech LCR Meter, Audio Oscillator (20-20,000hz), and I just bought a USB oscilloscope but havent received it yet.

Also, does anyone have insight as to how to read these charge... Use the one below for an example.. Can you tell me how some of these peaks or valley represent changes in tone...



...and dont worry spence, I know its not nessesary, and I still go by the tone first.

[shane1b4u]

What chart? Where? Below what? Am i missing something... I haven't gotten my new glasses yet, but they're on the way.

[shane1b4u]

some kind of glitch.. it wasn't there a min ago...

[tedmich]

maybe one of these?

Freeware: How Frequency Analyzer Works
YmecStore (Yoshimasa Electronic Inc.)
Real-time plot. Universal software oscilloscope graphical user interface GUI DLL library for data acquisition modeling debugging

[Possum]

Fuzzmeasure, its free.
Your chart shows a single coil that is very bright with a 10khz resonant peak, looks like ice pick tone to me. A handwound single coil would show a smoother slower curve up to 10khz. This may be an impedance curve and I don't know much about those....

[Possum]

This is what Fuzzmeasure puts out, its actually designed to measure speakers and rooms but it works perfectly for pickups and does a sweep from 20-20khz, this is an old comparison I did of two Little Charley prototypes. The free version will do 2 comparisons, if you want more you have to pay the license fee. Pretty simple to use and gives you a good picture of whats happening....

[Joe Gwinn]

Originally Posted by shane1b4u

some kind of glitch.. it wasn't there a min ago...

I saw that too. For some reason, it took a long time to load, although the file isn't large.

[Joe Gwinn]

Originally Posted by Possum

This is what Fuzzmeasure puts out, its actually designed to measure speakers and rooms but it works perfectly for pickups and does a sweep from 20-20khz, this is an old comparison I did of two Little Charley prototypes.

How did this pickup sound, man? Curves look like it should be pretty bright.

[JGundry]

I think the more interesting test would be to use real time frequency analysis software. If you cold figure out how to input white noise rather that a frequency sweep into the pickup you could see how changes react in real time. Cover material, screws, distance from the driver, heat.... could all be seen in real time.

I have used Signal Scope for real time frequency analysis for tap tuning and Helmholtz resonance measurements for violin making.

[Possum]

Yes the pickups are bright, these are blade pickups with not alot of wire on them. I don't think it makes a huge difference what software you use as long as you use it and only it for everything you measure. Fuzzmeasure will do a log sweep, MLS and MLS pink noise filtered. I'm using a 50 ohm drive coil the way Lemme shows and just the standard Mac in/out's. This was one of the few times I found any use for frequency analysis, I had two prototypes that sounded similar and I needed to know something about what was going on...

[David Schwab]

Originally Posted by Possum

Your chart shows a single coil that is very bright with a 10khz resonant peak, looks like ice pick tone to me.

It's probably a bass pickup. Maybe a Lane Poor? They have a very zingy top end.

[ModulusMK]

Originally Posted by David Schwab

It's probably a bass pickup. Maybe a Lane Poor? They have a very zingy top end.

Yes, it is the Lane Poor. David King posted it in my topic.

Also I do not know how to achieve the valley at 6KHz, the peak could be somehow done, but that valley... (I guess the valley is for to lower the 'chunky sound' when you hit the strings harder but with the peak at 10KHz you still keep the smooth crystal high end.)

You need a coil with somewhere 80pF of capacitance and about 3H of inductance to get the peak at about 10-10.5KHz.

Is there any possibility for a passive circuit inside the pup? :/ (maybe if it is two strand wire at the ends where they connect there is any cap in series...?)
It is strange for a coil to have that kind of curve without anything else... maybe if it is humbucker two coils with different wire gauges...?

[David Schwab]

They didn't design that to have that valley... it just happened. There's some examples like that in the book Animal Magnetism for Musicians.

One of the sidewinders in the book got a funky dip like that from having 4 poles, and another from having a thick aluminum cover, which produced eddy currents.

So it could be the result of phase cancelation due to the coil arrangement.

You really can't design for that kind of response IMO.

[ModulusMK]

It might be the valley of those factors but if so every LP pickup design must be the same if they have that kind of response curve.

I would really like to know the MMs' curve how it looks like. But if that is the signature sound for the pups I think the curves must be similar to each other.

