DISCLAIMER – if you're not sure about doing this and don't want to damage a precious instrument, DO NOT do this stuff yourself.
If you want to play your banjo through an amplifier or PA system you'll either need a microphone or pickup. I don't like using microphones because I play quite loud and microphones can tend towards feedback at high volume. So I looked into buying a pickup. There are a few models around, but most people seemed to say that a cheap one can cause trouble and a better one gives you a more natural sound. The best one I could find was a twin piezo system. Piezo pickups sense vibrations (in this case, the vibrating banjo head) and convert the vibrations into electrical signals that you can send to an amplifier. The 2-piece ones mean that you can have a good balance between the bass and treble strings on your instrument. But I couldn't really afford one of these nice units. Luckily, one day I remembered that a microphone is just a speaker in reverse, and I wondered if the same is true of transducers. It turns out it's true. So the piezo buzzers that you can buy really cheap at your local electronics store (roughly NZ$5.00 each) can also be used in reverse to capture your sound and send it to an amplifier!
Here's the kind that I bought: http://jaycar.co.nz/productResults.asp?keywords=AB3462&keyform=KEYWORD&SUBMIT.x=0&SUBMIT.y=0
So now all you need is an audio jack socket (I used this kind of thing: http://www.stewmac.com/shop/Electronics,_pickups/Components:_Jacks/Switchcraft_Output_Jack.html?actn=100101&xst=3&xsr=298), some wire like this single-conductor stuff: http://www.stewmac.com/shop/Electronics,_pickups/Supplies:_Wire,_cables/Shielded_Guitar_Circuit_Wire.html?tab=Pictures#details (although I used some non-shielded stuff I had lying around), a soldering iron and a hot-glue gun.
I did the whole project for about NZ$10.00 and it actually sounds pretty good!
DISCLAIMER again – if you're not sure about doing this and don't want to damage a precious instrument, DO NOT do this stuff yourself.
If you decide to proceed...
Firstly you have to get the piezo element out of the plastic buzzer casing. Be careful not to hurt yourself or the piezo element! I used a craft knife: very, very carefully.
You should be able to see that there are 2 separate areas on the element, so you'll have a positive and a negative to wire up (don't worry about which is which, we can find out by trial and error later).
Then cut the circular element in half (I just used common scissors) so you have 2 semi-circles, each with 2 separate areas within them. The reason I did that is 1) because one big element caused feedback to happen when I tried it that way, and 2) you'll have separate elements to cover the bass and treble strings, and get a better sound balance.
Start with one half of the element just to try things out.
Solder the shield or negative part of the wire to one part of the element and the positive part of the wire to the other. Don't hold the soldering iron onto the element for too long – you might damage it. Then solder the other end of your wire to the output jack connectors. Again, you'll hear it if you do it wrong, so just pick a connector to start with and solder it up. Now, to check if things are actually working, plug an instrument lead into the output jack and connect to it to an amplifier – TURN IT DOWN, do not have it up way loud or you may wreck yourself! Then hold the piezo element onto your banjo head, and pluck a string with your free hand and see if any sound is coming through. If not, you may have to switch the wires over on the output jack, or it might just be the way you're holding the piezo element that's shorting something out – try holding it with something non-conductive first before you go re-soldering stuff. Once you know you can get a sound allright, you'll need to plan how to fit the whole shebang. I have a resonator on my banjo so the output jack was able to just bolt onto the resonator ring. I did have to carve a small amount of wood out of the resonator bowl to accommodate the jack. If you don't want to do that you could always use a jack like this http://www.stewmac.com/shop/Electronics,_pickups/Components:_Jacks/Flush-mount_Output_Jack.html?actn=100101&xst=3&xsr=298 and have the wire come right out of the resonator. (If you do it this way you'll have to disassemble your initial setup so you can poke the wire through, screw the resonator back onto the banjo, then re-solder the jack.)
I attached the elements to the underside of my banjo head so there's no ugly stuff on top of the banjo and also so I won't hit things while I'm playing, and break them. To attach the piezo elements to the banjo head, I used a hot glue gun. The extra benefit of this is it adds a bit of dampening, making the tone nicer. Also, the banjo puts out a lot of energy, so it needs a little dampening so it doesn't overload (see below for more on this). You don't want to overheat the banjo head in case it distorts or melts! So firstly, find out where you want to position the elements. To do this you'll need to repeat your initial experiment, but this time with both elements hooked up to the output jack. Solder both positive elements to one of the jack connectors, and both negatives to the other (whichever way round worked for you last time!) Then play around with different positions to see what sounds best. I found that putting the treble-side pickup just off the underside of the bridge, and the bass side element a little further away from the bridge at the top, gave the best balance. Bass strings move more and put out more energy, so that makes sense, yeah? (NOTE: Later on I found there was a little overloading still going on so I made an alteration without moving the pickups – see below. You have the chance to get it right first time, so you might try moving your elements a little further away from the bridge) Putting the elements too far away can lessen the output too much. Click on the photo to enlarge and you'll be able to make out the bridge feet to see my placement.
By this stage you should have a fair idea of what length of wire you'll need to reach from the piezo elements to the output jack. You don't want a lot of extra wire rattling around inside the instrument.
Once you have decided on your positioning, put some hot glue on the bottom of the piezo element and stick it on the banjo head. By putting the glue on the element rather than the head it gets a chance to cool just a little, so it shouldn't damage the head. DISCLAIMER yet again – if you're not sure about doing this and don't want to damage a precious instrument, DO NOT do this stuff yourself.
Once the elements are attached, and wired to the output jack, you can just screw it onto the resonator ring (or whatever arrangement you decide to go for) and you should be ready to play.
FINAL FIX for my overloading problem. I found that there was still a little overloading after I'd attached the elements and I didn't want to chance ruining everything by pulling the piezo elements off the head. So I carefully slid a piece of foam between the head and that big rod thing that runs through the middle of the instrument. That dampened the head a little, took away any distortion from the pickups, and actually gave the banjo a nice mellow tone when unamplified as well – bonus!
Here's what it looks like from the outside:
So there you go – you can decide if you want to buy a top-quality professional piezo pickup, but if you have an instrument that isn't too precious then you can easily try your hand at doing it yourself. Most times, the worst thing that could happen is you might ruin a banjo head, so it's not the end of the world, although in my case I also carved a little wood from the resonator, which I certainly DO NOT recommend if you have a nice instrument! But if you use the other kind of output jack you wouldn't have to do that at all, in fact that's how I did it first time round and it worked fine, without any damage to the banjo.
I've used it at quite a few gigs now and have been very happy with the sound, just plugging it directly into the PA system. No doubt my less-than-professional soldering will cause me grief one day, but I'll just have to grab a microphone and make do if that happens.
Happy tinkering!
Bing Turkby
