Ukeclass, I play a Martin S-0 soprano, and I installed a single-disc "under-the-soundboard" surface-mount passive piezo pickup in it a few years ago. It was very inexpensive, and came from a company called "jjb Electronics." My gigging is pretty much limited to the retirement home circuit.
I run from the uke into an inexpensive Behringer ADI-21 preamp/eq box, and then from there into a little Kustom PA-50 portable p.a., which is very capable for such a small unit. I use one channel on the p.a. for my voice and the other for my uke. I must say, it's pretty astounding how well that combination can fill a room with sound. And people seem to find it pleasing to the ear.
Now, without a preamp, the disc pickup tends to deliver a very "hot" and harsh signal once you start to turn it up, but running it first thru the preamp allows you to buffer that signal, dial out the harsh or feedback-prone frequencies, and then send a nice smooth sound into the p.a.
My jjb Electronics pickup cost around $35. That's the version that features an "endpin jack" such as you'd see on many acoustic guitars. But they also make a simpler version which costs half as much and has a jack that you'll position more on the lower side-bout area of the uke. I've used both versions, and they both work great (installation on the less expensive version is quicker and easier).
My Behringer preamp also cost around $35. You can run it on an AC adapter or a 9V battery. So far I've opted for the convenience of battery power, and I just take care to freshen up the battery every few gigs (and keep a spare in my gig bag just in case).
For the kind of outings that I do, the above setup works really well. Honestly, I love the sound of a soprano that's properly "mic'd up", and I've done a lot of gigs with that approach, but I've found that using the pickup allows me to play with more "nuance", and to avoid "over-playing," knowing that the pickup will get the sound out there above the normal "room noise".
So, I would absolutely recommend a pickup in a soprano!
