DIY Magnetic Pickup

"A magnetic violin pickup consists of a permanent magnet wrapped with a coil of a few thousand turns of fine copper wire. The pickup is mounted on the body of the instrument. The vibration of the nearby soft-magnetic strings modulates the magnetic flux linking the coil. The signal created is then carried to amplification or recording equipment via a cable. There may also be an internal preamplifier stage between the pickup and cable. More generally, the pickup operation can be described using the concept of a magnetic circuit. In this description, the motion of the string varies the magnetic reluctance in the circuit created by the permanent magnet."


http://www.electricviolinshop.com/gear-accessories/pickups.html
http://www.youtube.com/watch?v=F7u0KEbQV_4
http://www.theviolinsite.com/violin_pickups.html

If you can get hold of a tone arm with pick up head of a vynl record player , that will be a good choice to start.

Piezo-electric pickups are routinely used in stringed (and other) instruments throughout the world. Some very expensive, I might add. My advice to you is to buy a book on guitar pickups and read it.

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The wheel has already been invented.Go to some of the dozens of guitar shops in Austin and get to know the guys who work on them.

For steel strings a guitar-like pick up would be fine. But on violins the core of the lower 3 strings is usually Perlon (except for the cheap strings).

Some piezo's are pretty good, like the Baggs which has the crystal embedded into the bridge. Still, there are some undesirable quality in the sound so some musicians use an equalizer to get closer to the acoustic sound they look for. Some others mix the piezo sound with the signal coming from a good quality mike suspended over the f-holes...

You answered the first question which popped up in my mind: are standard violin strings OK for electromagnetic pickup?

So the answer is no.

First thing to check is whether your strings can hold a small magnet. If not: forget it and start selecting other strings. For guitars you have a full wall of strings, if you play classical the choice is mostly reduced to 3.

Secondary is the question: for what reason do you want to do the direct string pickup?

The typical violin sound is formed in the body and it is the mixture of the body sounds in the air which is what we normally hear. (just as the classical guitar)

The sound picked up by the magnetic pickups will only contain a fraction of the wanted sound. You will need multiple pickups just like with electrical guitars to create some new sounds, eventually combined with a microphone mounted in the body (eventuall multiple) on well choozen locations.

What you can do is to start experimenting with guitar pickups and guitar amplifiers.

Mount the pickup from the top, easier to create a fixture without damaging.

But be attentive: you will not be the first being electrocuted through DIY electical instruments.

And keep us updated, I'm interested on how it sounds.

If you're going to do the experiment (and ignore all the good pickups already available on the open market), you'd probably be best with a coil wound round a rod magnet (many - as in about 1000 - turns of fine copper wire), with a piece of iron fixed to the bridge. The gap between the armature on the bridge and the coil core would have to be as small as practical.

BUT this would give a very strange sound, because it would be picking up displacement along the axis of the strings. The sound heard from a violin is from displacements of the sound-board, which are perpendicular to the axis of the strings. The same applies for pretty well any other stringed instrument (excluding harps and similar)

Suggest you think it through carefully before wasting time, money and maybe a good instrument.

If you go for it - and it works - please put it on you-tube (or similar) and post a link.

Good luck.

Dear John DG,

could you explain the difference between having a moving iron in the proximity of a coil with a magnetic core versus the moving magnet in front of a coil with iron on no core at all? Would it make sense to have a magnet moving INSIDE the 1000 turns coil?

Thanks

The object is to get as many lines of magnetic flux moving across the turns in the coil as possible (to maximize the signal). I could be wrong (it's not really my field) but I think the coil around the magnet would be better than the coil around iron (with a magnet fixed to the bridge). An air core would almost certainly give a lousy signal, as there'd be nothing to direct the flux into the coil and only the first few turns would "see" it.

If you can't find a definite answer to this one it would be pretty easy to lash up a test to compare results.

A moving magnet inside the coil would give a bigger signal (it would after all be closer to an electrical generator) but you'd have more probability of distorting the waveform (there'd be more mass fixed to the bridge), and even more problems of alignment that with the other methods.

Got it. Thanks. I might try to use some cylindrical magnets I have (1mm diameter/3mm length) and see if I can find a coil with a couple of mm diameter at the center. I remember I've seen something like this as a part of a servo mechanism in a remote controlled car...

Or you could use a mic designed for the instrument.

Here a site with some good info and some links.

One time I attached a Piezo phonograph pickup to the head of a guitar and fashoined a copper wire hoop placed in the needle hole that rested on the strings for a pickup. then I found it worked without the wire hoop. It sounded pretty good too.

In Soviet Russia during the sixties someine discovered a telephone reciever could be used for a guitar pickup. After that you couldn't find a working pay phone. They also started raiding the loudspeakers that were attached to the telephone poles.

The idea is sound (no pun intended) but the problem is always in the details.

You need to support the coil rigidly (as there will be mechanical forces on it), you're assuming the bridge (which will have a slight alteration of its mechanical properties due to the extra weight of the magnet) vibrates in a way that's faithful to the violin sound, you'll need to amplify the small signal from the coil but not the other induced signals (eg mains hum) and that the coil moves within the linear region of the magnetic field etc. etc etc.

If it's for fun or learning then it looks like an interesting project, if you want good quality sound then buy a commercial pick up.

Thank you guys for the inspiring ideas and feedback. Yes, it is an experiment for sure and I will post the result.

I am a violin maker/restorer and I have some customers looking constantly for the "perfect" pickup. And depending on the music they play, they look for different sounds.

