Rickenbacker pickups

[Les]

Hi, I'm new to the list.
Does anyone have any data on ric toaster and higain pickups as far as resistance, inductance, and stray capacitance measured at about 3kHz ac?
I do have an Agilant Impedance analyzer, but no pickups to test!

thanks

[salvarsan]

Hi, I'm new to the list.
Does anyone have any data on ric toaster and higain pickups as far as resistance, inductance, and stray capacitance measured at about 3kHz ac?
I do have an Agilant Impedance analyzer, but no pickups to test!

You want an awful lot for a noob.

When I had a reissue toaster in my grubby paws,
It measured 6060 ohms DC.

Bobbin dimensions were
Core length 2.165"
core width 0.26"
core height 0.185"
bobbin flange width 0.93"

The magnets were long alnico II rods, 0.25" diameter.

Depending upon the winding simulation model I use,
it comes to ~5000 winds #44 in a tight machine wind
or maybe as low as 4500 winds as a tight hand wind.

To find a US dealer near you, try
http://www.rickenbacker.com/dealer_find.asp

-drh

[Les]

Ric pickups

Thanks for replying salvarsan.

I should explain what I am trying to do.
I just bought a new Ric 360 12 string, and it has the hotter "higain" pickups. They sound very nice, but sometimes I want to record with the vintage bright jangly sound the toasters have.

I really don't want to take apart the Ric and swap/rewind/tap pickups. I want to leave it dead stock.

I'm a transducer engineer. I used to be an R&D engineer for Shure Brothers a long time ago. So I used some of my tools to make a spice lumped parameter model of the guitar and pickups.

I can then use a Fet pre at the guitar input jack to knock out cable capacitance then go direct in and eq the higher self resonance peak of the toasters and at least get closer to their sound. It may not be perfect, because the magnetic circuit reluctance is very different on the two pickup types.

In my tranducer lab I currently have an Agilent Impedance analyzer rented on a very high power transducer design job. If I use this to analyze pickups I can get a wealth of information because it shows real time curves of inductance, capacitance, and resistance. It should easily be able to see things like eddy current effects, winding vibration, cover microphonics, etc. It is sensitive enough to see a speaker's electrical impedance functions change just as you walk by!

So I guess I need to get some of these pickups and do impedance function runs. If I am able to, I'll be glad to share the data. The transducer job is almost done though, so I can't keep the Agilent much longer. The monthly rental for the thing is $1200!

[salvarsan]

I really don't want to take apart the Ric and swap/rewind/tap pickups. I want to leave it dead stock.

That sounds like you understand you must purchase a reissue toaster pickup but chafe at the prospect.
I sympathize completely.

I'm a transducer engineer. I used to be an R&D engineer for Shure Brothers a long time ago. So I used some of my tools to make a spice lumped parameter model of the guitar and pickups.

Outstanding! The science of guitar pickups has gone begging for people like you for decades.

Have you had time/motivation to characterize a pickup with an I/O model for output versus magnetic frequency at constant AC gauss, i.e., as a transducer instead of an idiosyncratic impedance curve?

the magnetic circuit reluctance is very different on the two pickup types.

Luv it when you talk dirty. The Toaster has more steel and a bigger magnetic aperture presented to the strings, certainly, than do the black tops.

In my tranducer lab I currently have an Agilent Impedance analyzer rented on a very high power transducer design job. If I use this to analyze pickups I can get a wealth of information because it shows real time curves of inductance, capacitance, and resistance. It should easily be able to see things like eddy current effects, winding vibration, cover microphonics, etc.

Some folks might even pay to have pickups characterized this way.

FWIW, you can get a set of toasters on eBay for $225 or find a Rick dealer with one in stock for $100 before shipping. Rickenbacker's online store claims to be temporarily out of stock.

-drh

[Les]

ric pickups

Salvarsan,

On Ricresource we are trying to get some pickups to run curves on before the analyzer has to go back.Hate to lose it. I may make a lower bandwidth version from a pc data aquisition card later. I don't need something that goes to 100 Megahertz. A four wire autonulling bridge is not that hard to make if it is just for audio range.

As far as the spice circuit, yeah all you said is possible. It is fairly crude now.
But things like delays, nonlinearities, and such could be modelled. Comb filter effects could be seen in a wide humbucker for instance. Shorted turns and eddy currents could be seen as well.

I expect all those effects will show up on the Agilent as well. I can even see metal fatigue on my transducer parts with it.

Just in passing...at Shure long ago I was a phono cartridge designer. I used a lot of laminated mu metal, #54 wire, Alnico 5 and 9 (mostly 9) beryllium, and such. Just like pickups we resonated the self inductance with cable or added capacitance to get the desired response.

These days I am making high power ultrasonic transducers. 10^5 pascal overpressures. Sound at that level will actually catch things on fire if properly impedance matched.

Anyway for the rough numbers on the spice I get a honkin 6db twang peak at 3.8kHz for the toasters. The higains are a 5 db peak at about 2.5, so HUGE difference in the high end. We need the better data to refine these numbers though.

