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jaredyates
04-08-2013, 07:50 AM
Hi everyone, I have a question about pickups. I have just built a very compact solid-body travel ukulele, which I plan to carry with me on my frequent travels. The small size was the primary goal, and to that end it is a success. I was primarily looking for strings and a fretboard that would allow me to practice- so sound quality and output are not important since I have a fancier ukulele at home. One secondary goal was to provide electric pickup that I could listen to on headphones, and a tertiary goal is perhaps one day even a line-in that would mix with my ipod's music out to allow me to play along silently in my hotel room. I installed one of these:
http://www.ebay.com/itm/NEW-2-Band-Ukulele-EQ-Pickup-UK-300T-W-Button-Cell-BL-Hard-Ukulele-Piezo-380-/321064926144
and it seems like a pretty good little unit. The tuner works, but the pickup is not working very well. If I hold the pickup so that it is pretty much touching the strings, then I can hear the strings in my headphones, but of course then the pickup fouls the strings. The pickup is a piezo fellow with four little bumps, and you can see him in the pictures on the auction link above.
I haven't found any instructions for how the piezo is supposed to be installed, so odds are good that I'm not doing it right in the first place. I should also add that I'm really new to all of this and could likely have a really basic problem.
Does anyone have any suggestions for how or where I should install the pickup, or how I can make it work with a little more distance from the strings? Once again, I'm not looking for concert quality, just basic functionality. Thanks in advance!

ukemunga
04-08-2013, 08:55 AM
It appears that you have bought what is called an "under saddle" pickup. The little flat strip at the end of the braided wire is meant to lay under your saddle in the bridge. That's what picks up the vibrations and translates it to sound. Typically the control box is mounted into the top side (edge) of an acoustic uke.

rudy
04-08-2013, 12:14 PM
Yes, you do have a under-saddle transducer. You can use about any installation guide for an under saddle piezo transducer to figure out how it is mounted.
If you're plugging headphones into the pre-amp directly it won't work, or the signal will be extremely low. The box you have referanced is a pre-amp which is designed to impediance match the piezo to an external amplification source, plus provide a simple tone shaping circuit. Unless "headphone amp" is expressly listed in the seller's ad you can be assured it won't drive headphones effectively.

jaredyates
04-08-2013, 04:31 PM
Thanks for the help! I have done a bit more research with your advice and see that I have a few problems. The first is that I now realize that the pickup needs to be rigidly in contact with the string vibration, not just sitting under the strings. This makes sense now that I see how it works. My combined bridge/saddle arrangement is great for keeping the size of the instrument down, but not so good for easy pickup installation. Some clothespin testing seems to indicate that I might be able to attach the pickup to the bridge/saddle inside the acute angle formed by the strings. Anywhere else on the circumference would be in the way during string changes. Now that I look closer, I also realize that I spaced the strings a little bit too far apart. Fortunately this is easy to correct by shortening the aluminum spacer tubes. As it is now, the bumps on the pickup don't quite line up with the strings. I think my error is in not accounting for width of the strings themselves. I've tried to include a picture just in case anyone else has a better idea for arriving at the end result.
Also, I didn't realize that the headphones need more than the preamp puts out. Is there a small circuit available that would amplify the preamp's output to meet the needs of the headphones? I'd be comfortable with making one up (construction, not design) if I could find a place to put it on the instrument. I did a little googling but I haven't found the search terms yet.51564

rudy
04-08-2013, 05:19 PM
One of the cheapest "amps" that you could put in for driving phones (or a small speaker) is the Artek 2.5watt amp board, available here:

https://www.cbgitty.com/cubecart/amplifier-parts/2-5w-artec-amp-circuit-board.html

Your under-saddle pickup is designed to be mounted under the saddle of a conventional bridge to put full pressure against the crystals. If you can figure out a way to put your string downforce against the pickup it would work; I'm not sure how you could do it with your design. The pickup will not tolerate strings pulled directly across it's face, or any abrasion for that matter. You could most likel do better with a simple piezo disc bonded to the "body" of your instrument. It would easily pick up induced vibration of the "body".

You can use the Artek with a piezo disc and not use the preamp you are presently using, although you would lose the ability to control the tone.

ukemunga
04-08-2013, 05:21 PM
Good one! I agree, and re: the photo, I simply wish to further obfuscate.

Rick Turner
04-09-2013, 04:31 AM
There is so much wrong with all of this that I advise that you go back to basics and learn just how piezo pickups work. There's plenty of information out there on the internet; you just have to do homework.

jaredyates
04-10-2013, 01:43 AM
There is so much wrong with all of this that I advise that you go back to basics and learn just how piezo pickups work. There's plenty of information out there on the internet; you just have to do homework.

Where is the instant gratification in that?:p

jaredyates
08-20-2013, 04:43 PM
For the benefit of the archives, I wanted to post a follow-up for how I was able to make some progress on the electronics of my travel ukulele. Since Rick suggested that I look to the internet for information (instead of asking people on the internet), that's what I did. As he suggested, there is lots of information about how piezo pickups work, though I didn't really find the answers that I was looking for, specifically what the Chinese UK300T would be expecting to see in the pickup. With that in mind, I just pressed on with the assumption that it didn't really care, and proceeded by making a simple disk pickup since the cost of trial and error in this case was low. That yielded an output that would work fine if I plugged the UK300 into a guitar amp, but it still wasn't making any noise in earbuds directly. I spent a few hours of searching that same internet (which took a few months, with this not being a really high-priority project) to try to find a stand-alone "box" that would take the output from the instrument at a level that was appropriate for an amp, input from my MP3 player, and make all of that available to my earbuds. I even looked for plans to build a circuit that would do that, but before I started the Digikey order, I found the Vox AmPlug. This does exactly what I needed, and for $40 for a proven, working solution, I consider it money well spent. I could have easily spent that in parts, not including a day of troubleshooting or adjusting a home-made solution.

There are still several areas for improvement in this project. One is to go back to a 1/4" output on the instrument, so that the AmPlug will plug directly into the instrument. Currently I have the output routed to a little headphone jack that I had planned to plug earbuds into, so I'm using a wire jumper that converts the plug size and sex to fit the AmPlug's 1/4" male. This is functional, but it unnecessarily adds to the parts count and complexity. I think I have enough material left in the body to flush mount it somewhere. Another improvement is to find a better placement of the piezo disk, since currently it is picking up lots more than I would like to, such as any contact that I make with the instrument near the current disk location. Finally, I need to make a little case for it, which might end up being a nice fuzzy sock intended for footwear. The overall dimension is 14" long, 3" wide at the widest, and 1.25" tall at the tallest, so it definitely meets my goals for compact size. So in summary, thanks for the tips about why the initial setup wouldn't work, and for anyone who might be looking for a similar "only listen to myself play" mission, the AmPlug is certainly worth a try.