Is there e-book version of the book? I've read reviews about it and it received very positive critics. If there isn't any can you scan all the pages about making pickups and make it as pdf?

[David Schwab]

Originally Posted by ModulusMK

It might be the valley of those factors but if so every LP pickup design must be the same if they have that kind of response curve.

Not really, because they had different models of pickups.... wide & narrow aperture, single coils, side winders, etc.

You would have to test each model to make that determination.

[ModulusMK]

Of course, but the high end I think is somewhere similar.
However, can you scan the pages of the book with pup info construction?

[Bruce Johnson]

Maybe I'm missing something in the discussion.....

I understand about the spectrum analysis software measuring the output of the pickup. But what are you using to drive the pickup? Is it in a guitar, and you're picking a string? Are you creating a sweeping field over it?

[belwar]

Originally Posted by Bruce Johnson

Maybe I'm missing something in the discussion.....

I understand about the spectrum analysis software measuring the output of the pickup. But what are you using to drive the pickup? Is it in a guitar, and you're picking a string? Are you creating a sweeping field over it?

BINGO.

Thats the million dollar question..

Im guessing there are several parts to making a graph like this..

1 - An oscilloscope.
2 - Some form of driver .. something that creates a uniform signal that can be produced the same over and over again.

What type of driver could be used? What would be an example?

[David Schwab]

Go to post #10 and read what Dave wrote. That's one way to do it. The other way, you put the pickup right into the circuit.

[Possum]

Helmut Lemme, read his translated article on pickups and how to use a driver coil. I think its the best way because putting the pickup IN a circuit is actually changing things, you're not actually reading what the pickup by itself is doing. If you're reading a pickup IN a guitar you're also getting a picture of your guitar, change guitars and you won't get the same results. this is sort of required reading in pickups 101, third classroom on the right, down the hall:
BuildYourGuitar.com :: The Secrets of Electric Guitar Pickups

[Possum]

I see he has a new version of his pickup analyzer, I emailed him once trying to get a price, no answer. He also added some comments about how humbuckers function and the difficulty of reading them. Very cool....

[belwar]

Ahh that mythical device.. If you ever get a price, or find out about it let me know. I dont think they exist..

So I get what I have to do know is build a driver.. and finish the work for gundry. the SOB is a slave driver.

[Joe Gwinn]

Originally Posted by Possum

I see he has a new version of his pickup analyzer, I emailed him once trying to get a price, no answer.

I recall that it was 1,000 Euros, which at current exchange rates is about $1,500, exclusive of shipping and taxes.

[JGundry]

Originally Posted by belwar

Ahh that mythical device.. If you ever get a price, or find out about it let me know. I dont think they exist..

So I get what I have to do know is build a driver.. and finish the work for gundry. the SOB is a slave driver.

Slacker.

[Yves]

Originally Posted by Possum

Yes the pickups are bright, these are blade pickups with not alot of wire on them. I don't think it makes a huge difference what software you use as long as you use it and only it for everything you measure. Fuzzmeasure will do a log sweep, MLS and MLS pink noise filtered. I'm using a 50 ohm drive coil the way Lemme shows and just the standard Mac in/out's. This was one of the few times I found any use for frequency analysis, I had two prototypes that sounded similar and I needed to know something about what was going on...

But I think your set up might not be ideal (correct me if I am wrong): if you are driving your coil with the standard Mac out, your are driving the coil with a voltage generator (I assume your sine sweep is constant in amplitude throughout the frequency?).
But the coil impedance makes the current flowing into it frequency dependant.
And the magnetic field produced by the coil is proportional to the current flowing into it.
So you are producing an exciting field that is frequency dependant, which is not exactly what you want (i.e. your are not only ploting the pickup frequency response curve, but also the exciting coil response).
You would need a "calibration file" (something like with acoustic software and measurment mic) to "reverse match" the coil influence and produce a constant field throughout the frequencies, or drive the coil with a constant current. Lemme states it actually, that he needs to drive the coil with a constant current source, hence his "black box" I guess.

Well, as long as you use this to compare pickups, you've got an idea of what's going on, but not an absolute measurement IMO.