[Spence]

The high Gain pickups have a rubberized ferrous magnet on the bottom. They have a semi-circular cut out on in the middle. I have tried to convert to AlNiCo by grinding the same curve in a humbucker bar magnet. Just couldn't get the damned magnets to stick in anything other than a permanent way.

[salvarsan]

As far as the spice circuit, It is fairly crude now.
But things like delays, nonlinearities, and such could be modelled. Comb filter effects could be seen in a wide humbucker for instance. Shorted turns and eddy currents could be seen as well.

Scuze, I wasn't specific enough. The idea was to collect empirical data
rather than run a simulation, i.e., to excite the pickup with a driver coil at
constant delta-gauss amplitude and swept frequency ~40-15000Hz.

When groping about for tools a few years back, we did some FEMM visualizations
of pickups. One Alnico5 rod figure I remember put a 50 Gauss dipole on a .046"
dia. low-E string. Too lazy to run the dPhi/dT numbers and estimate output.
(cough)
That, and I don't know how to extract weber/second numbers from
dipole, field, and recoil permeability numbers.

Excellent design gloss on variable reluctance sensor design at
http://www.integratedsoft.com/papers...s/tech_9mx.pdf

These days I am making high power ultrasonic transducers. 10^5 pascal overpressures. Sound at that level will actually catch things on fire if properly impedance matched.

I have a pleasantly abstract appreciation for brute-force Type-1 sonochemical reactions and would like to keep it abstract.

-drh

[Les]

Yeah I could do that I think. I have a B&K 2204 analyzer that can. These days I would use a psuedo random sequence rather than a swept sine...better s/n. It has a generator that does that.

Let's see....would have to drive a coil with a constant current source I think. No problem there. just an audio amp with a bit of series resistance would be an approximation. A true CC amp would not be hard to make either. It would have very high output impedance.

Actually you could do this yourself with a sound card, freebie spectrum analyzer, hifi amp with large series resistance, and some kind of coil. You could use white noise. You wouldn't get phase information like the psuedorandom, but you could get a nice amplitude response with a fourier transform. The whole thing would cost just about nothing if you had a spare amp laying around. I would think someone has done this....

Having the field created by the coil might not relate much to a string though.
What about vibrating a short damped bit of guitar string with a vibration transducer? In that case I think you would want a voltage source, like a regular amp. A pretty good vibration transducer can be made from a speaker motor if it has a feedback element. I have used eminence 4" vc motors for this, but moving a bit of guitar string wouldn't need anything so big. Put one of those tiny chip accelerometers on it, differentiate the signal, and feed it back after a phase flip. You would need some networks to maintain phase margin. My b&k shaker was good to about 10kHz. For a pickup you would need to put the string bit on a stinger so the leakage flux from the driver was far enough away to not muck things up. Different motion polarization (by tilting the assembly) might give some neat data.

[soundmasterg]

Les,

I'm glad you made it over here. Lots of interesting topics here and we can always use someone knowledgeable like you.

On those RIC pickups, I plan to get the info for you tonight after work, though the Extech only goes up to 1 Khz. I'll post the info on the RIC Resource forum when I get it.

Greg

[salvarsan]

Les,
Thanks for giving this serious consideration.

Let's see....would have to drive a coil with a constant current source I
think. No problem there. just an audio amp with a bit of series
resistance would be an approximation. A true CC amp would not be hard to
make either. It would have very high output impedance.

Considering that we only need to generate +/-50 gauss, albeit with some
accuracy as to waveform, it doesn't seem a difficult problem.

Actually you could do this yourself with a sound card, freebie spectrum
analyzer, hifi amp with large series resistance, and some kind of coil.
You could use white noise. You wouldn't get phase information like the
psuedorandom, but you could get a nice amplitude response with a fourier
transform. The whole thing would cost just about nothing if you had a
spare amp laying around. I would think someone has done this....

It has been done for speakers with the Speaker Workshop application
which is free and has source code over at sourceforge.net.

http://www.speakerworkshop.com/

This one creates MLS signals and your choice of deconvolution
to pulse or spectral density, so it has significant appeal if you
can figure out how to get around its calibration routine.

And yes, someone _must_ have done this, but few hobbyists have
and they aren't talking, at least, they haven't posted _here_.

The BruteFIR site also has assorted routines for rolling your own MLS
on the fly, although I suspect you've know about this one for a while.
http://www.ludd.luth.se/~torger/brutefir.html

Having the field created by the coil might not relate much to a string though.

Does it need to?
Using a drive coil, you can generate a greater variety of test signals.

What about vibrating a short damped bit of guitar string with a vibration
transducer? In that case I think you would want a voltage source, like a
regular amp. A pretty good vibration transducer can be made from a
speaker motor if it has a feedback element. I have used eminence 4" vc
motors for this, but moving a bit of guitar string wouldn't need anything
so big. Put one of those tiny chip accelerometers on it, differentiate
the signal, and feed it back after a phase flip. You would need some
networks to maintain phase margin.

Have you been talking to R.G.Keene?

My b&k shaker was good to about 10kHz.
For a pickup you would need to put the string bit on a stinger so the
leakage flux from the driver was far enough away to not muck things up.