Violin bridges are very interesting: the sawtooth wave produced by the bowed string is coupled to the body of the instrument and different areas of the bridge act as masses or springs therefore filtering out some frequencies. The overall motion of the bridge is very complicated but it moves mainly in a teeter-totter fashion so I will start attaching the magnet to the side of it.

I realize that is going to be a challenge to keep the coil stationary: I could either use the tail piece as base or something attached to the edges of the f-holes. In any case I see already that such system, even if could give good results, probably cannot be made "user friendly" as the others on the market. But, nevertheless, I want to investigate.

this remains me of a fellow i met many years ago who claimed he made the best filaments of copper wire in his factory in florida. has anybody heard of this factory if so pleaser let me know thanks

Professional Sound Engineers use FRAP's Flat response audio pickup ..Designed for exactly that reason and mounted directly on the bridge.. you might also look at the system devised by Goddly and Creme of the band 10cc Good luck..

I gess we have a principal error here :
1-st -- the TRUE WORLD SOUND is at least (non-relat.) 3 dimensional
2-nd -- if you "MAP" it from INSIDE it's GENERATOR part the "OUTPUT"
______ will be signifficantly different from that the listener will preceive
______ @ different relative locations from the instrument ... THUS THE
______ Fn. 2.solve is at least 2 sensors inside the Gen. => Outside AU-
______ DIO (involves transition wood.accoustic3Dsystem >> air.XYZ)
______ from the air.XYZ you can get then air.3D => air.2D => air.1D
(merry christmas - it's Ash­¡tLot of work)

http://en.wikipedia.org/wiki/Electric_violin

I never installed a Barbera Transducer but it seems like a good idea to have two sensors each string to detect both axis of motion. I believe it is also a piezo system.http://www.barberatransducers.com/violinpickups.html

I had a customer who had the strangest pickup ever: I think he got it in Denmark. Basically the upper nut had a little metal part that created an electrical contact between the four strings (even it the core is not steel, the ribbons around the synthetic core makes the string conductive). From there a wire would run inside the violin to one of the 5 poles jack. At the other end of each string (tailpiece) each of the four strings would also be electrically connected to the 5 poles jack. I noticed a pretty strong magnet under the fingerboard. Well, those five wires went into a sealed preamp and I have no idea what kind of electronic was inside. The truth is that the sound was very pleasing and no feedback problems at all. Probably it is not very popular because it requires a professional installation while many other systems don't.

Another thing I want to try is to have the coil with the magnetic core in front of the moving magnet in a way that they repell each other. Any guess?

This particular system, the Danish one, is called Stringamp. The principle is electrodynamic. Not strange at all... When the string passes through the magnetic field, a current is generated, it only needs to be connected to the jack. On electric guitars, the strings are sometimes grounded because of this effect. The signal is very weak and needs a strong preamp or a transformer before plugging in to the amplifier.

One of the first electric guitar brands - a Norweigan one - was amplified this way. I also know that there are people here and there who have amplified fiddles this way not even knowing of Michael Edinger's Stringamp.

It's very simple if you know how to get a signal from it. The only critical part is connecting the nut end. A cable under the fingerboard may be needed, but the strings can also be connected in series if G is connected to D in the tailpiece end, D to A in the nut end and A to E in the tailpiece end, the circuit is closed. If it's a guitar, it might be shortcircuited if using a metal bottleneck...

How do you filter out EMC?

A stage is a very hard environment for small electric signals.

I don't.

Johnny Ramone's philosophy was, that if you just play loud enough, the hum won't be heard.

It's no bigger problem with a fiddle than with a guitar.

There are a few things to think about. A guitar PU is sensitive to vertical string movements and won't pick bowed tones well. To sense the horizontal movements, the pickup must be positioned to the side of the string, and thus, each pickup can only pick a maximum of two strings. Ideally the pickups should be very small, some 5 mm wide and some 8 mm high. A thin metal core is prefered in favor of more windings of copper. Use strong magnets to magnetisize the thin core. The output will probably be rather low, so turn up the amp or get an overdrive pedal.

If anyone here likes winding coils, I'm in desperate need for three small ones, it's a five-string fiddle.

Where are you located?

I have a coil-winding machine, but not much time. I'd need to know details of and where to source formers (no time to make anything) and the wire size (and source) & number of turns. Also need to know where to send stuff. Don't post contact details on open forum (Admin will prob'ly delete them before I see them).

Sweden. I need three very small coils, some 5 mm wide and 8 mm high. A very thin core is recommended in favor of more windings, there are other ways of enhancing the magnetic power. The thinner wire, the more windings and the more output volume, which is how I like it.

Go to Constance Eller's Facebook page and you will see a picture of her playing an electric violin. She is a concert violinist and has been one since the 1960s when she led the high school orchestra. There's some good jokes about music there too.

There are 3 magnetic violin systems on the market:

only a solidbody instrument with the pickup installed sold

http://www.e-strings.de/

for acoustic instruments and solidbodies - installation by customer or luthier

http://www.uli-boesking.de/rebo/e_start.htm

mostly for acoustic instruments - installation by manufacturer and authorized luthiers

http://www.stringamp.com/

That German thing is similar to the pickup arrangement on Fender P-basses. Seems to be a bit overkill, that broad construction and all poles. The way magnetic pickups work with bowed sounds, it's only the movement out of and back into the sight of the coil that's registered and amplified.

Any way, nice to see that this subject is taken seriously and that commersial manufacturers make some experiments.