[Bruce Johnson]

But....If you use a driver coil like Lemme does, doesn't that take the pickup's magnets completely out of the test? If the driver coil is creating a sweeping cyclic magnetic field, which the pickup's coil is detecting, would any changes in the pickup's magnets make any difference in what you'd read on the spectrum analyzer? It seems to me that a driver coil setup could be useful for comparison testing of pickup coils, but not of much value for testing the complete pickup.

Or am I completely missing something here?

[Yves]

Originally Posted by Bruce Johnson

But....If you use a driver coil like Lemme does, doesn't that take the pickup's magnets completely out of the test? If the driver coil is creating a sweeping cyclic magnetic field, which the pickup's coil is detecting, would any changes in the pickup's magnets make any difference in what you'd read on the spectrum analyzer? It seems to me that a driver coil setup could be useful for comparison testing of pickup coils, but not of much value for testing the complete pickup.

Or am I completely missing something here?

Yes, I think you are right indeed: the exciting coil not only modifies the magnets field but also must intoduce mutual coupling with the pickup coil.

Anyway, for sure, such a setup is usefull for testing and comparison, but it doesn't replace a string vibration.

[Possum]

Yeah my setup is probably a bit crude but there really is no standard way to do this even at higher levels and expensive gear. That college that did a physics course on pickups came up with their version, very complex. If you only use one method and know what the results mean and keep it constant is all that matters. The driver coil needs to be low impedance, I used 38 gauge wire if I remember and only about 50 ohms. Yes the magnet is involved, you are exciting a coil that is butt up against the magnet in the field of the magnet so of course what magnet you have in there has a direct effect on what your graph will show.

[David Schwab]

Since we just discussed 'scopes, this very thing was talked about.

Take a look at Daniel's post here:

Which Oscilloscope for a pickup maker?

That's how he derived the graph he posted.

[Possum]

Here's a quick and dirty comparison of slug coil and screw pole coil on a '63 early Patent. Guess which is the slug coil? BTW, my driver coil is being driven by an amplified speaker for computers , not straight out of the Mac as I said before, crude but it works fine enough for my purposes. I'm actually setting up to do some experiments using this stuff since the LCR meter doesn't see very well in the higher frequencies...

[Possum]

One question I have is in the Lemme article he says this method is terrible for looking at humbucker frequency responses and mention there are notched frequencies even on each string because of the cancelling coils, I wonder what method would show these notches, I've known about this for years but have never actually seen it plotted on a graph. And how would you see harmonics of any pickup as well? I'm just full of questions aren't I

[Yves]

Originally Posted by Possum

BTW, my driver coil is being driven by an amplified speaker for computers , not straight out of the Mac as I said before

Still not driving a constant current though.

Actually, I've come accross this:
http://www.analog.com/static/importe...7846AN_843.pdf

I believe this could be a starting point for someone willing to set up something less "crude"

This article BTW describes the HOWLAND CURRENT SOURCE (p5): apart from the actual analog device chip this current source set up allow to drive an impedance with a fixed current independent on the frequency.

Finally, an evalluation board for the Anolog device chip is availlable (I think at arround 170$ or so), with a built in usb interface and a PC software that is ready to use the board.

Now this setup allows an impedance measure accross the frequency range, but I guess it could be used to drive a coil with a fixed current accross the frequency range (the device has a built in sweep tone generator)

FWIW

Originally Posted by Possum

crude but it works fine enough for my purposes

That's what count anyway

[Possum]

I'm finding Fuzzmeasure has its flaws, I tried substituting different slugs I know sound very different and getting the same graph. Plus if I lower the input volume the graph doesn't drop it stays the same. I looked for a couple hours to try to find some other audio software for the mac that will do similar graphs, and no luck. The only other software I know will do it is Mac The Scope for $500, too expensive for simple testing. That device someone posted for $200 looks interesting but that company doesn't answer email, I asked them if I couldn't navigate their very complex Mac installation instructions, written by someone else no less, could I get a refund. No reply. At this point I'm thinking of getting an LCR meter that will do 10khz test signal but that frequency is really up there past most pickups peaks, especially humbuckers, so wonder ho useful it would be not really getting a good reading on where the action is happening.

[Possum]

Is there such a thing as an AC resistance meter? It seems to me that would be the most useful instrument for pickups, if there was one I could use my own frequency generator and measure at pickup relevant frequencies....

[David Schwab]

Originally Posted by Possum

Is there such a thing as an AC resistance meter?

Doesn't the Extech measure AC resistance?