That's one of my concerns with the method.

Another measureable quality to consider is the pickup coil microphonicity --
this would give figures allowing one to distinguish winding tensions and/or
potting efficacy.

-drh

[Les]

Thanks, Greg.

1 kHz will be tons better than dc measurements.

You should see how squiggly the impedance function lines are on the agilent just hooked to the guitar. Know what it is? Body resonances....showing up as impedance anomalies!

[R.G.]

Yeah I could do that I think. I have a B&K 2204 analyzer that can. These days I would use a psuedo random sequence rather than a swept sine...better s/n. It has a generator that does that.

Let's see....would have to drive a coil with a constant current source I think. No problem there. just an audio amp with a bit of series resistance would be an approximation. A true CC amp would not be hard to make either. It would have very high output impedance.

Actually you could do this yourself with a sound card, freebie spectrum analyzer, hifi amp with large series resistance, and some kind of coil. You could use white noise. You wouldn't get phase information like the psuedorandom, but you could get a nice amplitude response with a fourier transform. The whole thing would cost just about nothing if you had a spare amp laying around. I would think someone has done this....

Having the field created by the coil might not relate much to a string though.
What about vibrating a short damped bit of guitar string with a vibration transducer? In that case I think you would want a voltage source, like a regular amp. A pretty good vibration transducer can be made from a speaker motor if it has a feedback element. I have used eminence 4" vc motors for this, but moving a bit of guitar string wouldn't need anything so big. Put one of those tiny chip accelerometers on it, differentiate the signal, and feed it back after a phase flip. You would need some networks to maintain phase margin. My b&k shaker was good to about 10kHz. For a pickup you would need to put the string bit on a stinger so the leakage flux from the driver was far enough away to not muck things up. Different motion polarization (by tilting the assembly) might give some neat data.

Hi, Les. I rambled down the same paths a few months ago before I got prempted by some other things. But I'll get back to it. I proposed a few different wire shaker mechanisms, including voice coil and mounting a segment of steel string in a slot on a plastic shaft that was spun on its axis. The MLS testing does look like the better way to get the response. I no longer have access to the instrument candy store back at work, so I'm limited to the instruments I can borrow or cobble. I also came up with a test bed for pickups that involved using a fence post for a base, a self-oscillating drive coil for the string and a movable bed for the pickup to get response curves by actually driving a string to self resonance at a fixed mechanical amplitude and then sweeping the frequency by moving a "fret" under the string on the base.


Pseudorandom is easier to generate than white noise in today's world of $1 programmable controllers.

I will get back to it at some point.

[Les]

Neat RG.

I still have to think about string vs coil. The coil is a heck of a lot easier. To get good high freqency response with a shaker things have to be very rigid. I have used carbon fiber arrow shafts as stingers (extensions) for shakers but only at lower frequencies. An aluminum tube would be good, but might have eddy current effects.

The best stuff is beryillium. It has the highest stiffness/weight ratio of any metal. I used it for phono cartridge cantilevers and tweeter diaphragms long ago, Unfortunately is is expensive, hard to fabricate, and poison.

Aww, I'm just in a "what did you want very badly as a teenager and never got " mode. A rickenbacker 12 is one of those things. I want the sound I heard back then though...at least sometimes. I am setting up a new music room, and am getting more recording gear. And more guitars. I have too many anyway. I used to make them. I have wound pickups too. A few. Last time I wound one was...let's see....<cough> about 1970 as a teenager. There was nothing as far as information. I could only disasemble things and see what was in them. The ones I made used #40 formvar on ceramic and alnico 2 I think. I still have them. They were "hifi" with the fat wire. only about one henry. They sounded rather dull but crisp. Right now I want the big upper midrange peak of ric toasters.

My son plays guitar in a rock band now, and I hope he enjoys the studio. We are going to 24 track 24 bit, although I think 4 tracks is plenty! But the stuff is so darn cheap nowdays...why not?

[Les]

Guys, I did do a little calculation for a tester coil with a typical pro amp.
Turns out using a thevinin equivalent of a current source using a series resistor may be a problem. I used 50 volts as a typical peak output....and I can only do a few gauss with any reasonable coil. With a bridged big amp I might get 200 volts and 10-15 gauss peak.

Had to open the old Fields books from school, haha. Biot-Savart stuff.

So if you really want 50 gauss it looks like either a dedicated transconductance amp or an audio step up transformer is in order.
Another is to drive it with a voltage source and compensate the results with software. The field strength would drop off rapidly with increasing frequency.

As you have helped me, I'll get something together if you really want me to do it.

What coil size would work for you?

Oh, BTW greg posted the ric inductances on ricresource. I'll be popping those values in the SPICE model and posting the response if anyone wants to see it.

[salvarsan]

Les,

We don't need much mag field, but how much is enough?

When you can put an old telephone earpiece against a pickup and
hear it in the amp, what, roughly, is the field strength that is
exciting the pickup?

Erno Zwaan (author: Animal Magnetism) allegedly got his pickup Bode plots by
placing the pickup near the voice coil of a wide range loudspeaker and running
frequency sweeps.

-drh