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Its a damn close to official as possible


 
5/17/2006 12:42 AM
Hummer Its a damn close to official as possible
Sat down earlier today with some Old timers from Gibson, who did all the work on the humbuckers in the 70s and 80s...and ALL 50s PAF humbuckers were....can you wait...  
 
Alnico II.  
 
But Gibson did use Alnico IV on another kind of pickup from its golden era...but it wasn't the PAF...  
 
Hence the confusion...  
 
Straight from the horse's mouth. You heard it here first...
 
5/17/2006 2:10 AM
Dave Stephens
Not really new news. What pickup did they use A4 on? WHO did you talk to, be aware that not all these guys are going to tell you the real deal, plus we've had a bunch of people claiming similar knowledge who are disinformation spies, not kidding. Your real name and occupation might add credability.  
 
There is proof too that A$ WAS used in PAFs, I think A2 was prevalent for the most part but not always. PAFs I 've heard so far area all A2.....Dave
 
 
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5/17/2006 5:30 AM
Steve A.
Dave:  
 
In the Donald Brosnac book, he suggests that back in the 50's Gibson often just ordered "magnets" without specifying the type. Then again even if they specified Alnico 2, maybe the supplier would just send what they had around, figuring that Gibson wouldn't know the difference...  
 
Not speaking for Gibson specifically, but a lot of employees don't know much about the parts they use- they just grab them from a box on the shelf. I would give more credence to what the purchasing agent would have to say...  
 
Steve Ahola
 
5/17/2006 6:02 AM
Dave Stephens
Don't believe everything you read, where did Brosnac get his info from, no one knows. Tim Shaw who designed the 80s reissue Gibson pickups after stuyding real PAFs said they were alnico 2 and then moved to alnico 5. PAF magnets were thicker than what you buy now. I don't know when they switched to 5, probably when the T Tops came along with their smaller magnets. I know A4 has been found in one sample of real PAFs, so maybe there WAS alot of unconscious random use of magnets. If Gibson is anything like they are now that makes perfect sense (as in sloppy quality control). We'll probably never really know since who the heck is going to rip their $5,000 pickup apart to find out what alnico it is and most don't really care, just us nut cases :-) I like A2 the best for smooth jazzy kinda tone, A4 for sharper sweet tone, and A5 for rock style. Haven't tried A3 yet, not enough time in the day. I did discover one thing using inductance swap out tests and thats that A2 and A3 give almost identical inductance and AC resistance readings using same size magnets on the same coil. The only difference is magnet strength. Unfortunately the Extech doesn't have a 10khz test signal, I wonder if we'd see a difference up in that range......Dave
 
5/17/2006 8:58 AM
moocow
The Extech would freak out at 10kHz. The meter is designed to work with inductors that don't have a significant amount of winding capacitance. At 10kHz, the winding capacitance will throw off the reading.  
 
A better choice would be a digital LCR impedance bridge like this one:  
 
http://www.quadtech.com/products/products.asp?familyid=15  
 
It measures the voltage vs. current characteristics of a component over a wide range of frequencies. Based on the data, the computer inside of the bridge calculates the values of inductance, capacitance, etc. that best fit the impedance data. The bridge can be programmed to expect a certain amount of winding capacitance so it won't be fooled as easily as the Extech at high frequencies. An even more accurate method is to take the digi-bridge data and use your own software to derive the component's characteristics. I'm not sure if the digi-bridge can model nonlinear characteristics such as eddy current losses, but that can be done using MATLAB. Unfortunately, the digital bridges are expensive, well over $10,000. Even some large companies don't have these in their labs. But at one time, I did have a chance to use one to study differences in guitar amplifier capacitors. I wasn't interested in pickups at the time so I never used it to study impedance characteristics.  
 
As for the magnet types, I wouldn't believe what anybody told me either. Even Seth Lover wouldn't know what kind of magnets were actually shipped to Gibson. I would only believe the results of a material science lab that gave me an analysis of the elements in the magnetic material. A quick way to do this would be to send an old Gibson magnet to a company like Arnold Magnetics and ask them to analyze the magnet and send you 1000 more just like it. I'm sure those guys have a good lab and they should do this sort of analysis if it means more business for them.
 
