Moving Coil Pickups for the Technically Curious

[thethreemusketeers]

Hello Musketeers,

Please identify the model of the toroid current transformer that you are using?

What is the actual input impedance of the mixer that you are using?

It seems that your goal is to obtain a good level and low noise output from each of the seven strings to allow individual fine tuning of the volume at the mixer?

Please identify your plan to test the output of your results?

What test equipment do you have access to?

It is good to see you tinkering in areas where few have gone before!

Joseph J. Rogowski

Hello Joseph,

We're using a transformer with 50 windings.

We're not sure yet which type of mixer we're going to use, but we're trying to get below 300 ohms impedance for each individual string.

The answer to you third question is yes, we're indeed trying to accomplish this.

We want to test our measurements and adjustments first by connecting one or more strings to an amplifier and then connect it to a speaker , once we are happy with the results(no humming and a loud enough signal) we want to use a mixing panel.

We have access to an analog and in the future a digital oscilloscope, and to a LCR-meter.

I hope this answers your questions!

Willem, Jessie and Davey

[bbsailor]

Hello Joseph,

We're using a transformer with 50 windings.

We're not sure yet which type of mixer we're going to use, but we're trying to get below 300 ohms impedance for each individual string.

The answer to you third question is yes, we're indeed trying to accomplish this.

We want to test our measurements and adjustments first by connecting one or more strings to an amplifier and then connect it to a speaker , once we are happy with the results(no humming and a loud enough signal) we want to use a mixing panel.

We have access to an analog and in the future a digital oscilloscope, and to a LCR-meter.

I hope this answers your questions!

Willem, Jessie and Davey

By 50 windings do you mean 50 primary turns? Or do you mean 50 secondary turn? Or do you mean a 1:50 turns ratio?

Here is a method to test your voltage needs. Place the oscilloscope across the test string with the magnets in place beneath the string and measure the output peak voltage from a plucked string. Place your test transformer across the string and now measure the primary voltage across the string again loaded by the transformer. It will be a lower reading due to the transformer loading. Now measure the output voltage from the transformer secondary. The voltage will be higher by about the turns ratio of the transformer you are using.

Please tell me me the turns ratio that you are using and the total length of wire connecting the string to the transformer plus the length of wire going through the transformer primary as well as the wire gauge being used.

Once I know a few facts, I can then guide you in a better way, if you have any questions.

Thanks

Joseph J. Rogowski

[thethreemusketeers]

Hello Joseph,
First of all my sincere apologies for our absence on this forum.
I (Willem) have some questions regarding magnets.
Currently it is my goal to find the ideal distance between a magnet and the guitar strings.
I tried to find out if there are any usable formula regarding this subject, but had trouble finding anything usable.
I would also like to know if you had any advice for experimenting with the ideal placement of the magnet regarding distance and positioning.
Hopefully Me Davey and Jessie can be a little bit more consistent with our replies this time, which means that other post/questions might follow.
I really appreciate any help you can provide.

Willem

[bbsailor]

Hello Joseph,
First of all my sincere apologies for our absence on this forum.
I (Willem) have some questions regarding magnets.
Currently it is my goal to find the ideal distance between a magnet and the guitar strings.
I tried to find out if there are any usable formula regarding this subject, but had trouble finding anything usable.
I would also like to know if you had any advice for experimenting with the ideal placement of the magnet regarding distance and positioning.
Hopefully Me Davey and Jessie can be a little bit more consistent with our replies this time, which means that other post/questions might follow.
I really appreciate any help you can provide.

Willem

Willem,

The best way to experiment is to place the longest length of magnet under the string to maximize the output from the transformer placed across the string. Putting a too strong magnet or a too close magnet will damp the ferrous guitar string. Adjust magnetic strength, length and distance from the string to minimize the magnetic damping on the transformer loaded string. There is little published research on this issue. The closest research is about ribbon microphone transformers. However because the ribbon is made from very thin aluminum closeness to the magnets is not an issue but the reflected preamp input impedance will be in parallel with the ribbon and tend to acoustically damp the ribbon vibrations. This is why typical ribbon microphone transformers have about a 1:35 turns ratio to try to keep the transformer output impedance near one tenth of the mic mixer impedance.

I hope this gets you going in the right direction. Keep up the research. This is what makes learning fun!!!

Joseph J. Rogowski

[bbsailor]

Willem,

The best way to experiment is to place the longest length of magnet under the string to maximize the output from the transformer placed across the string. Putting a too strong magnet or a too close magnet will damp the ferrous guitar string. Adjust magnetic strength, length and distance from the string to minimize the magnetic damping on the transformer loaded string. There is little published research on this issue. The closest research is about ribbon microphone transformers. However because the ribbon is made from very thin aluminum closeness to the magnets is not an issue but the reflected preamp input impedance will be in parallel with the ribbon and tend to acoustically damp the ribbon vibrations. This is why typical ribbon microphone transformers have about a 1:35 turns ratio to try to keep the transformer output impedance near one tenth of the mic mixer impedance.

I hope this gets you going in the right direction. Keep up the research. This is what makes learning fun!!!

Joseph J. Rogowski

Willem,

See this web link DIY Ribbon Microphone Design - Operation Principle Overview for some good information about how the ribbon, magnets and transformer operate to best pickup vibrating air. The ribbon is tightly coupled to the magnetic field and the mixer input impedance load is reflected back to the primary by the square of the transformer turns ratio. The guitar string acting as the ribbon is more loosely coupled to the magnetic field and is more related to the damping effect of the magnet strength and strength on the string mass.

Try using a variety of turns ratios on the toroidal matching transformer to balance the load on the string based on the strings frequency range, and the loading of the transformer on the open circuit (unloaded) string induced voltage. When the string impedance matches the transformer input impedance the loaded string input voltage (to the transformer) will be down -6dB or one half the unloaded voltage.

Above is the best web link I could find to get you moving in the right direction.

Joseph J. Rogowski

[SteikBacon]

This was done in Norway in the 40s.. Nilsen guitar.
Maybe the first line of electric guitars, production started in 47.
47-52 and they made 400-500 (though some have estimatet about 1000..)
Each string have a transformer.
The big block under strings are the magnet.
And I've played the one in the video
https://www.youtube.com/watch?v=4lbv2VFUAdw

Norwegian patent is dated to 49, but production was going by then.
http://norskegitarer.no/?page_id=961