5/18/2006 6:03 AM
Joe Gwinn
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On 5/17/2006 2:58 PM, moocow said:  
quote:
"The Extech would freak out at 10kHz. The meter is designed to work with inductors that don't have a significant amount of winding capacitance. At 10kHz, the winding capacitance will throw off the reading."
It's deeper than that. The capacitative reactance cancels some of the inductive reactance, and at resonance the reactances cancel, so no single-frequency measurement can untangle it. With measurements at a number of frequencies, one can then untangle it, to yield inductance, capacitance, and AC resistance. The fly in the ointment is that the actual inductance of a metal-cored coil varies with frequency.  
 
[QUOTE]A better choice would be a digital LCR impedance bridge like this one:  
 
http://www.quadtech.com/products/products.asp?familyid=15  
 
It measures the voltage vs. current characteristics of a component over a wide range of frequencies. Based on the data, the computer inside of the bridge calculates the values of inductance, capacitance, etc. that best fit the impedance data. The bridge can be programmed to expect a certain amount of winding capacitance so it won't be fooled as easily as the Extech at high frequencies. [/QUOTE]This is the multi-frequency measurement.  
 
quote:
"An even more accurate method is to take the digi-bridge data and use your own software to derive the component's characteristics."
Or, a Maxwell-Wein bridge and variable oscillator. This can be had for small dollars, but is slow to use.  
 
quote:
"I'm not sure if the digi-bridge can model nonlinear characteristics such as eddy current losses, but that can be done using MATLAB."
Such instruments all assume that component characteristics do not vary with frequency, and so will not model the effects of eddy currents, so it will be MATLAB (or Mathematica) to the rescue.  
 
quote:
"Unfortunately, the digital bridges are expensive, well over $10,000. Even some large companies don't have these in their labs. But at one time, I did have a chance to use one to study differences in guitar amplifier capacitors. I wasn't interested in pickups at the time so I never used it to study impedance characteristics."
What did you find with the capacitors?
 
5/18/2006 8:59 AM
moocow
I found that there was no significant difference between the capacitors. I used several .1uF caps, some old, some new, and one that was known to leak. All tested about the same, but two of the new ones were more 'ideal' at 100kHz than the others.  
 
The problem is that the machine tests with a small AC voltage. It can put a DC bias on the component but only a few volts. Guitar amps put a few hundred volts of DC on the caps and the AC signal is much higher. Some versions of the digi-bridge can use an external bias, but I didn't feel it was worth the risk of repeating the experiment with 400V of bias. This also wouldn't solve the probem of the small AC voltage test signal.  
 
The machine belonged to the UCLA material science lab and it was used to investigate the properties of various electrochemical cells. The low AC and DC voltages were appropriate for that application since they were interested in linear properties. I wanted to see the nonlinearites caused by DC voltageg and large AC signals so the machine wasn't too helpful.  
 
Even with the non-linear inductance of the pickup, the digi-bridge can make a guess as to the inductance value that best fits the data. I suppose that's worth something. I'm not sure how it reacts to eddy currents, though, but again, that's what MATLAB is for.  
 
I've posted this before, but here's a lab rig designed to measure impedance of guitar pickups:  
 
http://wug.physics.uiuc.edu/courses/phys398emi/398emi_guitar_pickup_results.html  
 
The payoff is a graph like this:  
 
http://wug.physics.uiuc.edu/courses/phys398emi/Experimental_Results/Pickup_Data/Lindy_Fralin_Hot_Strat_Bridge_Pickup_wCBP_IZI_vs_F.jpg  
 
Similar data can be obtained with much simpler equipment but you'll have to take data points by hand for each frequency measurement and input them by hand into your computer to see the plot. Perhaps the plot is enough information to see differences between pickup designs.  
 
Anyway, I only wanted to point out that the Extech meter has its limitations, but if you want to go farther than the Extech, you'll need to go through a great deal of time and effort to get there.
 
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